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Combined several sections together, hence the removal of several files. 

Binh.
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binh 2005-02-09 13:09:12 +00:00
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69
LDP/guide/docbook/Linux-Networking/ARCnet.xml
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<sect1 id="ARCnet">
<title>ARCnet</title>
<para>
ARCnet, developed in 1977, by Datapoint Corporation, is an older standard
that has largely been replaced by Ethernet in current networks. ARCnet,
uses RG-62 coaxial cable in a star, bus, or hybrid physical topology. This
networking scheme supports active and passive hubs, which must be connected
to an active hub. ARCnet requries 93-ohm terminators at the end of bus
cables, and on unused ports of passive hubs. It supports UTP, coaxial, or
fiber-optic cable. The distance between nodes is 400 feet with UTP cable,
and higher for coaxial or fiber-optic cable.
</para>
<para>
ARCnet uses a token-passing scheme similar to that of token ring. ARCnet
networks support a bandwidth of 2.5 Mbps. Newer standards (ARCnet Plus and
TCNS) support speeds of 20 Mbps and 100 Mbps, but have not really caught on.
</para>
<para>
ARCNet device names are `arc0e', `arc1e', `arc2e' etc. or `arc0s',
`arc1s', `arc2s' etc. The first card detected by the kernel is
assigned `arc0e' or `arc0s' and the rest are assigned sequentially in
the order they are detected. The letter at the end signifies whether
you've selected ethernet encapsulation packet format or RFC1051 packet
format.
</para>
<para>
<screen>
Kernel Compile Options:
Network device support --->
[*] Network device support
<*> ARCnet support
[ ] Enable arc0e (ARCnet "Ether-Encap" packet format)
[ ] Enable arc0s (ARCnet RFC1051 packet format)
</screen>
</para>
<para>
Once you have your kernel properly built to support your ethernet card
then configuration of the card is easy.
</para>
<para>
Typically you would use something like:
</para>
<para>
<screen>
root# ifconfig arc0e 192.168.0.1 netmask 255.255.255.0 up
root# route add -net 192.168.0.0 netmask 255.255.255.0 arc0e
</screen>
</para>
<para>
Please refer to the /usr/src/linux/Documentation/networking/arcnet.txt
and /usr/src/linux/Documentation/networking/arcnet-hardware.txt files
for further information.
</para>
<para>
ARCNet support on Linux was developed by Avery Pennarun, apenwarr@foxnet.net.
</para>
</sect1>

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LDP/guide/docbook/Linux-Networking/ATM.xml
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<sect1 id="ATM">
<title>ATM</title>
<para>
ATM (Asynchronous Transfer Mode), is a high speed packet switching format
that supports up to 622 Mbps. ATM can be used with T1 and T3 lines, FDDI,
and SONET OC1 and OC3 lines. ATM uses a technology called cell switching.
Data is sent in 53-byte packets called cells. Because packets are small and
uniform in size, they can be quickly routed by hardware switches. ATM uses
a virtual circuit between connection points for high reliability over
high-speed links.
</para>
<para>
ATM support for Linux is currently in pre-alpha stage. There is an
experimental release, which supports raw ATM connections (PVCs and
SVCs), IP over ATM, LAN emulation....
</para>
<para>
The Linux ATM-Linux home page is at, <http://lrcwww.epfl.ch/linux-atm/>
</para>
<para>
Werner Almesberger <werner.almesberger@lrc.di.epfl.ch> is managing a
project to provide Asynchronous Transfer Mode support for Linux.
Current information on the status of the project may be obtained from,
http://lrcwww.epfl.ch
</para>
</sect1>

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LDP/guide/docbook/Linux-Networking/About-the-Author.xml
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Linux Documentation Project ("Linux Dictionary" and "Linux Filesystem
Hierarchy", <ulink url="www.tldp.org/guides.html">
www.tldp.org/guides.html</ulink>). Furthermore, they are being
used as reference books in at least nine universities around the world
used as reference books in at least ten universities around the world
(University of Southern Queensland (Australia),
Universidad Michoacana (Mexico),
Hong Kong Polytechnic University (Hong Kong),
@ -54,6 +54,7 @@
University of Ulster (Ireland),
Universität Duisburg-Essen (Germany),
Universidad Rey Juan Carlos (Spain),
Insituto Superior Miguel Torga (Portugal),
and Universiti Sains Malaysia (Malaysia)). As well as this, he is also a
Development Lead and Project Administrator of the "Computer Dictionary
Project" <ulink url="http://computerdictionary.tsf.org.za/dictionary/index.html">

266
LDP/guide/docbook/Linux-Networking/Appletalk.xml
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<sect1 id="Appletalk">
<title>Appletalk</title>
<para>
Appletalk is the network architecture/internetworking stack developed
by Apple to work with Macintosh computers. It allows a peer-to-peer
network model which provides basic functionality such as file and printer
sharing. Each machine can simultaneously act as a client and a server,
and the software and hardware necessary are included with every Apple
computer. Appletalk actually supports three network transports:
Ethernet, Token Ring, and a dedicated system called Localtalk.
</para>
<para>
LocalTalk is traditionally wired in a star or hybrid topology using custom
connectors and STP cable. A popular third-party system allows ordinary phone
cable to be used instead of STP. LocalTalk supports up to 32 node per network.
The implementations of Ethernet and Token Ring (EtherTalk and TokenTalk)
support for more sophisticated networks. Localtalk uses CSMA/CA access method.
Rather than detect collisions as with Ethernet, this method requires nodes to
wait a certain amount of time after detecting an existing signal on the network
before attempting to transmit, avoiding most collisions.
</para>
<para>
Linux provides full Appletalk networking. Netatalk is a kernel-level
implementation of the AppleTalk Protocol Suite, originally for BSD-
derived systems. It includes support for routing AppleTalk, serving
Unix and AFS filesystems over AFP (AppleShare), serving Unix printers
and accessing AppleTalk printers over PAP. Linux systems just show up
as another Macintosh on the network.
</para>
<para>
To enable the Appletalk ( AF_APPLETALK ) protocol in the kernel
please add the following options to your kernel configuration.
The Appletalk support has no special device names as it uses
existing network devices.
</para>
<para>
<screen>
Kernel Compile Options:
Networking options --->
<*> Appletalk DDP
</screen>
</para>
<para>
Appletalk support allows your Linux machine to interwork with Apple
networks. An important use for this is to share resources such as
printers and disks between both your Linux and Apple computers.
