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<!DOCTYPE Article PUBLIC "-//OASIS//DTD DocBook V3.1//EN">
<Article id="index">
<ArtHeader>
<Title>DSL HOWTO for Linux</Title>
<PubDate>v0.99, 5 September 2000</PubDate>
<AuthorGroup>
<AUTHOR>
<FirstName>David</FirstName>
<SurName>Fannin</SurName>
<Affiliation>
<Address>
<Email>dfannin@sushisoft.com</Email>
</Address>
</Affiliation>
</AUTHOR>
<AUTHOR>
<FirstName>Updated by: Hal</FirstName>
<SurName>Burgiss</SurName>
<Affiliation>
<Address>
<Email>hal@foobox.net</Email>
</Address>
</Affiliation>
</AUTHOR>
<Editor>
<firstname>Greg</firstname>
<surname>LeBlanc</surname>
<Affiliation>
<Address>
<Email>GLeblanc@cu-portland.edu</Email>
</Address>
</Affiliation>
</Editor>
</AuthorGroup>
<!--
Broken...
<othercredit>
<firstname>Greg</firstname>
<surname>LeBlanc</surname>
<contrib>Help with layout, organization and various content suggestions.
</contrib>
</othercredit>
-->
<RevHistory>
<Revision>
<RevNumber>v0.99</RevNumber>
<Date>5 September 2000</Date>
<Authorinitials>hb</Authorinitials>
<RevRemark>
Various updates, additions and new sections.
</RevRemark>
</Revision>
<Revision>
<RevNumber>v0.92</RevNumber>
<Date>10 April 1999</Date>
<Authorinitials>df</Authorinitials>
<RevRemark>
First release.
</RevRemark>
</Revision>
</RevHistory>
<KeywordSet>
<Keyword>DSL</Keyword>
<Keyword>xDSL</Keyword>
<Keyword>ADSL</Keyword>
<Keyword>RADSL</Keyword>
<Keyword>IDSL</Keyword>
<Keyword>G.Lite</Keyword>
<Keyword>SDSL</Keyword>
<Keyword>VDSL</Keyword>
<Keyword>Broadband</Keyword>
<Keyword>Internet</Keyword>
</KeywordSet>
<Abstract>
<Para>
<Comment>
Converted to DocBook 3.1 HB 08/08/00.
This started as just some additions, but turned into major rewrite.
Todo:
Nada!
</Comment>
</Para>
<Para>
This document examines the DSL family of high speed Internet services now
being deployed in various markets worldwide. Information is included on the
technology behind DSL as well as subscribing, installing, configuring, and
troubleshooting, with an emphasis on how this impacts Linux users.
</Para>
</Abstract>
</ArtHeader>
<!-- ~ End Section ~ -->
<!-- ~~~~~~~~ New Section Header ~~~~~~~~~ -->
<Sect1 id="intro">
<Title>Introduction</Title>
<Para>
DSL, or Digital Subscriber Loop, is a high-speed Internet access technology
that uses a standard copper telephone line (a.k.a. 'loop' in telco parlance).
DSL provides a direct, dedicated connection to an ISP via the existing telco
network. DSL is designed to run on up to 80% of the telephones available in
the United States. By using line-adaptive modulation, DSL is capable of
providing data speeds up to 8 Mbps.
</Para>
<Para>
DSL services are now being aggressively marketed for home and small business
use. DSL is typically priced below ISDN, and well below T1 service, yet can
provide potentially even greater speeds than T1 without the
cost, complexity, and availability issues of T1. Since DSL is a dedicated,
often 'always on' service, it avoids the delays and use charges that are
common with ISDN. Making this quite a nice technology for the bandwidth
starved masses.
</Para>
<Para>
While all this sounds exciting, DSL does have some drawbacks. The quality of
the DSL signal, and thus the connection, depends on distance and various
other factors. Also, there is no such thing as standard 'xDSL'. There are
various flavors of DSL, and many, many ways DSL providers are implementing
their networks. In typical fashion, Linux users are often left to fend for
themselves, since the DSL providers are often taking the easy way out, and
catering only to 'mainstream' Operating Systems.
</Para>
<Para>
The topics included in this HOWTO include qualification and pre-installation,
installation, configuration, troubleshooting and securing a DSL connection. As
well as other related topics. There are also appendices including a
comprehensive <Link LinkEnd="overview">DSL Overview</Link>, <link
linkend="faq">Frequently Asked Questions</link>, a listing of <link
linkend="links">related links</link>, and a <link
linkend="glossary">glossary</link>. </Para>
<Para>
Due to the fast pace of change in the telco and DSL industries, please make
sure you have the latest version of this document. The current official
version can always be found at <Ulink
url="http://www.linuxdoc.org/HOWTO/DSL-HOWTO.html">http://www.linuxdoc.org/HOWTO/DSL-HOWTO.html</Ulink>.
</Para>
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>Document Structure and Reading Guidelines</Title>
<Para>
This document attempts to give a comprehensive discussion of DSL. All aspects
are hopefully addressed to one degree or another with what can be a complex
topic since it deals with networking, hardware, new fangled technologies, and
various approaches taken by various vendors.
</Para>
<Para>
To simplify the navigation of this document, below is a suggested reading
guideline. Everyone should read the Introduction. Please pay special
attention to the <Link LinkEnd="usage">Conventions and Terminology</Link>
section, as some of this terminology may be used somewhat differently in
other contexts. Also, there is a <Link LinkEnd="glossary">Glossary</Link> if
you get lost in the world of TA (telco acronyms) ;-).
</Para>
<Para>
<ItemizedList>
<ListItem>
<Para>
If you don't know anything about DSL, you should probably read the entire
document, with the possible exception of the 'Tuning and Troubleshooting'
section. You may want to start with the <Link LinkEnd="overview">DSL
Overview</Link> section in the Appendix, and then the <Link
LinkEnd="faq">FAQ</Link>. The DSL Overview explains how the various pieces
of the puzzle fit together. DSL network implementations are more complex
than traditional dialup networks.
</Para>
</ListItem>
<ListItem>
<Para>
If you have already done some homework, but have not ordered service from
anyone yet, read the <Link LinkEnd="cproviders">Choosing
Providers</Link> section, and the <Link LinkEnd="isps">Linux Friendly
ISPs</Link> sections. Also, you might get a head start by reading the
<Link LinkEnd="configure">Configuring Linux</Link> section so you know
what lies ahead.
</Para>
</ListItem>
<ListItem>
<Para>
If you have ordered service already, and are awaiting delivery, you can
skip the sections on choosing a Provider. If you will be doing a
self-install, you should read the pertinent parts of the <Link
LinkEnd="installation">Installation</Link> section, the <Link
LinkEnd="configure">Configuring Linux</Link> section, and the <Link
LinkEnd="secure">Securing Your Connection</Link> section.
</Para>
</ListItem>
<ListItem>
<Para>
If the installation is complete, and you can't get a working connection,
skip right to the <Link LinkEnd="tuning">Troubleshooting</Link> Section.
If you are confused by what protocols are required, or what software you
need to have installed, also read the <Link
LinkEnd="configure">Configuring Linux</Link> section. If not sure what
terms like 'sync' mean in this context, then be sure to read the <Link
LinkEnd="overview">DSL Overview</Link> section first so you know how it
all fits together.
</Para>
</ListItem>
<ListItem>
<Para>
If trying to decide between cable and DSL, read the
<Link LinkEnd="cable">Cable vs DSL</Link> section, and possibly the
<Link LinkEnd="overview">DSL Overview</Link> section.
</Para>
</ListItem>
<ListItem>
<Para>
There is a comprehensive <Link LinkEnd="links">Links section</Link> that
has references to some topics not touched on in the main body of the
Document itself.
</Para>
</ListItem>
</ItemizedList>
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>Copyright</Title>
<Para>
DSL HOWTO for Linux
</Para>
<Para>
Copyright (C)1998,1999 David Fannin.
</Para>
<Para>
This document is free; you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version.
</Para>
<Para>
This document is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
details.
</Para>
<Para>
You can get a copy of the GNU GPL at at <ULink
URL="http://www.gnu.org/copyleft/gpl.html">GNU GPL</ULink>.
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>Credits</Title>
<Para>
Thanks to all those that contributed information to this HOWTO. I have
anti-spammed their email addresses for their safety (and mine!). Remove the
X's from their names.
</Para>
<Para>
<ItemizedList>
<ListItem>
<Para>
<Emphasis remap="bf">B Ediger</Emphasis> (Xbediger@csn.net) Great
Description of loop impairment.
</Para>
</ListItem>
<ListItem>
<Para>
<Emphasis remap="bf">C Wiesner</Emphasis> ( Xcraig@wkmn.com) List of many ADSL URLs.
</Para>
</ListItem>
<ListItem>
<Para>
<Emphasis remap="bf">J Leeuw</Emphasis> ( Xjacco2@dds.nl) Many tips on ADSL,
especially in Europe
</Para>
</ListItem>
<!--
Dropped for this version.
<ListItem>
<Para>
<Emphasis remap="bf">J Kass</Emphasis> ( Xjeremie@umich.edu) Unofficial
Ameritech ADSL FAQ
</Para>
</ListItem>
-->
<ListItem>
<Para>
<Emphasis remap="bf">N Silberstein</Emphasis> ( Xnick@tpdinc.com) Info on
Netrunner and his experience with US Worst.
</Para>
</ListItem>
<ListItem>
<Para>
Many and various posters from comp.dcom.xdsl and
bellsouth.net.support.adsl, too numerous to mention individually.
(HB)
</Para>
</ListItem>
</ItemizedList>
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<sect2 id="disclaimer">
<title>Disclaimer</title>
<para>
The authors accept no liability for the contents of this document. Use the
concepts, examples and other content at your own risk. As this is a new
edition, there may be errors and inaccuracies. Hopefully these are few and
far between. The author(s) do not accept any responsibility for incorrect or
misleading information, and would certainly appreciate any corrections. Also,
this type of technology dates itself very quickly. What may be true today, is
not guaranteed to be true tomorrow.
</para>
<para>
All copyrights are held by their by their respective owners, unless
specifically noted otherwise. Use of a term in this document
should not be regarded as affecting the validity of any trademark
or service mark.
</para>
<para>
The naming of any particular product, brand, or company should not be construed
as an endorsement or recommendation.
</para>
</sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>New Versions</Title>
<Para>
Version .99 addresses some of the many changes that have occurred since the
original ADSL mini HOWTO was published. Originally, ADSL was the primary DSL
technology being deployed, but more and more some of the other DSL flavors are
entering the picture -- IDSL, SDSL, G.Lite, and RADSL. Thus the renaming from
'ADSL mini HOWTO' to the 'DSL HOWTO'. There have been many other changes in
DSL technology as well. PPPoE/A encapsulation has become more and more common
as many ISPs are jumping on this bandwagon.
</Para>
<Para>
The contents have additionally been re-organized, with new sections added on
security, and troubleshooting, and as well as many additions to the <link
Linkend="links">Links section</link>. Various and sundry other updates and
additions as well that are too numerous to mention.
</Para>
<Para>
Pre-release versions of this document can be found at <Ulink
URL="http://feenix.eyep.net/ldp/adsl/">http://feenix.eyep.net/ldp/adsl/</Ulink>.
<comment>
You should decide on 1, one, location to list as the home of this HOWTO.
Would prefer the dynamic dns address. But, worry about the longevity of these
services. Is there such a thing as 'pre-release version' as an alternate?
HB.
</comment>
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>Feedback</Title>
<Para>
Any and all comments on this document are most welcomed. Please make sure you have
the most current version before submitting corrections! These can be sent to
<email>hal@foobox.net</email>
</Para>
<Para>
Future versions of this document may include a section devoted to FAQs and
HOWTOs for specific providers. Please send in any links you may have. Also,
I need more Linux Friendly ISPs! See the <Link LinkEnd="isps">Linux Friendly
ISPs</Link> section for what qualifies.
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2 id="usage">
<Title>Conventions, Usage and Terminology</Title>
<Para>
For the sake of simplicity and sanity, let's clarify some of the terminology
that we will be using in this document, so that we are all on the same page.
While many of the definitions below are not always 100% technically correct,
they are close enough for our purposes here. In fast moving technologies like
DSL, there are so many 'ifs, ands, and buts' that it is difficult to say
anything with any degree of certainty and have it stick. And there are
exceptions to almost every rule. And sometimes exceptions to the exceptions.
We will be dealing with generalities to a large degree here, please keep that
in mind.
</Para>
<Para>
<ItemizedList>
<ListItem>
<Para>
'DSL' will be used to refer to the entire family of DSL technologies now
available -- ADSL, SDSL, IDSL, RADSL, etc. ADSL still seems to be the most
prevalent at this time, but the others are being deployed more and more. Where
it is important to differentiate one type of DSL from another, the full
proper name will be used: e.g. RADSL. xDSL also is also commonly used to
refer to the various DSL technologies as a group, but we will be using just
'DSL' here.
<comment>You should clearly state which you will use in this document, either
xDSL or DSL. The last sentence can easily be extended... , but we will be
using DSL in this document or something similar.
10-4. HB.
</comment>
</Para>
</ListItem>
<ListItem>
<Para>
The term 'telco' here refers to any potential DSL provider. This includes
the ILECs (Incumbent Local Exchange Carriers), a.k.a. the old guard phone
companies. And CLECs (Competitive Local Exchange Carriers), or independent
providers such as Covad and Rhythms. Both are providing DSL services over
existing copper lines.
<comment> The last two sentences there need a bit of work, but I wasn't sure
what to do with them. I'll take a look again later.
Chopped out one sentence, and minor re-wording (is that a word?). HB.
</comment>
</Para>
</ListItem>
<ListItem>
<Para>
'CO' is the telco acronym for 'Central Office'. Traditionally this is a
building where one end of your phone line physically terminates. The other
end terminates at your home, office, or wherever. It will be used here to
refer to the telco end termination point, regardless of whether it is a
traditional Central Office building or another, smaller, remote structure
or device.
</Para>
</ListItem>
<ListItem>
<Para>
'Loop' is telco speak for 'phone line'. Essentially, you should think of
your loop as one dedicated pair of copper wires that run uninterrupted from
your residence or office directly to the CO. This is perhaps an
oversimplification, but will serve our purposes. DSL availability, and
signal quality, is tied directly to the characteristics of your physical
line -- or 'loop' as they say.
</Para>
</ListItem>
<ListItem>
<Para>
'POTS' is the acronym for Plain Old Telephone Service. In other words,
traditional, non-digital devices like phones and answering machines.
</Para>
</ListItem>
<ListItem>
<Para>
'DSLAM' is the sophisticated hardware device in the telco's CO where your
phone line physically terminates, and thus makes DSL happen. Increasingly,
telcos are making use of smaller devices like the 'mini-RAM' in remote
locations. We'll use 'DSLAM' here as a catchall for any device that enables
DSL service from a telco.
</Para>
</ListItem>
<ListItem>
<Para>
'Modem' will be used to refer to the end user device that enables a DSL
connection. Your modem is connected to the telco's DSLAM in
the CO via your loop. When they are 'talking' DSL to each other, they are
in 'sync'. Without 'sync', no connection to the ISP is possible.
</Para>
<Para>
'Modem' is indeed the correct terminology since there is MOdulation and
DEModulation of the signal. These modems typically have other features too.
Some ISPs and manufacturers may be marketing simply 'routers', 'bridges',
or even 'brouters' for this purpose. These are essentially DSL modems with
enhancements. A compatible 'modem' of some kind is the minimum hardware
requirement at the customer's end of the connection. The most commonly
supplied modem is actually a combination bridge and modem.
</Para>
<Para>
Unless stated otherwise, we will also be assuming the 'modem' has an
ethernet interface, and will connect to a standard Network Card (NIC). For
right now, arguably the only workable configuration is an ethernet
interface. And perhaps is also the only viable option based on what
delivery systems and hardware are now being offered by the overwhelming
number of providers. This could be changing soon however.
</Para>
<Para>
It is worth noting that 'routers' as supplied by DSL providers are
typically modem/router combination devices. In our context, 'router' will
refer to these devices as such. There are also SOHO routers available that
are only dedicated routers and lack the modem functionality.
</Para>
</ListItem>
<ListItem>
<Para>
Previous versions of this document referred to the modem as an 'ANT' (ADSL
Network Termination). While this may be technically correct terminology, it
is not used by ISPs, manufacturers, telcos, or most users to any extent.
The 'modem' will be just called a modem, regardless of whatever other
features it may have (i.e. router, bridge, etc.).
</Para>
</ListItem>
<ListItem>
<Para>
PPPoX will be used to refer to PPPoE (PPP over Ethernet) and PPPoA
(PPP over ATM) collectively. These protocols are being used by many DSL
providers now.
<comment>Is a scream of agony warranted here?
AAAAEEEEEEEYYYYYYYYYYEEEEEEEEEEEEEEEEE!!!!!!!!!!!!!!
</comment>
</Para>
</ListItem>
<ListItem>
<Para>
The information provided in this document is based on the current state of
DSL in the U.S. I would assume there are enough similarities with
DSL services outside of the US that this document would still have some
merit for everyone. Correct me if I am wrong by emailing
<email>hal@foobox.net</email>
</Para>
</ListItem>
<ListItem>
<Para>
A '#' will be used to denote a command that typically is run by the root
user. Otherwise, a '$' will be used as the prompt for non-root users.
</Para>
</ListItem>
</ItemizedList>
</Para>
</Sect2>
</Sect1>
<!-- ~ End Section ~ -->
<!-- ~~~~~~~~ New Section Header ~~~~~~~~~ -->
<Sect1 id="installation">
<Title>Installation</Title>
<Comment>
This does not flow well, now with DSL Overview moved. I think we need more of
an intro either here or above on 1st page. Maybe a 'Getting Ready' section.
Short section ;) HB
Wed 08/30/00 3:39:16 PM
Added a brief new section here. HB.
</Comment>
<Para>
Before actually ordering service, there are several things you may want to
explore.
</Para>
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>Pre-Installation</Title>
<Para>
Beyond the obvious consideration of price, there are many reasons to
investigate which providers may be offering DSL services in your area. The
large Telephone companies are everywhere, and may advertise the most. But
increasingly smaller ISPs and independents are getting into the act. This is
creating diversity in the DSL marketplace. A good thing of course, but
possibly creating a little confusion too.
</Para>
<Para>
Not all DSL services are alike. Just because two local companies are offering
'ADSL', does not mean that necessarily there is much in common at all. In
fact, there are potentially a number of factors that make one ADSL provider's
service significantly different from another's. Some things to consider:
</Para>
<Para>
<ItemizedList>
<ListItem>
<Para>
Speed vs Price.
</Para>
</ListItem>
<ListItem>
<Para>
What hardware is provided, i.e. modem or router. Should be external ethernet in
either case.
</Para>
</ListItem>
<ListItem>
<Para>
The ISP's Network architecture. PPPoX? Static IP? Servers allowed?
</Para>
</ListItem>
<ListItem>
<Para>
Is it an 'always on' service, at least theorectically? Are there supplemental
usage fees, or idle timeouts?
</Para>
</ListItem>
<ListItem>
<Para>
Linux friendly, Linux hostile, or Linux agnostic?
</Para>
</ListItem>
<ListItem>
<Para>
Quality of service. How is news, mail, etc.?
</Para>
</ListItem>
</ItemizedList>
</Para>
<Para>
For a more lengthy discussion on some of these considerations and related
issues, see the <Link LinkEnd="overview">DSL Overview</Link> appendix for
more on <Link LinkEnd="dslmodems">modems</Link>,
<Link LinkEnd="qualify">qualifying for service</Link>, and
<Link LinkEnd="cproviders">choosing a provider</Link>.
</Para>
<Para>
Once you have chosen a provider, and ordered service, the next step is for
the telco to 'qualify' your loop. This essentially means testing your line to
make sure it can handle the DSL signal, and possibly what level of service
may be available to you. This may take some time, especially if the telco
encounters problems with the loop. If no problems are found during this
phase, then possibly there will be a two to three week wait for the installation.
</Para>
<Para>
After the telco has qualified the loop and readied their end of the
connection, the next step is installation of the necessary components at the
customer's end of the connection: wiring modifications, splitter or filters,
and, of course the modem and any necessary software.
</Para>
<Comment> End newly added section Wed 08/30/00 12:58:19 PM </Comment>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>Installation Options -- Self Install or Not</Title>
<Para>
You may or may not have a choice on how the installation is done, or who
does it. This is totally at the discretion of the provider. Many providers
offer a 'self install' option where you do all the work. In this scenario,
the provider will send a kit in order to save them from sending a tech, and
thus reducing cost. Typically, self install kits will include microfilters
for the POTS (Plain Old Telephone Service) phone jacks, the modem (and maybe
a NIC), and a CDROM with drivers, etc. on it. In some cases, a splitter may
be included instead of microfilters.
<comment>From what I understand (this may be completely rumor and
superstition) most of the time when a "splitter" needs to be installed
at, or near the telco's demarc, a "self install" is not an option. A
certified telco technician may need to come install the splitter.</comment>
</Para>
<Para>
The other possibility is for the provider to do the
installation. Obviously, the cost is higher here, but it may have the
advantage of having a trained tech do any wiring. There is also a
better chance of getting a <quote>splitter</quote>ed installation
with this option (a good thing!). Another benefit is that if
something is wrong with the line, or the telco has not provisioned
the line properly, an on-site tech may be able to help sort out some
kinds of problems quickly.
<comment>Most of the technicians here in Qwest land are "pole
jockeys", who don't know anything about DSL, or about computers. They
come out and install the line, but may not know more than "put this CD
in, click on install".</comment>
</Para>
<Para>
The self-install kit should come with full instructions, regardless of whether
the installation will be splittered or filtered. So we won't go into much
detail on this aspect.
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>Wiring/Installation Options</Title>
<Para>
There are various wiring schemes depending on how your service is being
provided, who is providing it, and which DSL service is being provided.
</Para>
<Para>
<ItemizedList>
<ListItem>
<Para>
<Emphasis>Dedicated Line</Emphasis>. Some DSLs require a dedicated, or
'dry', wire pair, e.g. IDSL. This means a separate line for DSL and
Internet connectivity. Also, DSL services from CLECs (independent telcos
like Covad or Rhythms), will use a dedicated line since the ILEC will not
share one line with another company. (Instead the CLEC will actually lease
a loop from the ILEC.) One your end, this simply means using one of the
unused wire pairs in the telco wire bundle, and connecting it to the DSL
jack.
