From ed7f4d11a109d7375755e68150fb1549e7fa5c7f Mon Sep 17 00:00:00 2001 From: binh <> Date: Fri, 18 Feb 2005 12:08:38 +0000 Subject: [PATCH] More consolidation. Binh. --- .../Protocols-Standards-Services.xml | 3700 +---------------- .../docbook/Linux-Networking/Sources.xml | 109 + 2 files changed, 116 insertions(+), 3693 deletions(-) diff --git a/LDP/guide/docbook/Linux-Networking/Protocols-Standards-Services.xml b/LDP/guide/docbook/Linux-Networking/Protocols-Standards-Services.xml index 2d7162cd..448d6582 100644 --- a/LDP/guide/docbook/Linux-Networking/Protocols-Standards-Services.xml +++ b/LDP/guide/docbook/Linux-Networking/Protocols-Standards-Services.xml @@ -293,236 +293,10 @@ and accessing AppleTalk printers over PAP. Linux systems just show up as another Macintosh on the network. - -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. - - - - - Kernel Compile Options: - Networking options ---> - <*> Appletalk DDP - - - - -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 - - - -To build and install the package do something like: - - - - - user% tar xvfz .../netatalk-1.4b2.tar.Z - user% make - root# make install - - - - -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. - - -8.2.1. Configuring the Appletalk software. - - -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: - - - - - 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 - - - - -The next step is to create the Appletalk configuration files in the -/usr/local/atalk/etc directory (or wherever you installed the -package). - - - -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: - - - - - eth0 - - - - -The Appletalk daemon program will add extra details after it is run. - - -8.2.2. Exporting a Linux filesystems via Appletalk. - - -You can export filesystems from your linux machine to the network so -that Apple machine on the network can share them. - - - -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. - - - -Full details on how to configure these files and what the various -options are can be found in the afpd man page. - - - -A simple example might look like: - - - - - /tmp Scratch - /home/ftp/pub "Public Area" - - - - -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. - - -8.2.3. Sharing your Linux printer across Appletalk. - - -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. - - - -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. - - - -A sample configuration might look like: - - - - - TricWriter:\ - :pr=lp:op=cg: - - - - -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. - - -8.2.4. Starting the appletalk software. - - -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: - - - - - root# /usr/local/atalk/etc/rc.atalk - - - - -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. - - -8.2.5. Testing the appletalk software. - - -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. - - -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 - - -For a much more detailed description of how to configure Appletalk for -Linux refer to Anders Brownworth Linux Netatalk-HOWTO page at -thehamptons.com. - - - -Netatalk faq and HOWTO: - - - -· http://thehamptons.com/anders/netatalk/ -· http://www.umich.edu/~rsug/netatalk/ -· http://www.umich.edu/~rsug/netatalk/faq.html - +- Netatalk faq and HOWTO: +- http://thehamptons.com/anders/netatalk/ +- http://www.umich.edu/~rsug/netatalk/ +- http://www.umich.edu/~rsug/netatalk/faq.html @@ -689,100 +463,6 @@ it is cheaper to use multiple lower speed lines than to have one high speed line installed. In short, EQL is multiple line traffic equaliser. - -EQL is integrated into the Linux kernel. The EQL device name is `eql'. -With the standard kernel source you may have only one EQL device per -machine. - - - - - Kernel Compile Options: - - Network device support ---> - [*] Network device support - <*> EQL (serial line load balancing) support - - - - -To support this mechanism the machine at the other end of the lines -must also support EQL. Linux, Livingstone Portmasters and newer dial- -in servers support compatible facilities. - - - -To configure EQL you will need the EQL tools which are available from: -metalab.unc.edu. - - - -Configuration is fairly straightforward. You start by configuring the -eql interface. The eql interface is just like any other network -device. You configure the IP address and mtu using the ifconfig -utility, so something like: - - - - - root# ifconfig eql 192.168.10.1 mtu 1006 - - - - -Next you need to manually initiate each of the lines you will use. -These may be any combination of point to point network devices. How -you initiate the connections will depend on what sort of link they -are, refer to the appropriate sections for further information. - - - -Lastly you need to associate the serial link with the EQL device, this -is called `enslaving' and is done with the eql_enslave command as -shown: - - - - - root# eql_enslave eql sl0 28800 - root# eql_enslave eql ppp0 14400 - - - - -The `estimated speed' parameter you supply eql_enslave doesn't do -anything directly. It is used by the EQL driver to determine what -share of the datagrams that device should receive, so you can fine -tune the balancing of the lines by playing with this value. - - - -To disassociate a line from an EQL device you use the eql_emancipate -command as shown: - - - - - root# eql_emancipate eql sl0 - - - - -You add routing as you would for any other point to point link, except -your routes should refer to the eql device rather than the actual -serial devices themselves, typically you would use: - - - - - root# route add default eql - - - - -The EQL driver was developed by Simon Janes, simon@ncm.com. - - @@ -861,35 +541,6 @@ disadvantage of FDDI is its high cost and the difficult in installing and maintaing fiber optic cable. - -FDDI device names are `fddi0', `fddi1', `fddi2' etc. The first card -detected by the kernel is assigned `fddi0' and the rest are assigned -sequentially in the order they are detected. - - - -Larry Stefani, lstefani@ultranet.com, has developed a driver for the -Digital Equipment Corporation FDDI EISA and PCI cards. - - - -When you have your kernel built to support the FDDI driver and -installed (the compilation options are given below), configuration -of the FDDI interface is virtually identical to that of an ethernet -interface. You just specify the need to replace the Ethernet interface -names with appropriate FDDI interface names in the ifconfig and route commands. - - - - - Kernel Compile Options: - - Network device support ---> - [*] FDDI driver support - [*] Digital DEFEA and DEFPA adapter support - - - @@ -919,239 +570,6 @@ that is of a `bursty' or intermittent nature. You connect to a Frame Relay network using a Frame Relay Access Device (FRAD). The Linux Frame Relay supports IP over Frame Relay as described in RFC-1490. - - -The Frame Relay device names are `dlci00', `dlci01' etc for the DLCI -encapsulation devices and `sdla0', `sdla1' etc for the FRAD(s). - - - - - Kernel Compile Options: - - - Network device support ---> - <*> Frame relay DLCI support (EXPERIMENTAL) - (24) Max open DLCI - (8) Max DLCI per device - <*> SDLA (Sangoma S502/S508) support - - - - -Mike McLagan, mike.mclagan@linux.org, developed the Frame Relay -support and configuration tools. - - - -Currently the only FRAD supported are the Sangoma Technologies S502A, -S502E and S508. - - - -To configure the FRAD and DLCI devices after you have rebuilt your -kernel you will need the Frame Relay configuration tools. These are -available from ftp.invlogic.com. Compiling and installing the tools -is straightforward, but the lack of a top level Makefile makes it a -fairly manual process: - - - - - user% tar xvfz .../frad-0.15.tgz - user% cd frad-0.15 - user% for i in common dlci frad; make -C $i clean; make -C $i; done - root# mkdir /etc/frad - root# install -m 644 -o root -g root bin/*.sfm /etc/frad - root# install -m 700 -o root -g root frad/fradcfg /sbin - root# install -m 700 -o root -g root dlci/dlcicfg /sbin - - - - -Note that the previous commands use sh syntax, if you use a csh -flavour instead (like tcsh), the for loop will look different. - - - -After installing the tools you need to create an /etc/frad/router.conf -file. You can use this template, which is a modified version of one of -the example files: - - - - - # /etc/frad/router.conf - # This is a template configuration for frame relay. - # All tags are included. The default values are based on the code - # supplied with the DOS drivers for the Sangoma S502A card. - # - # A '#' anywhere in a line constitutes a comment - # Blanks are ignored (you can indent with tabs too) - # Unknown [] entries and unknown keys are ignored - # - - [Devices] - Count=1 # number of devices to configure - Dev_1=sdla0 # the name of a device - #Dev_2=sdla1 # the name of a device - - # Specified here, these are applied to all devices and can be overridden for - # each individual board. - # - Access=CPE - Clock=Internal - KBaud=64 - Flags=TX - # - # MTU=1500 # Maximum transmit IFrame length, default is 4096 - # T391=10 # T391 value 5 - 30, default is 10 - # T392=15 # T392 value 5 - 30, default is 15 - # N391=6 # N391 value 1 - 255, default is 6 - # N392=3 # N392 value 1 - 10, default is 3 - # N393=4 # N393 value 1 - 10, default is 4 - - # Specified here, these set the defaults for all boards - # CIRfwd=16 # CIR forward 1 - 64 - # Bc_fwd=16 # Bc forward 1 - 512 - # Be_fwd=0 # Be forward 0 - 511 - # CIRbak=16 # CIR backward 1 - 64 - # Bc_bak=16 # Bc backward 1 - 512 - # Be_bak=0 # Be backward 0 - 511 - - - # - # - # Device specific configuration - # - # - - # - # The first device is a Sangoma S502E - # - [sdla0] - Type=Sangoma # Type of the device to configure, currently only - # SANGOMA is recognized - # - # These keys are specific to the 'Sangoma' type - # - # The type of Sangoma board - S502A, S502E, S508 - Board=S502E - # - # The name of the test firmware for the Sangoma board - # Testware=/usr/src/frad-0.10/bin/sdla_tst.502 - # - # The name of the FR firmware - # Firmware=/usr/src/frad-0.10/bin/frm_rel.502 - # - Port=360 # Port for this particular card - Mem=C8 # Address of memory window, A0-EE, depending on card - IRQ=5 # IRQ number, do not supply for S502A - DLCIs=1 # Number of DLCI's attached to this device - DLCI_1=16 # DLCI #1's number, 16 - 991 - # DLCI_2=17 - # DLCI_3=18 - # DLCI_4=19 - # DLCI_5=20 - # - # Specified here, these apply to this device only, - # and override defaults from above - # - # Access=CPE # CPE or NODE, default is CPE - # Flags=TXIgnore,RXIgnore,BufferFrames,DropAborted,Stats,MCI,AutoDLCI - # Clock=Internal # External or Internal, default is Internal - # Baud=128 # Specified baud rate of attached CSU/DSU - # MTU=2048 # Maximum transmit IFrame length, default is 4096 - # T391=10 # T391 value 5 - 30, default is 10 - # T392=15 # T392 value 5 - 30, default is 15 - # N391=6 # N391 value 1 - 255, default is 6 - # N392=3 # N392 value 1 - 10, default is 3 - # N393=4 # N393 value 1 - 10, default is 4 - - # - # The second device is some other card - # - # [sdla1] - # Type=FancyCard # Type of the device to configure. - # Board= # Type of Sangoma board - # Key=Value # values specific to this type of device - - - # - # DLCI Default configuration parameters - # These may be overridden in the DLCI specific configurations - # - CIRfwd=64 # CIR forward 1 - 64 - # Bc_fwd=16 # Bc forward 1 - 512 - # Be_fwd=0 # Be forward 0 - 511 - # CIRbak=16 # CIR backward 1 - 64 - # Bc_bak=16 # Bc backward 1 - 512 - # Be_bak=0 # Be backward 0 - 511 - - # - # DLCI Configuration - # These are all optional. The naming convention is - # [DLCI_D_] - # - - [DLCI_D1_16] - # IP= - # Net= - # Mask= - # Flags defined by Sangoma: TXIgnore,RXIgnore,BufferFrames - # DLCIFlags=TXIgnore,RXIgnore,BufferFrames - # CIRfwd=64 - # Bc_fwd=512 - # Be_fwd=0 - # CIRbak=64 - # Bc_bak=512 - # Be_bak=0 - - [DLCI_D2_16] - # IP= - # Net= - # Mask= - # Flags defined by Sangoma: TXIgnore,RXIgnore,BufferFrames - # DLCIFlags=TXIgnore,RXIgnore,BufferFrames - # CIRfwd=16 - # Bc_fwd=16 - # Be_fwd=0 - # CIRbak=16 - # Bc_bak=16 - # Be_bak=0 - - - - -When you've built your /etc/frad/router.conf file the only step -remaining is to configure the actual devices themselves. This is only -a little trickier than a normal network device configuration, you need -to remember to bring up the FRAD device before the DLCI encapsulation -devices. These commands are best hosted in a shell script, due to -their number: - - - - - #!/bin/sh - # Configure the frad hardware and the DLCI parameters - /sbin/fradcfg /etc/frad/router.conf || exit 1 - /sbin/dlcicfg file /etc/frad/router.conf - # - # Bring up the FRAD device - ifconfig sdla0 up - # - # Configure the DLCI encapsulation interfaces and routing - ifconfig dlci00 192.168.10.1 pointopoint 192.168.10.2 up - route add -net 192.168.10.0 netmask 255.255.255.0 dlci00 - # - ifconfig dlci01 192.168.11.1 pointopoint 192.168.11.2 up - route add -net 192.168.11.0 netmask 255.255.255.0 dlci00 - # - route add default dev dlci00 - # - - @@ -1232,18 +650,6 @@ in the packet. Typical frame types used in NetWare networks IPX networks through an IP only link - How do I configure the kernel for IPX networking support? - - - IPX ( AF_IPX ) - Kernel Compile Options: - - Networking options ---> - [*] The IPX protocol - [ ] Full internal IPX network - - - * IPX-SPX HOWTO @@ -1252,15 +658,6 @@ in the packet. Typical frame types used in NetWare networks Leased-Line -_______________________________________________________________________________ - - -Configuring your modem and pppd to use a 2 wire twisted pair leased -line. - - -1.2. What is a leased line - Any fixed, that is permanent, point to point data communications link, which is leased from a telco or similar organisation. The leased line @@ -1269,433 +666,7 @@ involve all sorts of other hardware such as (pupin) coils, transformers, amplifiers and regenerators. - - This document deals with: - Configuring your modem and pppd to use a 2 wire twisted pair - leased line. - - - - This document does NOT deal with: - SLIP, getting or installing pppd, synchronous data - communication, baseband modems, xDSL. - - -1.3. Assumptions - - -You should already have a working pppd on your system. You also need -Minicom or a similar program to configure your modems. - - -2. Modem - - -A leased line is not connected to a telephone exchange and does not -provide DC power, dial tone, busy tone or ring signal. This means that -your modems are on their own and have to be able to deal with this -situation. - - - -You should have 2 identical (including firmware version) external -modems supporting both leased line and dumb mode. Make sure your -modems can actually do this! Also make sure your modem is properly -documented. You also need: - - -· 2 fully wired shielded RS232 cables. The shield should be connected - to the connector shell (not pin 1) at both ends (not at one end). -· A RS232 test plug may be handy for test purposes. -· 2 RJ11 cords, one for each end of the leased line. -· A basic understanding of `AT' commands. - -2.1. Modem Configuration - - -A note on modem configuration and init strings in general: Configure -your modem software such as minicom or (m)getty to use the highest -possible speed; 57600 bps for 14k4 and 115200 bps for 28k8 or faster -modems. Lots of people use very long and complicated init strings, -often starting with AT&F and containing lots of modem brand and -type -specific commands. This however is needlessly complicated. Most -programs feel happy with the same modem settings, so why not write -these settings in the non volatile memory of all your modems, and only -use `ATZ' as an init string in all your programs. This way you can -swap or upgrade your modems without ever having to reconfigure any of -your software. - - - -Most programs require you to use the following settings; - - -· Fixed baud rate (no auto baud) -· Hardware bidirectional RTS-CTS flow control (no x-on/x-off) -· 8 Bits, no parity, 1 stopbit -· The modem should produce the TRUE DCD status (&C1) -· The modem should NOT ignore the DTR status (&D2 or &D3) - - -Check this with AT&V or AT&Ix (consult your modem documentation) - - - -These settings are not necessarily the same as the default factory -profile (&F), so starting an init string with AT&F is probably not a -good idea in the first place. The smart thing to do is probably to use -AT&F only when you have reason to believe that the modem setup stored -in the non