Additional software is required, this is called netatalk. Wesley Craig
netatalk@umich.edu represents a team called the `Research Systems Unix
Group' at the University of Michigan and they have produced the
netatalk package which provides software that implements the Appletalk
protocol stack and some useful utilities. The netatalk package will
either have been supplied with your Linux distribution, or you will
have to ftp it from its home site at the University of Michigan
</para>
<para>
To build and install the package do something like:
</para>
<para>
<screen>
user% tar xvfz .../netatalk-1.4b2.tar.Z
user% make
root# make install
</screen>
</para>
<para>
You may want to edit the `Makefile' before calling make to actually
compile the software. Specifically, you might want to change the
DESTDIR variable which defines where the files will be installed
later. The default of /usr/local/atalk is fairly safe.
</para>
8.2.1. Configuring the Appletalk software.
<para>
The first thing you need to do to make it all work is to ensure that
the appropriate entries in the /etc/services file are present. The
entries you need are:
</para>
<para>
<screen>
rtmp 1/ddp # Routing Table Maintenance Protocol
nbp 2/ddp # Name Binding Protocol
echo 4/ddp # AppleTalk Echo Protocol
zip 6/ddp # Zone Information Protocol
</screen>
</para>
<para>
The next step is to create the Appletalk configuration files in the
/usr/local/atalk/etc directory (or wherever you installed the
package).
</para>
<para>
The first file to create is the /usr/local/atalk/etc/atalkd.conf file.
Initially this file needs only one line that gives the name of the
network device that supports the network that your Apple machines are
on:
</para>
<para>
<screen>
eth0
</screen>
</para>
<para>
The Appletalk daemon program will add extra details after it is run.
</para>
8.2.2. Exporting a Linux filesystems via Appletalk.
<para>
You can export filesystems from your linux machine to the network so
that Apple machine on the network can share them.
</para>
<para>
To do this you must configure the
/usr/local/atalk/etc/AppleVolumes.system file. There is another
configuration file called /usr/local/atalk/etc/AppleVolumes.default
which has exactly the same format and describes which filesystems
users connecting with guest privileges will receive.
</para>
<para>
Full details on how to configure these files and what the various
options are can be found in the afpd man page.
</para>
<para>
A simple example might look like:
</para>
<para>
<screen>
/tmp Scratch
/home/ftp/pub "Public Area"
</screen>
</para>
<para>
Which would export your /tmp filesystem as AppleShare Volume `Scratch'
and your ftp public directory as AppleShare Volume `Public Area'. The
volume names are not mandatory, the daemon will choose some for you,
but it won't hurt to specify them anyway.
</para>
8.2.3. Sharing your Linux printer across Appletalk.
<para>
You can share your linux printer with your Apple machines quite
simply. You need to run the papd program which is the Appletalk
Printer Access Protocol Daemon. When you run this program it will
accept requests from your Apple machines and spool the print job to
your local line printer daemon for printing.
</para>
<para>
You need to edit the /usr/local/atalk/etc/papd.conf file to configure
the daemon. The syntax of this file is the same as that of your usual
/etc/printcap file. The name you give to the definition is registered
with the Appletalk naming protocol, NBP.
</para>
<para>
A sample configuration might look like:
</para>
<para>
<screen>
TricWriter:\
:pr=lp:op=cg:
</screen>
</para>
<para>
Which would make a printer named `TricWriter' available to your
Appletalk network and all accepted jobs would be printed to the linux
printer `lp' (as defined in the /etc/printcap file) using lpd. The
entry `op=cg' says that the linux user `cg' is the operator of the
printer.
</para>
8.2.4. Starting the appletalk software.
<para>
Ok, you should now be ready to test this basic configuration. There is
an rc.atalk file supplied with the netatalk package that should work
ok for you, so all you should have to do is:
</para>
<para>
<screen>
root# /usr/local/atalk/etc/rc.atalk
</screen>
</para>
<para>
and all should startup and run ok. You should see no error messages
and the software will send messages to the console indicating each
stage as it starts.
</para>
8.2.5. Testing the appletalk software.
<para>
To test that the software is functioning properly, go to one of your
Apple machines, pull down the Apple menu, select the Chooser, click on
AppleShare, and your Linux box should appear.
</para>
8.2.6. Caveats of the appletalk software.
· You may need to start the Appletalk support before you configure
your IP network. If you have problems starting the Appletalk
programs, or if after you start them you have trouble with your IP
network, then try starting the Appletalk software before you run
your /etc/rc.d/rc.inet1 file.
· The afpd (Apple Filing Protocol Daemon) severely messes up your
hard disk. Below the mount points it creates a couple of
directories called ``.AppleDesktop'' and Network Trash Folder.
Then, for each directory you access it will create a .AppleDouble
below it so it can store resource forks, etc. So think twice before
exporting /, you will have a great time cleaning up afterwards.
· The afpd program expects clear text passwords from the Macs.
Security could be a problem, so be very careful when you run this
daemon on a machine connected to the Internet, you have yourself to
blame if somebody nasty does something bad.
· The existing diagnostic tools such as netstat and ifconfig don't
support Appletalk. The raw information is available in the
/proc/net/ directory if you need it.
8.2.7. More information
<para>
For a much more detailed description of how to configure Appletalk for
Linux refer to Anders Brownworth Linux Netatalk-HOWTO page at
thehamptons.com.
</para>
<para>
Netatalk faq and HOWTO:
</para>
<para>
· http://thehamptons.com/anders/netatalk/
· http://www.umich.edu/~rsug/netatalk/
· http://www.umich.edu/~rsug/netatalk/faq.html
</para>
</sect1>

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LDP/guide/docbook/Linux-Networking/Ethernet.xml
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LDP/guide/docbook/Linux-Networking/Foreward.xml
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<title>Foreward</title>
A computer network is a group of two or more computers that communicate
through a transmission medium. Their main purpose is to share resources,
both physical and logical, such as files, devices (such as printers and
modems) and services.
<para>
It is generally thought that a computer network is a group of two or
more computers that communicate through a transmission medium with their
main purpose being to share resources, both physical and logical,
such as files, devices (such as printers and modems) and services.
Basically, they consist of two fundamental things, devices and
connections. However, even this will not be of any real practical
use since there is no way in which for humans to use the network to receive
or distribute data. Hence, the basic neccessities for a successful and
useful computer network are a communication link, an interface to the
link and software to access the link. Note that for the rest of this
document, the words "link" and "connection" will be loosely synonymous.
</para>
They could be thought though of being consisting of two fundamental things, devices and
connections. However, this will not be of any real practical use since there is no way
in which for humans to use the network to receive or distribute data.
<para>
So how does the theory of information distribution actually apply in the
real world?
</para>
Hence, the basic neccessities for a successful and useful computer network are a
communication link, an interface to the link and software to access the link.
NB - Throughtout this document, the words "link" and "connection" are loosely synonymous.
<para>
Well, firstly, communication can take a number of forms. Namely, simplex,
half-duplex and duplex. In the case of simplex, this form of communication
is when only one party can only listen and the other can only send. In the
case of half-duplex, each party must be listening or sending but not both.