</Para>
</ListItem>
<ListItem>
<Para>
<Emphasis>Shared Line with Splitter</Emphasis>. For DSLs, like ADSL, that
are provided over the same line as regular voice service (POTS), the signal
must be filtered somehow so that voice services are not adversely effected.
Installing a splitter splits the line into two pairs, and filters the DSL
signal from one of them. This results in a inside wiring scheme where DSL
goes to only one jack, and then POTS service to all other jacks. This is
considered by many to be a better type of installation than 'splitterless'.
</Para>
<Para>
Splitters are available from various manufacturers and come in various
shapes and sizes. Some are small enough to fit in the NID itself (sometimes
called 'SNI', this is the telco phone box on the outside of your house),
while others have a housing as large as the NID itself. Typically this is
mounted near the NID, on the customer's side of the demarcation point.
<comment>Is demarcation point explained elsewhere?</comment>
</Para>
</ListItem>
<ListItem>
<Para>
<Emphasis>Shared Line with Filters</Emphasis>. Again, for DSLs that
piggyback on the POTS line, the signal must be filtered or split at some
point. The other way of doing this is by placing RJ11 'microfilters' in
each phone jack -- <Emphasis>except where the DSL modem will be</Emphasis>.
These filters are relatively small, plug-in devices and remove the higher
frequencies associated with DSL. This is obviously much easier since no
tools or wiring is required. This is often what is included in self-install
kits, and is often referred to as a 'splitterless' installation.
</Para>
</ListItem>
<ListItem>
<Para>
<Emphasis>Shared Line, Splitterless and Filterless</Emphasis>. Newer DSLs,
like G.Lite, have no adverse effect on regular POTS devices and thus
require no filters or splitters. This would seem to be the wave of the
future. Just plug and play.
</Para>
</ListItem>
</ItemizedList>
</Para>
<BridgeHead renderas=sect3>
Figure 1: DSL Block Diagram, POTS with Splitter (NID not shown)
</BridgeHead>
<Para>
<Literal>
<MSGText>
<LiteralLayout>
<--------Home/Office-----><---Loop---><--Central Office-->
POTS X-------+
phone, |
fax, |
etc, |
| CO
| -------
| | |
| | |
| ----- | |
POTS X-------+----Voice--=| S | | D |
| P | | S |=- Voice Switch
| L | 2 wire | L |
| I |=------------=| A |
| T | Local Loop | M |=- ISP --> INET
--------- | T | | |
Linux X--=| Modem |=-Data-=| E | | |
--------- | R | | |
----- | |
-------
</LiteralLayout>
</MSGText>
</Literal>
</Para>
<BridgeHead renderas=sect3>
Figure 2: DSL Splitterless (a.k.a. filtered) Block Diagram
</BridgeHead>
<Para>
<Literal>
<MSGText>
<LiteralLayout>
<--------Home/Office-------><----Loop---><--Central Office-->
POTS X--Voice---[RJ11]------+
phone, (filter) |
fax, D CO
etc, a -------
t | |
a | |
POTS X--Voice---[RJ11]----- & | D |
(filter) V ----- | S |=- Voice Switch
o | N | 2 wire | L |
i-=| I |=-----------=| A |
c | D | Local Loop | M |=- ISP --> INET
e ----- | |
----------- | | |
Linux X--=| Modem |=-------| | |
----------- -------
</LiteralLayout>
</MSGText>
</Literal>
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2 id="wiring">
<Title>Self Install - Wiring</Title>
<Para>
If you are not doing the self-install option, then you may skip this section
and move to <Link LinkEnd="configure">Configuring Linux</Link>. The following
procedures are meant to illustrate the wiring process. Please note that your
procedures may be different at your location. Make sure you follow any
warnings or safety instructions provided, that you RTFM, and that you are
familiar with telco wiring procedures.
</Para>
<Para>
The first step will be to wire up the connections from your provider. Identify
the line on which service will be installed, and the locations of your
splitter and DSL jack(s). (For perhaps a better wiring scheme, see the
Homerun section immediately below.)
</Para>
<Para>
Be aware that typical telco wire has more than one pair per bundle. Often,
two pairs, but sometimes more. If you have but one phone line, the other
pair(s) are unused. This makes them available for use with wiring for DSL.
Wire pairs are color coded for easy identification. SDSL and IDSL require a
dedicated, or 'dry', pair. If an unused pair is available, then no real
re-wiring is required. It is just a matter of re-wiring an existing jack for
the correct pair of wires, and attaching the modem.
</Para>
<!-- ~~~~~ New Section ~~~~~ -->
<Sect3 id="homerun">
<Title>The Homerun</Title>
<comment>Try blockquote or quote, coupled with attribution for
better output. See these URLs
http://www.docbook.org/tdg/html/attribution.html
http://www.docbook.org/tdg/html/blockquote.html
http://www.docbook.org/tdg/html/quote.html</comment>
<Para>
<Emphasis>
"I would not use microfilters if I lived across the street
from my CO. A splitter is the only way to go."
</Emphasis>
</Para>
<Para>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;- A retired Bellsouth ADSL installer.
</Para>
<Para>
Perhaps a somewhat better method of wiring for the DSL modem is sometimes
called a 'homerun'. It is called this because it is one, straight shot from
the splitter to the modem's DSL jack. What this does is bypass the existing
inside wiring altogether, and any problems that might be lurking there --
like a corroded connection somewhere on a POTS jack. Inside wiring defects
can be a source of headaches, especially in older homes.
</Para>
<Para> It also allows you to route the cable to avoid any potential
RFI (Radio Frequency Interference) sources. RFI anywhere in the
circuit can be a DSL killer. Routing the cable away from items that
may have electric motors, transformers, power supplies, high
intensity lighting fixtures, dimmer switches and such, is a smart way
to go. And you are also less likely to have a failing microfilter
cause problems. You can also use a better grade of cable such as CAT
5 or shielded twisted pair wire.
</Para>
<Para>
If you are splitterless (i.e. using microfilters) now, this will entail
purchasing a splitter, and, of course, some rewiring. Microfilters also add
distance to the effective loop length -- as much as 700 ft per filter in some
cases! So if you have several of these, and your sync rate or distance is
marginal, eliminating the filters may result in a significant
improvement.
<comment>This paragraph could be clearer, I think. I've got a pretty
good idea what it means, after a few times reading it.</comment>
</Para>
</Sect3>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>Wire the Splitter</Title>
<Para>
If you have the splitterless design or a dedicated line, you may skip this part.
</Para>
<Para>
The splitter will typically consist of two parts, the splitter and a small
outdoor housing. Mount the splitter and accompanying housing per the telco's
instructions at the Subscriber Network Interface (SNI) point (also sometimes
called the NID or ONI), usually the side of your house where the phone line
is located. Put it on your side of the SNI or NID. The phone company may need
to access the splitter for maintenance, so its advisable to locate it on the
outside where they can get at it, but outside is not absolutely
necessary.
<comment>Which term are you going to use? SNI, NID, demarc,
ONI?</comment>
</Para>
<Para>
The wire bundle should have at least two separate wire pairs. The splitter
takes one pair, and separates the signal onto two pairs. One pair in the
bundle will then go to all POTS jacks, and the other to the modem's DSL wall
jack. So connect the incoming telco line to the LINE side of the splitter.
Then wire the inside pair for your telephone to the VOICE, and your inside
wire pair for the modem to DATA.
</Para>
<Para>
<Emphasis remap="bf">Checkstep </Emphasis> At this point, you should be able
to pull dial tone off the voice side of the splitter. If this doesn't work,
then you've wired it wrong. You can also plug the modem into the test jack in
the SNI/NID box (most should have this). Plug in the modem's power cord, and
if the line is provisioned correctly, you should 'sync' in less than a
minute. This test only requires the modem. (Internal and USB modems
probably will require a driver to be loaded before syncing. This means having
the computer there too.)
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>Wire the DSL Jack</Title>
<Para>
Wire the DSL wall jack (RJ11) at your computer location, which should already
be connected to the DATA side of the splitter. The specifics differ for each
situation, but basically you will have a wire pair that you will connect to
the DSL jack. Make sure you <Emphasis>read the directions</Emphasis>, as the
DSL-RJ11 wiring may be different for phones and DSL jacks.
<Emphasis>AND</Emphasis> -- different modems may expect the signal on
different pairs -- most on the inside pair, but some on the outside pair.
</Para>
<BridgeHead renderas=sect3>
Figure 3: RJ11 Wiring options
</BridgeHead>
<Para>
<Literal>
<MSGText>
<LiteralLayout>
||
||
||
/ \
|RJ11|
| |
----
||||
^^ <-- Inside Most modems on inside pair
^ ^ <-- Outside Some on outside, e.g. Alcatel 1000, SpeedTouch Home
</LiteralLayout>
</MSGText>
</Literal>
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>Install and Test the Modem</Title>
<Para>
To install, connect the modem's (or modem/router's) power cord, and connect
the phone line between the DSL wall jack and the modem. This cable should be
provided. If not, a regular phone cord will suffice. With the ethernet
interfaced modems, you may also connect the ethernet cable between the NIC
and the modem (but not really necessary at this point just to verify the
modem is working).
</Para>
<Para>
<Emphasis remap="bf">Checkstep </Emphasis> At this point, verify that
the modem syncs with the telco's DSLAM signal. Most modems have a
green LED that lights up when the signal is good, and red or orange
if not in sync. The modem's manual will have more details on the
LEDs. If it doesn't sync, then check your wiring, or make sure that
the DSL signal is being sent. Do this by calling your telco and
verifying they have activated the service. Or by testing the modem at
the test jack on the SNI/NID (see above). Note that having dial tone
on the line does NOT confirm the presence of the DSL data signal. And
vice versa -- perfectly possible to have dial tone and no DSL, or DSL
and no dial tone. There should also be no static or noise on the
voice line when everything is installed and functioning properly.
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>Install and Connect the Network Interface Card (NIC)</Title>
<Para>
If you haven't already done so, install your NIC card in your Linux machine,
configure the kernel, or load modules, etc., etc. This is sometimes the
biggest stumbling block -- getting the NIC recognized and working. See the
various Linux references for doing this, such as the <Ulink
url="http://www.linuxdoc.org/HOWTO/Ethernet-HOWTO.html">Ethernet HOWTO</Ulink> for
more information. Also, the <Link LinkEnd="tuning">Troubleshooting
section</Link>. This is certainly something you could conceivably do ahead of
time if you already have the NIC.
<comment>Which troubleshooting section? This is obvious from the
markup, but not from non-linked formats, like plain text.</comment>
</Para>
<Para>
Be sure the RJ45 cable between the NIC and the modem is now connected. You
can hot plug this cable.
<comment>You should define hot plug</comment>
</Para>
<Para>
We can do a few quick tests now to see if the NIC is functioning properly:
</Para>
<comment>this section could use a little work, since you don't
explain how you expect their network to be configured. The
commands are nice, but without some explanation of what each
command does, nearly worthless.</comment>
<Screen>
# ifconfig eth0 10.0.0.1 up
$ ping -c 50 10.0.0.1
PING 10.0.0.1 (10.0.0.1) from 10.0.0.1: 56(84) bytes of data.
64 bytes from 10.0.0.1: icmp_seq=0 ttl=255 time=0.2 ms
64 bytes from 10.0.0.1: icmp_seq=1 ttl=255 time=0.2 ms
64 bytes from 10.0.0.1: icmp_seq=2 ttl=255 time=0.1 ms
&lt;snip&gt;
- 10.0.0.1 ping statistics -
50 packets transmitted, 50 packets received, 0% packet loss
round-trip min/avg/max = 0.1/0.1/0.2 ms
$ ifconfig eth0
eth0 Link encap:Ethernet HWaddr 00:50:04:C2:09:AC
inet addr:10.0.0.1 Bcast:10.255.255.255 Mask:255.0.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:428 errors:0 dropped:0 overruns:0 frame:0
TX packets:421 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
Interrupt:10 Base address:0xc800
</Screen>
<Para>
If 'eth0' comes up without errors, and you can <Command>ping</Command>
it without errors, and <Command>ifconfig</Command> shows no errors, we should
have all our hardware in working order now, and are ready to start
configuring Linux. If not, see the <Link LinkEnd="tuning">Troubleshooting
section</Link> below.
</Para>
<Para>
<Emphasis remap="bf">Gotcha:</Emphasis> A few modems may already be wired as
a 10baseT crossover, and require a direct Category 5 cable for a direct
connection to a NIC, rather than a crossover cable. I lost around 12 hours
figuring this one out, so don't make the same mistake - make sure you RTFM
first.
</Para>
</Sect2>
</Sect1>
<!-- ~ End Section ~ -->
<!-- ~~~~~~~~ New Section Header ~~~~~~~~~ -->
<Sect1 id="configure">
<Title>Configuring Linux</Title>
<Para>
After you have connected the modem and it's getting sync, and the NIC is
functioning, then you're ready to configure Linux and verify your connection
to your ISP. Although I will refer to a Linux System, you can conceivably
connect any type of 10baseT device to the modem. This includes a router, hub,
switch, PC, or any other system that you wish to use. We'll just cover the
Linux PC aspect here.
</Para>
<Para>
<comment>perhaps another place to use the warning tag?</comment>
<Emphasis remap="bf"> Caution!</Emphasis> <Emphasis>Before you connect to
your ISP</Emphasis>, make sure you understand all security issues of having a
direct connection to the Internet via DSL. Depending on your ISP, most
outside users can access your system, and you should setup any firewalls,
deactivate ports/services, and setup any passwords prior to connecting your
machine to the world. See the <Link LinkEnd="secure">Security section
below</Link>, and the <Link LinkEnd="links">links section</Link> for more on
this <Emphasis>very important</Emphasis> topic. Do not make this an
afterthought! Be ready.
</Para>
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2 id="bridgevsppp">
<Title>Bridged vs PPPoX Networks</Title>
<Para>
Before we get too far into the final stages of installing and
configuring our system, let's look at how various DSL ISPs set up
their networks. It will be very important for you know how your ISP
does this, as there is more than one possibility and the steps
involved are quite different for each. This may not be the kind of
thing the ISP is advertising, and since you are not using Windows,
you may not have access to the setup disk that the ISP provides. If
you're not sure, ask the ISP's tech support staff, or other users.
</Para>
<Para>
To muddy the waters even more, some ISPs may be offering more than one kind
of service (over and above the various bit rate plans). Example: Bell
Atlantic originally offered static IPs with a Bridged connection. Now all new
installs use PPPoE with dynamic IPs. For installation and configuration
purposes, this is very different.
</Para>
<Para>
The two most common DSL network implementations are Bridged/DHCP and PPPoX.
Both have mechanisms for obtaining an IP address and other related networking
configuration details so we shouldn't have to worry about this. Our job will
be finding the right client, and doing what we have to, to get it up and
running.
</Para>
<Para>
<Emphasis>Important!</Emphasis> You need to know beforehand how your ISP is
setup for connecting to his network. To re-iterate, the two main
possibilities are Bridged/DHCP and PPPoE. These are mutually exclusive
implementations. So you will need either one or the other, and it must be the
right one or you will waste a lot of time and effort. You cannot choose which
one either. It is a matter of how the ISP is doing his network. Note that
PPPoE can run over Bridged networks, so just knowing whether you are Bridged
or not, is not necessarily good enough. PPPoA is yet another alternative. If
your provider is giving you a router, there is a good chance that the
router's firmware will handle all of this for you.
</Para>
<!-- ~~~~~ New Section ~~~~~ -->
<Sect3>
<Title>Bridged/DHCP</Title>
<Para>
In the good old days of a year or two ago, 'Bridged' connections were the
norm. This type of network puts you on a local subnet just like a big
LAN. You are exposed to much of the local subnet traffic, especially ARP and
broadcast traffic. The typical means of authenticating in this set up, is via
DHCP.
</Para
<Para>
DHCP is a standard, established networking protocol for obtaining an IP
address and other important network parameters (e.g. nameservers). This is a
standard, well documented networking scheme and is very easy to set up
from the end user's perspective. It is also a very stable connection. You
can actually unplug the modem for say 10 minutes, plug it back in, let it
re-sync, and the connection is still there -- same IP and everything.
</Para>
</Sect3>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect3>
<Title>PPPoX</Title>
<Para>
The main alternative now is PPPoX, meaning either PPPoE (PPP over Ethernet)
or PPPoA (PPP over ATM). Both of these related protocols are currently being
deployed, but at the moment, PPPoE seems to be the more common of the two.
PPPoX is a relative newcomer, and, as the name implies, is a variation of
Point-to-Point Protocol that has been adapted specifically for DSL providers.
</Para>
<Para>
There are several PPPoE clients for Linux (<Link LinkEnd="pppoe">see
below</Link>). At this moment, PPPoA support is in beta, but should be
available very soon. PPPoX simulates a dialup type environment. The user is
authenticated by user id and password which is passed to a RADIUS server,
just like good ol' dialup PPP. A routable IP address, and other related
information, is returned to the client. Of course, no actual dialing takes
place. The mechanics of how this is handled, will vary from client to client,
so best to RTFM closely. Typically you will set up configuration files like
<Filename>pap-secrets</FileName>, etc.
</Para>
<Para>
From the ISPs perspective, PPP is much easier to maintain and troubleshoot.
From the end user's perspective, it is more work to set up, uses more CPU,
and the connection is maybe not as stable. So anyway, this seems to be the
coming trend. Many of the large telcos, especially the RBOCs (Baby Bells),
have committed to PPPoX already. Setting up a PPPoX connection is completely
different from setting up a bridged/DHCP connection.
</Para>
</Sect3>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect3>
<Title>ATM</Title>
<Para>
Since the traffic on the wire from the DSLAM to the modem is ATM, a
raw ATM connection would seem to make sense. While possible, this is
rare, if it exists at all in the U.S, and would require a modem in
addition to a PCI ATM card, such as the Efficient Networks
3010. There is an ATM project for Linux, that is being incorporated
into the 2.4 kernel. (See the <Link LinkEnd="links">Links
section</Link> for more information.)
</Para>
<Para>
This may be a viable solution at some point, but it is just not 'there' yet.
</Para>
</Sect3>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>Configuring the WAN Interface</Title>
<Para>
The most common configuration is a DSL modem in 'bridging' mode. Both PPPoX
and DHCP can use this setup. In this scenario, the WAN interface typically
means your NIC. This is where your system meets the outside world. (If you
have a router see <Link LinkEnd="router">below</Link> for router specific
instructions.) So essentially we will be configuring the NIC, typically
'eth0' since it is an ethernet interface.
</Para>
<Para>
With PPPoX, once the connection comes up, there will be a 'ppp0', or similar,
interface, just like dialup. This will become the WAN interface once
the connection to the PPP server is up, but for configuration purposes we
will we be concerned with 'eth0' initially.
</Para>
<Para>
There are various ways an ISP may set up your IP connection:
</Para>
<Para>
<ItemizedList>
<ListItem>
<Para>
Static IP.
</Para>
</ListItem>
<ListItem>
<Para>
Dynamic IP on Bridged Network via DHCP.
</Para>
</ListItem>
<ListItem>
<Para>
Dynamic IP via PPPoX.
</Para>
</ListItem>
<ListItem>
<Para>
Static IP via PPPoX.
</Para>
</ListItem>
</ItemizedList>
</Para>
<Para>
Let's look at these individually.
</Para>
<!-- ~~~~~ New Section ~~~~~ -->
<Sect3>
<Title>Static IP Configuration</Title>
<Para>
A 'static' IP address is an IP that is guaranteed not to change. This is the
preferred way to go for those wanting to host a domain or run some type of
public server, but is not available from all ISPs. Skip this section if you
do not have a static IP, or if you have a router, and the router will be
assigned the static IP.
<comment>Again, a note about static IP's being less secure should be
mentioned.</comment>
</Para>
<Para>
Configure the IP address, subnet mask, default gateway, and DNS server
information as provided by the ISP. Each Linux Distribution (Redhat, Debian,
Slackware, SuSE, etc.) has a different way of doing this, so check on your
distro's docs on this. Each may have their own tools for this. Redhat has
<Command>netcfg</Command> for example. You can also do this manually using
the <Command>ifconfig </Command> and <Command>route</Command> commands. See
the man pages on these or the <Ulink
url="http://www.linuxdoc.org/HOWTO/Net-HOWTO">Net HOWTO</Ulink> for more
information and specifics. A quick command line example with bogus IPs:
</Para>
<Screen>
# ifconfig eth0 111.222.333.444 up netmask 255.255.255.0
# route add default gw 111.222.333.1 dev eth0
</Screen>
<Para>
Be sure to add the correct nameservers in <Filename>/etc/resolv.conf</FileName>.
</Para>
</Sect3>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect3>
<Title>Bridged/DHCP Configuration</Title>
<Para>
ISPs that have Bridged networks typically use DHCP to assign an IP addresses,
and authenticate the user. All distributions come with one or more DHCP
clients. <Command>dhcpcd</Command> seems to be the most common.
<Command>pump</Command> comes with Redhat based distributions as of Redhat
6.0. The DHCP client will obtain an IP 'lease' from the ISP's server as well as
other related information: gateway address, DNS servers, and network mask.
The lease will be 'renewed' at regular intervals according to the ISP's
configuration.
</Para>
<Para>
You will want the DHCP client started on boot, so use your distribution's
means of doing this. There generally is little to configure with DHCP as it
is fairly straightforward and easy to use. You may need to tell it which
interface to listen on if the NIC is something other than 'eth0'. You can
also start it from the command line to get started. See the respective man
pages for more.
</Para>
<Para>
Unless you have a static IP, the ISP will need some way to know who you are
when you connect. There are two ways this authentication process is
accomplished with DHCP. The first and most common method is via the MAC (or
hardware) address of the network device. Typically this would be the NIC. The
MAC address is a unique identifier and can be found among the boot messages,
or with <Command>ifconfig</Command>, and looks something like
<Literal>00:50:04:C2:19:BC</Literal>. You will need to give the ISP the MAC
address before your first connection.
</Para>
<Para>
The other DHCP authentication method is via an assigned hostname. In this
case, the ISP will have provided you with this information. Your DHCP client
will need to pass this information to the server in order for you to connect.
Both <Command>dhcpcd</Command> and <Command>pump</Command> accept the '-h'
command line option for this purpose. See the client's man page, or your
distribution's documentation, for specifics.