volatile memory is really screwed up. If you think you -have found the right setup for your modems, write it to non volatile -memory with AT&W and test it thoroughly with Z-modem file transfers of -both ASCII text and binary files. Only if all of this works perfectly -should you configure your modems for leased line. - - - -Find out how to put your modem into dumb mode and, more importantly, -how to get it out of dumb mode; The modem can only be reconfigured -when it is not in dumb mode. Make sure you actually configure your -modems at the highest possible speed. Once in dumb mode it will -ignore all `AT' commands and consequently will not adjust its speed to -that of the COM port, but will use the speed at which it was -configured instead (this speed is stored in a S-register by the AT&W -command). - - - -Now configure your modem as follows; - - -· Reset on DTR toggle (&D3, this is sometimes a S register). This - setting is required by some ISP's! -· Leased line mode (&L1 or &L2, consult your modem documentation) -· The remote modem auto answer (S0=1), the local originate (S0=0) -· Disable result codes (Q1, sometimes the dumb mode does this for - you) -· Dumb mode (\D1 or %D1, this is sometimes a jumper) In dumb mode the - modem will ignore all AT commands (sometimes you need to disable - the ESC char as well). - - -Write the configuration to non-volatile memory (&W). - - -2.2. Test - - -Now connect the modems to 2 computers using the RS232 cables and -connect the modems to each other using a RJ11 lead. Use a modem -program such as Minicom (Linux), procom or telix (DOS) on both -computers to test the modems. You should be able to type text from -one computer to the other and vice versa. If the screen produces -garbage check your COM port speed and other settings. Now disconnect -and reconnect the RJ11 cord. Wait for the connection to reestablish -itself. Disconnect and reconnect the RS232 cables, switch the modems -on and off, stop and restart Minicom. The modems should always -reconnect at the highest possible speed (some modems have speed -indicator leds). Check whether the modems actually ignores the ESC -(+++) character. If necessary disable the ESC character. - - - -If all of this works you may want to reconfigure your modems; Switch -off the sound at the remote modem (M0) and put the local modem at low -volume (L1). - - -2.3. Examples - -2.3.1. Hi-Tech - - -This is a rather vague `no name clone modem'. Its config string is -however typical and should work on most modems. - - - - Originate (local): - ATL1&C1&D3&L2%D1&W&W1 - - - - Answer (remote): - ATM0L1&C1&D3&L2%D1S0=1&W&W1 - - -2.3.2. Tornado FM 228 E - - -This is what should work; - - - - Originate (local): - ATB15L1Q1&C1&D3&L2&W&W1 - - - - Answer (remote): - ATM0B15M0Q1&C1&D3&L2S0=1&W&W1 - - - -Move the dumb jumper from position 2-3 to 1-2. - - - -Due to a firmware bug, the modems will only connect after being hard -reset (power off and on) while DTR is high. I designed a circuit which -hard resets the modem on the low to high transition of DTR. The -FreeBSD pppd however, isn't very happy about this. By combining the -setting &D0 with a circuit which resets on the high to low transition -instead, this problem can be avoided. - - -2.3.3. Tron DF - - -The ESC char should be disabled by setting S2 > 127; - - - - Originate: - ATL1&L1Q1&C1&D3S2=171\D1&W - - - - Answer: - ATM0&L2Q1&C1&D3S0=1S2=171\D1&W - - -2.3.4. US Robotics Courier V-Everything - - -The USR Sportster and USR Courier-I do not support leased line. You -need the Courier V-everything version for this job. There is a -webpage on the USR site `explaining' how to set-up your Courier for -leased line. However, if you follow these instructions you will end up -with a completely brain dead modem, which can not be controlled or -monitored by your pppd. - - - -The USR Courier can be configured with dip switches, however you need -to feed it the config string first. First make sure it uses the right -factory profile. Unlike most other modems it has three; &F0, &F1 and -&F2. The default, which is also the one you should use, is &F1. If you -send it an AT&F, however it will load the factory profile &F0! For -the reset on DTR toggle you set bit 0 of S register 13. This means you -have to set S13 to 1. Furthermore you need set it to leased line mode -with &L1; ATS13=1&L1&W The dip switches are all default except for the -following: - - - - 3 OFF Disable result codes - 4 ON Disable offline commands - 5 ON For originate, OFF For answer - 8 OFF Dumb mode - - -3. PPPD - - -You need a pppd (Point to Point Protocol Daemon) and a reasonable -knowledge of how it works. Consult the relevant RFC's or the Linux PPP -HOWTO if necessary. Since you are not going to use a login procedure, -you don't use (m)getty and you do not need a (fake) user associated -with the pppd controlling your link. You are not going to dial so you -don't need any chat scripts either. In fact, the modem circuit and -configuration you have just build, are rather like a fully wired null -modem cable. This means you have to configure your pppd the same way -as you would with a null modem cable. - - - -For a reliable link, your setup should meet the following criteria; - - -· Shortly after booting your system, pppd should raise the DTR signal - in your RS232 port, wait for DCD to go up, and negotiate the link. -· If the remote system is down, pppd should wait until it is up - again. -· If the link is up and then goes down, pppd should reset the modem - (it does this by dropping and then raising DTR), and then try to - reconnect. -· If the quality of the link deteriorates too much, pppd should reset - the modem and then reestablish the link. -· If the process controlling the link, that is the pppd, dies, a - watchdog should restart the pppd. - -3.1. Configuration - - -Suppose the modem is connected to COM2, the local IP address is -`Loc_Ip' and the remote IP address is `Rem_Ip'. We want to use 576 as -our MTU. The /etc/ppp/options.ttyS1 would now be: - - - - -crtscts -mru 576 -mtu 576 -passive -Loc_Ip:Rem_Ip --chap -modem -#noauth --pap -persist - - - - -Stuff like `asyncmap 0', `lock', `modem' and `-detach' are probably -already in /etc/ppp/options. If not, add them to your -/etc/ppp/options.ttyS1. So, if the local system is 192.168.1.1 and -the remote system is 10.1.1.1, then /etc/ppp/options.ttyS1 on the -local system would be: - - - - - crtscts - mru 576 - mtu 576 - passive - 192.168.1.1:10.1.1.1 - -chap - modem - #noauth - -pap - persist - - - - -The options.ttyS1 on the remote system would be: - - - - - crtscts - mru 576 - mtu 576 - passive - 10.1.1.1:192.168.1.1 - -chap - modem - #noauth - -pap - persist - - - - -The passive option limits the number of (re)connection attempts. The -persist option will keep pppd alive in case of a disconnect or when it -can't connect in the first place. If you telnet a lot while doing -filetransfers (FTP or webbrowsing) at the same time, you might want to -use a smaller MTU and MRU such as 296. This will make the remote sys­ -tem more responsive. If you don't care much about telnetting during -FTP, you could set the MTU and MRU to 1500. Keep in mind though, that -UDP cannot be fragmented. Speakfreely for instance uses 512 byte UDP -packets. So the minimum MTU for speakfreely is 552 bytes. The noauth -option may be necessary with some newer distributions. - - -3.2. Scripts - -3.2.1. Starting the pppd and keeping it alive - - -You could start the pppd form a boot (rc) script. However, if you do -this, and the pppd dies, you are without a link. A more stable -solution, is to start the pppd from /etc/inittab; - - - - - s1:23:respawn:/usr/sbin/pppd /dev/ttyS1 115200 - - - - -This way, the pppd will be restarted if it dies. Make sure you have a -`-detach' option (nodetach on newer systems) though, otherwise inittab -will start numerous instances of pppd, will complaining about -`respawning too fast'. - - - -Note: Some older systems will not accept the speed `115200'. In this -case you will have to set the speed to 38400 en set the `spd_vhi' flag -with setserial. Some systems expect you to use a `cua' instead of -`ttyS' device. - - -3.2.2. Setting the routes - - -The default route can be set with the defaultroute option or with the -/etc/ppp/ip-up script; - - - - - #!/bin/bash - case $2 in - /dev/ttyS1) - /sbin/route add -net 0.0.0.0 gw Rem_Ip netmask 0.0.0.0 - ;; - esac - - - - -Ip-up can also be used to sync your clock using netdate. - - - -Of course the route set in ip-up is not necessarily the default route. -Your ip-up sets the route to the remote network while the ip-up script -on the remote system sets the route to your network. If your network -is 192.168.1.0 and your ppp interface 192.168.1.1, the ip-up script on -the remote machine looks like this; - - - - - #!/bin/bash - case $2 in - /dev/ttyS1) - /sbin/route add -net 192.168.1.0 gw 192.168.1.1 netmask 255.255.255.0 - ;; - esac - - - - -The `case $2' and `/dev/ttyS1)' bits are there in case you use more -than one ppp link. Ip-up will run each time a link comes up, but only -the part between `/dev/ttySx)' and `;;' will be executed, setting the -right route for the right ttyS. You can find more about routing in -the Linux Networking HOWTO section on routing. - - -3.3. Test - - -Test the whole thing just like the modem test. If it works, get on -your bike and bring the remote modem to the remote side of your link. -If it doesn't work, one of the things you should check is the COM port -speed; Apparently, a common mistake is to configure the modems with -Minicom using one speed and then configure the pppd to use an other. -This will NOT work! You have to use the same speed all of the time! - - + @@ -3223,2201 +2194,15 @@ In times gone by, users would Telnet into the SMTP server itself and use a comma When a web browser retreives information from the Internet, it stores a copy of that information -in a cache on the local machine. When a user requests that information in future, the browser will -check to seee if the original source has updated; if not, the browser will simply use the cached version -rather than fetch the data again. +in a cache on the local machine. When a user requests that information in future, the browser will check to seee if the original source has updated; if not, the browser will simply use the cached version rather than fetch the data again. By doing this, there is less information that needs to be downloadded, which makes the connection seem responsive to users and reduces bandwidth costs. But if there are many browsers accessing the Internet through the same connection, it makes better sense to have a single, centralised cache so that once a single machine has requested some information, the next machine to try and download that information can also access it more quickly. This is the theory behind the proxy cache. Squid is by far the most popular cache used on the Web, and can also be used to accelerate Web serving. -By doing this, there is less information that needs to be downloadded, which makes the connection seem responsive -to users and reduces bandwidth costs. - -But if there are many browsers accessing the Internet through the same connection, it makes better sense to have -a single, centralised cache so that once a single machine has requested some information, the next -machine to try and download that information can also access it more quickly. This is the -theory behind the proxy cache. Squid is by far the most popular cache used on the Web, and can also be used -to accelerate Web serving. - -Although Squid is useful for an ISP, large businesses or even a small office can afford to use Squid to -speed up transfers and save money, and it can easily be used to the same effect in a home with a few -flatmates sharing a cable or ADSL connection. +Although Squid is useful for an ISP, large businesses or even a small office can afford to use Squid to speed up transfers and save money, and it can easily be used to the same effect in a home with a few flatmates sharing a cable or ADSL connection. Traffic Control HOWTO -Version 1.0.1 - -Martin A. Brown - - [http://www.securepipe.com/] SecurePipe, Inc. -Network Administration - - - -"Nov 2003" -Revision History -Revision 1.0.1 2003-11-17 Revised by: MAB -Added link to Leonardo Balliache's documentation -Revision 1.0 2003-09-24 Revised by: MAB -reviewed and approved by TLDP -Revision 0.7 2003-09-14 Revised by: MAB -incremental revisions, proofreading, ready for TLDP -Revision 0.6 2003-09-09 Revised by: MAB -minor editing, corrections from Stef Coene -Revision 0.5 2003-09-01 Revised by: MAB -HTB section mostly complete, more diagrams, LARTC pre-release -Revision 0.4 2003-08-30 Revised by: MAB -added diagram -Revision 0.3 2003-08-29 Revised by: MAB -substantial completion of classless, software, rules, elements and components -sections -Revision 0.2 2003-08-23 Revised by: MAB -major work on overview, elements, components and software sections -Revision 0.1 2003-08-15 Revised by: MAB -initial revision (outline complete) - - - Traffic control encompasses the sets of mechanisms and operations by which -packets are queued for transmission/reception on a network interface. The -operations include enqueuing, policing, classifying, scheduling, shaping and -dropping. This HOWTO provides an introduction and overview of the -capabilities and implementation of traffic control under Linux. - -© 2003, Martin A. Brown - - - Permission is granted to copy, distribute and/or modify this document - under the terms of the GNU Free Documentation License, Version 1.1 or any - later version published by the Free Software Foundation; with no - invariant sections, with no Front-Cover Texts, with no Back-Cover Text. A - copy of the license is located at [http://www.gnu.org/licenses/fdl.html] - http://www.gnu.org/licenses/fdl.html. - ------------------------------------------------------------------------------ -Table of Contents -1. Introduction to Linux Traffic Control - 1.1. Target audience and assumptions about the reader - 1.2. Conventions - 1.3. Recommended approach - 1.4. Missing content, corrections and feedback - - -2. Overview of Concepts - 2.1. What is it? - 2.2. Why use it? - 2.3. Advantages - 2.4. Disdvantages - 2.5. Queues - 2.6. Flows - 2.7. Tokens and buckets - 2.8. Packets and frames - - -3. Traditional Elements of Traffic Control - 3.1. Shaping - 3.2. Scheduling - 3.3. Classifying - 3.4. Policing - 3.5. Dropping - 3.6. Marking - - -4. Components of Linux Traffic Control - 4.1. qdisc - 4.2. class - 4.3. filter - 4.4. classifier - 4.5. policer - 4.6. drop - 4.7. handle - - -5. Software and Tools - 5.1. Kernel requirements - 5.2. iproute2 tools (tc) - 5.3. tcng, Traffic Control Next Generation - 5.4. IMQ, Intermediate Queuing device - - -6. Classless Queuing Disciplines (qdiscs) - 6.1. FIFO, First-In First-Out (pfifo and bfifo) - 6.2. pfifo_fast, the default Linux qdisc - 6.3. SFQ, Stochastic Fair Queuing - 6.4. ESFQ, Extended Stochastic Fair Queuing - 6.5. GRED, Generic Random Early Drop - 6.6. TBF, Token Bucket Filter - - -7. Classful Queuing Disciplines (qdiscs) - 7.1. HTB, Hierarchical Token Bucket - 7.2. PRIO, priority scheduler - 7.3. CBQ, Class Based Queuing - - -8. Rules, Guidelines and Approaches - 8.1. General Rules of Linux Traffic Control - 8.2. Handling a link with a known bandwidth - 8.3. Handling a link with a variable (or unknown) bandwidth - 8.4. Sharing/splitting bandwidth based on flows - 8.5. Sharing/splitting bandwidth based on IP - - -9. Scripts for use with QoS/Traffic Control - 9.1. wondershaper - 9.2. ADSL Bandwidth HOWTO script (myshaper) - 9.3. htb.init - 9.4. tcng.init - 9.5. cbq.init - - -10. Diagram - 10.1. General diagram - - -11. Annotated Traffic Control Links - -1. Introduction to Linux Traffic Control - - Linux offers a very rich set of tools for managing and manipulating the -transmission of packets. The larger Linux community is very familiar with the -tools available under Linux for packet mangling and firewalling (netfilter, -and before that, ipchains) as well as hundreds of network services which can -run on the operating system. Few inside the community and fewer outside the -Linux community are aware of the tremendous power of the traffic control -subsystem which has grown and matured under kernels 2.2 and 2.4. - - This HOWTO purports to introduce the concepts of traffic control, the -traditional elements (in general), the components