Finally, duplex or full-duplex communication occurs when both parties can
receive and send information at the same time.
</para>
The theory behind sending and receiving information is all well and good but how does
it actually occur especially in the case of communication between more than two parties?
<para>
Secondly, a common standard must be agreed to as to who will take precedence.
ie. a "common language" to determine whether there should be priority levels
on messages (in case there is an emergency), what type of error correction
should occur (ie. whether a simple mechanism such as even-parity will suffice
or whether something more sophisticated is required such as CRC-32), what
should happen when an error in communication does occur, etc.... In other
words, a protocol must be formed. In the network setting, a protocol is an
agreement between communicating parties/entities on how communication is to
progress.
</para>
Well, firstly, communication can take a number of forms in simplex, half-duplex and duplex.
In the case of simplex, this form of communication is when only one party can only
listen and the other can only send. In the case of half-duplex, each party must be
listening or sending but not both. Finally, duplex or full-duplex communication
occurs when both parties can receive and send information at the same time.
<para>
Thirdly, it has been generally found that the most efficient and least error
prone method by which to achieve these goals is through 'layering'. This idea
will be explained further on in the sections entitled Layering and the
OSI and TCP/IP network layering models but it basically involves abstracting
information starting from the top where humans see it (messages) and breaking
it down (ie. datagrames, packets, frames, cells and finally bits). As the
information is sent up or down further information will be removed or added
respectively to a 'header' which now forms a part of the original data. It is
this header which contains the information necessary for error correction,
message prioritisation, etc....
</para>
Secondly, a common standard must be agreed to as to who will take precedence. ie. a
"common language" to determine whether there should be priority levels on messages
(in case there is an emergency), what type of error correction should occur (ie. whether
a simple mechanism such as even-parity will suffice of whether something more
sophisticated is required such as CRC-32), what should happen when an error in
communication does occur, etc.... In other words, a protocol must be formed.
In the network setting, a protocol is an agreement between communicating parties/entities
on how communication is to progress.
Thirdly, it has been generally found that the most efficient and least error prone
method by which to achieve these goals is through 'layering'. This idea will be explained
further on in the section entitled the OSI and TCP/IP network layering models but it basically involves
abstracting information starting from the top where humans see it (messages) and breaking it down
(ie. datagrames, packets, frames, cells and finally bits). As the information is sent up or down
further information will be removed or added respectively to a 'header' which now forms a part of the
original data. It is this header which contains the information necessary for error correction, message
prioritisation, etc....
Using a virtual machine concept, each layer is a virtual machine, with layer one being the
real machine. The top layer provides the highest level functionality or the functions that
are most abstracted from the physical world. The top layer is directly interpreted by human beings.
The bottom layer provides the lowest level functionality, ie. it is strongly related to the
physical world and (preferably) is not interpreted by human beings.
In a layered model, entities forming the corresponding layers on different machines are
called peers and protocols forms a central part of network software. The layered approach
to networks and general software engineering principles adopted add to the structure
of network software. Each layer performs a small set of well defined functions (services)
required by the layer above it.
The layered approach offers a communication setting where layer n on one machine can have a
conversation with layer n on the other mahine. Layer n-protocol is essentially a set of rules
and conventions facilitating this conversation. This includes addressing and specification of
necessary DU's (Data Units).
You should note that this communication between layers is virtual. There is no physical or
direct communication between layers of two layer-n hosts. The actual communication takes
place at the lowest layer (usually called the physical layer). The conglomeration of layers
and corresponding layer protocols form a network architecture.
The general consensus in computing is that a typical data unit exchanged between systems
should consist of the address of the transmitting computer, the address of the receiving
computer, the actual data being transmitted, as well as a checksum.
This leads us to the problem of addressing. In order for computers to communicate properly
it was generally agreed by Ethernet card manufacturers that all NIC cards would possess a
48 bit unique address. This is called a MAC address but is often called the hardware address
of these cards. This aids portability and modularity of LAN (Local Area Network) technology and
software to a major extent. The data units here are called as frames. This is all you need
really to have a small network.
However, there exists a fundamental problem if you were to extend this idea to larger systems
(ie. greater than 100 nodes). It is extremely difficult to keep track of and maintain such a
network due to administrators having to keep track of the name of each and every system and
deciding what the name of new computers on the network will be.
For this reason, the idea of hostnames and network addresses were developed. For example,
on the LAN a computer may be called "computer" but on the internet it may be referred to
as "computer.network.com". The idea behind network addressing came to be known simply now
as IP (Internet Prococol) addressing.
You could say that the idea behind computer network addressing is roughly synonymous with that
of the rather mundane telephone network. To call a number in your region all you have to do
is dial that number. To call a number in another state you must add a number of other digits
to the start of the number. To call a number that is overseas you must add further digits
to the beginning of the now burgeoning number. The only difference between telephone and
network addressing is that you add numbers to the front rather than at the end of the address.
To this day, it has been found that by utilising so called layer architecture for networks,
suitable protocols and appropriate communication technologies the issues of network
application interfacing, network addressing and network functionality can be addressed
successfully.
There are eight main network technology issues that must be addressed at each layer in the
architecture though. These are outlined below:
1. Mechanism of identifying senders and receivers: addressing.
2. Rules for data transfer: simplex, half-duplex, or full-duplex.
3. Logical channels: sharing a link among a number of connections.
4. Error control strategies: correction and detection.
5. Sequencing protocols for the correct order of messages: put messages in the correct order.
6. Incompatible speed between fast sender and slow receiver.
7. Message fragmentation and assembly.
8. Strategies for choosing routes.
To study the above issues in detail please consult, Tannenbaum 4th edition.
These design issues become recurring themes that are usually addressed by each and every
layer in the architecture. As a stark example, although error detection and correction is
undertaken by the low level transmission protocol that sends characters from a terminal
to the display, the user will also implement error detection and correction at the highest
level by deleting an incorrect character and retyping.
A concept of an interface is central to layered network architecture. It is important
to recognise implementation and design issues and pertaining to interfaces of layers
and their respective functions and services.
- entity: in software, it is sometimes called a process; in hardware in hardware it
could mean in pratice an I/O chip
- peer enties: entities at the same layer in different machines/devices
- service provider: eg. layer n, a layer that provides a service
- service receiver: eg. layer n + 1, a layer that receives a service
- service access point (SAP): a point where service is accessed, for example a
function call in software, or the telephone for a telephone company
- protocol data unit (PDU): a data unit that is communicated between peer entities
- service data unit (SDU): the PDU from the serice receiver
- protocol control information (PCI): is appended by a service receiver to an SDU
in order to indicated the type of service required and forms the IDU
- interface data unit (IDU): the data unit that is given from a service receiver to
a service provider.