</Para>
<comment>Warning/note perhaps?</comment>
<Para>
<Emphasis>Caution!</Emphasis> If your ISP uses MAC address authentication,
and you change your network device (e.g. NIC), you will need to register the
new address with the ISP or you won't be able to connect.
</Para>
</Sect3>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect3 id="pppoe">
<Title>PPPoE Configuration</Title>
<Para>
PPPoE (PPP over Ethernet) is an alternate way for ISPs to control your
connection, and is becoming increasingly popular with ISPs. Setting this up
is quite different, and may be a little more work than with static IPs or
DHCP above. Some distros are now shipping PPPoE clients. If this is not the
case for you, then you will have to download one. Check any Linux archive
site like <Ulink URL="http://freshmeat.net">http://freshmeat.net</Ulink>,
etc. or look below.
</Para>
<Para>
Some of the current GPL PPPoE clients available:
</Para>
<Para>
<ItemizedList>
<ListItem>
<Para>
The Roaring Penguin, <Ulink
URL="http://www.roaringpenguin.com/pppoe/">http://www.roaringpenguin.com/pppoe/</Ulink>,
by David F. Skoll. This client is under very active development.
It is reportedly very easy to set up, and get started with. As of
right now, this is probably by far and away the most popular Linux
PPPoE client.
</Para>
</ListItem>
<ListItem>
<Para>
PPPoEd: <Ulink URL="http://www.davin.ottawa.on.ca/pppoe/">
http://www.davin.ottawa.on.ca/pppoe/</Ulink> by Jamal Hadi Salim. This
package requires some kernel patching and other configuration related
issues.
</Para>
</ListItem>
<ListItem>
<Para>
PPPoE Redirector: <Ulink
URL="http://www.ecf.toronto.edu/~stras/pppoe.html">
http://www.ecf.toronto.edu/~stras/pppoe.html</Ulink>. This is a redirector
which allows the use of PPPoE with pppd-2.3.7 or later. No recompiling of
other system components are required. It is meant as an interim solution
until the 2.4.x series, which will include kernel support of PPPoE/A. (Does
not seem to be under active development at this time.)
</Para>
</ListItem>
<ListItem>
<comment>a purely WHAT solution?</comment>
<Para>
A purely solution can be found at <Ulink
URL="http://www.math.uwaterloo.ca/~mostrows/">http://www.math.uwaterloo.ca/~mostrows/</Ulink>
solution by Michal Ostrowski. This requires a 2.3/2.4 kernel. As of this
writing, it is still 'experimental. Once the 2.4 kernel goes mainstream,
this will be a more viable option.
</Para>
</ListItem>
<ListItem>
<Para>
EnterNet is a non-GPL'd PPPoE client from NTS, <Ulink
URL="http://www.nts.com">http://www.nts.com</Ulink>, that is being
distributed by some ISPs as the Linux client. It does come with
source code but the it is not available for free download. (NTS
was just recently purchased by Efficient Networks.)
</Para>
</ListItem>
</ItemizedList>
</Para>
<Para>
Depending on which client you have chosen, just follow the
<Filename>INSTALL</FileName> instructions and other documentation included
with that package (<Filename>README</FileName>, <Filename>FAQ</FileName>, etc.).
</Para>
<Para>
Once a PPPoE client connects, your connection should look something like the
below example from Roaring Penguin, where 'eth0' is connected to the modem:
</Para>
<Screen>
$ route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.0.254 * 255.255.255.255 UH 0 0 0 eth1
208.61.124.1 * 255.255.255.255 UH 0 0 0 ppp0
192.168.0.0 * 255.255.255.0 U 0 0 0 eth1
127.0.0.0 * 255.0.0.0 U 0 0 0 lo
default 208.61.124.1 0.0.0.0 UG 0 0 0 ppp0
$ ifconfig
eth0 Link encap:Ethernet HWaddr 00:A0:CC:33:74:EB
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:297581 errors:0 dropped:0 overruns:0 frame:0
TX packets:266104 errors:1 dropped:0 overruns:0 carrier:2
collisions:79 txqueuelen:100
Interrupt:10 Base address:0x1300
eth1 Link encap:Ethernet HWaddr 00:A0:CC:33:8E:84
inet addr:192.168.0.254 Bcast:192.168.0.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:608075 errors:0 dropped:0 overruns:0 frame:0
TX packets:578065 errors:0 dropped:0 overruns:0 carrier:0
collisions:105408 txqueuelen:100
Interrupt:9 Base address:0x1200
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:3924 Metric:1
RX packets:1855 errors:0 dropped:0 overruns:0 frame:0
TX packets:1855 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
ppp0 Link encap:Point-to-Point Protocol
inet addr:208.61.124.28 P-t-P:208.61.124.1 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1492 Metric:1
RX packets:297579 errors:0 dropped:0 overruns:0 frame:0
TX packets:266102 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:10
</Screen>
<Para>
<Emphasis>Warning</Emphasis>! For PPPoX, the correct setting for the ppp0
interface MTU is 1492. If the MTU is set too high, it may cause failure of
some web pages to load properly, and possibly other annoying problems. You
may need to also set the MTU for interfaces on any masqueraded LAN
connections MTU to 1452.
<!--
8. Configure LAN Hosts
If you have a LAN behind the firewall, you have to lower the TCP
maximum segment size from the normal 1460 to 1452 (or better, 1412.)
You have two options: Either set the MTU of all the interfaces on
other hosts on the LAN to 1452, or use the "-m 1412" option to pppoe.
The "-m" option for pppoe is far simpler and makes it easier to add
hosts to the LAN, but consumes some extra CPU time.
If you want to manually configure the LAN hosts, here's how:
In Linux, use: "ifconfig eth0 mtu 1452". For best results, put this
in an /etc/rc.d/rc.local script.
For Windows, machines, see http://lan.cns.ksu.edu/OS/WIN95/slip95.htm.
Set the MaxMTU to 1452.
==
E) pppoe dies with the log message "Message too long"
You set the MTU of the Ethernet interface connected to the ADSL modem
to less than 1500. Don't do that.
-->
</Para>
<Para>
Actually, for PPPoE the real setting should be at least 8 bytes less than any
interface between you and the ultimate destination. All routers normally
would be set to 1500, thus 1492 is correct from your end. But, it may happen
that somewhere a router is misconfigured at a lower setting, and this can
cause problems, especially with web pages loading. The way to test this is to
keep dropping the MTU until things work.
</Para>
</Sect3>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect3 id="pppoa">
<Title>PPPoA</Title>
<Para>
PPPoA (PPP over ATM) is a cleaner solution than PPPoE since most of the work
is done in hardware, and since the raw DSL traffic is ATM. There is no client
necessary to manage the connection as with PPPoE. Authentication is still the
same: user id and password to connect, but the mechanics are different since
no ethernet encapsulation takes place.
</Para>
<Para>
As of this moment, there is not really a viable, working implementation of
PPPoA for Linux. There is an ATM patch for 2.2 kernels, support for ATM in
the 2.4.x kernel, and a project based on the Efficient Networks 3010
[possibly out of production], as well as other ATM cards. The ATM on Linux
homepage is here: <Ulink URL="http://lrcwww.epfl.ch/linux-atm/">
http://lrcwww.epfl.ch/linux-atm/</Ulink>. And even more info is at <Ulink
URL="http://www.sfgoth.com/~mitch/linux/atm/pppoatm/">
http://www.sfgoth.com/~mitch/linux/atm/pppoatm/</Ulink> from the kernel
developer of this project. Existing PPPoA implementations are hardware/driver
based, and Linux PPPoA modem drivers are scarce as hen's teeth at this time.
The above modem does not seem to be available through normal retail channels.
This may be a problem, if this is the only protocol an ISP delivers. At
the very least, some rather serious hoop jumping is in order.
</Para>
<Para>
If PPPoA is your ISP's only option, you should probably consider one of the
router/modems that can handle PPPoA, and let the hardware handle everything.
</Para>
<comment>clearly a good place to use the "note" tag</comment>
<Para>
<Emphasis>Note:</Emphasis> There is apparently a PPPoA beta program underway
based on the Efficient Networks SpeedStream 3060/3061 (PCI, DMT). Efficient is
working with kernel developers, and reportedly this program is in late beta
at this time. The initial release will be binary only drivers, but open
source may follow. This is a big improvement!
</Para>
</Sect3>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect3 id="router">
<Title>Modem/Router Configuration</Title>
<Para>
Some ISPs are providing 'routers' as the connection device. Essentially these
are mini routers with built in modems. These are all ethernet based devices
too, so Linux should be good to go here as well. Again, a compatible NIC
should be all that is required to make this work.
</Para>
<Para>
A 'router' has many advantages. The better ones can handle the connection
management, IP encapsulation, and authentication, as well as providing a
means of segregating your LAN from outside traffic, and possibly other
features too. In short they can do it all. One big advantage is that they can
handle whatever protocols your ISP requires in order to connect.
</Para>
<Para>
If the ISP is requiring PPPoX, then this makes life a little easier since you
will not have to install or configure any additional software just to use
their network. The modem's firmware will handle this. The downside is that
most of these do not have the flexibility of a Linux router, or other
software solution. Of course, you could set up a Linux router behind the
router, and have the best of both worlds. The ones with more and better
features are also going to cost significantly more.
</Para>
<Para>
While the physical installation of a router is very similar to the modem
installation (see above), the router configuration itself is different
since your first 'hop' will be the router's interface and not the ISP's
gateway. Routers will actually have two interfaces -- one that you
connect to from the LAN side, and one that connects to your ISP on the WAN
side. Your point of exposure here is the WAN interface of the router.
</Para>
<Para>
The router will also have a pre-configured, private IP address that you will
connect to from the LAN side. This will be your gateway. The public IP
address will be assigned to the WAN side interface. Typically these devices
also act as DHCP servers for the LAN side as well. So possibly all you have
to do is to start a DHCP client such as <Command>dhcpcd</Command> or
<Command>pump</Command> (Redhat based distros) to get up and running. Just
make sure the modem/router is syncing first. The appropriate steps and
configuration should be in the owner's manual, or available from your
provider.
<comment>which provider?</comment>
</Para>
<Para>
If you are a PPPoX customer, and the router is handling this part of the
connection, then you will have to configure at least your user id and
password before connecting. If a Bridged/DHCP customer, you should just have
to activate DHCP on the router, and possibly register the MAC (hardware
address) of the router with your provider. Some routers have 'MAC cloning'
which means that they will report the MAC address of the attached NIC. If
static IP, then you will have to configure this as well.
</Para>
<Para>
If you need to access the router directly, you will need to know the
manufacturer's default setting for its IP address. See the owner's manual, or
ask your provider. You will then have to set your NIC's interface to the same
network as the router. For instance, if the router has an IP of 10.0.0.1, set
your interface's address to 10.0.0.2 (typically eth0), and netmask to
255.0.0.0.
</Para>
<Screen>
# ifconfig eth0 10.0.0.2 up netmask 255.0.0.0
# route add -net 10.0.0.0
$ ping 10.0.0.1
</Screen>
<Para>
If everything is in working order, the router should respond to pings. How to
configure this permanently will vary from distro to distro. So check your
distribution's documentation. Now you should be able to ping the
modem/router, and, if all is well, beyond. Then use telnet or a web browser
to do any further configuration of the router.
</Para>
<Para>
Even if the ISP is not offering any router options, there are quite a few
available from third party manufacturers such as Netgear, Linksys, Cisco,
Zyxel, Cayman, Alcatel and others. These will have all the features already
mentioned and maybe more. Just make sure it matches your provider's DSL. This
is one good way around the PPPoX bugaboo.
</Para>
<Para>
<Emphasis>Warning!</Emphasis> Some manufacturers may be marketing these as
having 'firewall' capabilities. In some cases, this amounts to nothing more
than basic NAT (Network Address Translation or masquerading). Not a full,
true firewall by any means. Be sure to read the fine print before buying and
make sure you know how much real firewalling is included.
</Para>
</Sect3>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2 id="connect">
<Title>Connect</Title>
<Para>
Everything should be in place now. You probably have already tested your
connection. You should be seeing ping roundtrip times of 10-40 ms to the ISP's
gateway. If something has gone wrong, and you cannot connect, either
retrace the above steps, or see the <Link LinkEnd="trouble">Troubleshooting
Section</Link> below.
</Para>
<comment>I think the range of ping times given above is too small,
as I get about a 75ms ping to my ISPs gateway.</comment>
</Sect2>
</Sect1>
<!-- ~ End Section ~ -->
<!-- ~~~~~~~~ New Section Header ~~~~~~~~~ -->
<Sect1 id="secure">
<Title>Securing Your Connection</Title>
<Para>
This section is intended for those who have not previously dealt with the
security implications of having a full time Internet connection. Or may not
understand some of the basic concepts of security. This is meant to be just a
quick overview, not a comprehensive examination of all the issues! Just
enough to give you a quick push in the right direction. Please see the <Link
LinkEnd="links">Links section</Link> for sites with more details. Also, your
distribution surely has plenty of good information as well.
</Para>
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>Security Quickstart</Title>
<comment>I think in other places you've used full time instead of
full-time. Those should probably be consistent.</comment>
<Para>
Before going on-line full-time, do not underestimate the need for securing
your connection. You will have two things that mischief makers and crackers
of the world are looking for: bandwidth, and a Unix-like OS. You instantly
become an inviting target. It is just a matter of time before someone
comes knocking. Possibly a very short time. A quick start:
</Para>
<Para>
<ItemizedList>
<ListItem>
<Para>
Turn off any daemons and services that aren't absolutely essential, and
can be accessed from outside. You can't get compromised through a port
that isn't open. Use <Command>ps</Command> and <Command>netstat</Command>
to see what services are running. (See man pages for specifics). Do you
really need <Command>named</Command>, <Command>sendmail</Command>,
<Command>telnet</Command>, <Command>ftp</Command> running and accessible
to one and all? If not sure, then they should not be running. Then take
whatever steps necessary to make sure they don't start again on the next
boot. See your distribution's documentation on this.
</Para>
<Para>
Many distributions start some well known services by default. You may not
have done anything yourself explicitly to start these. And may not even
realize these are indeed running. But it is up to you to know what is
running, and how safe it is. Don't rely on a 'default' installation of any
distribution to do this for you, or to be secure. Chances are it isn't.
</Para>
</ListItem>
<ListItem>
<Para>
If you decide some services are essential, make sure you are running the
most current version. Exploits are found, and then get fixed quickly.
Don't get caught with your pants down. A full-time connection makes
staying updated very easy -- and very important. Check with your
distribution to see what new packages are available. Then stay in
touch, if they have a security mailing list, get on it.
</Para>
</ListItem>
<ListItem>
<Para>
Set up a firewall to limit access, and log connection attempts. This will
be different depending on which kernel series you are using:
<Command>ipfwadm</Command> for 2.0, <Command>ipchains</Command> for 2.2,
and <Command>iptables</Command> for 2.4. See these HOWTOs for details:
</Para>
</ListItem>
<ListItem>
<Para>
<ItemizedList>
<ListItem>
<Para>
<Ulink
URL="http://www.linuxdoc.org/HOWTO/Firewall-HOWTO.html">Firewall
HOWTO</Ulink>
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink
URL="http://www.linuxdoc.org/HOWTO/Security-HOWTO.html">Security
HOWTO</Ulink>
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink
URL="http://www.linuxdoc.org/HOWTO/IPCHAINS-HOWTO.html">IPCHAINS
HOWTO</Ulink>
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink URL="http://www.linuxdoc.org/HOWTO/IP-Masquerade-HOWTO.html">IP
Masquerade HOWTO</Ulink>
</Para>
</ListItem>
</ItemizedList>
</Para>
<Para>
Additional references are in the <Link LinkEnd="links">Links Section</Link>
below.
</Para>
</ListItem>
<ListItem>
<comment>This needs some more links and/or explanation of how to
go about these things.</comment>
<Para>
Take passwords seriously. Use shadow passwords. Do not allow remote root
logins.
</Para>
</ListItem>
<ListItem>
<comment>I would say that ssh and OpenSSH are applications
rather than commands, but that's just me.</comment>
<Para>
Use <Command>ssh</Command>, or <Command>OpenSSH</Command>, instead of
<Command>telnet</Command>.
</Para>
</ListItem>
</ItemizedList>
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>Which Ports?</Title>
<Para>
There are plenty of references around on how to setup firewalls with
<Command>ipfwadm</Command> or <Command>ipchains</Command>, but a little
harder to find just which ports <Emphasis>really need</Emphasis> to be open.
If you are not sure of the answer to this question, then the answer is 'as
few as possible'! Basic rule #1, your computer cannot be broken into through
a port that is not open. A port can't be open if nothing is listening on
that port. In other words, if no service or daemon is running that uses that
port, the port is closed and inaccessible.
</Para>
<Para>
There are 65,536 ports available for use on Linux and these fall into
several categories. The ones we are most concerned about are the
'privileged' ports, which are those below port 1024. This is where
most public services run, like SMTP on port 25, HTTP on port 80,
named on port 53, etc. These services are where most vulnerabilities
are on Linux. These are the ports that servers accept outside
connections on. If you are running the <Command>telnetd</Command>
daemon, it will 'listen' for connections on port 23. (Actually if
spawned by <Command>inetd</Command>, it may be
<Command>inetd</Command> that is listening.)
</Para>
<Para>
But, if you want to use a telnet <Emphasis>client</Emphasis> to
connect to someone else's telnet server, you do not need to be running the
<Command>telnetd</Command> daemon on your own system. You just need to start
the client program named '<Command>telnet</Command>' (different animal). Same
is true for ftp and other services. These daemons only need to be run for
excepting connections to your system from an outside source.
</Para>
<comment>I don't think that the telnet command needs to be set off
both by quotes, and by the command markup.</comment>
<Para>
Unless you have a good reason for doing so, and know what you are doing, then
you should not be running these <comment>which?</comment> services. In fact, you could probably survive
quite nicely with all TCP and UDP ports below 1024 closed down, or at least
not visible to outside connections (i.e. blocked via a firewall). A couple of
exceptions:
</Para>
<Para>
It is relatively safe, and probably reasonably safe, to run
<Command>identd</Command> (port 113). Many mail and irc servers aren't happy
without <Command>identd</Command> there. This is the one good exception to
the 'nothing below 1024' rule of thumb. Newer versions are relatively
secure, but be sure that you have the newest version available.
</Para>
<comment>both relatively safe and reasonably safe?</comment>
<Para>
Mail is a little more complicated. The only reason to have a publicly
accessible SMTP (port 25) server is if you are hosting your own mail server
and receiving direct incoming mail connections. If you are retrieving mail
via POP3 from your ISP, this port does not need to be open to the world. Such
mail does not come in via port 25. It comes in through a higher, randomly
assigned port.
</Para>
<Para>
But -- it may still be convenient to have a mail daemon like sendmail, qmail,
or postfix running to handle local mail delivery. In fact, this is a common
default set up. You can get around this by firewalling off SMTP (port 25)
from the outside world, or using another method to sort and deliver local
mail. One way is to use procmail in conjunction with fetchmail:
'<Literal>fetchmail -m /usr/bin/procmail -d hal</Literal>' will do this
without having to run sendmail or other mail daemons in daemon mode. These
programs are still capable of sending mail in non-daemon mode.
</Para>
<Para>
It is probably safe to run a web server if you want to. Most vulnerabilities
there are through CGI. Just keep the web server package updated.
</Para>
<Para>
OK, enough exceptions. Shut down, or firewall off, <Emphasis>everything
else</Emphasis> below port 1024.
</Para>
<Para>
Those ports above 1023 are known as 'non-privileged' ports. These are mostly
used for return connections that you have initiated to someone else's server.
For instance, if you telnet to someone else, you connect to their port 23.
The return data comes back to you on a randomly assigned port above 1023.
These are mostly safe, and should as a rule be left alone. The only
exceptions are where there are indeed services running on these ports. X
Windows runs on ports 6000-6009 for instance. If you are running a font
server, it may be on port 7100. Any servers running on these non-privileged
ports, should be firewalled too.
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>inetd</Title>
<Para>
Let's take a quick look at <Command>inetd</Command>, since it starts many
services. <Command>Inetd</Command> is a 'super' daemon. It is called this
because it controls the starting of other daemons. Telnet, ftp, rsh, identd
and pop3 are some of the server daemons commonly controlled by
<Command>inetd</Command>. You may not see <Command>telnetd</Command> running
when you use <Command>ps</Command> or <Command>netstat</Command> unless
<Command>inetd</Command> is configured to start <Command>telnetd</Command>,
<Emphasis>and</Emphasis> someone is actually connected to
<Command>telnetd</Command> at the time. So it may not be so obvious which of
these servers can be accessed from outside. These sub-services are controlled
by the configuration file <Filename>/etc/inetd.conf</FileName>. Open this
with your favorite text editor, and put a '#' character in front of any
service you don't want running. A brief excerpt:
</Para>
<Para>
<Literal>
<MSGText>
<LiteralLayout>
#ftp stream tcp nowait root /usr/sbin/tcpd in.wuftpd -l -a -L -i -o
#telnet stream tcp nowait root /usr/sbin/tcpd in.telnetd
#
# Shell, login, exec, comsat and talk are BSD protocols.
#
#shell stream tcp nowait root /usr/sbin/tcpd in.rshd
#login stream tcp nowait root /usr/sbin/tcpd in.rlogind
#exec stream tcp nowait root /usr/sbin/tcpd in.rexecd
#comsat dgram udp wait root /usr/sbin/tcpd in.comsat
#talk dgram udp wait root /usr/sbin/tcpd in.talkd
#ntalk dgram udp wait root /usr/sbin/tcpd in.ntalkd
</LiteralLayout>
</MSGText>
</Literal>
</Para>
<comment>It might be nice to show what an enabled service looks
like here.</comment>
<Para>
This will prevent them from running. <Command>identd</Command> may be started
from this file, and would be safe to leave uncommented. Then re-initialize:
<Command>inetd</Command>:
</Para>
<Screen>
# kill -HUP `pidof inetd`
</Screen
<Para>
Note those are 'backquotes'. For more on fine tuning inetd access via
'tcpwrappers', see the hosts_access and tcpd man pages.