of the Linux traffic -control implementation and provide some guidelines . This HOWTO represents -the collection, amalgamation and synthesis of the [http://lartc.org/howto/] -LARTC HOWTO, documentation from individual projects and importantly the LARTC -mailing list over a period of study. - - The impatient soul, who simply wishes to experiment right now, is -recommended to the [http://tldp.org/HOWTO/Traffic-Control-tcng-HTB-HOWTO/] -Traffic Control using tcng and HTB HOWTO and [http://lartc.org/howto/] LARTC -HOWTO for immediate satisfaction. - - ------------------------------------------------------------------------------ - -1.1. Target audience and assumptions about the reader - - The target audience for this HOWTO is the network administrator or savvy -home user who desires an introduction to the field of traffic control and an -overview of the tools available under Linux for implementing traffic control. - - I assume that the reader is comfortable with UNIX concepts and the command -line and has a basic knowledge of IP networking. Users who wish to implement -traffic control may require the ability to patch, compile and install a -kernel or software package [1]. For users with newer kernels (2.4.20+, see -also Section 5.1), however, the ability to install and use software may be -all that is required. - - Broadly speaking, this HOWTO was written with a sophisticated user in mind, -perhaps one who has already had experience with traffic control under Linux. -I assume that the reader may have no prior traffic control experience. ------------------------------------------------------------------------------ - -1.2. Conventions - - This text was written in [http://www.docbook.org/] DocBook ([http:// -www.docbook.org/xml/4.2/index.html] version 4.2) with vim. All formatting has -been applied by [http://xmlsoft.org/XSLT/] xsltproc based on DocBook XSL and -LDP XSL stylesheets. Typeface formatting and display conventions are similar -to most printed and electronically distributed technical documentation. ------------------------------------------------------------------------------ - -1.3. Recommended approach - - I strongly recommend to the eager reader making a first foray into the -discipline of traffic control, to become only casually familiar with the tc -command line utility, before concentrating on tcng. The tcng software package -defines an entire language for describing traffic control structures. At -first, this language may seem daunting, but mastery of these basics will -quickly provide the user with a much wider ability to employ (and deploy) -traffic control configurations than the direct use of tc would afford. - - Where possible, I'll try to prefer describing the behaviour of the Linux -traffic control system in an abstract manner, although in many cases I'll -need to supply the syntax of one or the other common systems for defining -these structures. I may not supply examples in both the tcng language and the -tc command line, so the wise user will have some familiarity with both. - - ------------------------------------------------------------------------------ - -1.4. Missing content, corrections and feedback - - There is content yet missing from this HOWTO. In particular, the following -items will be added at some point to this documentation. - -  *  A description and diagram of GRED, WRR, PRIO and CBQ. - -  *  A section of examples. - -  *  A section detailing the classifiers. - -  *  A section discussing the techniques for measuring traffic. - -  *  A section covering meters. - -  *  More details on tcng. - - - I welcome suggestions, corrections and feedback at . All errors and omissions are strictly my fault. Although I have made every -effort to verify the factual correctness of the content presented herein, I -cannot accept any responsibility for actions taken under the influence of -this documentation. - - ------------------------------------------------------------------------------ - -2. Overview of Concepts - - This section will introduce traffic control and examine reasons for it, -identify a few advantages and disadvantages and introduce key concepts used -in traffic control. ------------------------------------------------------------------------------ - -2.1. What is it? - - Traffic control is the name given to the sets of queuing systems and -mechanisms by which packets are received and transmitted on a router. This -includes deciding which (and whether) packets to accept at what rate on the -input of an interface and determining which packets to transmit in what order -at what rate on the output of an interface. - - In the overwhelming majority of situations, traffic control consists of a -single queue which collects entering packets and dequeues them as quickly as -the hardware (or underlying device) can accept them. This sort of queue is a -FIFO. - -Note The default qdisc under Linux is the pfifo_fast, which is slightly more - complex than the FIFO. - - There are examples of queues in all sorts of software. The queue is a way -of organizing the pending tasks or data (see also Section 2.5). Because -network links typically carry data in a serialized fashion, a queue is -required to manage the outbound data packets. - - In the case of a desktop machine and an efficient webserver sharing the -same uplink to the Internet, the following contention for bandwidth may -occur. The web server may be able to fill up the output queue on the router -faster than the data can be transmitted across the link, at which point the -router starts to drop packets (its buffer is full!). Now, the desktop machine -(with an interactive application user) may be faced with packet loss and high -latency. Note that high latency sometimes leads to screaming users! By -separating the internal queues used to service these two different classes of -application, there can be better sharing of the network resource between the -two applications. - - Traffic control is the set of tools which allows the user to have granular -control over these queues and the queuing mechanisms of a networked device. -The power to rearrange traffic flows and packets with these tools is -tremendous and can be complicated, but is no substitute for adequate -bandwidth. - - The term Quality of Service (QoS) is often used as a synonym for traffic -control. ------------------------------------------------------------------------------ - -2.2. Why use it? - - Packet-switched networks differ from circuit based networks in one very -important regard. A packet-switched network itself is stateless. A -circuit-based network (such as a telephone network) must hold state within -the network. IP networks are stateless and packet-switched networks by -design; in fact, this statelessness is one of the fundamental strengths of -IP. - - The weakness of this statelessness is the lack of differentiation between -types of flows. In simplest terms, traffic control allows an administrator to -queue packets differently based on attributes of the packet. It can even be -used to simulate the behaviour of a circuit-based network. This introduces -statefulness into the stateless network. - - There are many practical reasons to consider traffic control, and many -scenarios in which using traffic control makes sense. Below are some examples -of common problems which can be solved or at least ameliorated with these -tools. - - The list below is not an exhaustive list of the sorts of solutions -available to users of traffic control, but introduces the types of problems -that can be solved by using traffic control to maximize the usability of a -network connection. - -Common traffic control solutions - -  *  Limit total bandwidth to a known rate; TBF, HTB with child class(es). - -  *  Limit the bandwidth of a particular user, service or client; HTB - classes and classifying with a filter. traffic. - -  *  Maximize TCP throughput on an asymmetric link; prioritize transmission - of ACK packets, wondershaper. - -  *  Reserve bandwidth for a particular application or user; HTB with - children classes and classifying. - -  *  Prefer latency sensitive traffic; PRIO inside an HTB class. - -  *  Managed oversubscribed bandwidth; HTB with borrowing. - -  *  Allow equitable distribution of unreserved bandwidth; HTB with - borrowing. - -  *  Ensure that a particular type of traffic is dropped; policer attached - to a filter with a drop action. - - - Remember, too that sometimes, it is simply better to purchase more -bandwidth. Traffic control does not solve all problems! - - ------------------------------------------------------------------------------ - -2.3. Advantages - - When properly employed, traffic control should lead to more predictable -usage of network resources and less volatile contention for these resources. -The network then meets the goals of the traffic control configuration. Bulk -download traffic can be allocated a reasonable amount of bandwidth even as -higher priority interactive traffic is simultaneously serviced. Even low -priority data transfer such as mail can be allocated bandwidth without -tremendously affecting the other classes of traffic. - - In a larger picture, if the traffic control configuration represents policy -which has been communicated to the users, then users (and, by extension, -applications) know what to expect from the network. - - ------------------------------------------------------------------------------ - -2.4. Disdvantages - - - - Complexity is easily one of the most significant disadvantages of using -traffic control. There are ways to become familiar with traffic control tools -which ease the learning curve about traffic control and its mechanisms, but -identifying a traffic control misconfiguration can be quite a challenge. - - Traffic control when used appropriately can lead to more equitable -distribution of network resources. It can just as easily be installed in an -inappropriate manner leading to further and more divisive contention for -resources. - - The computing resources required on a router to support a traffic control -scenario need to be capable of handling the increased cost of maintaining the -traffic control structures. Fortunately, this is a small incremental cost, -but can become more significant as the configuration grows in size and -complexity. - - For personal use, there's no training cost associated with the use of -traffic control, but a company may find that purchasing more bandwidth is a -simpler solution than employing traffic control. Training employees and -ensuring depth of knowledge may be more costly than investing in more -bandwidth. - - Although traffic control on packet-switched networks covers a larger -conceptual area, you can think of traffic control as a way to provide [some -of] the statefulness of a circuit-based network to a packet-switched network. ------------------------------------------------------------------------------ - -2.5. Queues - - Queues form the backdrop for all of traffic control and are the integral -concept behind scheduling. A queue is a location (or buffer) containing a -finite number of items waiting for an action or service. In networking, a -queue is the place where packets (our units) wait to be transmitted by the -hardware (the service). In the simplest model, packets are transmitted in a -first-come first-serve basis [2]. In the discipline of computer networking -(and more generally computer science), this sort of a queue is known as a -FIFO. - - Without any other mechanisms, a queue doesn't offer any promise for traffic -control. There are only two interesting actions in a queue. Anything entering -a queue is enqueued into the queue. To remove an item from a queue is to -dequeue that item. - - A queue becomes much more interesting when coupled with other mechanisms -which can delay packets, rearrange, drop and prioritize packets in multiple -queues. A queue can also use subqueues, which allow for complexity of -behaviour in a scheduling operation. - - From the perspective of the higher layer software, a packet is simply -enqueued for transmission, and the manner and order in which the enqueued -packets are transmitted is immaterial to the higher layer. So, to the higher -layer, the entire traffic control system may appear as a single queue [3]. It -is only by examining the internals of this layer that the traffic control -structures become exposed and available. ------------------------------------------------------------------------------ - -2.6. Flows - - A flow is a distinct connection or conversation between two hosts. Any -unique set of packets between two hosts can be regarded as a flow. Under TCP -the concept of a connection with a source IP and port and destination IP and -port represents a flow. A UDP flow can be similarly defined. - - Traffic control mechanisms frequently separate traffic into classes of -flows which can be aggregated and transmitted as an aggregated flow (consider -DiffServ). Alternate mechanisms may attempt to divide bandwidth equally based -on the individual flows. - - Flows become important when attempting to divide bandwidth equally among a -set of competing flows, especially when some applications deliberately build -a large number of flows. ------------------------------------------------------------------------------ - -2.7. Tokens and buckets - - Two of the key underpinnings of a shaping mechanisms are the interrelated -concepts of tokens and buckets. - - In order to control the rate of dequeuing, an implementation can count the -number of packets or bytes dequeued as each item is dequeued, although this -requires complex usage of timers and measurements to limit accurately. -Instead of calculating the current usage and time, one method, used widely in -traffic control, is to generate tokens at a desired rate, and only dequeue -packets or bytes if a token is available. - - Consider the analogy of an amusement park ride with a queue of people -waiting to experience the ride. Let's imagine a track on which carts traverse -a fixed track. The carts arrive at the head of the queue at a fixed rate. In -order to enjoy the ride, each person must wait for an available cart. The -cart is analogous to a token and the person is analogous to a packet. Again, -this mechanism is a rate-limiting or shaping mechanism. Only a certain number -of people can experience the ride in a particular period. - - To extend the analogy, imagine an empty line for the amusement park ride -and a large number of carts sitting on the track ready to carry people. If a -large number of people entered the line together many (maybe all) of them -could experience the ride because of the carts available and waiting. The -number of carts available is a concept analogous to the bucket. A bucket -contains a number of tokens and can use all of the tokens in bucket without -regard for passage of time. - - And to complete the analogy, the carts on the amusement park ride (our -tokens) arrive at a fixed rate and are only kept available up to the size of -the bucket. So, the bucket is filled with tokens according to the rate, and -if the tokens are not used, the bucket can fill up. If tokens are used the -bucket will not fill up. Buckets are a key concept in supporting bursty -traffic such as HTTP. - - The TBF qdisc is a classical example of a shaper (the section on TBF -includes a diagram which may help to visualize the token and bucket -concepts). The TBF generates rate tokens and only transmits packets when a -token is available. Tokens are a generic shaping concept. - - In the case that a queue does not need tokens immediately, the tokens can -be collected until they are needed. To collect tokens indefinitely would -negate any benefit of shaping so tokens are collected until a certain number -of tokens has been reached. Now, the queue has tokens available for a large -number of packets or bytes which need to be dequeued. These intangible tokens -are stored in an intangible bucket, and the number of tokens that can be -stored depends on the size of the bucket. - - This also means that a bucket full of tokens may be available at any -instant. Very predictable regular traffic can be handled by small buckets. -Larger buckets may be required for burstier traffic, unless one of the -desired goals is to reduce the burstiness of the flows. - - In summary, tokens are generated at rate, and a maximum of a bucket's worth -of tokens may be collected. This