The term "service" can be deemed to mean a number of things. These are outlined
below.
Quality of Service: each service is chractereised by a quality of service. For example,
reliable service by such applications as file transfer - the data must be delivered
correctly but it may be unusually delayed. However, voice and video transmission may
allow some error in the data but does not allow delayed data.
Connection and connectionless services are the two fundamental categories. The
distinctions between them may be intuitive but there are subtle differences. For
example, a connection-orientated services allows two communicating parties to make
use of the connection in any way they like - a telephone connection can even be
used for transmitting fax and digital information as the service provider doesn't
process the communication at any point through the network.
However a connectionless services does not provide such a convenience because
for example a letter may be packaged and processed along the way, being stamped
for accounting, delivered using a car or plane, etc....
A service is formally specified by a set of primitives (operations) that define
the service interface. The primitives differ for different services. As a simple
example, a service may provide the following primitives:
1. LISTEN: listen for an incoming communication request
2. CONNECT: make a communication request
3. RECEIVE: receive data of a communication
4. SEND: send data of a communication
5. DISCONNECT: disconnect or discontinue a communication
As discussed before, each layer has specfic functions and offers certain services
to the layer above it. A service is a set of primitives (operations) that a layer
provides to the layer above it. In the definition of services, we do not specify
their implementation. The implementation is only visible to the provider of the
service.
A protocol defines the implementation of the service and is not visible to the
user of the service. A protocol is a set of rules governing the format and
meaning of the frames, packets, or messages within a layer and can be changed
at will by entities, provided that they do not change the service visible to their
users.
Attentuation is a physical phenomenon which causes a signal to gradually lose
power as it propogates through a medium. This is mainly due to due to two
factors, signal dispersion and signal absorption. Unfortunately, there is some
noise which generates a constant noise power, N, and so eventually, as the
signal travels a long enough distance, the signal poower will decrease to a
value less than the noise power.
This is similar to the effect observed when you are attempting to communicate
with another person with your natural voice. As the person moves further away
the voice is harder to hear as the signal power spreads out and is absorbed
by obstacles, etc....
Attenuation is generally a factor of distance and frequency.
This is very much in accordance with our current laws of physics.
The intensity if a signal is inversely proportional to the inverse square of the the signal distance.
You'll often notice that in military applications the usage of broad
frequency radar for spotting targets over great ranges and then the utilisation
of higher frequency signals as greater precision positioning is required.
Most transmission medium will have a rating which gives the attenuation as a
function of frequency and distance, eg. the attenuation per kilometer. Ideally
the attenuation is zero because this represents no loss in the signal power.
This leads us to the issue of digital transmission versus analogue
transmission. The primary advantage of digital transmission over analogue
transmission is the reduction in noise. The digital transmission system
reduces noise over successive transmissions because small variations in
the signal can be rounded off to the nearest level. Analogue transmission
systems need to filter out the noise, but the filter itself can sometimes
be a source of noise and generally, noise can accumulate to an unacceptable
level in an analogue tranmission system.
Consider two types of repeater to understand of digital transmission. In the
first instance (analogue) the situation is roughly synonymous with someone
who doesn't know Korean and who is trying to relay a message from one Korean
to another. It can be done if the person simply repeats the sounds that are
heard. In digital tranmission repitition would be more along the lines of
someone knowing Korean and actually "re-saying" what was heard (perhaps even
correcting for errors in what was heard).
Systems which transmit ananlogue signals (such as the calssical radio and
television broadcasting systems) can use one of three well known techniques,
Amplitude Modulation (AM), Frequency Modulation (FM), and Phase Modulation (PM).
AM works by varying the amplitude of a signal to code the bit stream. FM works
by varying frequency of a signal to code the bit stream. PM works by varying
the phase of a signal to code the bit stream.
To allow two transmission medium (usually of the same type) to be directly
connected the concept of a switch was developed. A general switch can be
built from many basic switches and is somtimes referred to as a switching
fabric. A lot of research and development contines in an attempt to build
better switching fabrics.
A circuit switched network operates at the physical layer to provide a single,
continuous transmission medium between any two hosts or end devices in the
network. Circuit switching is perhaps the most straightforward approach to building
communication network. Computer networks didn't actually evolve using circuit
switching though circuit switching is being considered for certain computer
applications such as video and voice. Because circuit switching constucts a
single long transmission medium with at most analogue repeaters the end devices
(in this case telephones) are able to modulate the signal on the medium however
they choose. This is also why two modems can communicate with one another over
a telephone network.
Multiplexing is used to share a single transmission medium among a number of
individual transmissions. The demultiplexer just undoes what the multiplexer
does. Therefore the multiplexer and demultiplexer must directly cooperate.
Multiplexers and demultiplexers are not so much network devices are not so much
network devices but functionality that is contained within a network device.
Switches (in the sense described here) may be similarly categorized in this way.
The transmission medium can be multiplexed in the time domain, called TDM (Time Domain
Multiplexing), using a simple switch and clocked control. Because of delays incurred
in the transmission line, the clocks may need to be out of phase with one another.
See that with the TDM, the shared medium must be able to transmit at a bit rate
that equals (or is better than) the sum of input bit rates. The swithes must also
be able to switch fast enough.
The previous example was assuming a synchronous transmission mode. In general, bit
streams can be divided into DU's called cells. Cells are fixed in length so that the
receiver knows when one cell finishes and the next cell begins.
Alternatively there is ATM (Asynchronous Transmission Mode, ATM is also the name
given to a popular network layer device that uses this multiplexing technique.),
where signals are irregularly multiplexed. How does the receiver know what order
the signals were multiplexed in?
Additional information is needed in the multiplexed signal. One way is to add a
header or label to the front of each cell. The header identifies the cell.
Using a header means using additional bits, which becomes overhead. Thus, to reduce
the overhead the cells should be reasonably larger than the header. Cells for
modern ATM transmission systems are about 50 butes in size.
Because modulators can transmit signals at different frequency bands, it is possible
to transmit several signals at one, with each signal transmitted within a different
frequency band. In this case the different signals have been frequency domain multiplexed.
This is known as FDM, (Frequency Domain Multiplexing).
Similar to FDM, WDM (Wavelength Division Multiplexing) uses each wavelength of light to
transmit a signal. WDM is for fiber optic systems. The number of wavelengths per
fiber, currently available, is about 300. Each wavelength can carry about 10Gbps.
This makes 3Tbps. AT&amp;T predict that up to 1024 wavelengths may be available in the future.
The hub/optical hub is clearly an analogue device - input signals are reflected to all
outputs. It is also called passive, because it does not introduce any power to the signal
(otherwise it would be called active). Considering the hub as a device which repeats
input from an incoming signal on all outputs is quite simplistic however the basic
function should be understandable. When examining the Data-link layer it will become
clearer how computers communicate using a hub. For wireless communication, the
transmission of each device is implicity received by every other device. This is an
implicit hub.