</Para>
</Sect2>
</Sect1>
<!-- ~ End Section ~ -->
<!-- ~~~~~~~~ New Section Header ~~~~~~~~~ -->
<Sect1 id="tuning">
<Title>Performance Tuning and Troubleshooting</Title>
<comment>Since there are no performance tweaks, why even mention
it?</comment>
<Para>
There really are no tweaks, or performance tuning tricks that are likely to
increase your performance to any significant degree -- all other things being
equal. Windows 9x users often get a big boost by increasing their TCP Receive
Window. But this is because it is too small to start with. This is not the
case with Linux.
</Para>
<Para>
The only exception is if you have to routinely deal with a high latency
connection. Such as maybe your provider has a satellite uplink that is
consistently adding unusual latency (250ms or greater?). Then maybe a larger
window will help. For the overwhelming majority of us, this is not necessary.
For more on TCP Receive Window and related issues, look at <Ulink
URL="http://www.psc.edu/networking/perf_tune.html">http://www.psc.edu/networking/perf_tune.html</Ulink>.
</Para>
<Para>
If your connection is not performing up to what you think it should be, then
possibly there is a problem somewhere. This is more worth looking into than
any magical 'tweak'.
</Para>
<Para>
A very rough guideline on what you might reasonably expect as a maximum, based
on distance from CO:
</Para>
<LiteralLayout>
&nbsp;&nbsp;0-12 Kft - 1500 Kbps or more
12-16 Kft - 1500 Kbps -&gt; 1000 Kbps
16-18 Kft - 1200 Kbps -&gt; 512 Kbps
18-?? Kft - &nbsp;&nbsp;512 Kbps -&gt; &nbsp;128 Kbps or less :(
</LiteralLayout>
<Para>
Remember too that you will loose 10-20% of throughput to networking overhead.
So a 1500 Kbps connection, is only going to realize about 1200-1300 Kbps or
so of real world throughput. No tweaking is going to change this. And
remember that if your service is capped at a lesser speed by your provider,
then you can't get above that speed no matter what. <Emphasis>AND</Emphasis>
-- that there are numerous variables that can effect your loop/signal
quality, and subsequently your speed. Most of these are out of your control.
</Para>
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2 id="trouble">
<Title>Installation Problems</Title>
<Para>
Read this section, if you have no sync at all or are completely unable to
connect. See your modem's owner's manual for interpreting the modem's LEDs.
(Many will show a solid red (or orange) light if not in sync.)
</Para>
<!-- ~~~~~ New Section ~~~~~ -->
<Sect3 id="nosync">
<Title>No sync</Title>
<Para>
The modem sync LED has never been green.
</Para>
<Para>
<ItemizedList>
<ListItem>
<comment>This reads like a list. Perhaps try using sub-lists,
or complete sentences. (sorry, I abhor sentence fragments)</comment>
<Para>
If self-installing, the DSL jack may be wired wrong. The splitter may be
wired wrong. The modem may be wired differently than standard telco POTS
devices. See above.
</Para>
</ListItem>
<ListItem>
<Para>
Is the modem Linux compatible? If ethernet interfaced, this should not be
a problem. But PCI or USB modems may require drivers just to achieve sync.
This could be a show stopper.
</Para>
</ListItem>
<ListItem>
<Para>
Call your provider and make sure the line was provisioned. It is always
possible someone dropped the ball. They may even be able to run a remote
test on your line just to verify. A remote possibility that the
DSLAM is down. They should know this as well.
</Para>
</ListItem>
<ListItem>
<comment>You must think I'm harping by now... Which term are
you going to use for demarc?</comment>
<Para>
Disconnect modem power cord and disconnect from wall jack. Plug it
into the test jack inside the SNI/NID (outside phone box), and run
extension cord if necessary for power cord. Temporarily disconnect the
wiring to the inside phone circuit. This should effectively bypass any
inside wiring and environmental issues. The ethernet cable to the NIC does
not need to be connected to run this test. The modem will sync fine
without it. (Easier said than done, I know.) But if
possible, move enough of your system where you can view the modem's
diagnostics (if available) and get the sync rate. If this works,
there is probably
something is wired incorrectly inside, or a short in a connection
somewhere, or there is severe electrical interference on the DSL line.
Check splitter and wall jack. If a splitterless installation, look for bad
(e.g. corroded) connections on <Emphasis>all</Emphasis> jacks, bad
splices, or defective microfilters!
</Para>
<Para>
If no sync on the above test, either the line was not readied, the
modem is defective, or the DSLAM is down. Note that PCI and USB
modems will need to load drivers before syncing, and thus make
this test a little more complicated.
</Para>
</ListItem>
<ListItem>
<Para>
If you installed microfilters, remove these temporarily and unplug
<Emphasis>all</Emphasis> telco devices, such as fax machines, etc. Possibly
a mircofilter is defective and shorting out the line.
</Para>
</ListItem>
</ItemizedList>
</Para>
</Sect3>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect3>
<Title>NIC Problems</Title>
<Para>
Symptoms here are: NIC is not recognized, modules won't load, or
<Command>ifconfig</Command> shows the interface is not up or is generating
lots of errors.
</Para>
<Para>
<ItemizedList>
<ListItem>
<Para>
Turn off PnP in BIOS. This may be labeled as 'non-Microsoft'
OS. Other times, it will be labeled as <quote>PNP-OS
Installed</quote>. A sometimes symptom here is that the NIC is
assigned IRQ 0.
</Para>
</ListItem>
<ListItem>
<Para>
Check for IRQ conflicts with '<Command>cat /proc/interrupts</Command>'. If
the NIC is sharing an IRQ, try moving cards around in slots, or tinker
with BIOS IRQ settings. If an ISA card, you may need to get the setup
utility from the manufacturer and use it to set IRQ, etc. This may
require booting to DOS.
</Para>
</ListItem>
<ListItem>
<Para>
Possibly the wrong module is being loaded. Look through the kernel source
documentation in <Filename>/usr/src/linux/Documentation/*</FileName> for
your card or chipset. Also, for comments and update information in
<Filename>/usr/src/linux/drivers/net/*.c</FileName> for your respective
chipset. It is worth noting that there is more than one module for some
card types. This seems to be true of tulip and 3Com cards. Check boot
messages or use '<Command>lspci -v</Command>' to see how the kernel is
identifying your card. You can use <Command>insmod</Command>,
<Command>rmmod</Command>, and <Command>modprobe</Command> to test
different modules. See the respective man pages for more information.
</Para>
</ListItem>
<ListItem>
<Para>
Check the manufacturer's web site for Linux documentation. Or look at
Donald Becker's informative site at <Ulink
URL="http://www.scyld.com/network/">http://www.scyld.com/network/</Ulink>.
</Para>
</ListItem>
<ListItem>
<Para>
Some Linux NIC drivers reportedly work better as non-modular. In other
words, compile them into the kernel instead of as a module.
</Para>
</ListItem>
<ListItem>
<Para>
The card is bad, or the drivers just aren't up to snuff. Try another card.
</Para>
</ListItem>
</ItemizedList>
</Para>
</Sect3>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect3>
<Title>IP Connection Problems</Title>
<Para>
Read this section if the modem is syncing, the NIC is recognized and seems to
be working properly, client software is installed and running without error,
but connection to the ISP fails. Verify the modem is indeed syncing by the
LED(s). This may be evidenced by <Command>ifconfig</Command> not showing an
active eth0 interface (and ppp0 for PPPoX), or <quote><Command>ping</Command>ing</quote>
gateway and other destinations generates <Literal>network
unreachable</Literal> or similar errors.
</Para>
<Para>
<ItemizedList>
<ListItem>
<Para>
Make sure you know which protocol your ISP is using. Are they using DHCP?
PPPoX? It is critical that you have this right. You may have to ask tech
support.
</Para>
</ListItem>
<ListItem>
<Para>
If you are using DHCP, does the ISP require MAC address authentication,
and if so, do they have the right address? Did they or you typo it?
</Para>
</ListItem>
<ListItem>
<Para>
Look at <Filename>/var/log/messages</FileName> and see if any useful clues
are there. Also, run <Command>tcpdump</Command> while trying to initiate
the connection. <Command>tcpdump</Command> output is fairly cryptic, but
you should certainly be able to see if there is any response at all.
</Para>
</ListItem>
<ListItem>
<Para>
If PPPoX, is the ISP using <Literal>username</Literal> as an id, or
<Literal>username@isp.com</Literal>?
</Para>
</ListItem>
<ListItem>
<Para>
Try pinging the default gateway's address. Get this with '<Command>route
-n</Command>'. If you can <Command>ping</Command> by IP address (i.e.
111.222.333.444), but not by hostname, then likely nameservers are not
correctly setup in <Filename>/etc/resolv.conf</FileName>.
</Para>
</ListItem>
<ListItem>
<Para>
If running a firewall (e.g. with ipchains), temporarily take it down.
Possibly this is misconfigured, and not allowing packets through.
</Para>
</ListItem>
<ListItem>
<Para>
If the modem was purchased from a source other than your ISP, it may the
wrong kind of modem. SDSL needs an SDSL modem, for instance. Also, for
ADSL there are CAP and DMT encodings, and these are incompatible with
each other.
</Para>
<Para>
The modem may need to be configured for your ISP's service. All modems
have configurations for VCI, VPI, encapsulation, etc. Call tech support
for this information.
</Para>
</ListItem>
</ItemizedList>
</Para>
</Sect3>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2 id="synctr">
<Title>Sync Problems</Title>
<Para>
Read this section if you have had a working connection, but now have lost
sync, are intermittently losing sync, your sync rate has dropped
significantly, or are getting a 'sync/no surf' condition. (Better quality
modems will have a way to report sync rate, usually via telnet or a web
browser interface. See the owner's manual.)
</Para>
<Para>
A loss of sync indicates a problem with the DSLAM, your line (inside or
outside) or your modem. DSLAMs typically have 'shelves' with 'cards'. Alcatel
DSLAM cards, just for instance, have a capacity of four connections each. If
the card goes bad, at most four customers are effected. The point being that
sync loss outages can be very isolated. Unlike network outages that tend to
effect large numbers of users. Sync outages are a telco problem, not an
ISP problem. If your service agreement is with the ISP, you will need to
contact them, who will in turn contact the telco.
</Para>
<Para>
Degraded sync rates, and disruption of the DSL signal, can cause various
problems. Obviously, you will never get your maximum throughput under these
conditions. But, the symptoms are not always obvious as to whether the
problem is on your end or the provider's.
</Para>
<Para> For instance, a poor inside wire connection may result in
retransmissions of packets that have been lost, or dropped. This can
drasticly reduce throughput. It is tempting to think of lost packets
as a traditional networking problem, but with DSL it is possible to
be the result of a bad line, impaired signal, or even the modem
itself.
</Para>
<Para>
Some things to try:
<ItemizedList>
<ListItem>
<Para>
Power cycle the modem. Turn off the power button/switch, and physically
unplug the cable to the wall jack for 30 seconds or so. Turn back on, and
re-attach to wall jack. This will force a resync. Unfortunately, the only
way to power down a PCI modem, is to reboot. This should fix a 'sync/no
surf' condition that is caused by the modem, and maybe other conditions
too.
</Para>
</ListItem>
<ListItem>
<Para>
See the <Link LinkEnd="nosync">above section</Link> on moving the modem
lock, stock and barrel to the NID/SNI and thus bypassing all inside wiring.
If the situation is improved there, then the problem is inside somewhere. If
not, it is a telco problem.
</Para>
</ListItem>
<ListItem>
<Para>
RFI Bear-hunt: The DSL signal is fragile, there are a number of
things that can degrade it. RFI, or Radio Frequency Interference,
from sources in and around the home/office is one common source of
reduced signal strength, and/or intermittent sync loss and/or low
sync rates. Our test tool here is simply a portable AM radio. Tune
it to any channel where you can get clear reception -- it makes no
difference where. The AM radio will pick up RFI that is in the same
frequency range as the DSL signal. It will sound like 'frying
bacon' type static. Put it against your computer's power
supply. You should hear some static. Move it away and the static
should fade pretty quickly. This will give you an idea of what RFI
sounds like. A decent quality power supply should produce only weak
RFI -- probably not enough to cause a problem. Use the radio like a
Geiger counter and move it around your modem and DSL line. If you
hear static, follow it to the source. Things to be suspicious of:
power supplies, transformers, ballasts, electric motors, dimmer
switches, high intensity lighting. Moving the modem, or rerouting
cables is sometimes enough. Keeping the line between the modem and
the wall jack as short as possible is a good idea too.
</Para>
</ListItem>
<ListItem>
<Para>
Chronic sync problems are often due to a line problem somewhere.
Sometimes it is something as simple as a bad splice, and easily remedied
if it can be found. Most such conditions can be isolated by a good telco
tech. Check with your provider, and politely harass them if you have to. If you
get the run-around, ask to go over their heads.
</Para>
</ListItem>
<ListItem>
<Para>
If you are near the distance limits of DSL, and having off and on sync
problems, try the 'homerun' installation. See <Link
LinkEnd="homerun">above</Link>. This can be effective in improving
marginal signal/sync conditions.
</Para>
</ListItem>
<ListItem>
<Para>
If using a surge protector, try it without the surge protector. Some may
interfere with the DSL signal.
</Para>
</ListItem>
</ItemizedList>
</Para>
<Para>
Another possibility is a nearby AM radio station, or bandit ham radio
operator that are disrupting the DSL signal since they operate in a similar
frequency range. These may only cause problems at certain times of day, like
when the station boosts its signal at night. A good telco DSL tech may be
able to help minimize the impact of this. YMMV.
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>Network and Throughput Problems</Title>
<Para>
Read this section if your connection is up, but are having throughput
problems. In other words, your speed isn't what it should be based on your
bit rate plan, and your distance from the CO. 'Network' here is the WAN --
the ISP's gateway and local subnet/backbone, etc. Remember that a
marginal line can cause a reduced sync rate, and this will impact throughput.
See <Link LinkEnd="synctr">above</Link>.
</Para>
<Para>
The two factors we will be looking for are 'latency' and 'packet loss'. Both
are pretty easy to track down with the standard networking tools
<Command>ping</Command> and <Command>traceroute</Command>. If either of these
occur in our path, they will impact performance. Latency means
'responsiveness' or 'lag time'. Actually what we are interested in is
abnormally high latency, since there is always some latency. Packet loss is
when a packet of data gets dropped somewhere along the way. TCP/IP will know
it's been 'lost', and there will be a retransmission of the lost data. Enough
of this can really slow things down. Ideally packet loss should be 0%.
</Para>
<Para>
What we really need to be concerned about is that part of the WAN
route that we routinely traverse. If you do a traceroute to several different
sites, you will probably see that the first few 'hops' tend to be the
same. These are your ISP's local backbone, and your ISP's upstream provider's
gateway. Any problem with any of this, and it will effect everywhere you go
and everything you do.
</Para>
<Para>
We can start looking for packet loss and latency by pinging two or three
different sites, hopefully in at least a couple of different directions. We
will be looking for packet loss and/or unusually high latency.
</Para>
<Screen>
$ ping -c 12 -n www.linuxdoc.org
PING www.linuxdoc.org (152.19.254.81) : 56(84) bytes of data.
64 bytes from 152.19.254.81: icmp_seq=0 ttl=242 time=62.1 ms
64 bytes from 152.19.254.81: icmp_seq=1 ttl=242 time=60.8 ms
64 bytes from 152.19.254.81: icmp_seq=2 ttl=242 time=59.9 ms
64 bytes from 152.19.254.81: icmp_seq=3 ttl=242 time=61.8 ms
64 bytes from 152.19.254.81: icmp_seq=4 ttl=242 time=64.1 ms
64 bytes from 152.19.254.81: icmp_seq=5 ttl=242 time=62.8 ms
64 bytes from 152.19.254.81: icmp_seq=6 ttl=242 time=62.6 ms
64 bytes from 152.19.254.81: icmp_seq=7 ttl=242 time=60.3 ms
64 bytes from 152.19.254.81: icmp_seq=8 ttl=242 time=61.1 ms
64 bytes from 152.19.254.81: icmp_seq=9 ttl=242 time=60.9 ms
64 bytes from 152.19.254.81: icmp_seq=10 ttl=242 time=62.4 ms
64 bytes from 152.19.254.81: icmp_seq=11 ttl=242 time=63.0 ms
--- www.linuxdoc.org ping statistics ---
12 packets transmitted, 12 packets received, 0% packet loss
round-trip min/avg/max = 59.9/61.8/64.1 ms
</Screen>
<Para>
The above example is pretty normal from here. (You probably have a very
different route to this site, and your results may thus be quite different.)
Apparently no serious underlying problems that would slow me down. The below
example reveals a problem:
</Para>
<Screen>
$ ping -c 20 -n www.debian.org
PING www.debian.org (198.186.203.20) : 56(84) bytes of data.
64 bytes from 198.186.203.20: icmp_seq=0 ttl=241 time=404.9 ms
64 bytes from 198.186.203.20: icmp_seq=1 ttl=241 time=394.9 ms
64 bytes from 198.186.203.20: icmp_seq=2 ttl=241 time=402.1 ms
64 bytes from 198.186.203.20: icmp_seq=4 ttl=241 time=2870.3 ms
64 bytes from 198.186.203.20: icmp_seq=7 ttl=241 time=126.9 ms
64 bytes from 198.186.203.20: icmp_seq=12 ttl=241 time=88.3 ms
64 bytes from 198.186.203.20: icmp_seq=13 ttl=241 time=87.9 ms
64 bytes from 198.186.203.20: icmp_seq=14 ttl=241 time=87.7 ms
64 bytes from 198.186.203.20: icmp_seq=15 ttl=241 time=85.0 ms
64 bytes from 198.186.203.20: icmp_seq=16 ttl=241 time=84.5 ms
64 bytes from 198.186.203.20: icmp_seq=17 ttl=241 time=90.7 ms
64 bytes from 198.186.203.20: icmp_seq=18 ttl=241 time=87.3 ms
64 bytes from 198.186.203.20: icmp_seq=19 ttl=241 time=87.6 ms
--- www.debian.org ping statistics ---
20 packets transmitted, 13 packets received, 35% packet loss
round-trip min/avg/max = 84.5/376.7/2870.3 ms
</Screen>
<Para>
High packet loss at 35%, and some really slow roundtrip times in there as
well. A little digging on this showed that it was a backbone router 13 hops
into the traceroute that was the problem. While making this site really slow
from here, it would only effect those routes that happen to hit that same
router. Now what would really hurt us is if something similar happens with a
router that we tend to go through consistently. Like our gateway, or maybe
the second hop router too. Find these with <Command>traceroute</Command>, by
just picking a random site:
</Para>
<Screen>
$ traceroute www.bellsouth.net
traceroute to bellsouth.net (192.223.22.134), 30 hops max, 38 byte packets
1 adsl-78-196-1.sdf.bellsouth.net (216.78.196.1) 14.86ms 7.96ms 12.59ms
2 205.152.133.65 (205.152.133.65) 7.90ms 8.12ms 7.73ms
3 205.152.133.248 (205.152.133.248) 8.99ms 8.52ms 8.17ms
4 Hssi4-1-0.GW1.IND1.ALTER.NET (157.130.100.153) 11.36ms 11.48ms 11.72ms
5 125.ATM3-0.XR2.CHI4.ALTER.NET (146.188.208.106) 14.46ms 14.23ms 14.40ms
6 194.at-1-0-0.TR2.CHI2.ALTER.NET (152.63.65.66) 16.48ms 15.69ms 16.37ms
7 126.at-5-1-0.TR2.ATL5.ALTER.NET (152.63.0.213) 65.66ms 66.18ms 66.39ms
8 296.ATM6-0.XR2.ATL1.ALTER.NET (152.63.81.37) 66.86ms 66.42ms 66.40ms
9 194.ATM8-0.GW1.ATL3.ALTER.NET (146.188.233.53) 67.87ms 68.69ms 69.63ms
10 IMVI-gw.customer.ALTER.NET (157.130.69.202) 69.88ms 69.25ms 69.35ms
11 www.bellsouth.net (192.223.22.134) 68.74ms 69.06ms 68.05ms
</Screen>
<Para>
The first hop is the gateway. In fact, for me the first two hops are
<Emphasis>always</Emphasis> the same, and the first three or four are often
the same. So a problem with any of these may cause a problem anywhere I go.
(The specifics of your own situation may be a little different than this
example.) A 'normal' gateway ping (for me!):
</Para>
<Screen>
$ ping -c 12 -n 216.78.196.1
PING 216.78.196.1 (216.78.196.1) : 56(84) bytes of data.
64 bytes from 216.78.196.1: icmp_seq=0 ttl=64 time=14.6 ms
64 bytes from 216.78.196.1: icmp_seq=1 ttl=64 time=15.4 ms
64 bytes from 216.78.196.1: icmp_seq=2 ttl=64 time=15.0 ms
64 bytes from 216.78.196.1: icmp_seq=3 ttl=64 time=15.2 ms
64 bytes from 216.78.196.1: icmp_seq=4 ttl=64 time=14.9 ms
64 bytes from 216.78.196.1: icmp_seq=5 ttl=64 time=15.3 ms
64 bytes from 216.78.196.1: icmp_seq=6 ttl=64 time=15.4 ms
64 bytes from 216.78.196.1: icmp_seq=7 ttl=64 time=15.0 ms
64 bytes from 216.78.196.1: icmp_seq=8 ttl=64 time=14.7 ms
64 bytes from 216.78.196.1: icmp_seq=9 ttl=64 time=14.9 ms
64 bytes from 216.78.196.1: icmp_seq=10 ttl=64 time=16.2 ms
64 bytes from 216.78.196.1: icmp_seq=11 ttl=64 time=14.8 ms
--- 216.78.196.1 ping statistics ---
12 packets transmitted, 12 packets received, 0% packet loss
round-trip min/avg/max = 14.6/15.1/16.2 ms
</Screen>
<Para>
And a problem with the same gateway on a different day:
</Para>
<Screen>
$ ping -c 12 -n 216.78.196.1
PING 216.78.196.1 (216.78.196.1) : 56(84) bytes of data.