allows bursty traffic to be handled, while -smoothing and shaping the transmitted traffic. - - The concepts of tokens and buckets are closely interrelated and are used in -both TBF (one of the classless qdiscs) and HTB (one of the classful qdiscs). -Within the tcng language, the use of two- and three-color meters is -indubitably a token and bucket concept. ------------------------------------------------------------------------------ - -2.8. Packets and frames - - The terms for data sent across network changes depending on the layer the -user is examining. This document will rather impolitely (and incorrectly) -gloss over the technical distinction between packets and frames although they -are outlined here. - - The word frame is typically used to describe a layer 2 (data link) unit of -data to be forwarded to the next recipient. Ethernet interfaces, PPP -interfaces, and T1 interfaces all name their layer 2 data unit a frame. The -frame is actually the unit on which traffic control is performed. - - A packet, on the other hand, is a higher layer concept, representing layer -3 (network) units. The term packet is preferred in this documentation, -although it is slightly inaccurate. ------------------------------------------------------------------------------ - -3. Traditional Elements of Traffic Control - - ------------------------------------------------------------------------------ - -3.1. Shaping - - Shapers delay packets to meet a desired rate. - - Shaping is the mechanism by which packets are delayed before transmission -in an output queue to meet a desired output rate. This is one of the most -common desires of users seeking bandwidth control solutions. The act of -delaying a packet as part of a traffic control solution makes every shaping -mechanism into a non-work-conserving mechanism, meaning roughly: "Work is -required in order to delay packets." - - Viewed in reverse, a non-work-conserving queuing mechanism is performing a -shaping function. A work-conserving queuing mechanism (see PRIO) would not be -capable of delaying a packet. - - Shapers attempt to limit or ration traffic to meet but not exceed a -configured rate (frequently measured in packets per second or bits/bytes per -second). As a side effect, shapers can smooth out bursty traffic [4]. One of -the advantages of shaping bandwidth is the ability to control latency of -packets. The underlying mechanism for shaping to a rate is typically a token -and bucket mechanism. See also Section 2.7 for further detail on tokens and -buckets. ------------------------------------------------------------------------------ - -3.2. Scheduling - - Schedulers arrange and/or rearrange packets for output. - - Scheduling is the mechanism by which packets are arranged (or rearranged) -between input and output of a particular queue. The overwhelmingly most -common scheduler is the FIFO (first-in first-out) scheduler. From a larger -perspective, any set of traffic control mechanisms on an output queue can be -regarded as a scheduler, because packets are arranged for output. - - Other generic scheduling mechanisms attempt to compensate for various -networking conditions. A fair queuing algorithm (see SFQ) attempts to prevent -any single client or flow from dominating the network usage. A round-robin -algorithm (see WRR) gives each flow or client a turn to dequeue packets. -Other sophisticated scheduling algorithms attempt to prevent backbone -overload (see GRED) or refine other scheduling mechanisms (see ESFQ). ------------------------------------------------------------------------------ - -3.3. Classifying - - Classifiers sort or separate traffic into queues. - - Classifying is the mechanism by which packets are separated for different -treatment, possibly different output queues. During the process of accepting, -routing and transmitting a packet, a networking device can classify the -packet a number of different ways. Classification can include marking the -packet, which usually happens on the boundary of a network under a single -administrative control or classification can occur on each hop individually. - - The Linux model (see Section 4.3) allows for a packet to cascade across a -series of classifiers in a traffic control structure and to be classified in -conjunction with policers (see also Section 4.5). ------------------------------------------------------------------------------ - -3.4. Policing - - Policers measure and limit traffic in a particular queue. - - Policing, as an element of traffic control, is simply a mechanism by which -traffic can be limited. Policing is most frequently used on the network -border to ensure that a peer is not consuming more than its allocated -bandwidth. A policer will accept traffic to a certain rate, and then perform -an action on traffic exceeding this rate. A rather harsh solution is to drop -the traffic, although the traffic could be reclassified instead of being -dropped. - - A policer is a yes/no question about the rate at which traffic is entering -a queue. If the packet is about to enter a queue below a given rate, take one -action (allow the enqueuing). If the packet is about to enter a queue above a -given rate, take another action. Although the policer uses a token bucket -mechanism internally, it does not have the capability to delay a packet as a -shaping mechanism does. ------------------------------------------------------------------------------ - -3.5. Dropping - - Dropping discards an entire packet, flow or classification. - - Dropping a packet is a mechanism by which a packet is discarded. - - ------------------------------------------------------------------------------ - -3.6. Marking - - Marking is a mechanism by which the packet is altered. - -Note This is not fwmark. The iptablestarget MARKand the ipchains--markare - used to modify packet metadata, not the packet itself. - - Traffic control marking mechanisms install a DSCP on the packet itself, -which is then used and respected by other routers inside an administrative -domain (usually for DiffServ). ------------------------------------------------------------------------------ - -4. Components of Linux Traffic Control - - - - - - - - -Table 1. Correlation between traffic control elements and Linux components -+-------------------+-------------------------------------------------------+ -|traditional element|Linux component | -+-------------------+-------------------------------------------------------+ -|shaping |The class offers shaping capabilities. | -+-------------------+-------------------------------------------------------+ -|scheduling |A qdisc is a scheduler. Schedulers can be simple such | -| |as the FIFO or complex, containing classes and other | -| |qdiscs, such as HTB. | -+-------------------+-------------------------------------------------------+ -|classifying |The filter object performs the classification through | -| |the agency of a classifier object. Strictly speaking, | -| |Linux classifiers cannot exist outside of a filter. | -+-------------------+-------------------------------------------------------+ -|policing |A policer exists in the Linux traffic control | -| |implementation only as part of a filter. | -+-------------------+-------------------------------------------------------+ -|dropping |To drop traffic requires a filter with a policer which | -| |uses "drop" as an action. | -+-------------------+-------------------------------------------------------+ -|marking |The dsmark qdisc is used for marking. | -+-------------------+-------------------------------------------------------+ ------------------------------------------------------------------------------ - -4.1. qdisc - - Simply put, a qdisc is a scheduler (Section 3.2). Every output interface -needs a scheduler of some kind, and the default scheduler is a FIFO. Other -qdiscs available under Linux will rearrange the packets entering the -scheduler's queue in accordance with that scheduler's rules. - - The qdisc is the major building block on which all of Linux traffic control -is built, and is also called a queuing discipline. - - The classful qdiscs can contain classes, and provide a handle to which to -attach filters. There is no prohibition on using a classful qdisc without -child classes, although this will usually consume cycles and other system -resources for no benefit. - - The classless qdiscs can contain no classes, nor is it possible to attach -filter to a classless qdisc. Because a classless qdisc contains no children -of any kind, there is no utility to classifying. This means that no filter -can be attached to a classless qdisc. - - A source of terminology confusion is the usage of the terms root qdisc and -ingress qdisc. These are not really queuing disciplines, but rather locations -onto which traffic control structures can be attached for egress (outbound -traffic) and ingress (inbound traffic). - - Each interface contains both. The primary and more common is the egress -qdisc, known as the root qdisc. It can contain any of the queuing disciplines -(qdiscs) with potential classes and class structures. The overwhelming -majority of documentation applies to the root qdisc and its children. Traffic -transmitted on an interface traverses the egress or root qdisc. - - For traffic accepted on an interface, the ingress qdisc is traversed. With -its limited utility, it allows no child class to be created, and only exists -as an object onto which a filter can be attached. For practical purposes, the -ingress qdisc is merely a convenient object onto which to attach a policer to -limit the amount of traffic accepted on a network interface. - - In short, you can do much more with an egress qdisc because it contains a -real qdisc and the full power of the traffic control system. An ingress qdisc -can only support a policer. The remainder of the documentation will concern -itself with traffic control structures attached to the root qdisc unless -otherwise specified. ------------------------------------------------------------------------------ - -4.2. class - - Classes only exist inside a classful qdisc (e.g., HTB and CBQ). Classes are -immensely flexible and can always contain either multiple children classes or -a single child qdisc [5]. There is no prohibition against a class containing -a classful qdisc itself, which facilitates tremendously complex traffic -control scenarios. - - Any class can also have an arbitrary number of filters attached to it, -which allows the selection of a child class or the use of a filter to -reclassify or drop traffic entering a particular class. - - A leaf class is a terminal class in a qdisc. It contains a qdisc (default -FIFO) and will never contain a child class. Any class which contains a child -class is an inner class (or root class) and not a leaf class. ------------------------------------------------------------------------------ - -4.3. filter - - The filter is the most complex component in the Linux traffic control -system. The filter provides a convenient mechanism for gluing together -several of the key elements of traffic control. The simplest and most obvious -role of the filter is to classify (see Section 3.3) packets. Linux filters -allow the user to classify packets into an output queue with either several -different filters or a single filter. - -  *  A filter must contain a classifier phrase. - -  *  A filter may contain a policer phrase. - - - Filters can be attached either to classful qdiscs or to classes, however -the enqueued packet always enters the root qdisc first. After the filter -attached to the root qdisc has been traversed, the packet may be directed to -any subclasses (which can have their own filters) where the packet may -undergo further classification. - - ------------------------------------------------------------------------------ - -4.4. classifier - - Filter objects, which can be manipulated using tc, can use several -different classifying mechanisms, the most common of which is the u32 -classifier. The u32 classifier allows the user to select packets based on -attributes of the packet. - - The classifiers are tools which can be used as part of a filter to identify -characteristics of a packet or a packet's metadata. The Linux classfier -object is a direct analogue to the basic operation and elemental mechanism of -traffic control classifying. ------------------------------------------------------------------------------ - -4.5. policer - - This elemental mechanism is only used in Linux traffic control as part of a -filter. A policer calls one action above and another action below the -specified rate. Clever use of policers can simulate a three-color meter. See -also Section 10. - - Although both policing and shaping are basic elements of traffic control -for limiting bandwidth usage a policer will never delay traffic. It can only -perform an action based on specified criteria. See also Example 5. - - - - ------------------------------------------------------------------------------ - -4.6. drop - - This basic traffic control mechanism is only used in Linux traffic control -as part of a policer. Any policer attached to any filter could have a drop -action. - -Note The only place in the Linux traffic control system where a packet can be - explicitly dropped is a policer. A policer can limit packets enqueued at - a specific rate, or it can be configured to drop all traffic matching a - particular pattern [6]. - - There are, however, places within the traffic control system where a packet -may be dropped as a side effect. For example, a packet will be dropped if the -scheduler employed uses this method to control flows as the GRED does. - - Also, a shaper or scheduler which runs out of its allocated buffer space -may have to drop a packet during a particularly bursty or overloaded period. - - ------------------------------------------------------------------------------ - -4.7. handle - - Every class and classful qdisc (see also Section 7) requires a unique -identifier within the traffic control structure. This unique identifier is -known as a handle and has two constituent members, a major number and a minor -number. These numbers can be assigned arbitrarily by the user in accordance -with the following rules [7]. - - - -The numbering of handles for classes and qdiscs - -major - This parameter is completely free of meaning to the kernel. The user - may use an arbitrary numbering scheme, however all objects in the traffic - control structure with the same parent must share a major handle number. - Conventional numbering schemes start at 1 for objects attached directly - to the root qdisc. - -minor - This parameter unambiguously identifies the object as a qdisc if minor - is 0. Any other value identifies the object as a class. All classes - sharing a parent must have unique minor numbers. - - - The special handle ffff:0 is reserved for the ingress qdisc. - - The handle is used as the target in classid and flowid phrases of tc filter -statements. These handles are external identifiers for the objects, usable by -userland applications. The kernel maintains internal identifiers for each -object. ------------------------------------------------------------------------------ - -5. Software and Tools - - ------------------------------------------------------------------------------ - -5.1. Kernel requirements - - Many distributions provide kernels with modular or monolithic support for -traffic control (Quality of Service). Custom kernels may not already provide -support (modular or not) for the required features. If not, this is a very -brief listing of the required kernel options. - - The user who has little or no experience compiling a kernel is recommended -to Kernel HOWTO. Experienced kernel compilers should be able to determine -which of the below options apply to the desired configuration, after reading -a bit more about traffic control and planning. - - -Example 1. Kernel compilation options [8] -# -# QoS and/or fair queueing -# -CONFIG_NET_SCHED=y -CONFIG_NET_SCH_CBQ=m -CONFIG_NET_SCH_HTB=m -CONFIG_NET_SCH_CSZ=m -CONFIG_NET_SCH_PRIO=m -CONFIG_NET_SCH_RED=m -CONFIG_NET_SCH_SFQ=m -CONFIG_NET_SCH_TEQL=m -CONFIG_NET_SCH_TBF=m -CONFIG_NET_SCH_GRED=m -CONFIG_NET_SCH_DSMARK=m -CONFIG_NET_SCH_INGRESS=m -CONFIG_NET_QOS=y -CONFIG_NET_ESTIMATOR=y -CONFIG_NET_CLS=y -CONFIG_NET_CLS_TCINDEX=m -CONFIG_NET_CLS_ROUTE4=m -CONFIG_NET_CLS_ROUTE=y -CONFIG_NET_CLS_FW=m -CONFIG_NET_CLS_U32=m -CONFIG_NET_CLS_RSVP=m -CONFIG_NET_CLS_RSVP6=m -CONFIG_NET_CLS_POLICE=y - - - A kernel compiled with the above set of options will provide modular -support for almost everything discussed in this documentation. The user may -need to modprobe module before using a given feature. Again, the confused -user is recommended to the Kernel HOWTO, as this document cannot adequately -address questions about the use of the Linux kernel. ------------------------------------------------------------------------------ - -5.2. iproute2 tools (tc) - - iproute2 is a suite of command line utilities which manipulate kernel -structures for IP networking configuration on a machine. For technical -documentation on these tools, see the iproute2 documentation and for a more -expository discussion, the documentation at [http://linux-ip.net/] -linux-ip.net. Of the tools in the iproute2 package, the binary tc is the only -one used for traffic control. This HOWTO will ignore the other tools in the -suite. - - - Because it interacts with the kernel to direct the creation, deletion and -modification of traffic control structures, the tc binary needs to be -compiled with support for all of the qdiscs you wish to use. In particular, -the HTB qdisc is not supported yet in the upstream iproute2 package. See -Section 7.1 for more information. - - The tc tool performs all of the configuration of the kernel structures -required to support traffic control. As a result of its many uses, the -command syntax can be described (at best) as arcane. The utility takes as its -first non-option argument one of three Linux traffic control components, -qdisc, class or filter. - - -Example 2. tc command usage -[root@leander]# tc -Usage: tc [ OPTIONS ] OBJECT { COMMAND | help } -where OBJECT := { qdisc | class | filter } - OPTIONS := { -s[tatistics] | -d[etails] | -r[aw] } - - - Each object accepts further and different options, and will be incompletely -described and documented below. The hints in the examples below are designed -to introduce the vagaries of tc command line syntax. For more examples, -consult the [http://lartc.org/howto/] LARTC HOWTO. For even better -understanding, consult the kernel and iproute2 code. - - -Example 3. tc qdisc -[root@leander]# tc qdisc add \ (1) -> dev eth0 \ (2) -> root \ (3) -> handle 1:0 \ (4) -> htb (5) - - -(1) Add a queuing discipline. The verb could also be del. -(2) Specify the device onto which we are attaching the new queuing - discipline. -(3) This means "egress" to tc. The word root must be used, however. Another - qdisc with limited functionality, the ingress qdisc can be attached to - the same device. -(4) The handle is a user-specified number of the form major:minor. The - minor number for any queueing discipline handle must always be zero (0). - An acceptable shorthand for a qdisc handle is the syntax "1:", where the - minor number is assumed to be zero (0) if not specified. -(5) This is the queuing discipline to attach, HTB in this example. Queuing - discipline specific parameters will follow this. In the example here, we - add no qdisc-specific parameters. - - Above was the simplest use of the tc utility for adding a queuing -discipline to a device. Here's an example of the use of tc to add a class to -an existing parent class. - - -Example 4. tc class -[root@leander]# tc class add \ (1) -> dev eth0 \ (2) -> parent 1:1 \ (3) -> classid 1:6 \ (4) -> htb \ (5) -> rate 256kbit \ (6) -> ceil 512kbit (7) - - -(1) Add a class. The verb could also be del. -(2) Specify the device onto which we are attaching the new class. -(3) Specify the parent handle to which we are attaching the new class. -(4) This is a unique handle (major:minor) identifying this class. The minor - number must be any non-zero (0) number. -(5) Both of the classful qdiscs require that any children classes be - classes of the same type as the parent. Thus an HTB qdisc will contain - HTB classes. -(6) (7) - This is a class specific parameter. Consult Section 7.1 for more detail - on these parameters. - - - - -Example 5. tc filter -[root@leander]# tc filter add \ (1) -> dev eth0 \ (2) -> parent 1:0 \ (3) -> protocol ip \ (4) -> prio 5 \ (5) -> u32 \ (6) -> match ip port 22 0xffff \ (7) -> match ip tos 0x10 0xff \ (8) -> flowid 1:6 \ (9) -> police \ (10) -> rate 32000bps \ (11) -> burst 10240 \ (12) -> mpu 0 \ (13) -> action drop/continue (14) - - -(1) Add a filter. The verb could also be del. -(2) Specify the device onto which we are attaching the new filter. -(3) Specify the parent handle to which we are attaching the new filter. -(4) This parameter is required. It's use should be obvious, although I - don't know more. -(5) The prio parameter allows a given filter to be preferred above another. - The pref is a synonym. -(6) This is a classifier, and is a required phrase in every tc filter - command. -(7) (8) - These are parameters to the classifier. In this case, packets with a - type of service flag (indicating interactive usage) and matching port 22 - will be selected by this statement. -(9) The flowid specifies the handle of the target class (or qdisc) to which - a matching filter should send its selected packets. -(10) - This is the policer, and is an optional phrase in every tc filter - command. -(11) The policer will perform one action above this rate, and another action - below (see action parameter). -(12) The burst is an exact analog to burst in HTB (burst is a buckets - concept). -(13) The minimum policed unit. To count all traffic, use an mpu of zero (0). -(14) The action indicates what should be done if the rate based on the - attributes of the policer. The first word specifies the action to take if - the policer has been exceeded. The second word specifies action to take - otherwise. - - As evidenced above, the tc command line utility has an arcane and complex -syntax, even for simple operations such as these examples show. It should -come as no surprised to the reader that there exists an easier way to -configure Linux traffic control. See the next section, Section 5.3. ------------------------------------------------------------------------------ - -5.3. tcng, Traffic Control Next Generation - - FIXME; sing the praises of tcng. See also [http://tldp.org/HOWTO/ -Traffic-Control-tcng-HTB-HOWTO/] Traffic Control using tcng and HTB HOWTO -and tcng documentation. - - Traffic control next generation (hereafter, tcng) provides all of the power -of traffic control under Linux with twenty percent of the headache. - - ------------------------------------------------------------------------------ - -5.4. IMQ, Intermediate Queuing device - - - - FIXME; must discuss IMQ. See also Patrick McHardy's website on [http:// -trash.net/~kaber/imq/] IMQ. - - ------------------------------------------------------------------------------ - -6. Classless Queuing Disciplines (qdiscs) - - Each of these queuing disciplines can be used as the primary qdisc on an -interface, or can be used inside a leaf class of a classful qdiscs. These are -the fundamental schedulers used under Linux. Note that the default scheduler -is the pfifo_fast. - - ------------------------------------------------------------------------------ - -6.1. FIFO, First-In First-Out (pfifo and bfifo) - -Note This is not the default qdisc on Linux interfaces. Be certain to see - Section 6.2 for the full details on the default (pfifo_fast) qdisc. - - The FIFO algorithm forms the basis for the default qdisc on all Linux -network interfaces (pfifo_fast). It performs no shaping or rearranging of -packets. It simply transmits packets as soon as it can after receiving and -queuing them. This is also the qdisc used inside all newly created classes -until another qdisc or a class replaces the FIFO. - -[fifo-qdisc] - - A real FIFO qdisc must, however, have a size limit (a buffer size) to -prevent it from overflowing in case it is unable to dequeue packets as -quickly as it receives them. Linux implements two basic FIFO qdiscs, one -based on bytes, and one on packets. Regardless of the type of FIFO used, the -size of the queue is defined by the parameter limit. For a pfifo the unit is -understood to be packets and for a bfifo the unit is understood to be bytes. - - -Example 6. Specifying a limit for a packet or byte FIFO -[root@leander]# cat bfifo.tcc -/* - * make a FIFO on eth0 with 10kbyte queue size - * - */ - -dev eth0 { - egress { - fifo (limit 10kB ); - } -} -[root@leander]# tcc < bfifo.tcc -# ================================ Device eth0 ================================ - -tc qdisc add dev eth0 handle 1:0 root dsmark indices 1 default_index 0 -tc qdisc add dev eth0 handle 2:0 parent 1:0 bfifo limit 10240 -[root@leander]# cat pfifo.tcc -/* - * make a FIFO on eth0 with 30 packet queue size - * - */ - -dev eth0 { - egress { - fifo (limit 30p ); - } -} -[root@leander]# tcc < pfifo.tcc -# ================================ Device eth0 ================================ - -tc qdisc add dev eth0 handle 1:0 root dsmark indices 1 default_index 0 -tc qdisc add dev eth0 handle 2:0 parent 1:0 pfifo limit 30 - ------------------------------------------------------------------------------ - -6.2. pfifo_fast, the default Linux qdisc - - The pfifo_fast qdisc is the default qdisc for all interfaces under Linux. -Based on a conventional FIFO qdisc, this qdisc also provides some -prioritization. It provides three different bands (individual FIFOs) for -separating traffic. The highest priority traffic (interactive flows) are -placed into band 0 and are always serviced first. Similarly, band 1 is always -emptied of pending packets before band 2 is dequeued. - -[pfifo_fast-qdisc] - - There is nothing configurable to the end user about the pfifo_fast qdisc. -For exact details on the priomap and use of the ToS bits, see the pfifo-fast -section of the LARTC HOWTO. ------------------------------------------------------------------------------ - -6.3. SFQ, Stochastic Fair Queuing - - The SFQ qdisc attempts to fairly distribute opportunity to transmit data to -the network among an arbitrary number of flows. It accomplishes this by using -a hash function to separate the traffic into separate (internally maintained) -FIFOs which are dequeued in a round-robin fashion. Because there is the -possibility for unfairness to manifest in the choice of hash function, this -function is altered periodically. Perturbation (the parameter perturb) sets -this periodicity. - -[sfq-qdisc] - - -Example 7. Creating an SFQ -[root@leander]# cat sfq.tcc -/* - * make an SFQ on eth0 with a 10 second perturbation - * - */ - -dev eth0 { - egress { - sfq( perturb 10s ); - } -} -[root@leander]# tcc < sfq.tcc -# ================================ Device eth0 ================================ - -tc qdisc add dev eth0 handle 1:0 root dsmark indices 1 default_index 0 -tc qdisc add dev eth0 handle 2:0 parent 1:0 sfq perturb 10 - - - Unfortunately, some clever software (e.g. Kazaa and eMule among others) -obliterate the benefit of this attempt at fair queuing by opening as many TCP -sessions (flows) as can be sustained. In many networks, with well-behaved -users, SFQ can adequately distribute the network resources to the contending -flows, but other measures may be called for when obnoxious applications have -invaded the network. - - See also Section 6.4 for an SFQ qdisc with more exposed parameters for the -user to manipulate. ------------------------------------------------------------------------------ - -6.4. ESFQ, Extended Stochastic Fair Queuing - - Conceptually, this qdisc is no different than SFQ although it allows the -user to control more parameters than its simpler cousin. This qdisc was -conceived to overcome the shortcoming of SFQ identified above. By allowing -the user to control which hashing algorithm is used for distributing access -to network bandwidth, it is possible for the user to reach a fairer real -distribution of bandwidth. - - -Example 8. ESFQ usage -Usage: ... esfq [ perturb SECS ] [ quantum BYTES ] [ depth FLOWS ] - [ divisor HASHBITS ] [ limit PKTS ] [ hash HASHTYPE] - -Where: -HASHTYPE := { classic | src | dst } - - - FIXME; need practical experience and/or attestation here. ------------------------------------------------------------------------------ - -6.5. GRED, Generic Random Early Drop - - FIXME; I have never used this. Need practical experience or attestation. - - Theory declares that a RED algorithm is useful on a backbone or core -network, but not as useful near the end-user. See the section on flows to see -a general discussion of the thirstiness of TCP. ------------------------------------------------------------------------------ - -6.6. TBF, Token Bucket Filter - - This qdisc is built on tokens and buckets. It simply shapes traffic -transmitted on an interface. To limit the speed at which packets will be -dequeued from a particular interface, the TBF qdisc is the perfect solution. -It simply slows down transmitted traffic to the specified rate. - - Packets are only transmitted if there are sufficient tokens available. -Otherwise, packets are deferred. Delaying packets in this fashion will -introduce an artificial latency into the packet's round trip time. - -[tbf-qdisc] - - -Example 9. Creating a 256kbit/s TBF -[root@leander]# cat tbf.tcc -/* - * make a 256kbit/s TBF on eth0 - * - */ - -dev eth0 { - egress { - tbf( rate 256 kbps, burst 20 kB, limit 20 kB, mtu 1514 B ); - } -} -[root@leander]# tcc < tbf.tcc -# ================================ Device eth0 ================================ - -tc qdisc add dev eth0 handle 1:0 root dsmark indices 1 default_index 0 -tc qdisc add dev eth0 handle 2:0 parent 1:0 tbf burst 20480 limit 20480 mtu 1514 rate 32000bps - - - ------------------------------------------------------------------------------ - -7. Classful Queuing Disciplines (qdiscs) - - The flexibility and control of Linux traffic control can be unleashed -through the agency of the classful qdiscs. Remember that the classful queuing -disciplines can have filters attached to them, allowing packets to be -directed to particular classes and subqueues. - - There are several common terms to describe classes directly attached to the -root qdisc and terminal classes. Classess attached to the root qdisc are -known as root classes, and more generically inner classes. Any terminal class -in a particular queuing discipline is known as a leaf class by analogy to the -tree structure of the classes. Besides the use of figurative language -depicting the structure as a tree, the language of family relationships is -also quite common. ------------------------------------------------------------------------------ - -7.1. HTB, Hierarchical Token Bucket - - HTB uses the concepts of tokens and buckets along with the class-based -system and filters to allow for complex and granular control over traffic. -With a complex borrowing model, HTB can perform a variety of sophisticated -traffic control techniques. One of the easiest ways to use HTB immediately is -that of shaping. - - By understanding tokens and buckets or by grasping the function of TBF, HTB -should be merely a logical step. This queuing discipline allows the user to -define the characteristics of the tokens and bucket used and allows the user -to nest these buckets in an arbitrary fashion. When coupled with a -classifying scheme, traffic can be controlled in a very granular fashion. - - - - Below is example output of the syntax for HTB on the command line with the -tc tool. Although the syntax for tcng is a language of its own, the rules for -HTB are the same. - - -Example 10. tc usage for HTB -Usage: ... qdisc add ... htb [default N] [r2q N] - default minor id of class to which unclassified packets are sent {0} - r2q DRR quantums are computed as rate in Bps/r2q {10} - debug string of 16 numbers each 0-3 {0} - -... class add ... htb rate R1 burst B1 [prio P] [slot S] [pslot PS] - [ceil R2] [cburst B2] [mtu MTU] [quantum Q] - rate rate allocated to this class (class can still borrow) - burst max bytes burst which can be accumulated during idle period {computed} - ceil definite upper class rate (no borrows) {rate} - cburst burst but for ceil {computed} - mtu max packet size we create rate map for {1600} - prio priority of leaf; lower are served first {0} - quantum how much bytes to serve from leaf at once {use r2q} - -TC HTB version 3.3 - - - ------------------------------------------------------------------------------ - -7.1.1. Software requirements - - Unlike almost all