Wireless communication usually takes place using the IEEE 802.11 standard which specifies
an unlicensed radio spectrum at 2.4GHz and provides wireless Ethernet access at 11Mbps.
There is also some spectrum allocated between 5GHz ad 6GHz that provides 54Mbps.
Sophisticated codes and frequency sharing technology is used to maximise the usage of
this communication medium. This topic is strictly concerned with Medium Access Control,
to be discussed later. Wireless also allows point-to-point communication in the sense
that each point-to-point link or channel is a dedicated frequency range that no other
pair of devices will use.
Analogue telephone networks use conventional circuit switching networks to
construct a connection between two telephones. You have seen that a modem
converts digital signals to analogue to be transmitted over an analogue
telephone network.
Digital telephone networks use a codec or coder-decoder to convert analogue
telephone (or modem) signals into digital form! This is so that new digital
techniques can be used within a conventionally an analogue network, ie.
transparently to the analogue devices. The codec is used to convert from
analogue to digital and digital to analogue.
Enough is known now to consider the complexity of a large digital network
that supporst communication of various kinds. As technologies improve some
networks become more dominant than others. In todays world we see a
significant shift towards computer networks, away from conventional
telecommunication networks.
This doesn't mean the end of telecommunications, but rather a collapse of
outdated technological layers towards the "core" networks that they connect
to. It will become more apparent to you as we progres through this subject
that networks can be built on top of other networks which are themseleves
built on top of ther networks.
The size and scale of a network can vary substantially from Local Area Networks
(LANs) which usually connect 10-15 computers in a
small area (usually a small building) to Metropolitan Area Networks (MANs)
which use long-distance links (such as telephone lines or dedicated media)
to connect two or more locations within a single city or metropolitan area
to Wide Area Networks (WANs) which use the same technology as MANs to
connect computers in distant locations but in different cities
or even different countries.
There are two basic types of networks: client-server networks, which use
dedicated servers; and peer-to-peer networks, which (normally) share files
between workstations.
Server-based networks (also called client-server networks) use a dedicated
server machine which provides files and printers to network workstations
called clients. Client machines are simply used by network users, and usually
do not share files or printers. The key benefit of the server-client model is
in centralization. There is only a single point of control for network acccess,
security, and management. The disadvantages of a server-based network are the
higher cost of dedicated servers and network operating systems, as well as the
increased level of administrative effort required.
Conversely, peer-to-peer networks consist solely of workstations called peers.
Each workstation can be used by a user, and can also make shared files or
printers available to users at other workstations. The advantages of peer
networks include their ease of installation and use, their relative
inexpensiveness in comparison with server-based networks (since a dedicated
server is not required) and the fact that an administrator mightn't be required
(if users are able to manage resource sharing). The primary disadvantage of
peer networks is the lack of a central control mechanism. Each user controls
access to their own workstation's shared files and printers. In a large scale
network network, such a security policy is difficult to manage without
compromising security. Further, a workstation that is being accessed by peers
can also be slowed down, inconveniencing the user at that workstation. Hence,
its clear that this system is best suited to smaller networks.
The basic idea behind this layering approach is to be able to abstract the
entire process to make it easier to network, program and solve problems
that may arise during networking. Each layer serves a specific purpose
with the application layer being the most visible to the user (in terms of
interfacing with the network) and physical layer being the least.
From a users persepective the impact of this approach is fairly nelgigible.
However, to the programmer it allows them to be able to add information to
the data being manipulated so that there is a lower chance of data
<para>
Further, it is as a direct consequence of this abstraction process
that problems associated with network usage, programming and troubleshooting
can be eased. For example, to the programmer it allows them to be able to add
information to the data being manipulated so that there is a lower chance of data
corruption as it travels through the network, so that transportation of
the data is sped up and also so that there is some flow control. To the
system administrator, it can form a valuable idea as to how to fix any
potential issues. For example, let's say that there seems to be a network
connection issue. The administrator can proceed in one of either two ways.
He can move upwards through the hierarchy or downwards, either way he is
eliminating possible issues at each point which therefore reduces the
possible number of problems at each point. The purpose of each layer will
be explained in the sections on the TCP/IP and OSI networking models.
connection problem. The administrator can proceed in one of either two ways.
He can move upwards through the layer hierarchy or downwards. Either way, he is
reducing the problem search space as he proceeds through the stack.
</para>
</sect1>

24
LDP/guide/docbook/Linux-Networking/Linux-Networking.xml
View File

@ -8,7 +8,8 @@
<!ENTITY Feedback SYSTEM "Feedback.xml">
<!ENTITY GFDL SYSTEM "fdl.xml">
<!ENTITY Foreward SYSTEM "Foreward.xml">
<!ENTITY var SYSTEM "var.xml">
<!ENTITY OSI SYSTEM "OSI.xml">
<!ENTITY TCP-IP SYSTEM "TCP-IP.xml">
<!ENTITY Glossary SYSTEM "Glossary.xml">
<!ENTITY Sources SYSTEM "Sources.xml">
]>
@ -17,8 +18,8 @@
<bookinfo>
<title>Linux Networking Study Guide</title>
<subtitle>Version 0.05</subtitle>
<pubdate>2004-10-02</pubdate>
<subtitle>Version 0.10</subtitle>
<pubdate>2005-02-08</pubdate>
<author>
<firstname>Binh</firstname>
@ -43,17 +44,16 @@ more popular derivatives of Unix. It is meant to be distribution-independant and
accessible to all members of the Linux community. However, a working knowledge of Linux as
well as its CLI (Command Line Interface) is assumed. Please note that this guide is not
meant to be an all encompassing guide of networking under Linux and that little consideration
towards security is made. It was only designed to provide an overview of this subject and
For such issues please consult other pieces of documentation such
as those made available at the Linux Documentation Project,
towards security is made. It was only intended to provide an overview of this subject and
provide a means by which to extend one's knowledge of networking under Linux and other
well established documents. For issues related to networking under Linux that are outside
the scope of this document please consult the Linux Documentation Project,
<ulink url="http://www.tldp.org"/>http://www.tldp.org</ulink>.
</para>
</abstract>
<legalnotice>
<para>Copyright 2004 Binh Nguyen</para>
<para>Copyright 2005 Binh Nguyen</para>
<para>Trademarks are owned by their owners.</para>
<para>Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License,
@ -75,10 +75,10 @@ http://cvsview.tldp.org/index.cgi/LDP/guide/docbook/Linux-Networking/</ulink>
</preface>
<chapter>
<title>Linux Networking</title>
<title>Linux Networking Study Guide</title>
&Foreward;
&var;
&OSI;
&TCP-IP;
</chapter>
&Glossary;

184
LDP/guide/docbook/Linux-Networking/Overview.xml
View File

@ -2651,6 +2651,188 @@ the sections below.
http://www.secretagent.com/networking/wan.html
>Start Binh
Attentuation is a physical phenomenon which causes a signal to gradually lose
power as it propogates through a medium. This is mainly due to due to two
factors, signal dispersion and signal absorption. Unfortunately, there is some
noise which generates a constant noise power, N, and so eventually, as the
signal travels a long enough distance, the signal poower will decrease to a
value less than the noise power.