64 bytes from 216.78.196.1: icmp_seq=0 ttl=64 time=20.5 ms
64 bytes from 216.78.196.1: icmp_seq=3 ttl=64 time=22.0 ms
64 bytes from 216.78.196.1: icmp_seq=4 ttl=64 time=21.8 ms
64 bytes from 216.78.196.1: icmp_seq=6 ttl=64 time=32.0 ms
64 bytes from 216.78.196.1: icmp_seq=8 ttl=64 time=21.7 ms
64 bytes from 216.78.196.1: icmp_seq=9 ttl=64 time=42.0 ms
64 bytes from 216.78.196.1: icmp_seq=10 ttl=64 time=26.8 ms
--- adsl-78-196-1.sdf.bellsouth.net ping statistics ---
12 packets transmitted, 7 packets received, 41% packet loss
round-trip min/avg/max = 20.5/25.6/42.0 ms
</Screen>
<Para>
41% packet loss is very high, to the point where many services, like HTTP,
come to a screeching halt. Those services that were working, were working
very, very slowly.
</Para>
<Para>
It's a little tempting on this last real-life example to think this gateway
router is acting up. But, as it turned out, this was the result of a problem
in the DSLAM/ATM segment of the telco's network. So any first hop problem
with packet loss or high latency, may actually be the result of something
occurring before the first hop. We just don't have the tools to isolate
where it is starting well enough. Packet loss can be a telco problem, just as
much as an ISP/NSP problem.
</Para>
<Para>
It is also quite possible for the modem itself to cause packet loss. The fix
here is to power cycle the modem, and resync by unplugging the DSL connection
for 30 seconds or so. In fact, any part of the connection can be a source of
packet loss -- modem, DSLAM, ATM network, etc.
</Para>
<Para>
If you do find a problem within your ISP's network, it's time to report the
problem to tech support.
</Para>
<!-- ~~~~~ New Section ~~~~~ -->
<Sect3>
<Title>Miscellaneous Network Problems</Title>
<Para>
Some odds and ends:
</Para>
<Para>
<ItemizedList>
<ListItem>
<comment>This might be better as a different kind of list.
Perhaps a variablelist or possibly even a segmentedlist.</comment>
<Para>
<Emphasis>Some Web pages won't load.</Emphasis> For PPPoX users, the
MTU value could be too high. The correct ppp0 device setting should be
1492, but actually it needs to be 8 bytes less than any router you pass
through on the way to the site. If a router somewhere is misconfigured,
you could have problems. Try experimenting with lower MTU values. Any LAN
hosts behind the connection, may even need to be lower -- 1452 or maybe
even 1412.
</Para>
</ListItem>
<ListItem>
<Para>
<Emphasis>Ping by IP address</Emphasis> works, but not hostname. The
nameservers are not being setup correctly in
<Filename>/etc/resolv.conf</FileName>. Check your client's (DHCP, PPPoX)
documentation or enter these manually with a text editor.
</Para>
</ListItem>
<ListItem>
<Para>
<Emphasis>PPPoX disconnects</Emphasis>. Unfortunately, there is a tendency
for PPPoX to drop connections. PPP is apparently sensitive to any line
condition which results in a temporary interruption of the connection.
This may not be completely solvable, depending on what and where the
problem is. You might try a different client, or check your current
client's documentation on this issue. If worse comes to worse, set up a cron
job to watch the connection, and re-establish if necessary.
</Para>
</ListItem>
<ListItem>
<Para>
<Emphasis>Interface or route goes down for no reason</Emphasis>. If
<Command>ifconfig</Command> and/or <Command>route</Command> show the
interface and/or route has automagically disappeared, it may be due to
a buggy NIC driver. This may also happen with DHCP if the server does not
respond for long periods of time. (Possibly a bug in the client? I have
seen this with early versions of <Command>pump</Command> from Redhat. HB.)
</Para>
</ListItem>
<ListItem>
<Para>
Sub-par performance, or errors with the interface (e.g. eth0), may
possibly be caused by a duplex mismatch. This would be most apparent when
maxing out the connection. Most DSL modems and routers typically are set
to half duplex, and your NIC should be set likewise.
</Para>
</ListItem>
</ItemizedList>
</Para>
</Sect3>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2 id="throughput">
<Title>Measuring Throughput</Title>
<Para>
No such thing as too fast, right? One of the first things most of us do is
check our speeds to make sure we aren't getting short changed, and that our
system is up to snuff. Doing this accurately is easier said than done
however. First, remember you are losing 10-20% right off the top due to
networking overhead. Just how much is 'lost' here depends on your provider's
network architecture and other considerations.
</Para>
<Para>
Then, any time you hit the Internet, there is some slight degradation of
performance with each hop you take. Now this may not amount to much, as long
as you are not taking too many hops and all the components -- your system,
your ISP's network, your ISP's upstream provider, and the destination itself
-- are all working like well oiled machines. But there's the rub -- how do
you really know with so many variables in the mix? One flaky interface, on
one router, on one hop along the path, may cause misleading results.
</Para>
<Para>
Your absolute max speed is going to be at your point of connection to your
ISP -- the ISP's gateway. It can only go downhill from there, not up! So the
ideal test is as close to home as possible. This eliminates as many unknown
variables as possible. If your ISP has a local ftp server, this is an
excellent place to run your own tests. (Run a traceroute though just to see
how local it really is.)
</Para>
<Para>
If your ISP does not have this, look for an ftp site that is close -- the
fewer the hops, the better. And look for one that isn't too busy, or you will
get misleading results. Find a large file -- like 10 Megs -- and time the
download. Try this over several days, and at different times of day. The
server, and the backbone, are going to be busier at certain times of day,
which can skew results and you want to eliminate these variables as much as
possible. Your provider cannot compensate for heavy backbone traffic,
backbone bottlenecks, slow or busy servers, etc.
</Para>
<Para>
There are many test sites scattered around the web. Some are better than
others, but take these with a grain of salt. There are just too many
variables for these tests to reliably give you an accurate snapshot of your
connection and throughput. They may give you a general picture of whether you
are in the ballpark of where you think you should be or not. One good speed
test is <Ulink
URL="http://www.dslreports.com/stest/0">http://www.dslreports.com/stest/0</Ulink>.
Another test is <Ulink
URL="http://speedtest.mybc.com/">http://speedtest.mybc.com/</Ulink> (both are
java). I find these to be better than some of the others out there.
</Para>
<Para>
Now keeping in mind that we are limited by the ~10-20% networking overhead rule,
here is an example. My speed is capped at 1472 Kbps. Minus the ~15% is 1275
Kbps. My sync rate is known to be good and my distance to the CO is about
9000 Ft, which is close enough that I should be able to hit my real world
maximum throughput of 1275 Kbps or roughly 1.2-1.3 Mbps -- all other things
being equal. From dslreports.com speed test:
</Para>
<Screen>
Test running..Downloaded 60900bytes in 5918ms
Downloaded 696000bytes in 4914ms
First guess is 1133kbps
fairly fast line - now test 2mb
Downloaded 1679100bytes in 11090ms
Upload got ok 1 bytes uploaded
Uploaded 1bytes in 211ms
Upload got ok 1 bytes uploaded
Uploaded 1bytes in 205ms
Upload got ok 1 bytes uploaded
Uploaded 1bytes in 207ms
Upload got ok 50000 bytes uploaded
Uploaded 50000bytes in 2065ms
Upload got ok 100000 bytes uploaded
Uploaded 100000bytes in 3911ms
** Speed 1211(down)/215(up) kbps **
(At least 24 times faster than a 56k modem)
Finish.
</Screen>
<Para>
1.211 Mbps is probably about as good as I can realistically expect based on
my service. There is no reason for me to go troubleshooting or looking for
tweaks.
</Para>
<Para>
<Emphasis>Big Caution</Emphasis>: my ISP uses a caching proxy server for
web pages. This is a big equalizer for these kinds of web based
tests. Without that, I surely would have been significantly slower on this
test. The effect of the proxy is that you are actually testing throughput
from the proxy -- NOT the test site. Just FYI. Another note: at the same time
I tried another test site and was consistently getting 600-700 Kbps. So YMMV
with these tests. (Usually I get the same on each, more or less.) Timing a
large ftp download, I calculated about 1.25 Mbps.
</Para>
</Sect2>
</Sect1>
<!-- ~ End Section ~ -->
<!-- ~~~~~~~~ New Section Header ~~~~~~~~~ -->
<Sect1 id="overview">
<Title>Appendix: DSL Overview</Title>
<Para>
DSL is a telephone loop technology that uses existing copper phones lines,
and provides a dedicated, high speed Internet connection. One of the big
advantages of some DSLs (notably ADSL), are that they can co-exist on the
same line with a traditional voice service or 'POTS' (Plain Old Telephone
Service). This is accomplished by utilizing different frequency ranges above
the voice range (voice is up to 4KHz). Essentially, this gives two lines in
one: one for POTS, and one for Internet connectivity. When all is working
normally, there should be no interference between the two 'lines'. This gives
DSL a potentially broad consumer base, and helps minimize costs for
providers.
</Para>
<Para>
DSL is positioned for the Home and Small Office (SOHO) market that is
looking for high speed Internet access at reasonable prices. Since it also
typically provides dedicated, 'always on' access, it can be used for
interconnecting low to mid range bandwidth servers, and provides a great
access solution for small LANs. It is also great for those Linux power users
that just want a fast pipe :-).
</Para>
<Para>
Phone companies, and other independent telecommunications providers (CLECs),
are now deploying DSL as fast as they can to stay ahead of the Cable
companies -- the main consumer and SOHO competition for DSL providers. This
mad rush to get 'a piece of the pie', is bringing much competition (a good
thing!), much diversity, and some confusion, into the consumer market.
The DSL provider (often, but not always, the phone company) will provide the
DSL infrastructure. This would include your line, the DSLAM, and physical
connection to the outside world. From there it is typically picked up by an
ISP, who provides the traditional Internet services.
</Para>
<Para>
Consumer DSL plans are typically 'best effort' services. While boasting
speeds approaching T1, and even surpassing that in some cases, it is not
necessarily as reliable as T1 however. Business class DSL offers more
reliability at a higher cost than consumer plans, and is a good compromise
where both reliability and bandwidth are at a premium. All in all, the cost
of DSL compared to traditional telco services, such as T1, is attractive and
substantially more affordable for home and small business users.
<comment> DSL generally does not offer service contracts for home users, while
DSL for business offers similar SLAs (Service Level Agreements) to that offered
when getting a T1 line.
See next para. HB.
</comment>
</Para>
<Para>
DSL providers generally do not have service contracts for home users,
while business class DSL services typically do include similar SLA (service
level agreements) to that offered for a T1 line.
</Para>
<Para>
The downside is that DSL is not available everywhere. Availability, and
available bit rate (speed), are purely a function of where you live, where
the telco has installed the prerequisite hardware, how far you are from the
DSLAM/CO, and the quality of your phone line (loop). Not all loops are
created equal, unfortunately. The primary limitation is distance.
</Para>
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2 id="family">
<Title>The DSL Family</Title>
<Para>
<ItemizedList>
<ListItem>
<BridgeHead renderas=sect3>ADSL</BridgeHead>
<comment>I tend to think that these would flow better as complete
sentences, rather than sentence fragments. The rendering does not lend
itself to the partial sentences leading into these paragraphs. Check out
both <markup>segmententedlist</markup> and <markup>variablelist</markup> as
alternatives to the current markup.</comment>
<Para>
Asymmetric Digital Subscriber Loop. This DSL type currently supports
downstream rates up to 8 Mbps, and upstream of 1024 Kbps, hence the
'asymmetric'. The most widely deployed form of DSL at this time, and was
specifically developed for the home and SOHO markets. The higher downstream
rates lends itself to those not running serious servers -- at least
anything more than a small, personal web site. ADSL is capable of sharing
data with a POTS voice line, so an additional line is not required. A big
selling point. ADSL, like other DSLs, is limited by distance. 18,000 ft
(5.5 km) is a typical cut-off point for telcos. ADSL does typically require
either a splitter or filters to isolate the DSL signal from POTS.
Sometimes referred to as 'full rate' ADSL in order to differentiate it from
G.Lite DSL. There are two common line encodings for ADSL: DMT and CAP. DMT
(a.k.a. Alcatel compatible) has won the standards battle and is now the
more common of the two. Also, note that modems must be compatible with the
encoding. In other words, a CAP modem will not work with a DMT service, and
vice versa.
</Para>
</ListItem>
<ListItem>
<BridgeHead renderas=sect3>G.Lite</BridgeHead>
<Para>
Sometimes called 'DSL Lite', 'Universal DSL' or 'splitterless ADSL', is a
slower version of ADSL that require no splitters <Emphasis>or </Emphasis>
filters. The isolation of voice and data signals is handled at the CO.
Currently G.Lite supports speeds up to 1.5 Mbps/512 Kbps, and is expected
to eventually become the dominant consumer DSL service. As of this writing,
it is not as wide spread as 'full rate' ADSL however.
</Para>
</ListItem>
<ListItem>
<BridgeHead renderas=sect3>SDSL</BridgeHead>
<Para>
Single-pair Digital Subscriber Loop, or also sometimes referred to
as 'Symmetric Digital Subscriber Loop' since it is indeed symmetric with a
current maximum rate of 1.5 Mbps/1.5 Mbps. SDSL requires a dedicated line,
and thus true SDSL is not as readily adaptable to the consumer market as
ADSL. SDSL also uses a 2B1Q encoding (same as ISDN and some T1) which is
considered more robust than the DMT or CAP encoding of ADSL. True SDSL is
generally considered more of a server quality DSL. It is worth noting that
some providers may be marketing a 'SDSL' service that is really ADSL pinched
so that upstream/downstream are the same. Wasn't all this confusing enough
already?
<comment> Why is Symmetric DSL wrong? It IS always symmetric...
Actually the term here 'Single Line (or pair)' was coined to explicitly to
differentiate it from HDSL, which required multiple pairs for significant
speeds. This was (is) is big drawback to HDSL. It is coincidence that it is
also symmetric. So a technicality really, and who really cares anyway ;)
Also, noted that 'some T1' uses 2B1Q, but cannot find the reference where I
originally got that from.
HB.
</comment>
</Para>
</ListItem>
<ListItem>
<BridgeHead renderas=sect3>IDSL</BridgeHead>
<Para>
ISDN Digital Subscriber Loop, 144 Kbps/144 Kbps is really a new and
improved ISDN from Lucent Technologies and uses the same 2B1Q line encoding
as ISDN, SDSL and others. IDSL does require a dedicated line however. The
benefits are that it is an 'always on' technology, like other DSLs, and
provides an additional 16 Kbps over traditional ISDN. It is being marketed
by some DSL providers as a low end bit rate option, where line quality is
not sufficient for higher speeds such as that of ADSL.
<comment> What in the HECK is 2B1Q? I've got a total of 8 fiber T1s, and 4
copper t1s coming into our office, and I've NEVER heard of that. Out basic
DSS trunks for voice are using AMI, while our Internet circuts are using B8ZS.
Where can I get more information on this 1B2Q thing?
See above. HB.
</comment>
</Para>
</ListItem>
<ListItem>
<BridgeHead renderas=sect3>RADSL</BridgeHead>
<Para>
Rate Adaptive Digital Subscriber Loop was developed by Westell and has a
potential of 2.2 Mbps downstream and 1.0 Mbps upstream. What makes RADSL
more flexible is that the sync rate can be dynamically adjusted up or down
as line conditions change. This makes it more of a viable alternative where
line conditions are marginal. In many respects, RADSL is an enhanced ADSL
to meet a more diverse set of line conditions. Like ADSL, RADSL can
piggyback on the POTS line.
</Para>
</ListItem>
<ListItem>
<BridgeHead renderas=sect3>HDSL</BridgeHead>
<Para>
High bit-rate DSL was one of earliest versions of DSL. HDSL
requires multiple, dedicated wire pairs, and is symmetric at 1.5
Mbps/1.5 Mbps (the speed actually depends on number of wire pairs
used). Not a viable alternative for the consumer or SOHO markets.
</Para>
</ListItem>
<ListItem>
<BridgeHead renderas=sect3>VDSL</BridgeHead>
<Para>
Very high rate Digital Subscriber Loop, a DSL still in development
with a current downstream capacity of 52.8 Mbps, and upstream of
2.3 Mbps. At this time, VDSL is limited to very short loop lengths,
and is not yet a viable alternative. It may find application where
there is fiber to the neighborhood, and thus the copper loop
segment is relatively short.
</Para>
</ListItem>
<ListItem>
<BridgeHead renderas=sect3>UDSL</BridgeHead>
<Para>
Unidirectional Digital Subscriber Loop is a proposal from Europe that is
not yet in use.
</Para>
</ListItem>
<ListItem>
<BridgeHead renderas=sect3>G.SHDSL</BridgeHead>
<Para>
Standard not finalized yet. Supposedly includes many enhancements.
</Para>
</ListItem>
</ItemizedList>
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>The DSLAM</Title>
<Para>
This technology is made possible by the placement of DSLAMs, or Digital
Subscriber Loop Access Multiplexers, from such suppliers as <Ulink
url="http://www.alcatel.com">Alcatel</Ulink> and
<Ulink
URL="http://www.cisco.com/warp/public/cc/pd/si/6000/prodlit/c6160_ds.htm">Cisco</Ulink>,
in the telco's Central Office. DSLAMs come in various shapes and sizes, and
are the one, single complex and costly component of a DSL connection. When
a qualified phone line is connected to a modem at the user's end of the loop,
a high speed digital connection is established, typically over ATM, or
sometimes frame relay. The DSLAM splits the signal back into separate voice
and data channels. The voice channel stays within the telco network, whereas
the data is picked up by an ISP.
</Para>
<BridgeHead renderas=sect3>
Figure 4: A Typical DSL Connection Path
</Bridgehead>
<Para>
<Literal>
<MSGText>
<LiteralLayout>
Voice -+ +---> Voice
|<-- copper loop --> DSLAM/CO <--{ATM cloud}--->|
modem -+ | +---> Inet
| | |
ether..|..... DSL/ATM here ....|.... raw ATM here .....|.. TCP/IP ..
| |
SOHO...|............ telco (ILEC or CLEC) .............|.. ISP ..| NSP
</LiteralLayout>
</MSGText>
</Literal>
</Para>
<comment>Our tools seem to suck on this "ASCII art". I'm not sure
if trying a graphic would be worth-while.</comment>
<!-- ~~~~~ New Section ~~~~~ -->
<Sect3>
<Title>Sync</Title>
<Para>
A good, working connection to the DSLAM is referred to as 'syncing'. Without
sync, nothing happens. The modem will establish a sync rate which is often
throttled by the provider at a predefined limit. This limit, or 'cap', is at
the provider's discretion and is part of the service that is being provided.
Your modem may well sync at a higher rate than the 'cap', but your speed will
be limited to whatever 'cap' the provider is enforcing. So while ADSL has an
upward theoretical limit of 8 Mbps, you will not see that speed -- unless of
course your provider is selling an 8 Mbps plan. Most plans are well below
this.
</Para>
<Para>
Below is the status information from a SpeedStream 5660 modem/router via the
built-in telnet interface. In this example, the customer is on a 1.5 Mbps/384
Kbps service:
</Para>
<Screen>
Command-> show dslstatus
--- Channel Info ATU-R ATU-C
Current TX Rate - 384000 1500000
Previous TX Rate - 0 0
CRC Block Length - - -
Interleave Delay - - -
--- Physical Layer Info ATU-R ATU-C
Current Attainable Rate - 448433 3890243
Current SNR Margin - 10.5 17.0
Current Attenuation - 54.5 31.5
Current Output Power - 3.0 16.0
Current Status:
Defects detected - No No
Loss of Framing - No Loss No Loss
Loss of Signal - No Loss No Loss
Loss of Power - No Loss No Loss
Loss of Signal Quality - No Loss No Loss
--- ATU-R Line Status
Line Coding - DMT
Line Type - Fast or Interleaved
Command->
</Screen>
<Para>
First notice the 'Current Attainable Rate' in the 'ATU-C' column. This is the
downstream sync rate negotiated by the modem and DSLAM, which is over
3.5 Mbps. The actual speed is limited, however, to 1.5 Mbps/384 Kbps from the
first row 'TX Rate'. This is the theoretical limit of this connection. This
limit, or 'cap', can be enforced at the DSLAM, as is the case the here, or
further upstream. Had the first row 'TX Rate' been lower than the provider's
imposed limit, then this would indicate some kind of problem with the
connection, perhaps due to distance or some kind of line impairment.
</Para>
<Para>
The attainable sync rate is the result of a number of factors, including wire
distance to the DSLAM, quality of both inside and outside wiring, the loop
wire gauge and various other factors within the loop. Actual measurable,
real world throughput, on the other hand, is first of all dependent on sync
rate. Low sync rate means low throughput. In the above example, had the sync
rate been lower, say 500 Kbps, then that would be the maximum for that
connection, even though the customer is paying for a 1.5 Mbps service.
</Para>
<Para>
Secondarily, throughput will depend also on the ISP's network, and then the
ISP's upstream provider. You will lose approximately 10-20% of potential
throughput to networking overhead. In the above example where the connection
is throttled at 1.5 Mbps, the actual, real-world maximum throughput would be
somewhere around 1.2-1.3 Mbps when overhead is taken into account. Moreover,
once you hit the Internet proper, all bets are off as there are any number of
factors that may impact throughput. A overloaded or busy server is likely to
be slow no matter how fast your DSL connection is.
</Para>
</Sect3>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2 id="dslmodems">
<Title>DSL Modems</Title>
<Para>
The modem is the last piece of the connection. The modem is connected
directly to the DSLAM via the copper loop on the telco end, and plugs into a
wall jack on your end. When all is well, the modem 'syncs' with the DSLAM,
and then makes an IP connection to the ISP, and off we go!
</Para>
<Para>
For Linux users, <Emphasis>the modem is a very important
consideration</Emphasis>! You will need an external, ethernet interfaced
modem (or modem/router combo) that connects via a standard NIC, since
virtually all other modem options (PCI, USB, onboard) will not work due to a
lack of drivers at this time! All ethernet based modems will work fine.
</Para>
<Para>
The only potential compatibility issue is the Network Card (NIC). (And really
any compatible ethernet NIC should do just fine -- 100 Mbps is not
necessary.) You are probably better off anyway, since PCI and USB modems are
more problem prone. If your chosen provider does not offer a compatible
modem as an option, then you either need to look elsewhere, or you will have
to buy one outright from a third party.