of the other software discussed, HTB is a newer queuing -discipline and your distribution may not have all of the tools and capability -you need to use HTB. The kernel must support HTB; kernel version 2.4.20 and -later support it in the stock distribution, although earlier kernel versions -require patching. To enable userland support for HTB, see [http:// -luxik.cdi.cz/~devik/qos/htb/] HTB for an iproute2 patch to tc. ------------------------------------------------------------------------------ - -7.1.2. Shaping - - One of the most common applications of HTB involves shaping transmitted -traffic to a specific rate. - - All shaping occurs in leaf classes. No shaping occurs in inner or root -classes as they only exist to suggest how the borrowing model should -distribute available tokens. - - - - ------------------------------------------------------------------------------ - -7.1.3. Borrowing - - A fundamental part of the HTB qdisc is the borrowing mechanism. Children -classes borrow tokens from their parents once they have exceeded rate. A -child class will continue to attempt to borrow until it reaches ceil, at -which point it will begin to queue packets for transmission until more tokens -/ctokens are available. As there are only two primary types of classes which -can be created with HTB the following table and diagram identify the various -possible states and the behaviour of the borrowing mechanisms. - - - - -Table 2. HTB class states and potential actions taken -+------+-----+--------------+-----------------------------------------------+ -|type |class|HTB internal |action taken | -|of |state|state | | -|class | | | | -+------+-----+--------------+-----------------------------------------------+ -|leaf |< |HTB_CAN_SEND |Leaf class will dequeue queued bytes up to | -| |rate | |available tokens (no more than burst packets) | -+------+-----+--------------+-----------------------------------------------+ -|leaf |> |HTB_MAY_BORROW|Leaf class will attempt to borrow tokens/ | -| |rate,| |ctokens from parent class. If tokens are | -| |< | |available, they will be lent in quantum | -| |ceil | |increments and the leaf class will dequeue up | -| | | |to cburst bytes | -+------+-----+--------------+-----------------------------------------------+ -|leaf |> |HTB_CANT_SEND |No packets will be dequeued. This will cause | -| |ceil | |packet delay and will increase latency to meet | -| | | |the desired rate. | -+------+-----+--------------+-----------------------------------------------+ -|inner,|< |HTB_CAN_SEND |Inner class will lend tokens to children. | -|root |rate | | | -+------+-----+--------------+-----------------------------------------------+ -|inner,|> |HTB_MAY_BORROW|Inner class will attempt to borrow tokens/ | -|root |rate,| |ctokens from parent class, lending them to | -| |< | |competing children in quantum increments per | -| |ceil | |request. | -+------+-----+--------------+-----------------------------------------------+ -|inner,|> |HTB_CANT_SEND |Inner class will not attempt to borrow from its| -|root |ceil | |parent and will not lend tokens/ctokens to | -| | | |children classes. | -+------+-----+--------------+-----------------------------------------------+ - - This diagram identifies the flow of borrowed tokens and the manner in which -tokens are charged to parent classes. In order for the borrowing model to -work, each class must have an accurate count of the number of tokens used by -itself and all of its children. For this reason, any token used in a child or -leaf class is charged to each parent class until the root class is reached. - - Any child class which wishes to borrow a token will request a token from -its parent class, which if it is also over its rate will request to borrow -from its parent class until either a token is located or the root class is -reached. So the borrowing of tokens flows toward the leaf classes and the -charging of the usage of tokens flows toward the root class. - -[htb-borrow] - - Note in this diagram that there are several HTB root classes. Each of these -root classes can simulate a virtual circuit. ------------------------------------------------------------------------------ - -7.1.4. HTB class parameters - - - -default - An optional parameter with every HTB qdisc object, the default default - is 0, which cause any unclassified traffic to be dequeued at hardware - speed, completely bypassing any of the classes attached to the root - qdisc. - -rate - Used to set the minimum desired speed to which to limit transmitted - traffic. This can be considered the equivalent of a committed information - rate (CIR), or the guaranteed bandwidth for a given leaf class. - -ceil - Used to set the maximum desired speed to which to limit the transmitted - traffic. The borrowing model should illustrate how this parameter is - used. This can be considered the equivalent of "burstable bandwidth". - -burst - This is the size of the rate bucket (see Tokens and buckets). HTB will - dequeue burst bytes before awaiting the arrival of more tokens. - -cburst - This is the size of the ceil bucket (see Tokens and buckets). HTB will - dequeue cburst bytes before awaiting the arrival of more ctokens. - -quantum - This is a key parameter used by HTB to control borrowing. Normally, the - correct quantum is calculated by HTB, not specified by the user. Tweaking - this parameter can have tremendous effects on borrowing and shaping under - contention, because it is used both to split traffic between children - classes over rate (but below ceil) and to transmit packets from these - same classes. - -r2q - Also, usually calculated for the user, r2q is a hint to HTB to help - determine the optimal quantum for a particular class. - -mtu - - -prio - - - - ------------------------------------------------------------------------------ - -7.1.5. Rules - - Below are some general guidelines to using HTB culled from [http:// -docum.org/] http://docum.org/ and the LARTC mailing list. These rules are -simply a recommendation for beginners to maximize the benefit of HTB until -gaining a better understanding of the practical application of HTB. - - - -  *  Shaping with HTB occurs only in leaf classes. See also Section 7.1.2. - -  *  Because HTB does not shape in any class except the leaf class, the sum - of the rates of leaf classes should not exceed the ceil of a parent - class. Ideally, the sum of the rates of the children classes would match - the rate of the parent class, allowing the parent class to distribute - leftover bandwidth (ceil - rate) among the children classes. - - This key concept in employing HTB bears repeating. Only leaf classes - actually shape packets; packets are only delayed in these leaf classes. - The inner classes (all the way up to the root class) exist to define how - borrowing/lending occurs (see also Section 7.1.3). - -  *  The quantum is only only used when a class is over rate but below ceil. - -  *  The quantum should be set at MTU or higher. HTB will dequeue a single - packet at least per service opportunity even if quantum is too small. In - such a case, it will not be able to calculate accurately the real - bandwidth consumed [9]. - -  *  Parent classes lend tokens to children in increments of quantum, so for - maximum granularity and most instantaneously evenly distributed - bandwidth, quantum should be as low as possible while still no less than - MTU. - -  *  A distinction between tokens and ctokens is only meaningful in a leaf - class, because non-leaf classes only lend tokens to child classes. - -  *  HTB borrowing could more accurately be described as "using". - - - ------------------------------------------------------------------------------ - -7.2. PRIO, priority scheduler - - The PRIO classful qdisc works on a very simple precept. When it is ready to -dequeue a packet, the first class is checked for a packet. If there's a -packet, it gets dequeued. If there's no packet, then the next class is -checked, until the queuing mechanism has no more classes to check. - - This section will be completed at a later date. ------------------------------------------------------------------------------ - -7.3. CBQ, Class Based Queuing - - CBQ is the classic implementation (also called venerable) of a traffic -control system. This section will be completed at a later date. - - ------------------------------------------------------------------------------ - -8. Rules, Guidelines and Approaches - - ------------------------------------------------------------------------------ - -8.1. General Rules of Linux Traffic Control - - There are a few general rules which ease the study of Linux traffic -control. Traffic control structures under Linux are the same whether the -initial configuration has been done with tcng or with tc. - -  *  Any router performing a shaping function should be the bottleneck on - the link, and should be shaping slightly below the maximum available link - bandwidth. This prevents queues from forming in other routers, affording - maximum control of packet latency/deferral to the shaping device. - -  *  A device can only shape traffic it transmits [10]. Because the traffic - has already been received on an input interface, the traffic cannot be - shaped. A traditional solution to this problem is an ingress policer. - -  *  Every interface must have a qdisc. The default qdisc (the pfifo_fast - qdisc) is used when another qdisc is not explicitly attached to the - interface. - -  *  One of the classful qdiscs added to an interface with no children - classes typically only consumes CPU for no benefit. - -  *  Any newly created class contains a FIFO. This qdisc can be replaced - explicitly with any other qdisc. The FIFO qdisc will be removed - implicitly if a child class is attached to this class. - -  *  Classes directly attached to the root qdisc can be used to simulate - virtual circuits. - -  *  A filter can be attached to classes or one of the classful qdiscs. - - - - - - - - - ------------------------------------------------------------------------------ - -8.2. Handling a link with a known bandwidth - - HTB is an ideal qdisc to use on a link with a known bandwidth, because the -innermost (root-most) class can be set to the maximum bandwidth available on -a given link. Flows can be further subdivided into children classes, allowing -either guaranteed bandwidth to particular classes of traffic or allowing -preference to specific kinds of traffic. - - - - ------------------------------------------------------------------------------ - -8.3. Handling a link with a variable (or unknown) bandwidth - - In theory, the PRIO scheduler is an ideal match for links with variable -bandwidth, because it is a work-conserving qdisc (which means that it -provides no shaping). In the case of a link with an unknown or fluctuating -bandwidth, the PRIO scheduler simply prefers to dequeue any available packet -in the highest priority band first, then falling to the lower priority -queues. - - - - ------------------------------------------------------------------------------ - -8.4. Sharing/splitting bandwidth based on flows - - Of the many types of contention for network bandwidth, this is one of the -easier types of contention to address in general. By using the SFQ qdisc, -traffic in a particular queue can be separated into flows, each of which will -be serviced fairly (inside that queue). Well-behaved applications (and users) -will find that using SFQ and ESFQ are sufficient for most sharing needs. - - The Achilles heel of these fair queuing algorithms is a misbehaving user or -application which opens many connections simultaneously (e.g., eMule, -eDonkey, Kazaa). By creating a large number of individual flows, the -application can dominate slots in the fair queuing algorithm. Restated, the -fair queuing algorithm has no idea that a single application is generating -the majority of the flows, and cannot penalize the user. Other methods are -called for. - - ------------------------------------------------------------------------------ - -8.5. Sharing/splitting bandwidth based on IP - - For many administrators this is the ideal method of dividing bandwidth -amongst their users. Unfortunately, there is no easy solution, and it becomes -increasingly complex with the number of machine sharing a network link. - - To divide bandwidth equitably between N IP addresses, there must be N -classes. - - ------------------------------------------------------------------------------ - -9. Scripts for use with QoS/Traffic Control - - - - - - ------------------------------------------------------------------------------ - -9.1. wondershaper - - More to come, see [http://lartc.org/wondershaper/] wondershaper. ------------------------------------------------------------------------------ - -9.2. ADSL Bandwidth HOWTO script (myshaper) - - More to come, see [http://www.tldp.org/HOWTO/ -ADSL-Bandwidth-Management-HOWTO/implementation.html] myshaper. ------------------------------------------------------------------------------ - -9.3. htb.init - - More to come, see htb.init. ------------------------------------------------------------------------------ - -9.4. tcng.init - - More to come, see tcng.init. ------------------------------------------------------------------------------ - -9.5. cbq.init - - More to come, see cbq.init. ------------------------------------------------------------------------------ - -10. Diagram - - - - ------------------------------------------------------------------------------ - -10.1. General diagram - - Below is a general diagram of the relationships of the components of a -classful queuing discipline (HTB pictured). A larger version of the diagram -is [http://linux-ip.net/traffic-control/htb-class.png] available. - - - - -Example 11. An example HTB tcng configuration -/* - * - * possible mock up of diagram shown at - * http://linux-ip.net/traffic-control/htb-class.png - * - */ - -$m_web = trTCM ( - cir 512 kbps, /* commited information rate */ - cbs 10 kB, /* burst for CIR */ - pir 1024 kbps, /* peak information rate */ - pbs 10 kB /* burst for PIR */ - ) ; - -dev eth0 { - egress { - - class ( <$web> ) if tcp_dport == PORT_HTTP && __trTCM_green( $m_web ); - class ( <$bulk> ) if tcp_dport == PORT_HTTP && __trTCM_yellow( $m_web ); - drop if __trTCM_red( $m_web ); - class ( <$bulk> ) if tcp_dport == PORT_SSH ; - - htb () { /* root qdisc */ - - class ( rate 1544kbps, ceil 1544kbps ) { /* root class */ - - $web = class ( rate 512kbps, ceil 512kbps ) { sfq ; } ; - $bulk = class ( rate 512kbps, ceil 1544kbps ) { sfq ; } ; - - } - } - } -} - - -[htb-class] - - ------------------------------------------------------------------------------ - -11. Annotated Traffic Control Links - - This section identifies a number of links to documentation about traffic -control and Linux traffic control software. Each link will be listed with a -brief description of the content at that site. - -  *  HTB site, HTB user guide and HTB theory (Martin "devik" Devera) - - Hierarchical Token Bucket, HTB, is a classful queuing discipline. - Widely used and supported it is also fairly well documented in the user - guide and at [http://www.docum.org/] Stef Coene's site (see below). - -  *  General Quality of Service docs (Leonardo Balliache) - - - There is a good deal of understandable and introductory documentation on - his site, and in particular has some excellent overview material. See in - particular, the detailed [http://opalsoft.net/qos/DS.htm] Linux QoS - document among others. -  *  tcng (Traffic Control Next Generation) and tcng manual (Werner - Almesberger) - - The tcng software includes a language and a set of tools for creating - and testing traffic control structures. In addition to generating tc - commands as output, it is also capable of providing output for non-Linux - applications. A key piece of the tcng suite which is ignored in this - documentation is the tcsim traffic control simulator. - - The user manual provided with the tcng software has been converted to - HTML with latex2html. The distribution comes with the TeX documentation. - -  *  iproute2 and iproute2 manual (Alexey Kuznetsov) - - This is a the source code for the iproute2 suite, which includes the - essential tc binary. Note, that as of - iproute2-2.4.7-now-ss020116-try.tar.gz, the package did not support HTB, - so a patch available from the [http://luxik.cdi.cz/~devik/qos/htb/] HTB - site will be required. - - The