This is similar to the effect observed when you are attempting to communicate
with another person with your natural voice. As the person moves further away
the voice is harder to hear as the signal power spreads out and is absorbed
by obstacles, etc....
Attenuation is generally a factor of distance and frequency.
This is very much in accordance with our current laws of physics.
The intensity if a signal is inversely proportional to the inverse square of the the signal distance.
You'll often notice that in military applications the usage of broad
frequency radar for spotting targets over great ranges and then the utilisation
of higher frequency signals as greater precision positioning is required.
Most transmission medium will have a rating which gives the attenuation as a
function of frequency and distance, eg. the attenuation per kilometer. Ideally
the attenuation is zero because this represents no loss in the signal power.
This leads us to the issue of digital transmission versus analogue
transmission. The primary advantage of digital transmission over analogue
transmission is the reduction in noise. The digital transmission system
reduces noise over successive transmissions because small variations in
the signal can be rounded off to the nearest level. Analogue transmission
systems need to filter out the noise, but the filter itself can sometimes
be a source of noise and generally, noise can accumulate to an unacceptable
level in an analogue tranmission system.
Consider two types of repeater to understand of digital transmission. In the
first instance (analogue) the situation is roughly synonymous with someone
who doesn't know Korean and who is trying to relay a message from one Korean
to another. It can be done if the person simply repeats the sounds that are
heard. In digital tranmission repitition would be more along the lines of
someone knowing Korean and actually "re-saying" what was heard (perhaps even
correcting for errors in what was heard).
Systems which transmit ananlogue signals (such as the calssical radio and
television broadcasting systems) can use one of three well known techniques,
Amplitude Modulation (AM), Frequency Modulation (FM), and Phase Modulation (PM).
AM works by varying the amplitude of a signal to code the bit stream. FM works
by varying frequency of a signal to code the bit stream. PM works by varying
the phase of a signal to code the bit stream.
To allow two transmission medium (usually of the same type) to be directly
connected the concept of a switch was developed. A general switch can be
built from many basic switches and is somtimes referred to as a switching
fabric. A lot of research and development contines in an attempt to build
better switching fabrics.
A circuit switched network operates at the physical layer to provide a single,
continuous transmission medium between any two hosts or end devices in the
network. Circuit switching is perhaps the most straightforward approach to building
communication network. Computer networks didn't actually evolve using circuit
switching though circuit switching is being considered for certain computer
applications such as video and voice. Because circuit switching constucts a
single long transmission medium with at most analogue repeaters the end devices
(in this case telephones) are able to modulate the signal on the medium however
they choose. This is also why two modems can communicate with one another over
a telephone network.
Multiplexing is used to share a single transmission medium among a number of
individual transmissions. The demultiplexer just undoes what the multiplexer
does. Therefore the multiplexer and demultiplexer must directly cooperate.
Multiplexers and demultiplexers are not so much network devices are not so much
network devices but functionality that is contained within a network device.
Switches (in the sense described here) may be similarly categorized in this way.
The transmission medium can be multiplexed in the time domain, called TDM (Time Domain
Multiplexing), using a simple switch and clocked control. Because of delays incurred
in the transmission line, the clocks may need to be out of phase with one another.
See that with the TDM, the shared medium must be able to transmit at a bit rate
that equals (or is better than) the sum of input bit rates. The swithes must also
be able to switch fast enough.
The previous example was assuming a synchronous transmission mode. In general, bit
streams can be divided into DU's called cells. Cells are fixed in length so that the
receiver knows when one cell finishes and the next cell begins.
Alternatively there is ATM (Asynchronous Transmission Mode, ATM is also the name
given to a popular network layer device that uses this multiplexing technique.),
where signals are irregularly multiplexed. How does the receiver know what order
the signals were multiplexed in?
Additional information is needed in the multiplexed signal. One way is to add a
header or label to the front of each cell. The header identifies the cell.
Using a header means using additional bits, which becomes overhead. Thus, to reduce
the overhead the cells should be reasonably larger than the header. Cells for
modern ATM transmission systems are about 50 butes in size.
Because modulators can transmit signals at different frequency bands, it is possible
to transmit several signals at one, with each signal transmitted within a different
frequency band. In this case the different signals have been frequency domain multiplexed.
This is known as FDM, (Frequency Domain Multiplexing).
Similar to FDM, WDM (Wavelength Division Multiplexing) uses each wavelength of light to
transmit a signal. WDM is for fiber optic systems. The number of wavelengths per
fiber, currently available, is about 300. Each wavelength can carry about 10Gbps.
This makes 3Tbps. AT&amp;T predict that up to 1024 wavelengths may be available in the future.
The hub/optical hub is clearly an analogue device - input signals are reflected to all
outputs. It is also called passive, because it does not introduce any power to the signal
(otherwise it would be called active). Considering the hub as a device which repeats
input from an incoming signal on all outputs is quite simplistic however the basic
function should be understandable. When examining the Data-link layer it will become
clearer how computers communicate using a hub. For wireless communication, the
transmission of each device is implicity received by every other device. This is an
implicit hub.
Wireless communication usually takes place using the IEEE 802.11 standard which specifies
an unlicensed radio spectrum at 2.4GHz and provides wireless Ethernet access at 11Mbps.
There is also some spectrum allocated between 5GHz ad 6GHz that provides 54Mbps.
Sophisticated codes and frequency sharing technology is used to maximise the usage of
this communication medium. This topic is strictly concerned with Medium Access Control,
to be discussed later. Wireless also allows point-to-point communication in the sense
that each point-to-point link or channel is a dedicated frequency range that no other
pair of devices will use.
Analogue telephone networks use conventional circuit switching networks to
construct a connection between two telephones. You have seen that a modem
converts digital signals to analogue to be transmitted over an analogue
telephone network.
Digital telephone networks use a codec or coder-decoder to convert analogue
telephone (or modem) signals into digital form! This is so that new digital
techniques can be used within a conventionally an analogue network, ie.
transparently to the analogue devices. The codec is used to convert from
analogue to digital and digital to analogue.
Enough is known now to consider the complexity of a large digital network
that supporst communication of various kinds. As technologies improve some
networks become more dominant than others. In todays world we see a
significant shift towards computer networks, away from conventional
telecommunication networks.