</Para>
<Para>
As always, there are exceptions. Diamond makes an internal PCI modem
which has binary-only drivers, but it is not in widespread
use. <Ulink url="http://www.efficient.com">Efficient Networks</Ulink>
is beta testing Linux drivers for their SpeedStream 3060 and 3061 PCI
modems, and is expected to release them <quote>any day</quote>. This
will require a 2.4.x kernel, and a patch for the necessary ATM
support. Efficient is working with kernel developers to make their
products Linux compatible. The initial version will have binary
drivers only, but open sourced drivers are a future possibility. It
is also possible to make a direct ATM connection using a modem plus
an ATM card, though this delivery system is not used in the U.S. as
far as I know, and should not be considered as a viable option. This
would also require a 2.4 kernel.
</Para>
<Para>
The most common type of modem in use today is actually a combination 'bridge'
and modem device. The bridge is a simple device, typically with little
configuration. Network traffic passes blindly across the bridge in either
direction. Your point of exposure is the interface (typically a NIC) that is
connected to the modem/bridge.
</Para>
<Para>
Some ISPs may also be offering 'routers'. These are basically combination
modem/routers that can handle NAT, and may have other feature enhancements
such as port forwarding, a built in hub, etc. These are all external, so
should work too. But probably not a big deal for Linux users, since Linux can
do anything these do, and more. A locked down Linux box makes a most
excellent firewall/gateway/proxy!
</Para>
<Para>
To confuse things even more, there are also all-in-one devices: combo
bridge+router+modem, sometimes called 'brouters'. In this case, the modem can
be configured for either bridging or routing -- but it can't be both at the
same time.
</Para>
<Para>
All providers should make available a 'modem' of some sort. Many ISPs will have
more than one modem option. Some may give away the modem at no additional
charge. Some may offer a free base model, and charge the difference for the
better models with more features. Many of the modems that ISPs supply are not
available through normal retail channels. Should you want to buy one
yourself, this leaves used equipment outlets (e.g. ebay), or possibly buying
a modem that your ISP may not support (i.e. a possibility of no tech support
if you have a problem).
</Para>
<Para>
While some ISPs provide modems that are not readily available through normal
retail channels, there are a number of manufacturers that are getting on the
DSL modem bandwagon, and offering a good selection. Most have a
number of enhancements. At this time Netgear, Linksys, Zyxel, Cisco, 3Com,
and Cayman have products available. Depending on model and feature set,
prices range from a little over $100 US to $800 and up. Many of these
handle their own authentication and encapsulation (DHCP, PPPoE, etc).
</Para>
<Para>
Are some modems better than others? Well, fortunately for us the external,
ethernet interfaced modems are the most reliable anyway. Fewer IRQ hassles,
no buggy drivers, etc. So a blessing in disguise really. Are any of these
better than others? Probably not. None are faster anyway. Certainly some may
have more features, like the combo modem/routers. But realistically, most of
this is so new there is not enough of a track record to compare brands and
models with any degree of assurance. In other words, any old external,
ethernet modem should do -- provided it matches your provider's DSL, and is
configured for that service.
<comment>I don't see the question "Are some modems better than
others?" being answered here. The second sentence isn't very readable
to me, possibly just because of punctuation.</comment>
</Para>
<Para>
<comment>How about using the "warning" tag here instead?
http://www.docbook.org/tdg/html/warning.html</comment>
<Emphasis remap="bold">Warning!</Emphasis> Make sure any third party modem
or router you may purchase is compatible with your DSL provider. There are
two major line encodings for ADSL (CAP, DMT a.k.a. Alcatel compatible), and
several options for IP encapsulation. And different DSLs (SDSL, IDSL, etc)
will require their own modem too. Your provider should have a list of
compatible options. It may well have to be configured for your ISP's service
too. Don't expect it to work right out of the box either (unless it comes
from your provider). Many are accessible via telnet, or a web browser, where
the configuration options are available. See the owner's manual for this.
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2 id="ispconn">
<Title>The ISP Connection</Title>
<Para>
The modem connects to the DSLAM, and then the DSLAM is connected to the
telco's ATM network (or frame relay), where it is picked up by the ISP. The
ISP will take over at what we 'see' as the first hop on a
<Command>traceroute</Command>. Everything up to that point is in the hands
of the telco/DSL provider. The ISP will connect to the ATM side of the DSLAM
via a high-speed data connection, usually ATM over a T3 (45 Mbps) or OC-3
(155 Mbps). The important thing here is that an ISP must 'subscribe' with
your telco to provide this connection. The ISP will provide traditional ISP
type services: email, DNS, news, etc. It is really a two step connection --
DSL from one provider, Internet from a second -- even though these may be
combined into one billing.
</Para>
<Para>
The Baby Bells (RBOCs) all own ISPs. These, of course, are
connected to their DSLAMs, and are providing Internet services via the
telco's ISP subsidiary. Many independent ISPs are availing
themselves of the ILEC's DSL services, and in essence 'reselling' the DSL
services of the ILEC. While the underlying infrastructure is the same in this
case, having more than one ISP working out of a CO may mean a better
selection of features and prices for the consumer.
<comment>I have a note on my printed copy to "pick and acronym", but
I'm not sure which term I wanted you to pick an acronym for. It would
be good to make sure that you're consistent throughout the whole
document with your use of acronyms, just as good authoring policy.
</comment>
</Para>
<Para>
CLECs (independent telcos) are now installing their own DSLAMs. This
makes them a direct competitor to the ILEC. In this scenario, there would be
two (or more) DSL providers in the same CO, each with their own DSLAM(s), and
each competing against each other. This complicates the ISP situation even
further, as each DSL provider will be 'partnered' with one or more ISPs. If
you are lucky here, you will have many choices of plans and pricing
structures.
</Para>
<Para>
Typically, your service agreement is with the ISP, and not the DSL
provider. This makes the actual DSL provider a 'behind the scenes'
player. This may vary, and in some cases, you may wind up with a
separate service agreement for both the DSL provider and the ISP.
</Para>
<Para>
See the Appendix for a list of <Link LinkEnd="isps">Linux Friendly ISPs</Link>.
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>Availability</Title>
<Para>
Who can get DSL? The first requirement is that a telco has installed the
necessary hardware in your CO. You have no choice on which CO is yours -- it
is wherever your loop terminates. If your CO has a DSLAM, and the necessary
other components, then DSL may be available to you. This is often known as
'pre-qualifying', and is Step One in getting service.
</Para>
<!-- ~~~~~ New Section ~~~~~ -->
<Sect3>
<Title>Ordering</Title>
<Para>
<comment>Which kind of provider? ISP? Telco/DSL provider? Both?
Please replace "provider" with something more specific, or give a
clearer idea of what it means.</comment>
Before ordering service, check to see what providers there are in your area.
You may have several options, including the large phone companies, as well as
smaller, local ISPs. Once an order is placed, you must wait for the
qualification process before a provider will agree to provide service.
</Para>
</Sect3>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect3 id="qualify">
<Title>Qualifying</Title>
<Para>
Once local availability is established, the next step is 'qualifying' your
loop. The provider will run various tests to make sure that your loop can
handle the DSL signal. This is to determine how suitable your line is for
DSL, and maybe what level of service will be available to you. You probably
will have to order service just to find out this much. It can be a fairly
involved process, with a variety of different tests being run. There
are a number of things that may 'disqualify' a line. The most common
limitation is distance.
</Para>
<Para>
All DSLs have distance limitations. ADSL is limited
to a loop length of roughly 18,000 ft (5.5 km), but the actual cut off point
will vary from provider to provider. The further away you are, the weaker the
signal, and the potential for poor connections is greater. With ADSL, if you
are within approximately 12,000 ft (3.7 km), you should be able to get at
least 1.5 Mbps -- all other things being equal. IDSL has even greater reach,
mainly because the maximum speed for IDSL is considerably lower at 144
Kbps/144 Kbps.
</Para>
<Para>
Still even if you're close enough, there are a number of potential
impediments that may disqualify a line. Two such common impediments
are load coils and bridge taps. These are aspects of the old telco
infrastructure that once were deemed beneficial, but now are getting
in the way of the newer, digital technologies. <comment>This next
sentence could stand rephrasing</comment> Whether you hit a snag like
this, is pretty much hit or miss. Fiber anywhere in the loop is also
a disqualifier. The provider may take steps to 'clean' the line. Just
how far they are willing to go will vary from provider to provider,
and this will likely add additional time to the installation process.
</Para>
<Para>
Once the line is 'qualified', the next step is deciding on which plan is
suitable for your situation. The provider may have differing plans available
depending on how strong a signal they think your line can handle. If you are
marginal, you will not be qualified for the higher speed plans. And if price
is a factor, having a tiered pricing structure is good also since the lower
end plans are obviously less expensive. How this is structured also varies
wildly from provider to provider. Since, DSL is a new service, and providers
are trying to find the right price/feature combinations that will attract the
most users and thus gain a competitive edge.
</Para>
<Para>
Some common data rates:
</Para>
<Para>
<BlockQuote>
<LiteralLayout>
Downstream/Upstream
128 Kbps/128 Kbps
256 Kbps/256 Kbps
384 Kbps/128 Kbps
640 Kbps/90 Kbps
1.5 Mbps/384 Kbps
2.0 Mbps/512 Kbps
7.1 Mbps/1024 Kbps
</LiteralLayout>
</BlockQuote>
</Para>
<Para>
and a near infinite number of other possibilities. The cost of different
plans generally goes up with their speed.
</Para>
<Para>
Should you be disqualified, and have other options, get a second opinion.
Calculating the effective loop length is by no means an exact science. There
is plenty of room for errors. Also, some providers may go to greater lengths
to 'clean' the loop than others. And, if you have more than one phone line,
and are disqualified, then try the other line. Just because they both
terminate at your location, does not necessarily mean they are the same
length! The telco network is full of surprises.
</Para>
</Sect3>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2 id="cproviders">
<Title>Choosing Providers</Title>
<Para>
Should you have more than one choice, here are some things to keep in mind
when comparing services from different providers. If you are in a populous
area, chances are you do have a number of choices. There is a dizzying array
of possibilities at this time. Remember too, that it is a two step
connection: DSL provider and ISP. You may have choices for each.
</Para>
<Para>
<ItemizedList>
<ListItem>
<Para>
<Emphasis>A compatible modem</Emphasis>. For now with Linux (or any
alternative OS) this essentially means an ethernet interface. 'Routers'
(i.e. combo modem/routers) should be OK too since these seem to be all
external, ethernet. Anything else is a no-go! (This situation may be
changing soon.)
</Para>
</ListItem>
<ListItem>
<Para>
<Emphasis>Installation</Emphasis>. A self-install option, of course, let's
anyone get up and running, and is less expensive. But if there is no
self-install available, will the the provider install onto a Linux only
site? Many will not! Having a Windows (or Mac) box temporarily available
is a work around here. Even a laptop may be enough.
</Para>
</ListItem>
<ListItem>
<Para>
<Emphasis>Static vs Dynamic IP Address</Emphasis>. If wanting to run
servers, or hosting your own domain, static is the way to go.
<comment>It might be worth noting that dynamic IP is slighly more
secure than a static IP. With a static IP, the crackers will always
know right where to look to find you.
</comment>
</Para>
</ListItem>
<ListItem>
<Para>
<Emphasis>Encapsulation</Emphasis>. Is the connection 'Bridged' or 'PPP'.
PPPoX has the reputation of being not as stable a connection, and not
'always on'. PPPoE requires client software to manage the connection, so
one more layer of code.
</Para>
</ListItem>
<ListItem>
<Para>
<Emphasis>Server Policy</Emphasis>. Some ISPs are fairly open about this,
while others forbid any servers -- even personal web sites. Others may even
go so far as to block certain ports.
</Para>
</ListItem>
<ListItem>
<Para>
<Emphasis>Contract</Emphasis>. Is there a contract, and what are the out
clauses? Cancellation fees?
</Para>
</ListItem>
<ListItem>
<Para>
<Emphasis>Connection Limits</Emphasis>. Is it 'always on' (at least
theoretically :-)? Are there session limits, or idle timeouts? Is
bandwidth metered and limited to so much per month? Do they forbid a LAN
behind the connection (dumb!)?
</Para>
</ListItem>
<ListItem>
<Para>
<Emphasis>Linux Support</Emphasis>. A few ISPs may offer some degree of
tech support for Linux, but most will not. This isn't so bad, as long as
they don't go overboard and refuse to help with anything just because you
run a non-supported OS. ('Supported' means like 'tech support'.) If they
say 'we don't care', you should be good to go.
</Para>
</ListItem>
<ListItem>
<Para>
<Emphasis>Free Dialup Account</Emphasis>. A nice thing to have if the
connection is down, or you just need to check mail from another location.
</Para>
</ListItem>
<ListItem>
<Para>
<Emphasis>Setup program</Emphasis>. A few ISPs may have a setup program you
are required to run the first time you connect in order to setup your
account. This will likely not have a Linux version. (BellAtlantic.net was
doing this at last report.) Other than this, there is nothing proprietary
about DSL, and related protocols.
</Para>
</ListItem>
<ListItem>
<Para>
<Emphasis>Reliability and Quality of Service</Emphasis>. Ask around in your
local area from those that have the same DSL provider and ISP. A local LUG
is a good place to get this kind of info. How much down time (hopefully not
much)? Are mail and news services good? Backbone routing? Tech support?
</Para>
</ListItem>
</ItemizedList>
</Para>
<Para>
There are a number of other options and features that might be worth looking
at too: multiple IPs, domain hosting (DNS), free web space, number of
email accounts, web mail, etc.
</Para>
</Sect2>
</Sect1>
<!-- ~ End Section ~ -->
<!-- ~~~~~~~~ New Section Header ~~~~~~~~~ -->
<Sect1 id="faq">
<Title>Appendix: FAQ</Title>
<Para>
Some Frequently Asked Questions about DSL and Linux.
</Para>
<Para>
<OrderedList>
<ListItem>
<Para>
Q. Does DSL work with Linux?
</Para>
<Para>
DSL is a technology, or more correctly, a group of related technologies.
This is akin to asking if Linux works with telephones. The technology
itself does not care. So, the short answer is 'Yes, of course!'. The long
answer is that if there are any impediments, they are being imposed by the
provider. There are things they may do that can make getting Linux up and
running a more of a challenge than it needs to be. Not having a compatible
modem option available is one common gotcha. If the telco or ISP is
doing the installation, they may require a Windows or Mac system to be
available. This saves them the costs of training their techs on various
'alternative' OSes. Buyer beware!
</Para>
<Para>
Basically all DSL does, is facilitate a high speed Internet connection. At
some point, it is all TCP/IP, and Linux, of course, handles TCP/IP quite
well.
</Para>
</ListItem>
<ListItem>
<Para>
Q. Where can I find drivers for my PCI (or USB) modem?
</Para>
<Para>
As of this moment, you probably can't, because they are not available. You
need an external, ethernet interfaced modem for all intents and purposes.
If your provider does not offer one, you will have to find another
provider, or buy your own modem outright. Just make sure it is compatible
with your provider's flavor of DSL.
</Para>
<Para>
If an incompatible modem puts you in a bind, hopefully you will take the
time to politely harass the manufacturer :-).
</Para>
<Para>
This situation will likely change soon however. <Ulink
URL="http://www.efficient.com">Efficient Networks</Ulink> is in late Beta
stages with their SpeedStream 3060/3061 PCI drivers. Others will likely
follow suit. (Make sure you are reading the latest version of this
document, as I have intentions of keeping this situation updated as
needed.)
</Para>
</ListItem>
<ListItem>
<Para>
Q. How fast or good of a network card do I need?
</Para>
<Para>
Any card that is compatible with Linux should work fine. Remember even
low-end cards are 10 Mbps, and no consumer class DSL is near that at this
time. I would suggest a reasonably good quality card, just to help
eliminate the possibility of errors and premature failure.
</Para>
</ListItem>
<ListItem>
<Para>
Q. How can I find out when DSL will be available in my area?
</Para>
<Para>
Just where and when DSL gets deployed is totally in the hands of
your friendly local telco. They obviously can't do everyone at
once, so they probably are selecting areas based on competitive
factors. Getting a straight answer from a telco on this question
can also be a challenge. Probably so as not to tip their hand to
competitors. Unfortunately, it is a question only they can answer.
</Para>
</ListItem>
<ListItem>
<Para>
Q. I was disqualified because I am too far away. What can I do?
</Para>
<Para>
Move? Seriously, there isn't much you can do. If there are other providers,
get another opinion. You never know. Determining the loop length is an
inexact science, and there is room for errors. Many use databases for
this, and these databases routinely have some inaccuracies. Some providers
too, may be more aggressive in taking steps to help you out and clean up
the line. Also, some providers offer low-end speed services that have
greater reach. Maybe this will become available in your area. Or, the telco
will install, at some point, remote devices for customers who are now too
far away.
</Para>
</ListItem>
<ListItem>
<Para>
Q. What are the speed tweaks for Linux?
</Para>
<Para>
There aren't any really. Linux is pre-tweaked, unlike some versions of
Windows that really need some registry hacks to get optimum performance.
</Para>
<Para>
Now if you are convinced you are not getting the performance you should
based on your distance and line conditions, then maybe there is a problem
somewhere. See the <Link LinkEnd="tuning">Troubleshooting</Link> section for
more. What you need is a fix, more than a tweak.
</Para>
</ListItem>
<ListItem>
<comment>Perhaps make it clear that 640K is an example, or just
use some "variable" instead of 640K.</comment>
<Para>
Q. My service is limited to 640K. Can I get better speed by getting a
faster modem? Any way around this?
</Para>
<Para>
No, and no. The modem has little bearing on how fast your connection is for
all intents and purposes. The provider has a mechanism in place for
limiting your speed somewhere in the pipe before you hit the Internet.
There is no way to defeat this.
</Para>
</ListItem>
<ListItem>
<Para>
Q. I am paying for 768 Kbps service, and the best I ever get is 640 Kbps or
so. Why? Is the service oversold? I am not getting what I pay for.
</Para>
<Para>
You will lose 10-20% of the rated capacity due to networking overhead. This
is just a fact of life for everybody. Just how much is lost here depends on
a number of factors, and may vary from provider to provider. You seem to be
close to your maximum when this is taken into consideration. Also, if you
read the fine print, many ISPs are advertising speeds 'up to' such and
such. Check your service agreement and see if there are any guarantees. If
there are, they probably are well below the advertised maximum speed.
</Para>
<Para>
Also, be careful how you test this. Some of the so-called test sites can be
pretty unreliable. There can be many factors between you and that site that
can impact your throughput and skew results -- not the least of which is
how many people might be trying that same test at the same time. The best
test is via FTP download from a known good, close site.
</Para>
</ListItem>
<ListItem>
<Para>
Q. Why does PPPoX have such a bad rap?
</Para>
<Para>
The tendency to abruptly disconnect is one of the biggest gripes. PPP is
sensitive to any interruptions in the connection. Generally a disconnect
means a new IP. And there are those that say PPP, by its very nature, was
never meant to be an 'always on' protocol. PPP is a session management
protocol at heart, that requires a user to initiate a connection and
authenticate him or herself. PPPoE/A are not particularly mature protocols
either. They do not have much of a history or track record. Some would say
the telcos and hardware manufacturers have rushed this out the door. PPPoE
also requires an additional layer of software just to maintain the
connection. This is one more layer of code and one more potential point of
failure. Also, more system overhead is utilized to manage the connection.
</Para>
</ListItem>
<ListItem>
<Para>
Q. Why PPPoX? This seems like a bad idea!
</Para>
<Para>
PPP gives several advantages to the provider: they can use their existing
infrastructure and hardware that they now use for their (larger) dialup
customer base. It is easier to control user authentication and potential
abuse situations, and easier to manage their network and related issues. In
fact, it most boils down to its just easier for them. Easier, means saves
man hours, and therefore saves costs (at least from their perspective).
</Para>
<Para>
It is not a conspiracy to conserve IP addresses, or thwart heavy users. IP
address costs are insignificant in the overall scheme of things.
</Para>
<comment>In case you're not aware, it's illegal to sell or lease
IP addresses. Most ISPs get around this via a "service charge"
associated with having multiple IPs. </comment>
</ListItem>
<ListItem>
<Para>
Q. The only provider in my area does not support Linux. What can I do?
Will I have to use Windows?
</Para>
<Para>
NO! 'Support' here is support as in 'tech support'. They are just saying
that they will not give you tech support when and if you have problems.
This does not mean you cannot use Linux on their network. Just that you may
have to fend for yourself when and if a problem does arise. Anything that
is forbidden will be in their Acceptable Use Policy (AUP), or Terms of
Service (TOS) agreement.
</Para>
<Para>
I have heard stories where a new tech or installer has misinterpreted their
own company's policy on this and told someone 'you can't use Linux here'.
Same with NT server. But this is almost always a misinformed individual.
</Para>
<Para>
But -- if a provider does not support Linux, they may balk at installing
onto a Linux box. Hopefully, they will have a self-install option to get
around this annoyance. YMMV.
</Para>
</ListItem>
<ListItem>
<Para>
Q. My fax software does not work with my DSL modem. Why is that?
</Para>
<Para>
Faxes are normally transmitted over typical analog phone lines by dialing
the fax machine on the other end. Analog modems can handle this, but
DSL modems have no dialing capability. Don't throw out that 56K yet!
</Para>
</ListItem>
<ListItem>
<Para>
Q. How fast and powerful of a computer do I need for DSL? My ISP says I
need at least a Pentium 200.
</Para>
<Para>
At the most basic level, a 386 will work fine. In most situations, you are
connected to what is essentially an ethernet based network. So
theoretically anything that can handle a very slow ethernet connection
would work. No comment on well Netscape will run on a 386 though ;-) But as
far as managing the connection, a 386 is indeed workable. What else you
can do with it is another matter.
</Para>
<Para>
Where this gets a little more complicated is the modem, and the client
that the ISP may require. Any PCI or USB modem is going to require
drivers, which means more CPU and system resources. Also, PPPoE does even
more processing, so again the potential CPU load is increased. Windows
tends to be not so efficient with all this going on, hence the requirement
for mid range Pentiums by some ISPs.
</Para>
<Para>
With Linux it will depend on what you are going to do. A low end Pentium
should be fine for most uses. Just remember if you are running PPPoE, you
may take a performance hit on low end hardware.
</Para>
</ListItem>
<ListItem>
<Para>
Q. I just got my DSL installed, and my speed sucks, and/or my connection
constantly drops. What is the problem?
</Para>
<Para>
Not enough information to say, really. There are many, many things that
can cause a lousy connection. The list is too long to mention them all.