manual documents the entire suite of tools, although the tc utility - is not adequately documented here. The ambitious reader is recommended to - the LARTC HOWTO after consuming this introduction. - -  *  Documentation, graphs, scripts and guidelines to traffic control under - Linux (Stef Coene) - - Stef Coene has been gathering statistics and test results, scripts and - tips for the use of QoS under Linux. There are some particularly useful - graphs and guidelines available for implementing traffic control at - Stef's site. - -  *  [http://lartc.org/howto/] LARTC HOWTO (bert hubert, et. al.) - - The Linux Advanced Routing and Traffic Control HOWTO is one of the key - sources of data about the sophisticated techniques which are available - for use under Linux. The Traffic Control Introduction HOWTO should - provide the reader with enough background in the language and concepts of - traffic control. The LARTC HOWTO is the next place the reader should look - for general traffic control information. - -  *  Guide to IP Networking with Linux (Martin A. Brown) - - Not directly related to traffic control, this site includes articles - and general documentation on the behaviour of the Linux IP layer. - -  *  Werner Almesberger's Papers - - Werner Almesberger is one of the main developers and champions of - traffic control under Linux (he's also the author of tcng, above). One of - the key documents describing the entire traffic control architecture of - the Linux kernel is his Linux Traffic Control - Implementation Overview - which is available in [http://www.almesberger.net/cv/papers/tcio8.pdf] - PDF or [http://www.almesberger.net/cv/papers/tcio8.ps.gz] PS format. - -  *  Linux DiffServ project - - Mercilessly snipped from the main page of the DiffServ site... - - Differentiated Services (short: Diffserv) is an architecture for - providing different types or levels of service for network traffic. - One key characteristic of Diffserv is that flows are aggregated in - the network, so that core routers only need to distinguish a - comparably small number of aggregated flows, even if those flows - contain thousands or millions of individual flows. - - -Notes - -[1] See Section 5 for more details on the use or installation of a - particular traffic control mechanism, kernel or command line utility. -[2] This queueing model has long been used in civilized countries to - distribute scant food or provisions equitably. William Faulkner is - reputed to have walked to the front of the line for to fetch his share - of ice, proving that not everybody likes the FIFO model, and providing - us a model for considering priority queuing. -[3] Similarly, the entire traffic control system appears as a queue or - scheduler to the higher layer which is enqueuing packets into this - layer. -[4] This smoothing effect is not always desirable, hence the HTB parameters - burst and cburst. -[5] A classful qdisc can only have children classes of its type. For - example, an HTB qdisc can only have HTB classes as children. A CBQ qdisc - cannot have HTB classes as children. -[6] In this case, you'll have a filter which uses a classifier to select the - packets you wish to drop. Then you'll use a policer with a with a drop - action like this police rate 1bps burst 1 action drop/drop. -[7] I do not know the range nor base of these numbers. I believe they are - u32 hexadecimal, but need to confirm this. -[8] The options listed in this example are taken from a 2.4.20 kernel source - tree. The exact options may differ slightly from kernel release to - kernel release depending on patches and new schedulers and classifiers. -[9] HTB will report bandwidth usage in this scenario incorrectly. It will - calculate the bandwidth used by quantum instead of the real dequeued - packet size. This can skew results quickly. -[10] In fact, the Intermediate Queuing Device (IMQ) simulates an output - device onto which traffic control structures can be attached. This - clever solution allows a networking device to shape ingress traffic in - the same fashion as egress traffic. Despite the apparent contradiction - of the rule, IMQ appears as a device to the kernel. Thus, there has been - no violation of the rule, but rather a sneaky reinterpretation of that - rule. - ProxyARP Subnetting HOWTO -Bob Edwards - - Robert.Edwards@anu.edu.au - - v2.0, 27 August 2000 - - This HOWTO discusses using Proxy Address Resolution Protocol (ARP) - with subnetting in order to make a small network of machines visible - on another Internet Protocol (IP) subnet (I call it sub-subnetting). - This makes all the machines on the local network (network 0 from now - on) appear as if they are connected to the main network (network 1). - - This is only relevent if all machines are connected by Ethernet or - ether devices (ie. it won't work for SLIP/PPP/CSLIP etc.) - _________________________________________________________________ - - Table of Contents - 1. [1]Acknowledgements - 2. [2]Why use Proxy ARP with subnetting? - 3. [3]How Proxy ARP with subnetting works - 4. [4]Setting up Proxy ARP with subnetting - 5. [5]Other alternatives to Proxy ARP with subnetting - 6. [6]Other Applications of Proxy ARP with subnetting - 7. [7]Copying conditions - -1. Acknowledgements - - This document, and my Proxy ARP implementation could not have been - made possible without the help of: - - * Andrew Tridgell, who implemented the subnetting options for arp in - Linux, and who personally assisted me in getting it working - * the Proxy-ARP mini-HOWTO, by Al Longyear - * the Multiple-Ethernet mini-HOWTO, by Don Becker - * the arp(8) source code and man page by Fred N. van Kempen and - Bernd Eckenfels - _________________________________________________________________ - -2. Why use Proxy ARP with subnetting? - - The applications for using Proxy ARP with subnetting are fairly - specific. - - In my case, I had a wireless Ethernet card that plugs into an 8-bit - ISA slot. I wanted to use this card to provide connectivity for a - number of machines at once. Being an ISA card, I could use it on a - Linux machine, after I had written an appropriate device driver for it - - this is the subject of another document. From here, it was only - necessary to add a second Ethernet interface to the Linux machine and - then use some mechanism to join the two networks together. - - For the purposes of discussion, let network 0 be the local Ethernet - connected to the Linux box via an NE-2000 clone Ethernet interface on - eth0. Network 1 is the main network connected via the wireless - Ethernet card on eth1. Machine A is the Linux box with both - interfaces. Machine B is any TCP/IP machine on network 0 and machine C - is likewise on network 1. - - Normally, to provide the connectivity, I would have done one of the - following: - - * Used the IP-Bridge software (see the Bridge mini-HOWTO) to bridge - the traffic between the two network interfaces. Unfortunately, the - wireless Ethernet interface cannot be put into "Promiscuous" mode - (ie. it can't see all packets on network 1). This is mainly due to - the lower bandwidth of the wireless Ethernet (2MBit/sec) meaning - that we don't want to carry any traffic not specifically destined - to another wireless Ethernet machine - in our case machine A - or - broadcasts. Also, bridging is rather CPU intensive! - * Alternatively, use subnets and an IP-router to pass packets - between the two networks (see the IP-Subnetworking mini-HOWTO). - This is a protocol specific solution, where the Linux kernel can - handle the Internet Protocol (IP) packets, but other protocols - (such as AppleTalk) need extra software to route. This also - requires the allocation of a new IP subnet (network) number, which - is not always an option. - - In my case, getting a new subnet (network) number was not an option, - so I wanted a solution that allowed all the machines on network 0 to - appear as if they were on network 1. This is where Proxy ARP comes in. - Other solutions are used to connect other (non-IP) protocols, such as - netatalk to provide AppleTalk routing. - _________________________________________________________________ - -3. How Proxy ARP with subnetting works - - The Proxy ARP is actually only used to get packets from network 1 to - network 0. To get packets back the other way, the normal IP routing - functionality is employed. - - In my case, network 1 has an 8-bit subnet mask (255.255.255.0). I have - chosen the subnet mask for network 0 to be 4-bit (255.255.255.240), - allowing 14 IP nodes on network 0 (2 ^ 4 = 16, less two for the all - zeros and all ones cases). Note that any size of subnet mask up to, - but not including, the size of the mask of the other network is - allowable here (eg. 2, 3, 4, 5, 6 or 7 bits in this case - for one - bit, just use normal Proxy ARP!) - - All the IP numbers for network 0 (16 in total) appear in network 1 as - a subset. Note that it is very important, in this case, not to allow - any machine connected directly to network 1 to have an IP number in - this range! In my case, I have "reserved" the IP numbers of network 1 - ending in 64 .. 79 for network 0. In this case, the IP numbers ending - in 64 and 79 can't actually be used by nodes - 79 is the broadcast - address for network 0. - - Machine A is allocated two IP numbers, one within the network 0 range - for it's real Ethernet interface (eth0) and the other within the - network 1 range, but outside of the network 0 range, for the wireless - Ethernet interface (eth1). - - Say machine C (on network 1) wants to send a packet to machine B (on - network 0). Because the IP number of machine B makes it look to - machine C as though it is on the same physical network, machine C will - use the Address Resolution Protocol (ARP) to send a broadcast message - on network 1 requesting the machine with the IP number of machine B to - respond with it's hardware (Ethernet or MAC layer) address. Machine B - won't see this request, as it isn't actually on network 1, but machine - A, on both networks, will see it. - - The first bit of magic now happens as the Linux kernel arp code on - machine A, with a properly configured Proxy ARP with subnetting entry, - determines that the ARP request has come in on the network 1 interface - (eth1) and that the IP number being ARP'd for is in the subnet range - for network 0. Machine A then sends it's own hardware (Ethernet) - address back to machine C as an ARP response packet. - - Machine C then updates it's ARP cache with an entry for machine B, but - with the hardware (Ethernet) address of machine A (in this case, the - wireless Ethernet interface). Machine C can now send the packet for - machine B to this hardware (Ethernet) address, and machine A receives - it. - - Machine A notices that the destination IP number in the packet is that - of machine B, not itself. Machine A's Linux kernel IP routing code - attempts to forward the packet to machine B by looking at it's routing - tables to determine which interface contains the network number for - machine B. However, the IP number for machine B is valid for both the - network 0 interface (eth0), and for the network 1 interface (eth1). - - At this point, something else clever happens. Because the subnet mask - for the network 0 interface has more 1 bits (it is more specific) than - the subnet mask for the network 1 interface, the Linux kernel routing - code will match the IP number for machine B to the network 0 - interface, and not keep looking for the potential match with the - network 1 interface (the one the packet came in on). - - Now machine A needs to find out the "real" hardware (Ethernet) address - for machine B (assuming that it doesn't already have it in the ARP - cache). Machine A uses an ARP request, but this time the Linux kernel - arp code notes that the request isn't coming from the network 1 - interface (eth1), and so doesn't respond with the Proxy address of - eth1. Instead, it sends the ARP request on the network 0 interface - (eth0), where machine B will see it and respond with it's own (real) - hardware (Ethernet) address. Now machine A can send the packet (from - machine C) onto machine B. - - Machine B gets the packet from machine C (via machine A) and then - wants to send back a response. This time, machine B notices that - machine C in on a different subnet (machine B's subnet mask of - 255.255.255.240 excludes all machines not in the network 0 IP address - range). Machine B is setup with a "default" route to machine A's - network 0 IP number and sends the packet to machine A. This time, - machine A's Linux kernel routing code determines the destination IP - number (of machine C) as being on network 1 and sends the packet onto - machine C via Ethernet interface eth1. - - Similar (less complicated) things occur for packets originating from - and destined to machine A from other machines on either of the two - networks. - - Similarly, it should be obvious that if another machine (D) on network - 0 ARP's for machine B, machine A will receive the ARP request on it's - network 0 interface (eth0) and won't respond to the request as it is - set up to only Proxy on it's network 1 interface (eth1). - - Note also that all of machines B and C (and D) are not required to do - anything unusual, IP-wise. In my case, there is a mixture of Suns, - Macs and PC/Windoze 95 machines on network 0 all connecting through - Linux machine A to the rest of the world. - - Finally, note that once the hardware (Ethernet) addresses are - discovered by each of machines A, B, C (and D), they are placed in the - ARP cache and subsequent packet transfers occur without the ARP - overhead. The ARP caches normally expire entries after 5 minutes of - non-activity. - _________________________________________________________________ - -4. Setting up Proxy ARP with subnetting - - I set up Proxy ARP with subnetting on a Linux kernel version 2.0.30 - machine, but I am told that the code works right back to some kernel - version in the 1.2.x era. - - The first thing to note is that the ARP code is in two parts: the part - inside the kernel that sends and receives ARP requests and responses - and updates the ARP cache etc.; and other part is the arp(8) command - that allows the super user to modify the ARP cache manually and anyone - to examine it. - - The first problem I had was that the arp(8) command that came with my - Slackware 3.1 distribution was ancient (1994 era!!!) and didn't - communicate with the kernel arp code correctly at all (mainly - evidenced by the strange output that it gave for "arp -a"). - - The arp(8) command in "net-tools-1.33a" available from a variety of - places, including (from the README file that came with it) - [8]ftp.linux.org.uk:/pub/linux/Networking/base/ works properly and - includes new man pages that explain stuff a lot better than the older - arp(8) man page. - - Armed with a decent arp(8) command, all the changes I made were in the - /etc/rc.d/rc.inet1 script (for Slackware - probably different for - other flavours). First of all, we need to change the broadcast - address, network number and netmask of eth0: - -NETMASK=255.255.255.240 # for a 4-bit host part -NETWORK=x.y.z.64 # our new network number (replace x.y.z with your net) -BROADCAST=x.y.z.79 # in my case - - Then a line needs to be added to configure the second Ethernet port - (after any module loading that might be required to load the driver - code): - -/sbin/ifconfig eth1 (name on net 1) broadcast (x.y.z.255) netmask 255.255.255.0 - - Then we add a route for the new interface: - -/sbin/route add -net (x.y.z.0) netmask 255.255.255.0 - - And you will probably need to change the default gateway to the one - for network 1. - - At this point, it is appropriate to add the Proxy ARP entry: - -/sbin/arp -i eth1 -Ds ${NETWORK} eth1 netmask ${NETMASK} pub - - This tells ARP to add a static entry (the s) to the cache for network - ${NETWORK}. The -D tells ARP to use the same hardware address as - interface eth1 (the second eth1), thus saving us from having to look - up the hardware address for eth1 and hardcoding it in. The netmask - option tells ARP that we want to use subnetting (ie. Proxy for all (IP - number) & ${NETMASK} == ${NETWORK} & ${NETMASK}). The pub option tells - ARP to publish this ARP entry, ie. it is a Proxy entry, so respond on - behalf of these IP numbers. The -i eth1 option tells ARP to only - respond to requests that come in on interface