This doesn't mean the end of telecommunications, but rather a collapse of
outdated technological layers towards the "core" networks that they connect
to. It will become more apparent to you as we progres through this subject
that networks can be built on top of other networks which are themseleves
built on top of ther networks.
The size and scale of a network can vary substantially from Local Area Networks
(LANs) which usually connect 10-15 computers in a
small area (usually a small building) to Metropolitan Area Networks (MANs)
which use long-distance links (such as telephone lines or dedicated media)
to connect two or more locations within a single city or metropolitan area
to Wide Area Networks (WANs) which use the same technology as MANs to
connect computers in distant locations but in different cities
or even different countries.
There are two basic types of networks: client-server networks, which use
dedicated servers; and peer-to-peer networks, which (normally) share files
between workstations.
Server-based networks (also called client-server networks) use a dedicated
server machine which provides files and printers to network workstations
called clients. Client machines are simply used by network users, and usually
do not share files or printers. The key benefit of the server-client model is
in centralization. There is only a single point of control for network acccess,
security, and management. The disadvantages of a server-based network are the
higher cost of dedicated servers and network operating systems, as well as the
increased level of administrative effort required.
Conversely, peer-to-peer networks consist solely of workstations called peers.
Each workstation can be used by a user, and can also make shared files or
printers available to users at other workstations. The advantages of peer
networks include their ease of installation and use, their relative
inexpensiveness in comparison with server-based networks (since a dedicated
server is not required) and the fact that an administrator mightn't be required
(if users are able to manage resource sharing). The primary disadvantage of
peer networks is the lack of a central control mechanism. Each user controls
access to their own workstation's shared files and printers. In a large scale
network network, such a security policy is difficult to manage without
compromising security. Further, a workstation that is being accessed by peers
can also be slowed down, inconveniencing the user at that workstation. Hence,
its clear that this system is best suited to smaller networks.
</para>
</sect1>

370
LDP/guide/docbook/Linux-Networking/Protocols-and-Standards.xml
View File

@ -257,3 +257,373 @@ servers can have network cards bound to multiple protocols. Microsoft's
implementation of the IPX protocol, NWLink, also supports the ODI standard.
</sect1>
<sect1 id="Appletalk">
<title>Appletalk</title>
<para>
Appletalk is the network architecture/internetworking stack developed
by Apple to work with Macintosh computers. It allows a peer-to-peer
network model which provides basic functionality such as file and printer
sharing. Each machine can simultaneously act as a client and a server,
and the software and hardware necessary are included with every Apple
computer. Appletalk actually supports three network transports:
Ethernet, Token Ring, and a dedicated system called Localtalk.
</para>
<para>
LocalTalk is traditionally wired in a star or hybrid topology using custom
connectors and STP cable. A popular third-party system allows ordinary phone
cable to be used instead of STP. LocalTalk supports up to 32 node per network.
The implementations of Ethernet and Token Ring (EtherTalk and TokenTalk)
support for more sophisticated networks. Localtalk uses CSMA/CA access method.
Rather than detect collisions as with Ethernet, this method requires nodes to
wait a certain amount of time after detecting an existing signal on the network
before attempting to transmit, avoiding most collisions.
</para>
<para>
Linux provides full Appletalk networking. Netatalk is a kernel-level
implementation of the AppleTalk Protocol Suite, originally for BSD-
derived systems. It includes support for routing AppleTalk, serving
Unix and AFS filesystems over AFP (AppleShare), serving Unix printers
and accessing AppleTalk printers over PAP. Linux systems just show up
as another Macintosh on the network.
</para>
<para>
To enable the Appletalk ( AF_APPLETALK ) protocol in the kernel
please add the following options to your kernel configuration.
The Appletalk support has no special device names as it uses
existing network devices.
</para>
<para>
<screen>
Kernel Compile Options:
Networking options --->
<*> Appletalk DDP
</screen>
</para>
<para>
Appletalk support allows your Linux machine to interwork with Apple
networks. An important use for this is to share resources such as
printers and disks between both your Linux and Apple computers.
Additional software is required, this is called netatalk. Wesley Craig
netatalk@umich.edu represents a team called the `Research Systems Unix
Group' at the University of Michigan and they have produced the
netatalk package which provides software that implements the Appletalk
protocol stack and some useful utilities. The netatalk package will
either have been supplied with your Linux distribution, or you will
have to ftp it from its home site at the University of Michigan
</para>
<para>
To build and install the package do something like:
</para>
<para>
<screen>
user% tar xvfz .../netatalk-1.4b2.tar.Z
user% make
root# make install
</screen>
</para>
<para>
You may want to edit the `Makefile' before calling make to actually
compile the software. Specifically, you might want to change the
DESTDIR variable which defines where the files will be installed
later. The default of /usr/local/atalk is fairly safe.
</para>
8.2.1. Configuring the Appletalk software.
<para>
The first thing you need to do to make it all work is to ensure that
the appropriate entries in the /etc/services file are present. The
entries you need are:
</para>
<para>
<screen>
rtmp 1/ddp # Routing Table Maintenance Protocol
nbp 2/ddp # Name Binding Protocol
echo 4/ddp # AppleTalk Echo Protocol
zip 6/ddp # Zone Information Protocol
</screen>
</para>
<para>
The next step is to create the Appletalk configuration files in the
/usr/local/atalk/etc directory (or wherever you installed the
package).
</para>
<para>
The first file to create is the /usr/local/atalk/etc/atalkd.conf file.
Initially this file needs only one line that gives the name of the
network device that supports the network that your Apple machines are
on:
</para>
<para>
<screen>
eth0
</screen>
</para>
<para>
The Appletalk daemon program will add extra details after it is run.
</para>
8.2.2. Exporting a Linux filesystems via Appletalk.
<para>
You can export filesystems from your linux machine to the network so
that Apple machine on the network can share them.
</para>
<para>
To do this you must configure the
/usr/local/atalk/etc/AppleVolumes.system file. There is another
configuration file called /usr/local/atalk/etc/AppleVolumes.default
which has exactly the same format and describes which filesystems
users connecting with guest privileges will receive.
</para>
<para>
Full details on how to configure these files and what the various
options are can be found in the afpd man page.
</para>
<para>
A simple example might look like:
</para>
<para>
<screen>
/tmp Scratch
/home/ftp/pub "Public Area"
</screen>
</para>
<para>
Which would export your /tmp filesystem as AppleShare Volume `Scratch'
and your ftp public directory as AppleShare Volume `Public Area'. The
volume names are not mandatory, the daemon will choose some for you,
but it won't hurt to specify them anyway.
</para>
8.2.3. Sharing your Linux printer across Appletalk.
<para>
You can share your linux printer with your Apple machines quite
simply. You need to run the papd program which is the Appletalk
Printer Access Protocol Daemon. When you run this program it will
accept requests from your Apple machines and spool the print job to
your local line printer daemon for printing.