</Para>
<Para>
One of DSL's weaknesses is that the signal can be fairly fragile. Many
things can degrade the signal, making for poor connections, and thus
speed. This can be caused by poor or substandard inside wiring, a wiring
problem outside (like bad splice), RFI from any number of sources, AM
radio signal interference, excessive distance from the DSLAM. Not to
mention possible hardware problems with your modem, NIC, or the telco's
DSLAM, etc. Not always easy to sort out.
</Para>
<Para>
Your provider should be able to assist you. First, make sure the problem
isn't with your setup as they likely won't help solve a Linux problem. Then
be persistent, and don't hesitate to go over someone's head if the help is
not forthcoming. Most problems are solvable. The trick is isolating it. A
good telco tech, trained for DSL, can find all kinds of obscure wiring
problems.
</Para>
</ListItem>
<ListItem>
<Para>
Q: Are there ADSL Standards?
</Para>
<Para>
A: Sort of. The U.S. Bell Operating Companies have standardized on Discrete
Multi-Tone (DMT) (ANSI T1.413) in their current rollout. Most others
should follow their lead in the states. There are other types of modems, most
notably Carrier-less Amplitude Phase Modulation (CAP), which of course, is
incompatible with DMT.
</Para>
<Para>
A biased comparison from an DMT-based vendor on this subject can be found at
the <ULink URL="http://www.aware.com">http://www.aware.com</ULink>. Still,
it provides the best detail on this issue I have seen so far.
</Para>
<Para>
A rather expensive copy of the ANSI standard can be ordered at: American
National Standards Institute <ULink URL="http://www.ansi.org">ANSI Home
Page</ULink>
</Para>
<Para>
Asymmetric Digital Subscriber Loop (ADSL) Metallic Interface
</Para>
<Para>
ANSI TI.413-1995
</Para>
<Para>
Note: ANSI TI.413 Issue 2 was released September 26, 1997
</Para>
</ListItem>
<ListItem>
<Para>
Q: Can I use ATM to connect to DSL?
</Para>
<Para>
A: Technically speaking, you can. Some DSL modems (at least the Alcatel
version) has a ATM Forum 25Mbps interface, which connects to a PCI ATM
card. See <Ulink
URL="http://lrcwww.epfl.ch/linux-atm/">http://lrcwww.epfl.ch/linux-atm/</Ulink>
for more details.
</Para>
</ListItem>
<ListItem>
<Para>
Q: Why does DSL have all these bit rates (384/1.5/7.1M/20M/etc) options?
</Para>
<Para>
A: The basic problem is the 100 year old design of the copper loop. It works
great for analog phone, but it presents a real challenge for a digital
signal. Remember that the distance of a loop is inversely proportional to the
data rate that it can carry. Rate adaptive technologies are great for making
a digital signal work in many situations, but it can't provide a consistent
bandwidth for all applications, especially for very long (over 18,000 ft)
loops. The different bandwidths that you see advertised reflect various
marketing wars of vendors equipment, and the telco struggle to finalize on a
'standard' set of data rates. The bottom line is for the telco to be able
to reach as broad a customer base as possible.
</Para>
<Para>
Check out the next question on the loop impairments that cause this to
happen.
</Para>
</ListItem>
<ListItem>
<Para>
Q: What are all these loop impairments (bridge taps, load coils, DLCs) that
could disqualify my line from DSL? (thanks to Bruce Ediger)
</Para>
<comment>A consistent definition format is needed here. I'd use
a variablelist, but it doesn't really matter as long as you use
the same format for all of the definitions.</comment>
<Para>
Load coils: in-line inductances that improve voice-frequency transmission
characteristics of a telephone circuit. Essentially, a "load" steals energy
from high frequencies and gives it to lower frequencies. Typically only used
in very long (&gt;9,000 ft) phone lines.
</Para>
<Para>
By "bridges" I assume you mean "bridged taps". In older neighborhoods, the
phone wiring will have been used by more than one customer. Perhaps these
customers lived at different (though near-by) addresses. The unconnected
"spur" of wiring is a "bridged tab" on the currently connected circuit.
</Para>
<Para>
DLCs, Digital Loop Carriers: there's a bunch of systems for carrying more
than one voice transmission on a single pair of wires. You can shift the
frequencies up or down, or you can digitize the voice transmissions and
divide the telephone circuit by time or code or something. The more
general term is "pair gain".
</Para>
<Para>
These things cause different problems for high-frequency communications.
</Para>
<Para>
Load coils will completely mess up things by filtering high frequencies and
passing low frequencies. They probably also change the "delay envelope",
allowing some frequencies to arrive before others. One byte's tones will
interfere with the next byte's.
</Para>
<comment>This next paragraph is Greek to me. Well, maybe just
Russian. :-) In any case, it's certainly geek...</comment>
<Para>
Bridged taps act as shunt capacitances if they're long in relation to the
signals wavelength, and they'll actually act as band pass filters if they're
about 1/4 wavelength of the signal. That is, they'll pass particular
frequencies freely. Particular tones of a DMT modem might get shunted back,
rather than passed along to the receiving modem, reducing bandwidth for that
telephone line.
</Para>
<Para>
Pair gain, digital or analog, limit the bandwidth available to one
transmission in order to multiplex several on one wire. High and low tones
of a DMT transmission get filtered out by the apparatus.
</Para>
<Para>
The book "Subscriber Loop Signaling and Transmission Handbook", by Whitham D.
Reeve, , IEEE Press 1992, ISBN 0-87942-274-2 covers the math of how to
calculate the effect of line length, bridged tap, etc on the transmission
characteristics of a telephone line. It's pretty expensive, however.
</Para>
</ListItem>
<ListItem>
<Para>
Q: Do you have examples of DSL Modems?
</Para>
<Para>
A: Short Answer: Yes. Real Answer: The evolution of this technology is
moving too rapidly for anyone to keep up to date in a HOWTO. A good source
of ADSL Modems is the ADSL Forum Home Page at <ULink
URL="http://www.adsl.com">http://www.adsl.com</ULink>. Go to the Vendors
pages to see what's happening. Also, check <Ulink
URL="http://dslreports.com/information/equiprated/all">http://dslreports.com/information/equiprated/all</Ulink>.
</Para>
<comment>Is this really as of June 1998?</comment>
<Para>
However, I will provide a list of some of the current technology as of June
1998. All are ADSL 'modems' with 'DMT' encoding (a.k.a. Alcatel
compatible), unless specified otherwise. [Updated Aug 2000.]
</Para>
<Para>
<ItemizedList>
<ListItem>
<Para>
Router/Modems with 10/100baseT Ethernet Interface:
</Para>
<Para>
Examples: Flowpoint 2000 DSL(CAP), 3COM Viper-DSL (CAP), Westell
ATU-R-Flexcap (CAP), Aware x200, Zyxel P641, Efficient Networks
SpeedStream 5660, Cayman 3220H, Cisco 673 (SDSL), Cisco 675 (ADSL/CAP),
Cisco 677 (ADSL/DMT), Alcatel SpeedTouch Pro.
</Para>
</ListItem>
<ListItem>
<Para>
Bridge/Modems with 10/100baseT Ethernet Interface:
</Para>
<Para>
Examples: Alcatel 1000, Alcatel SpeedTouch Home [note: there are also USB
and PCI versions of this one!], Westell ATU-R-Flexcap2 (CAP), Efficient
Networks SpeedStream 5260, Efficient Networks SpeedStream 5251 (SDSL),
Westell WireSpeed.
</Para>
</ListItem>
<ListItem>
<Para>
Modems with ATMF Interface:
</Para>
<Para>
Examples: Alcatel 1000, Alcatel SpeedTouch Home, Cisco 627 (DMT), Ariel
Horizon II
</Para>
</ListItem>
<ListItem>
<Para>
Bridge/Modems with V.35 Serial Interface (T1, Serial Router)
</Para>
<Para>
Examples: Westell ATU-R
</Para>
</ListItem>
<ListItem>
<Para>
Modems with USB Interface:
</Para>
<Para>
Efficient Networks SpeedStream 4060, Intel 3100
</Para>
</ListItem>
<ListItem>
<Para>
PCI Modems:
</Para>
<Para>
Examples: Cisco 605, Efficient Networks SpeedStream 3060/3061, Intel 2100
</Para>
</ListItem>
<ListItem>
<Para>
Dedicated Router (no built in modem) with 10/100baseT Ethernet Interface:
</Para>
<Para>
Examples: Netgear RT311
</Para>
</ListItem>
</ItemizedList>
</Para>
</ListItem>
</OrderedList>
</Para>
<Para>
This is but a very small sampling. It should not be construed as
endorsements of the products lists. It is just a simple illustration
of some of the available products.
</Para>
</Sect1>
<!-- ~ End Section ~ -->
<!-- ~~~~~~~~ New Section Header ~~~~~~~~~ -->
<Sect1 id="appendix">
<Title>Appendix: Miscellaneous</Title>
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2 id="links">
<Title>Links</Title>
<comment>At some point, it might be nice to break these links up
into categories.</comment>
<Para>
<ItemizedList>
<ListItem>
<Para>
Other related documentation from the Linux Documentation Project:
</Para>
<Para>
<ItemizedList>
<ListItem>
<Para>
<Ulink URL="http://www.linuxdoc.org/HOWTO/Firewall-HOWTO.html">Firewall HOWTO</Ulink>
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink URL="http://www.linuxdoc.org/HOWTO/Security-HOWTO.html">Security HOWTO</Ulink>
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink URL="http://www.linuxdoc.org/HOWTO/IPCHAINS-HOWTO.html">IPCHAINS HOWTO</Ulink>
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink URL="http://www.linuxdoc.org/HOWTO/IP-Masquerade-HOWTO.html">IP Masquerade HOWTO</Ulink>
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink URL="http://www.linuxdoc.org/HOWTO/mini/Home-Network-mini-HOWTO.html">Home Network mini HOWTO</Ulink>
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink URL="http://www.linuxdoc.org/HOWTO/Ethernet-HOWTO.html">Ethernet HOWTO</Ulink>
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink URL="http://www.linuxdoc.org/HOWTO/Networking-Overview-HOWTO.html">Networking Overview HOWTO</Ulink>
</Para>
</ListItem>
<ListItem>
<comment>Hmm, I'd like to see either summaries with the
HOWTOs, or no summaries with the HOWTOs. They should be
easily enough stolen from the HOWTO-INDEX, if you want to
include them.</comment>
<Para>
<Ulink URL="http://www.linuxdoc.org/HOWTO/Net-HOWTO/">Net HOWTO</Ulink>,
previously named the NET3-4-HOWTO, the definitive guide to various Linux
networking topics.
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink URL="http://www.linuxdoc.org/HOWTO/Adv-Routing-HOWTO.html">Linux
2.4 Advanced Routing HOWTO</Ulink>. All the new, improved features are
explained here.
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink URL="http://www.linuxdoc.org/HOWTO/mini/DHCP/">DHCP HOWTO</Ulink>
</Para>
</ListItem>
</ItemizedList>
</Para>
</ListItem>
<ListItem>
<comment>FIXME: Greg: go through this nested list, and re-format
it for easier reading. Hal, don't worry about this
comment.</comment>
<Para>
More on the 2.4 kernel packet filtering from The Netfilter Project at <Ulink
URL="http://netfilter.kernelnotes.org/">http://netfilter.kernelnotes.org/</Ulink>.
Several good HOWTOs for the new features in 2.4.
</Para>
</ListItem>
<ListItem>
<Para>
Check your security and see what ports are open at
<Ulink
URL="http://hackerwhacker.com/">http://hackerwhacker.com/</Ulink>. This
is one of the better sites for this. Some only test a relatively few
ports.
</Para>
</ListItem>
<ListItem>
<Para>
SuSE's Linux PPPoE page is at <Ulink
Url="http://www.suse.de/~bk/PPPoE-project.html">http://www.suse.de/~bk/PPPoE-project.html</Ulink>.
Good information on most of the available Linux PPPoE implementations.
</Para>
</ListItem>
<ListItem>
<Para>
Bob Carrick's definitive PPPoE site is at <Ulink
Url="http://www.carricksolutions.com/">http://www.carricksolutions.com/</Ulink>.
His Linux PPPoE page is at <Ulink
URL="http://www.carricksolutions.com/linuxpppoe.htm">http://www.carricksolutions.com/linuxpppoe.htm</Ulink>.
It has some other DSL related information as well. All OSes are covered.
</Para>
</ListItem>
<ListItem>
<Para>
The NTS EnterNet for Linux FAQ can be found at <Ulink
URL="http://www.nts.com/support/FaqEnterNetLinux.html">
http://www.nts.com/support/FaqEnterNetLinux.html</Ulink>. This is a
non-GPL'd PPPoE client that is distributed by some ISPs.
</Para>
</ListItem>
<ListItem>
<Para>
A white paper from Redback on the technology and rationale behind PPPoE can
be found at
<Ulink
URL="http://www.redback.com/frameset.asp?page=whitepp/wp_pppoe_comparison.html">http://www.redback.com/frameset.asp?page=whitepp/wp_pppoe_comparison.html</Ulink>.
This is how the ISPs see it. (Redback is the leading manufacturer of PPPoX
termination routers.)
</Para>
</ListItem>
<ListItem>
<Para>
ATM on Linux: <Ulink URL="http://lrcwww.epfl.ch/linux-atm/">
http://lrcwww.epfl.ch/linux-atm/</Ulink>. Where to find the latest info on
PPPoA and raw ATM connections.
</Para>
</ListItem>
<ListItem>
<Para>
A step by step report on getting Linux going with raw ATM is here: <Ulink
URL="http://linux.com.sg/news/atm/">http://linux.com.sg/news/atm/</Ulink>.
</Para>
</ListItem>
<ListItem>
<Para>
An open source project based on the Alcatel SpeedTouch Home USB modem can be
found at <Ulink
URL="http://kapu.name.daemon.xs4all.be:8080/Projects/">http://kapu.name.daemon.xs4all.be:8080/Projects/</Ulink>. This is a beta project that requires 2.4 kernel
and patches.
</Para>
</ListItem>
<ListItem>
<Para>
FreeSwan, <Ulink
URL="http://www.freeswan.org">http://www.freeswan.org</Ulink>, is an
IPSec & IKE VPN implementation for Linux.
</Para>
</ListItem>
<ListItem>
<Para>
VPN and Masquerading on Linux: <Ulink URL="http://www.wolfenet.com/~jhardin/ip_masq_vpn.html">http://www.wolfenet.com/~jhardin/ip_masq_vpn.html</Ulink>
</Para>
</ListItem>
<ListItem>
<Para>
PPTP-linux allows you to connect to a PPTP server with Linux. The home page is
<Ulink URL="http://cag.lcs.mit.edu/~cananian/Projects/PPTP/">http://cag.lcs.mit.edu/~cananian/Projects/PPTP/</Ulink>.
</Para>
</ListItem>
<ListItem>
<Para>
Justin Beech's
<Ulink Url="http://dslreports.com">http://dslreports.com</Ulink>, a great
site for anything and everything related to DSL. If it's not there, then
there is a link to it. (Site runs on Linux.)
</Para>
</ListItem>
<ListItem>
<Para>
John Navas's Cable and DSL site, <Ulink
Url="http://cable-dsl.home.att.net">http://cable-dsl.home.att.net</Ulink>,
has good general info, tweaks, troubleshooting, hardware info, etc. for
all OSes.
</Para>
</ListItem>
<ListItem>
<Para>
TCP Performance Tuning tips: <Ulink
URL="http://www.psc.edu/networking/perf_tune.html">
http://www.psc.edu/networking/perf_tune.html</Ulink>. Tips on Linux, and
other OSes.
</Para>
</ListItem>
<ListItem>
<Para>
A great Linux security site is <Ulink
URL="http://linux-firewall-tools.com/linux/">
http://linux-firewall-tools.com/linux/</Ulink>. Lots of info from Robert
L. Ziegler, author of <CiteTitle>Linux Firewalls</CiteTitle>. Many links
to other security related sites as well.
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink URL="http://www.securityportal.com/lasg/">
http://www.securityportal.com/lasg/</Ulink>, The Linux Administrator's
Security Guide by Kurt Seifried. Good tutorials on a variety of
topics -- not just firewalls, but the big picture.
</Para>
</ListItem>
<ListItem>
<Para>
The Seattle firewall is an ipchains based firewall that can be used on a
dedicated masquerading firewall machine (including LRP), a multi-function
masquerade gateway/server or on a standalone Linux system. The project is
located at <Ulink
URL="http://seawall.sourceforge.net/">http://seawall.sourceforge.net/</Ulink>
</Para>
</ListItem>
<ListItem>
<Para>
My ipchains script is at <Ulink
URL="http://personal.bellsouth.net/~hburgiss/linux/ipchains.html">
http://personal.bellsouth.net/~hburgiss/linux/ipchains.html</Ulink>.
This has IP Masquerading already set up, is reasonably well commented, and
may make a quick starting point for your own script with only
minor adjustments to suit your situation.
</Para>
</ListItem>
<ListItem>
<Para>
Now that you have a full-time connection, want a routable hostname for
your computer? Dynamic DNS services can do this, even if your IP changes from
time to time. A few of the available services:
</Para>
<Para>
<ItemizedList>
<ListItem>
<Para>
<Ulink URL="http://dyndns.org">http://dyndns.org</Ulink>
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink URL="http://tzo.org">http://tzo.org</Ulink>
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink URL="http://eyep.net">http://eyep.net</Ulink>
</Para>
</ListItem>
</ItemizedList>
</Para>
</ListItem>
<ListItem>
<Para>
ADSL Forum Home Page: <ULink
URL="http://www.adsl.com">http://www.adsl.com</ULink> A comprehensive web
site created by the ADSL vendors. Fairly complete for reference information
on ADSL.
</Para>
</ListItem>
<!--
Way out of date. 1996.
<ListItem>
<Para>
<ULink URL="http://www.alumni.caltech.edu/~dank/isdn/adsl.html">Dan Kegels
ADSL Page</ULink> A good general reference on DSL - includes vendor,
service provider, and other links. This page was getting a little long in
the tooth as of 2Q98. Dan also maintains a super page on ISDN.
</Para>
</ListItem>
-->
<!--
Leaving this out for now, until more can be included. HB Sun 09/03/00 02:19:22
PM
<ListItem>
<Para>
<ULink
URL="http://www.pacbell.com/products/business/fastrak/adsl/index.html">PacBell's
ADSL Page</ULink> Pacific Bell is the local Telco and my provider of ADSL
service (DF).
</Para>
</ListItem>
-->
<ListItem>
<Para>
<ULink URL="http://conk.com/world/dsl/">ADSL
Deployment 'round the World</ULink> Claims to have a complete list -
looked accurate for my area - gives providers, prices, speeds, etc.
</Para>
</ListItem>
<ListItem>
<Para>
<ULink
URL="http://homepage.interaccess.com/~jkristof/xdsl-faq.txt">comp.dcom.xdsl
FAQ</ULink>. Actively maintained, and a great technical reference for DSL
technologies.
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink Url="news://comp.dcom.xdsl">comp.dcom.xdsl</Ulink>, DSL discussions,
vents, and flames on Usenet. Good place to get technical questions answered
that your ISP can't.
</Para>
</ListItem>
</ItemizedList>
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2 id="glossary">
<Title>Glossary</Title>
<comment>There are a bunch of tags designed for marking up
glossaries. Take a look at
http://www.docbook.org/tdg/html/glossary.html and some of the
pages following it.</comment>
<Para>
A dictionary of some of the jargon used in this Document, and in the
telco and DSL industries.
</Para>
<Para>
<VariableList>
<VarListEntry>
<Term>ADSL</Term>
<ListItem>
<comment>Is ADSL still the most popular? How are you
determining popularity?</comment>
<Para>
Asymmetric Digital Subscriber Loop. 'Asymmetric' in that the downstream
potential is greater than the upstream. ADSL is capable of sharing on
a single POTS wire pair. Maximum speed is 8 Mbps, though typically is
limited by the provider to lesser speeds. The most popular DSL at this
time.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>ANT</Term>
<ListItem>
<Para>
ADSL Network Termination (a.k.a. the ADSL modem).
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>ARP</Term>
<ListItem>
<Para>
Address Resolution Protocol. Converts MAC addresses to IP addresses.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>ASAM</Term>
<ListItem>
<Para>
Alcatel's terminology for a DSLAM.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>ATM</Term>
<ListItem>
<Para>
Asynchronous Transfer Mode - provides high-speed packet switching from 155
Mbps to (currently) 2Gbps. Used to provide backbone switching for the
Internet.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>ATMF-25Mbps</Term>
<ListItem>
<comment>ANT? Pick a term, si vous plait. I realize this one
is taken from the miniHOWTO :-)</comment>
<Para>
ATM Forum Interface - 25Mbps speed, provided by a PCI NIC card.. One of the
interfaces used between the ANT and PC.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>brouter</Term>
<ListItem>
<Para>
A combination DSL modem that can be configured to act as either a bridge
or a router.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>CAP</Term>
<ListItem>
<Para>
Carrierless Amplitude Phase. A proprietary ADSL line encoding technique,
that is (or was) in competition with 'DMT'. DMT has won the standards
battle. CAP and DMT modems are not compatible with each other.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>Central Office, or CO</Term>
<ListItem>
<Para>
Usually refers to one of two meanings -1) The local Telco building that
houses telephone equipment, and where local loops terminate 2) The Telco
voice switch that provides dial tone. Often referred to as just 'CO'.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>CLEC</Term>
<ListItem>
<Para>
Competitive Local Exchange Carrier. 'Competitors' to the ILECs. They do
not own any lines, and must lease their lines from ILEC in order to
provide any service.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>CPE</Term>
<ListItem>
<Para>
Customer Premises Equipment - The Telco term for customer owned equipment
(i.e. the stuff you are responsible for fixing). Examples are CSU/DSU,
modems, fax machines, and your phone.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>DHCP</Term>
<ListItem>
<Para>
Dynamic Host Configuration Protocol - A protocol used to distribute
dynamically assigned IP addresses and other important networking
parameters. The DHCP server 'leases' an IP from its pool to clients on
request. The lease is renewed at regular intervals. This is a common
protocol on 'bridged' DSL networks.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>DMT</Term>
<ListItem>
<Para>
Discrete Multitone Technology. This is a line encoding common among ADSL
deployments, and now is the standard. Sometimes referred to as 'Alcatel
compatible'. Most telcos in the U.S. are now standardizing on DMT.