</para>
<para>
You need to edit the /usr/local/atalk/etc/papd.conf file to configure
the daemon. The syntax of this file is the same as that of your usual
/etc/printcap file. The name you give to the definition is registered
with the Appletalk naming protocol, NBP.
</para>
<para>
A sample configuration might look like:
</para>
<para>
<screen>
TricWriter:\
:pr=lp:op=cg:
</screen>
</para>
<para>
Which would make a printer named `TricWriter' available to your
Appletalk network and all accepted jobs would be printed to the linux
printer `lp' (as defined in the /etc/printcap file) using lpd. The
entry `op=cg' says that the linux user `cg' is the operator of the
printer.
</para>
8.2.4. Starting the appletalk software.
<para>
Ok, you should now be ready to test this basic configuration. There is
an rc.atalk file supplied with the netatalk package that should work
ok for you, so all you should have to do is:
</para>
<para>
<screen>
root# /usr/local/atalk/etc/rc.atalk
</screen>
</para>
<para>
and all should startup and run ok. You should see no error messages
and the software will send messages to the console indicating each
stage as it starts.
</para>
8.2.5. Testing the appletalk software.
<para>
To test that the software is functioning properly, go to one of your
Apple machines, pull down the Apple menu, select the Chooser, click on
AppleShare, and your Linux box should appear.
</para>
8.2.6. Caveats of the appletalk software.
· You may need to start the Appletalk support before you configure
your IP network. If you have problems starting the Appletalk
programs, or if after you start them you have trouble with your IP
network, then try starting the Appletalk software before you run
your /etc/rc.d/rc.inet1 file.
· The afpd (Apple Filing Protocol Daemon) severely messes up your
hard disk. Below the mount points it creates a couple of
directories called ``.AppleDesktop'' and Network Trash Folder.
Then, for each directory you access it will create a .AppleDouble
below it so it can store resource forks, etc. So think twice before
exporting /, you will have a great time cleaning up afterwards.
· The afpd program expects clear text passwords from the Macs.
Security could be a problem, so be very careful when you run this
daemon on a machine connected to the Internet, you have yourself to
blame if somebody nasty does something bad.
· The existing diagnostic tools such as netstat and ifconfig don't
support Appletalk. The raw information is available in the
/proc/net/ directory if you need it.
8.2.7. More information
<para>
For a much more detailed description of how to configure Appletalk for
Linux refer to Anders Brownworth Linux Netatalk-HOWTO page at
thehamptons.com.
</para>
<para>
Netatalk faq and HOWTO:
</para>
<para>
· http://thehamptons.com/anders/netatalk/
· http://www.umich.edu/~rsug/netatalk/
· http://www.umich.edu/~rsug/netatalk/faq.html
</para>
</sect1 id="Appletalk">
<sect1 id="ARCnet">
<title>ARCnet</title>
<para>
ARCnet, developed in 1977, by Datapoint Corporation, is an older standard
that has largely been replaced by Ethernet in current networks. ARCnet,
uses RG-62 coaxial cable in a star, bus, or hybrid physical topology. This
networking scheme supports active and passive hubs, which must be connected
to an active hub. ARCnet requries 93-ohm terminators at the end of bus
cables, and on unused ports of passive hubs. It supports UTP, coaxial, or
fiber-optic cable. The distance between nodes is 400 feet with UTP cable,
and higher for coaxial or fiber-optic cable.
</para>
<para>
ARCnet uses a token-passing scheme similar to that of token ring. ARCnet
networks support a bandwidth of 2.5 Mbps. Newer standards (ARCnet Plus and
TCNS) support speeds of 20 Mbps and 100 Mbps, but have not really caught on.
</para>
<para>
ARCNet device names are `arc0e', `arc1e', `arc2e' etc. or `arc0s',
`arc1s', `arc2s' etc. The first card detected by the kernel is
assigned `arc0e' or `arc0s' and the rest are assigned sequentially in
the order they are detected. The letter at the end signifies whether
you've selected ethernet encapsulation packet format or RFC1051 packet
format.
</para>
<para>
<screen>
Kernel Compile Options:
Network device support --->
[*] Network device support
<*> ARCnet support
[ ] Enable arc0e (ARCnet "Ether-Encap" packet format)
[ ] Enable arc0s (ARCnet RFC1051 packet format)
</screen>
</para>
<para>
Once you have your kernel properly built to support your ethernet card
then configuration of the card is easy.
</para>
<para>
Typically you would use something like:
</para>
<para>
<screen>
root# ifconfig arc0e 192.168.0.1 netmask 255.255.255.0 up
root# route add -net 192.168.0.0 netmask 255.255.255.0 arc0e
</screen>
</para>
<para>
Please refer to the /usr/src/linux/Documentation/networking/arcnet.txt
and /usr/src/linux/Documentation/networking/arcnet-hardware.txt files
for further information.
</para>
<para>
ARCNet support on Linux was developed by Avery Pennarun, apenwarr@foxnet.net.
</para>
</sect1 id="ARCnet">
<sect1 id="ATM">
<title>ATM</title>
<para>
ATM (Asynchronous Transfer Mode), is a high speed packet switching format
that supports up to 622 Mbps. ATM can be used with T1 and T3 lines, FDDI,
and SONET OC1 and OC3 lines. ATM uses a technology called cell switching.
Data is sent in 53-byte packets called cells. Because packets are small and
uniform in size, they can be quickly routed by hardware switches. ATM uses
a virtual circuit between connection points for high reliability over
high-speed links.
</para>
<para>
ATM support for Linux is currently in pre-alpha stage. There is an
experimental release, which supports raw ATM connections (PVCs and
SVCs), IP over ATM, LAN emulation....
</para>
<para>
The Linux ATM-Linux home page is at, <http://lrcwww.epfl.ch/linux-atm/>
</para>
<para>
Werner Almesberger <werner.almesberger@lrc.di.epfl.ch> is managing a
project to provide Asynchronous Transfer Mode support for Linux.
Current information on the status of the project may be obtained from,
http://lrcwww.epfl.ch
</para>
</sect1 id="ATM">

4
LDP/guide/docbook/Linux-Networking/Sources.xml
View File

@ -1181,8 +1181,10 @@ found [http://www.gnu.org/copyleft/fdl.html] here.
Documentation License. You should have received a copy along with it.
If not, it is available from http://www.fsf.org/licenses/fdl.html.
Linux-Filesystem-Hierarchy, Binh Nguyen, www.tldp.org/guides.html
Linux-Dictionary, Binh Nguyen, www.tldp.org/guides.html
Computer-Dictionary, Binh Nguyen, www.tldp.org/guides.html
</appendix>