The other, less common, ADSL encoding is 'CAP'. CAP and DMT modems are
incompatible with each other.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>DS0</Term>
<ListItem>
<Para>
The basic digital circuit for Telcos - offered at 56 kbps or 64kbps. Can
support one analog voice channel.
</Para>
<comment>Don't you love Telco? A digitized voice quality
signal only needs 8Kbps.</comment>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>DSLAM</Term>
<ListItem>
<Para>
Digital Subscriber Loop Access Multiplexer - The Telco equipment installed
at the CO that concentrates and multiplexes the DSL lines. One end of the
copper loop connects to the DSLAM, the other to your modem. The DSLAM
is essentially what makes DSL work.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>DSL</Term>
<ListItem>
<Para>
Digital Subscriber Loop - A term describing a family of
DSL services, including ADSL, SDSL, IDSL, RADSL, HDSL, VDSL, SHDSL, etc.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>G.DMT</Term>
<ListItem>
<Para>
Synonymous with 'full rate' ADSL. Used to distinguish between full rate
ADSL, and G.Lite. See <Link LinkEnd="family">DSL Family</Link> for more.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>G.Lite</Term>
<ListItem>
<Para>
A lesser version of ADSL that has lower maximum speeds, and requires no
splitter or filters. Not DMT compatible. See <Link LinkEnd="family">DSL
Family</Link> in this HOWTO for more. </Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>HDSL</Term>
<ListItem>
<Para>
High bit rate DSL. See <Link LinkEnd="family">DSL Family</Link> in
this HOWTO for more.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>ILEC</Term>
<ListItem>
<Para>
Incumbent Local Exchange Carrier. The Regional phone company that
physically owns the lines. Examples: Bell Atlantic and U.S. West. FCC
regulations are forcing the ILECs to open up their networks to independent
providers. This is allowing the independents like Covad and Rhythms to
offer competitive services. This is a good thing for consumers IMHO.
</Para>
<comment><quote>U.S. West is not Qwest</quote>, just ask
them.</comment>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term><acronym>ISDN</acronym></Term>
<ListItem>
<Para>
Innovations Subscribers Don't Need; I Still Don't kNow; or maybe Integrated
Services Digital Network, a digital phone service that uses a single
copper pair to run 2B (64k) + 1D(16k) channels that can be used for
switched voice or data.
</Para>
<comment>Sometimes ISDN is sold for "consumer" use as dual 56K
channels, plus a 16K data channel.</comment>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>IP</Term>
<ListItem>
<Para>
Internet Protocol. Often used to simply refer to an IP address.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>ISP</Term>
<ListItem>
<Para>
Internet Service Provider.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>LAN</Term>
<ListItem>
<Para>
Local Area Network. A network of computers that are segregated from the
WAN (Wide Area Network, i.e. the Internet). Typically using private,
non-routable IP addressing, e.g. 192.168.1.1 or 10.0.0.1.
</Para>
<comment>Actually, I have my doubts about "typically" using
private IPs, although more and more are going that way. It
should be less of an issue if IPv6 ever gets going.</comment>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>Loop</Term>
<ListItem>
<Para>
The two wire twisted pair from the telco Central Office that terminates at
a customer location. For DSL, a 'clean' copper loop within the distance
limitations is required.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>MAC Address</Term>
<ListItem>
<comment>Not 100% sure on this one, but I think it's supposed
to be MAC address.</comment>
<Para>
Media Access Control Address. Sometimes also called 'hardware' address, it is a
unique identifier of network devices and is an important aspect of some
network environments.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>mini-RAM</Term>
<ListItem>
<Para>
Remote Access Multiplexer, a mini DSLAM. Typically with very few
connections -- eight is common. Used for remote areas too far from a CO.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>MTU</Term>
<ListItem>
<Para>
Maximum Transmission Unit, the largest packet size, measured in bytes,
that a network can transmit. Any packets larger than the MTU are divided
into smaller packets before being transmitted.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>NAT</Term>
<ListItem>
<Para>
Network Address Translation. A means of allowing computers on a LAN with
private, non-routable address to access the WAN while 'masquerading' with
the IP address of a host with a suitable address and configuration. With
Linux this is called 'ip-masquerading'.
</Para>
<comment>NAT does not require that 1 side is non-routable IP
addresses. It's quite possible to do NAT with any IPs that you
like. Also, there is such a thing as "static NAT", which is a
direct mapping of one IP address to another.</comment>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>NID</Term>
<ListItem>
<Para>
Network Interface Device - The telco housing on the side of your house.
Typically where the telco's responsibility ends, and the owner's begins.
Also, called the 'SNI'.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>NIC</Term>
<ListItem>
<Para>
Network Interface Card - A PC card (PCI/ISA) that supports the required
network interface. Usually an Ethernet 10baseT or an ATMF-25Mbps Card..
</Para>
<comment>There are many other buses that could be used for a
network card, including SBUS, EISA, MCA (microchannel), EIO,
and bazzillions more. I don't think that anybody is still
making pure 10baseT cards anymore, and if so, I can't imagine
why. 10/100 cards are so cheap that they should be
ubiquitous.</comment>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>NSP</Term>
<ListItem>
<Para>
Network Service Provider. An ISP's upstream provider or backbone
provider.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>OC-3</Term>
<ListItem>
<Para>
A fiber optic line capable of 155 Mbps.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>POTS</Term>
<ListItem>
<Para>
Plain Old Telephone Service - The service that provides a single analog
voice line (i.e. a traditional phone line).
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>PPPoA</Term>
<ListItem>
<Para>
Point-to-Point Protocol over ATM (RFC 2364). One of the PPP protocols
being used by some ISPs. Linux support is beta at this particular
moment. May be changing very soon. A hardware device, i.e. a combination
modem/router, is one alternative if this is the only option available to
you.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>PPPoE</Term>
<ListItem>
<Para>
Point-to-Point Protocol over Ethernet (RFC 2516). Another PPP protocol in
use by providers. This one is more common, and there are several Linux
clients available. See the <link LinkEnd="links">Links section</link> for
more.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>PPPoX</Term>
<ListItem>
<Para>
Used to refer to PPPoE and PPPoA collectively.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>RADSL</Term>
<ListItem>
<Para>
Rate Adaptive DSL. See <Link LinkEnd="family">DSL Family</Link> in
this HOWTO for more.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>RBOC</Term>
<ListItem>
<Para>
Regional Bell Operating Company. The 'Baby Bells'. The U.S. phone
companies that have had a state sponsored monopoly since the break up of
AT&amp;T.
</Para>
<comment>FIXME: ask Greg Ferguson if the numeric entities or
the named ones work better</comment>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>RFI</Term>
<ListItem>
<Para>
Radio Frequency Interference. DSL is susceptible to RFI if in the right
frequency range, and if close enough to the DSL signal.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>SDSL</Term>
<ListItem>
<Para>
Single Line DSL. Also, sometimes erroniously 'Symmetric DSL'. See <Link
LinkEnd="family">DSL Family</Link> for more.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>SNI</Term>
<ListItem>
<Para>
Subscriber Network Interface - The Telco term for the phone wiring housing
on the side of your house. It designates the point between the Telco side
and the Inside Wire. This is also called the Demarcation Point. Sometimes
called a 'NID' also.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>Splitter</Term>
<ListItem>
<Para>
The passive device (low-bandpass filter) at or near the SNI/SNI that
splits the DSL signal into separate voice and data channels. Typically
installed near the demarcation point.
</Para>
<comment>Which term is being used for the demarcation
point?</comment>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>Splitterless</Term>
<ListItem>
<Para>
A DSL installation that does not require a splitter. For higher
speeds, a RJ11 filter (sometimes called microfilters) is placed on every
extension phone jack where an analog phone or other non-DSL device is
used, thus filtering the DSL signal at the jack, rather than at the
SNI/NID. For lower speeds, no filter is necessary. Without a filter or
splitter, the DSL signal tends to cause audible interference on voice
phones. G.Lite needs no splitter, nor filter, but this is the exception to
the rule.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>SOHO</Term>
<ListItem>
<Para>
Small Office/Home Office
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>T-DSL</Term>
<ListItem>
<Para>
German Telekom's ADSL implementation. See <Link LinkEnd="family">DSL
Family</Link> for more.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>T1</Term>
<ListItem>
<Para>
a.k.a DS1 - A digital dedicated line at 1.544 Mbps comprised of 24
channels, used for both voice (24 DS0s) and data.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>T3</Term>
<ListItem>
<Para>
a.k.a DS3 - T1's big brother, a digital dedicated line at 44.736 Mbps,
used for both voice (672 DS0s or 28 DS1s) and data.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>VCI/VPI</Term>
<ListItem>
<Para>
VCI is 'Virtual Circuit Identifier' and is part of an ATM cell header. VPI
is 'Virtual Path Identifier', also part of an ATM cell header which
contains circuit information. These are both important configuration
aspects for modems and routers. They must match what the provider is
using. Frequently used VPI/VCI pairs are 0/32 or 8/35.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>VDSL</Term>
<ListItem>
<Para>
Very high bit rate DSL. See <Link LinkEnd="family">DSL Family</Link> for
more.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>VoD</Term>
<ListItem>
<Para>
Video on Demand.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>VoDSL</Term>
<ListItem>
<Para>
Voice over DSL.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>WAN</Term>
<ListItem>
<Para>
Wide Area Network. For example, the Internet.
</Para>
</ListItem>
</VarListEntry>
<VarListEntry>
<Term>xDSL</Term>
<ListItem>
<Para>
Used to refer to the entire DSL family of related technologies: ADSL,
SDSL, IDSL, etc.
</Para>
</ListItem>
</VarListEntry>
</VariableList>
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title>Other Consumer Class High Speed Services</Title>
<!-- ~~~~~ New Section ~~~~~ -->
<Sect3 id="cable">
<Title>Cable Modem vs DSL</Title>
<Para>
The Telcos see DSL as a competitor to the Cable Company's Cable
Modem, and as such, are providing competitive pricing and configuration
offerings. Although Cable Modems are advertised as having 10-30Mbps potential
bandwidth, they use a shared transmission medium with many other users on the
same line, and therefore performance varies, perhaps greatly, with the amount
of traffic, time of day, and number of other users on the same node.
</Para>
<Para>
It is often heard that DSL has an advantage in that it is a private pipe to
the Internet, with dedicated bandwidth. This is mostly a myth. You do have a
private pipe to the DSLAM, but at that point, you enter the telco's ATM (or
frame relay) network, and start sharing bandwidth. You are at the mercy of
how well your DSL provider and ISP manage their networks. The consensus seems
to be that DSL providers and ISPs are doing a better job of managing
bandwidth than the Cable companies. It is easier for them to add and adjust
bandwidth as needed to meet demand. You are less likely to have speed
fluctuations due to other users being on line at the same time. But, again,
this gets down to how well the network and bandwidth are managed.
</Para>
<Para>
DSL probably has a small security advantage too. With most Cable modem
networks, it is like being on a big LAN. You are sharing your connection (and
bandwidth) right at the point of connection. But if you are not doing
something to filter incoming connections already, you are asking for trouble
either way.
</Para>
<Para>
There also seems to be a better chance of having ISP alternatives with DSL
than Cable. Choice is a good thing, and so is competition. It seems most
Cable outfits give you just one choice for an ISP. If you don't like it, you
are out of luck. The number of options with DSL probably varies greatly by
geographic areas. Populous areas, like Northeast U.S., seem to have many
options.
</Para>
<Para>
So which is better? The differences aren't as much with the technology, as they
are with the implementations. If you look around, you can find plenty of
horror stories on either. And plenty of happy customers too. The way
to know what may be the best for you, is to do comparative shopping based on
experiences of other users in your area. Don't base your choice on one
person's opinion. This is statistically invalid. Likewise, don't base your
choice on someone's opinion who has had a particular service for only a short
time. Again, statistically not worth much. Get as many opinions from those
that are using the <Emphasis>exact same services</Emphasis> that you are
looking at.
</Para>
</Sect3>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect3>
<Title>Integrated Fiber in the Loop (IFITL or FTTC)</Title>
<Para>
In some areas, newer neighborhoods are being built with fiber optic cable
instead of the traditional telco copper lines. While the fiber is a definite
problem for DSL services, it has it's own potential advantages. Existing
fiber is potentially capable of 100 Mbps, and it looks like this could easily
go up soon.
</Para>
<Para>
So while telco fiber customers are being shut out of the DSL market, they may
have much to look forward to. Technologies are under development, and in some
cases just now being deployed, to take advantage of fiber telco phone loops.
Known as 'FTTC' (Fiber To The Curb), or 'IFITL' (Integrated Fiber In The
Loop), this technology is another high speed service that telcos can offer.
The speeds are sufficient for VoD (Video on Demand) and VoDSL (Voice over
DSL), and other high bandwidth services. One nice advantage here is, that
since there is no DSL signal on the wire, the only required CPE is a network
card. In other words, no modem -- just connect a NIC to the wall jack and off
you go!
</Para>
</Sect3>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2 id='modems'>
<Title>Compatible Modems</Title>
<Para>
This is an easy one right now ;-):
</Para>
<Para>
<ItemizedList>
<ListItem>
<Para>
<Emphasis>All</Emphasis> external, ethernet based modems, and modem
combination devices, should work with no problems. The only requirement is a
compatible network card. (Technically speaking, there are a few, rare and
very minor exceptions.)
</Para>
</ListItem>
</ItemizedList>
</Para>
<Para>
This list is limited to those modems and delivery systems that are readily
available, and should work with any current Linux distribution without having
to go to extraordinary lengths. Alpha and Beta projects are not included.
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2 id="isps">
<Title>Linux Friendly DSL ISPs</Title>
<Para>
By 'friendly' we mean ISPs that don't put up any unnecessary impediments just
because you aren't running that other guy's OS. And yes, there is some of
that going around. If your choices are limited, and you are forced to deal
with one of these, then having a Windows box available temporarily is one work
around. Another, may be to sweet talk the installer into letting you finish
the installation (NIC, etc). Of course, self installation, if available,
should be completely 'Linux compatible'.
</Para>
<Para>
So to make this list, the ISP/provider must make available some type of
workable modem (ethernet interface at this point in time), nor should
penalize you, or make things difficult, just because you are running an
alternate OS. Installing directly onto Linux should be an available option,
and should not cause you any undue hardship. Technical support for Linux is a
nice bonus, but not necessary to make the list. Please do not take these as
recommendations, do your own homework.
</Para>
<Para>
To add a name to this list, mail <ULink
URL="mailto:hal@foobox.net?Subject=LinuxFriendlyISP">Linux
Friendly</ULink>. Please included ISP's official name, URL (if not obvious),
location and coverage area, modem type, server policy, and any other
pertinent details.
</Para>
<BridgeHead renderas=sect3>
National ISPs (U.S.):
</BridgeHead>
<Para>
<ItemizedList>
<ListItem>
<Para>
<Ulink Url="http://www.speakeasy.net">Speakeasy.net</Ulink>: Static IP and
no PPPoX, servers explicitly allowed. Highly rated. National. Multiple IPs
available.
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink Url="http://www.phoenixdsl.com">PhoenixDSL</Ulink>: Static IP and
no PPPoX. National. Linux is supported. Servers apparently OK for
non-commercial use. Tiered pricing plan.
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink Url="http://www.telocity.com">Telocity</Ulink>: Static IP, no
PPPoX, liberal server policy. Reports of abysmal tech support. (Unenforced
monthly bandwidth usage limit ???). National. They have their own
proprietary modem, but it is ethernet based.
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink Url="http://www.geekcast.com/dsl_request.html">Penguinista
DSL</Ulink>, DSL with a twist. Not just Linux friendly, but Linux lovers.
Sponsored by the Benevolent Penguin Society. National. Static IP
available. "Theoretical" timeouts and session limits though. Encapsulation
protocol (PPP?) unknown. ???
</Para>
</ListItem>
</ItemizedList>
</Para>
<BridgeHead renderas=sect3>
Regional and Local ISPs (U.S.):
</BridgeHead>
<Para>
<ItemizedList>
<ListItem>
<Para>
<Ulink Url="http://qx.net/dsl/index.html">qx.net</Ulink>, Lexington, Ky.,
and areas of Central and Eastern KY. Officially supports Linux. Static IP.
Personal servers allowed. Tiered pricing plans. Highly rated.
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink Url="http://www.ctsi.net">Commonwealth Technical Services</Ulink>,
Richmond, Va. Officially, and happily support Linux. Static IP. Personal
servers allowed. No bandwidth restrictions. This ISP runs on Linux!
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink Url="http://www.execdsl.com">ExecDSL</Ulink>, Baltimore, MD,
Washington, DC and surrounding areas. Static IP. Servers are OK. Various
plans and DSL providers. Secondary MX and DNS available (nice touch!).
(Apparently no official Linux support.)
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink Url="http://netexpress.net">Netexpress.net</Ulink>, Moline, Ill.
Tiered pricing. Static IP available. Apparently, no official support. Runs
on Linux!
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink Url="http://www.iglou.com">iglou.com</Ulink>, Lexington, Ky., and
soon in Louisville, Ky, Cincinnati, OH, and maybe Nashville, TN. Static IP
available. Personal servers allowed. Tiered pricing plans with various
options.
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink
Url="http://bluegrass.net/internetaccess.html">Bluegrass.net</Ulink>,
Lexington, Ky., and surrounding areas. Static IP. Personal servers allowed.
Tiered pricing plans.
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink Url="http://www.drizzle.com/dsl">Drizzle.com</Ulink>, greater
Seattle, WA area. Static IP, servers OK.
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink
Url="http://www.netsync.net/services/dedicated.html">Netsync.net</Ulink>,
Chautauqua County, NY (Fredonia, Jamestown, and surrounding areas). Static
IP available, PPPoA, servers are OK. Linux is supported!
</Para>
</ListItem>
<ListItem>
<Para>
<Ulink Url="http://www.aracnet.com/adsl/">Aracnet</Ulink>, greater Seattle,
WA., and Portland and Salem, OR. areas. Static IP. Linux friendly! Tiered
pricing. Shell access account is included (RH)!
</Para>
</ListItem>
</ItemizedList>
</Para>
</Sect2>
<!-- ~ End Section ~ -->
<!-- ~~~~~ New Section ~~~~~ -->
<Sect2>
<Title id="linrouter">Setting up Linux as a Router</Title>
<Para>
Depending on your local setup, you should consider some other issues. These
include a firewall setup, and any associated configurations. For my setup,
shown in Figure 5 below, I use an old i486 machine configured as a
firewall/router between the DSL connection and the rest of my home network.
I use private IP addresses on my private LAN subnet, and have configured my
router to provide IP Masquerading and Firewalling between the LAN and
WAN connection.
</Para>
<Para>
See the <Ulink
URL="http://www.linuxdoc.org/HOWTO/IP-Masquerade-HOWTO.html">IP
Masquerade HOWTO</Ulink> , and <Ulink
URL="http://www.linuxdoc.org/HOWTO/Firewall-HOWTO.html">Firewall
HOWTO</Ulink> for more information. For 2.4 kernels see the <Ulink
URL="http://www.linuxdoc.org/HOWTO/Adv-Routing-HOWTO.html"
>Linux 2.4 Advanced Routing HOWTO</Ulink>. My experience is that Linux is more
flexible and provides superior routing/firewalling performance. It is
much less expensive than a commercial router -- if you find an old 486 machine
that you may be using as a doorstop somewhere.
</Para>
<BridgeHead renderas=sect3>
Figure 5: A typical SOHO Network Setup
</BridgeHead>
<Para>
<Literal>
<MSGText>
<LiteralLayout>
<--Private Subnet/LAN-> Linux <-----ISP's Public Subnet----><--inet-->
192.168.1.0
X--+ --------
| | | -------- (eth0:0)---------
+--=| Hub/ | | Linux | +------=| DSL |=-DSL-> ISP's
X-----=|Switch|=-----=| System |=----+ | Modem | Gateway
+--=| | eth1 |(Router)| eth0 ---------
| -------- | -------- |
X--+ | IP_Masq |
| IP_Firewall |
| Gateway |
| |
V V
192.168.1.1 Dynamic or
LAN Gateway Static IP
IP Address from ISP pool
</LiteralLayout>
</MSGText>
</Literal>
</Para>
<Para>
What I did is setup a Linux router (Redhat Linux 5.0 on a i486) with two
ethernet interfaces. One interface routes to the ISP subnet/gateway (eth0 in
above example), and the other interface (eth1 above) goes to a hub (or switch)
and then connects the LAN with private network addresses (e.g. 192.168.1.x).
Using the private network address behind your router/firewall allows some
additional security because it is not directly addressable from outside. You
have to explicitly masquerade your private addresses in order to connect to
the Internet from the LAN. The LAN hosts will access the Internet via the
second NIC (eth1) in the Linux router. Just set their gateway to the IP
address of the second NIC, and assign them addresses on the same network.
</Para>
<Para>
<Emphasis remap="bf">Caution</Emphasis> Make sure your kernel is complied
with IP forwarding and the IP forwarding is turned on. You can check this
with '<Command>cat /proc/sys/net/ipv4/ip_forward</Command>'. The value is '1'
for on, and '0' for off. You can change this value by echoing the desired
value into this file:
</Para>
<Screen>
# echo 1 > /proc/sys/net/ipv4/ip_forward
</Screen>
<Para>
You will also need to set up 'IP Masquerading' on the Linux router. Depending
on your kernel version, this is done with <Command>ipfwadm</Command> (2.0),
<Command>ipchains</Command> (2.2), or <Command>iptables</Command> (2.4).
See the documentation for specifics on each. AND -- do not forget to have
that firewall set up too!
</Para>
<Para>
There are also several projects that are devoted specifically to using Linux
as a router, just for this type of situation. These are all-in-one solutions,
that include security and various other features. Installation and
configuration, is reportedly very easy. And these will run on very minimal
hardware -- like a floppy drive only. The best known is <Ulink
URL="http://www.linuxrouter.org">http://www.linuxrouter.org</Ulink>. You
might also want to look at <Ulink
URL="http://www.freesco.org">http://www.freesco.org</Ulink> and <Ulink
URL="http://www.coyotelinux.com">http://www.coyotelinux.com</Ulink>.
</Para>
</Sect2>
</Sect1>
</Article>
<!-- ~~~~~~~~~~~~~~~~~~~~ finis ~~~~~~~~~~~~~~~~~~~~~~~~~ -->
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