eth1. - - Hopefully, at this point, when the machine is rebooted, all the - machines on network 0 will appear to be on network 1. You can check - that the Proxy ARP with subnetting entry has been correctly installed - on machine A. On my machine (names changed to protect the innocent) it - is: - -bash$ /sbin/arp -an -Address HWtype HWaddress Flags Mask Iface -x.y.z.1 ether 00:00:0C:13:6F:17 C * eth1 -x.y.z.65 ether 00:40:05:49:77:01 C * eth0 -x.y.z.67 ether 08:00:20:0B:79:47 C * eth0 -x.y.z.5 ether 00:00:3B:80:18:E5 C * eth1 -x.y.z.64 ether 00:40:96:20:CD:D2 CMP 255.255.255.240 eth1 - - Alternatively, you can examine the /proc/net/arp file with eg. cat(1). - - The last line is the proxy entry for the subnet. The CMP flags - indicate that it is a static (Manually entered) entry and that it is - to be Published. The entry is only going to reply to ARP requests on - eth1 where the requested IP number, once masked, matches the network - number, also masked. Note that arp(8) has automatically determined the - hardware address of eth1 and inserted this for the address to use (the - -Ds option). - - Likewise, it is probably prudent to check that the routing table has - been set up correctly. Here is mine (again, the names are changed to - protect the innocent): - -#/bin/netstat -rn -Kernel routing table -Destination Gateway Genmask Flags Metric Ref Use Iface -x.y.z.64 0.0.0.0 255.255.255.240 U 0 0 71 eth0 -x.y.z.0 0.0.0.0 255.255.255.0 U 0 0 389 eth1 -127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 7 lo -0.0.0.0 x.y.z.1 0.0.0.0 UG 1 0 573 eth1 - - Alternatively, you can examine the /proc/net/route file with eg. - cat(1). - - Note that the first entry is a proper subset of the second, but the - routing table has ranked them in netmask order, so the eth0 entry will - be checked before the eth1 entry. - _________________________________________________________________ - -5. Other alternatives to Proxy ARP with subnetting - - There are several other alternatives to using Proxy ARP with - subnetting in this situation, apart from the ones mentioned about - (bridging and straight routing): - - * IP-Masquerading (see the IP-Masquerade mini-HOWTO), in which - network 0 is "hidden" behind machine A from the rest of the - Internet. As machines on network 0 attempt to connect outside - through machine A, it re-addresses the source address and port - number of the packets and makes them look like they are coming - from itself, rather than from the machine on the hidden network 0. - This is an elegant solution, although it prevents any machine on - network 1 from initiating a connection to any machine on network - 0, as the machines on network 0 effectively don't exist outside of - network 0. This effectively increases security of the machines on - network 0, but is also means that servers on network 1 cannot - check the identity of clients on network 0 using IP numbers (eg. - NFS servers use IP hostnames for access to mountable file - systems). - * Another option is IP in IP tunneling, which isn't supported on all - platforms (such as Macs and Windoze machines) so I opted not to go - this way. - * Use Proxy ARP without subnetting. This is certainly possible, it - just means that a separate entry needs to be created for each - machine on network 0, instead of a single entry for all machines - (current and future) on network 0. - * Possibly IP Aliasing might also be useful here, but I haven't - looked into this at all. - _________________________________________________________________ - -6. Other Applications of Proxy ARP with subnetting - - There is only one other application that I know about that uses Proxy - ARP with subnetting, also here at the Australian National University. - It is the one that Andrew Tridgell originally wrote the subnetting - extensions to Proxy ARP for. However, Andrew reliably informs me that - there are, in fact, several other sites around the world using it as - well (I don't have any details). - - The other A.N.U. application involves a teaching lab set up to teach - students how to configure machines to use TCP/IP, including setting up - the gateway. The network used is a Class C network, and Andrew needed - to "subnet" it for security, traffic control and the educational - reason mentioned above. He did this using Proxy ARP, and then decided - that a single entry in the ARP cache for the whole subnet would be - faster and cleaner than one for each host on the subnet. Voila...Proxy - ARP with subnetting! - _________________________________________________________________ - -7. Copying conditions - - Copyright 1997 by Bob Edwards <[9]Robert.Edwards@anu.edu.au> - - Voice: (+61) 2 6249 4090 - - Unless otherwise stated, Linux HOWTO documents are copyrighted by - their respective authors. Linux HOWTO documents may be reproduced and - distributed in whole or in part, in any medium physical or electronic, - as long as this copyright notice is retained on all copies. Commercial - redistribution is allowed and encouraged; however, the author would - like to be notified of any such distributions. All translations, - derivative works, or aggregate works incorporating any Linux HOWTO - documents must be covered under this copyright notice. That is, you - may not produce a derivative work from a HOWTO and impose additional - restrictions on its distribution. Exceptions to these rules may be - granted under certain conditions; please contact the Linux HOWTO - coordinator at the address given below. In short, we wish to promote - dissemination of this information through as many channels as - possible. However, we do wish to retain copyright on the HOWTO - documents, and would like to be notified of any plans to redistribute - the HOWTOs. If you have questions, please contact the Linux HOWTO - coordinator, at <[10]linux-howto@metalab.unc.edu> via email. - -References - - 1. Proxy-ARP-Subnet.html#INTRO - 2. Proxy-ARP-Subnet.html#WHY - 3. Proxy-ARP-Subnet.html#HOW - 4. Proxy-ARP-Subnet.html#SETUP - 5. Proxy-ARP-Subnet.html#ALTERNATIVES - 6. Proxy-ARP-Subnet.html#APPLICATIONS - 7. Proxy-ARP-Subnet.html#COPYING - 8. ftp://ftp.linux.org.uk/pub/linux/Networking/base/ - 9. mailto:Robert.Edwards@anu.edu.au - 10. mailto:linux-howto@metalab.unc.edu - @@ -6370,356 +3155,6 @@ World Wide Web and ftp offerings for their customers. You can refer to the ``IP-Alias mini-HOWTO'' for more information than you find here. - -Quickstart: - - - -After compiling and installing your kernel with IP_Alias support -configuration is very simple. The aliases are added to virtual network -devices associated with the actual network device. A simple naming -convention applies to these devices being :, -e.g. eth0:0, ppp0:10 etc. Note that the the ifname:number device can -only be configured after the main interface has been set up. - - - -For example, assume you have an ethernet network that supports two -different IP subnetworks simultaneously and you wish your machine to -have direct access to both, you could use something like: - - - - - root# ifconfig eth0 192.168.1.1 netmask 255.255.255.0 up - root# route add -net 192.168.1.0 netmask 255.255.255.0 eth0 - root# ifconfig eth0:0 192.168.10.1 netmask 255.255.255.0 up - root# route add -net 192.168.10.0 netmask 255.255.255.0 eth0:0 - - - ------------------------------------------------------------------------------ - -1. My Setup - - - -  * IP Alias is standard in kernels 2.0.x and 2.2.x, and available as a - compile-time option in 2.4.x (IP Alias has been deprecated in 2.4.x and - replaced by a more powerful firewalling mechanism.) -  * IP Alias compiled as a loadable module. You would have indicated in the - "make config" command to make your kernel, that you want the IP Masq to - be compiled as a (M)odule. Check the Modules HOW-TO (if that exists) or - check the info in /usr/src/linux/Documentation/modules.txt. -  * I have to support 2 additional IPs over and above the IP already - allocated to me. -  * A D-Link DE620 pocket adapter (not important, works with any Linux - supported network adapter). - - - - - Kernel Compile Options: - - Networking options ---> - .... - [*] Network aliasing - .... - <*> IP: aliasing support - - - - ------------------------------------------------------------------------------ - - -2. Commands - - - -1. Load the IP Alias module (you can skip this step if you compiled the -module into the kernel): - - - - - /sbin/insmod /lib/modules/`uname -r`/ipv4/ip_alias.o - - - - -2. Setup the loopback, eth0, and all the IP addresses beginning with the -main IP address for the eth0 interface: - - - - - /sbin/ifconfig lo 127.0.0.1 - /sbin/ifconfig eth0 up - /sbin/ifconfig eth0 172.16.3.1 - /sbin/ifconfig eth0:0 172.16.3.10 - /sbin/ifconfig eth0:1 172.16.3.100 - - - - -172.16.3.1 is the main IP address, while .10 and .100 are the aliases. -The magic is the eth0:x where x=0,1,2,...n for the different IP -addresses. The main IP address does not need to be aliased. - - - -3. Setup the routes. First route the loopback, then the net, and finally, -the various IP addresses starting with the default (originally allocated) -one: - - - - - /sbin/route add -net 127.0.0.0 - /sbin/route add -net 172.16.3.0 dev eth0 - /sbin/route add -host 172.16.3.1 dev eth0 - /sbin/route add -host 172.16.3.10 dev eth0:0 - /sbin/route add -host 172.16.3.100 dev eth0:1 - /sbin/route add default gw 172.16.3.200 - - - - -That's it. - - - -In the example IP address above, I am using the Private IP addresses (RFC -1918) for illustrative purposes. Substitute them with your own official or -private IP addresses. - - - -The example shows only 3 IP addresses. The max is defined to be 256 in /usr/ -include/linux/net_alias.h. 256 IP addresses on ONE card is a lot :-)! - - - -Here's what my /sbin/ifconfig looks like: - - - - -lo Link encap:Local Loopback - inet addr:127.0.0.1 Bcast:127.255.255.255 Mask:255.0.0.0 - UP BROADCAST LOOPBACK RUNNING MTU:3584 Metric:1 - RX packets:5088 errors:0 dropped:0 overruns:0 - TX packets:5088 errors:0 dropped:0 overruns:0 - -eth0 Link encap:10Mbps Ethernet HWaddr 00:8E:B8:83:19:20 - inet addr:172.16.3.1 Bcast:172.16.3.255 Mask:255.255.255.0 - UP BROADCAST RUNNING PROMISC MULTICAST MTU:1500 Metric:1 - RX packets:334036 errors:0 dropped:0 overruns:0 - TX packets:11605 errors:0 dropped:0 overruns:0 - Interrupt:7 Base address:0x378 - -eth0:0 Link encap:10Mbps Ethernet HWaddr 00:8E:B8:83:19:20 - inet addr:172.16.3.10 Bcast:172.16.3.255 Mask:255.255.255.0 - UP BROADCAST RUNNING MTU:1500 Metric:1 - RX packets:0 errors:0 dropped:0 overruns:0 - TX packets:0 errors:0 dropped:0 overruns:0 - -eth0:1 Link encap:10Mbps Ethernet HWaddr 00:8E:B8:83:19:20 - inet addr:172.16.3.100 Bcast:172.16.3.255 Mask:255.255.255.0 - UP BROADCAST RUNNING MTU:1500 Metric:1 - RX packets:1 errors:0 dropped:0 overruns:0 - TX packets:0 errors:0 dropped:0 overruns:0 - - - - -And /proc/net/aliases: - - - - -device family address -eth0:0 2 172.16.3.10 -eth0:1 2 172.16.3.100 - - - - -And /proc/net/alias_types: - - - - -type name n_attach -2 ip 2 - - - - -Of course, the stuff in /proc/net was created by the ifconfig command and not -by hand! - ------------------------------------------------------------------------------ - - -3. Troubleshooting: Questions and Answers - - - -3.1. Question: How can I keep the settings through a reboot? - - - -Answer: Whether you are using BSD-style or SysV-style (Redhat?? for example) -init, you can always include it in /etc/rc.d/rc.local. Here's what I have on -my SysV init system (Redhat?? 3.0.3 and 4.0): - - - -My /etc/rc.d/rc.local: (edited to show the relevant portions) - - - - -#setting up IP alias interfaces -echo "Setting 172.16.3.1, 172.16.3.10, 172.16.3.100 IP Aliases ..." -/sbin/ifconfig lo 127.0.0.1 -/sbin/ifconfig eth0 up -/sbin/ifconfig eth0 172.16.3.1 -/sbin/ifconfig eth0:0 172.16.3.10 -/sbin/ifconfig eth0:1 172.16.3.100 -#setting up the routes -echo "Setting IP routes ..." -/sbin/route add -net 127.0.0.0 -/sbin/route add -net 172.16.3.0 dev eth0 -/sbin/route add -host 172.16.3.1 eth0 -/sbin/route add -host 172.16.3.10 eth0:0 -/sbin/route add -host 172.16.3.100 eth0:1 -/sbin/route add default gw 172.16.3.200 -# - - ------------------------------------------------------------------------------ - - -3.2. Question: How do I set up the IP aliased machine to receive e-mail on -the various aliased IP addresses (on a machine using sendmail)? - - - -Answer: Create (if it doesn't already exist) a file called, /etc/ -mynames.cw,for example. The file does not have to be this exact name nor in -the /etc directory. - - - -In that file, place the official domain names of the aliased IP addresses. If -these aliased IP addresses do not have a domain name, then you can place the -IP address itself. - - - -The /etc/mynames.cw might look like this: - - - - -# /etc/mynames.cw - include all aliases for your machine here; # is a comment -domain.one.net -domain.two.com -domain.three.org -4.5.6.7 - - - - -In your sendmail.cf file, where it defines a file class macro Fw, add the -following: - - - - -################## -# local info # -################## - -# file containing names of hosts for which we receive email -Fw/etc/mynames.cw - -That should do it. Test out the new setting by invoking sendmail in test -mode. The following is an example: -ganymede$ /usr/lib/sendmail -bt -ADDRESS TEST MODE (ruleset 3 NOT automatically invoked) -Enter < ruleset> < address> -> 0 me@4.5.6.7 -rewrite: ruleset 0 input: me @ 4 . 5 . 6 . 7 -rewrite: ruleset 98 input: me @ 4 . 5 . 6 . 7 -rewrite: ruleset 98 returns: me @ 4 . 5 . 6 . 7 -rewrite: ruleset 97 input: me @ 4 . 5 . 6 . 7 -rewrite: ruleset 3 input: me @ 4 . 5 . 6 . 7 -rewrite: ruleset 96 input: me < @ 4 . 5 . 6 . 7 > -rewrite: ruleset 96 returns: me < @ 4 . 5 . 6 . 7 . > -rewrite: ruleset 3 returns: me < @ 4 . 5 . 6 . 7 . > -rewrite: ruleset 0 input: me < @ 4 . 5 . 6 . 7 . > -rewrite: ruleset 98 input: me < @ 4 . 5 . 6 . 7 . > -rewrite: ruleset 98 returns: me < @ 4 . 5 . 6 . 7 . > -rewrite: ruleset 0 returns: $# local $: me -rewrite: ruleset 97 returns: $# local $: me -rewrite: ruleset 0 returns: $# local $: me -> 0 me@4.5.6.8 -rewrite: ruleset 0 input: me @ 4 . 5 . 6 . 8 -rewrite: ruleset 98 input: me @ 4 . 5 . 6 . 8 -rewrite: ruleset 98 returns: me @ 4 . 5 . 6 . 8 -rewrite: ruleset 97 input: me @ 4 . 5 . 6 . 8 -rewrite: ruleset 3 input: me @ 4 . 5 . 6 . 8 -rewrite: ruleset 96 input: me < @ 4 . 5 . 6 . 8 > -rewrite: ruleset 96 returns: me < @ 4 . 5 . 6 . 8 > -rewrite: ruleset 3 returns: me < @ 4 . 5 . 6 . 8 > -rewrite: ruleset 0 input: me < @ 4 . 5 . 6 . 8 > -rewrite: ruleset 98 input: me < @ 4 . 5 . 6 . 8 > -rewrite: ruleset 98 returns: me < @ 4 . 5 . 6 . 8 > -rewrite: ruleset 95 input: < > me < @ 4 . 5 . 6 . 8 > -rewrite: ruleset 95 returns: me < @ 4 . 5 . 6 . 8 > -rewrite: ruleset 0 returns: $# smtp $@ 4 . 5 . 6 . 8 $: me < @ 4 . 5 . 6 . 8 > -rewrite: ruleset 97 returns: $# smtp $@ 4 . 5 . 6 . 8 $: me < @ 4 . 5 . 6 . 8 > -rewrite: ruleset 0 returns: $# smtp $@ 4 . 5 . 6 . 8 $: me < @ 4 . 5 . 6 . 8 > -> - - - - -Notice when I tested me@4.5.6.7, it delivered the mail to the local machine, -while me@4.5.6.8 was handed off to the smtp mailer. That is the correct -response. - - - -3.3. Question: How do I delete an alias? - - - -Answer: To delete an alias you simply add a `-' to the end of its name and -refer to it and is as simple as: - - - - - root# ifconfig eth0:0- 0 - - - - -All routes associated with that alias will also be deleted -automatically. - - - - - -You are all set now. - - @@ -6728,115 +3163,6 @@ You are all set now. * Multicast HOWTO - - A good page providing comparisons between reliable multicast protocols - is - - . - - A very good and up-to-date site, with lots of interesting links - (Internet drafts, RFCs, papers, links to other sites) is: - - . - - is also a good source of - information on the subject. - - Katia Obraczka's "Multicast Transport Protocols: A Survey and - Taxonomy" article gives short descriptions for each protocol and tries - to classify them according to different features. You can read it in - the IEEE Communications magazine, January 1998, vol. 36, No. 1. - - - - 10. References. - - 10.1. RFCs. - - - o RFC 1112 "Host Extensions for IP Multicasting". Steve Deering. - August 1989. - - o RFC 2236 "Internet Group Management Protocol, version 2". W. - Fenner. November 1997. - - o RFC 1458 "Requirements for Multicast Protocols". Braudes, R and - Zabele, S. May 1993. - - o RFC 1469 "IP Multicast over Token-Ring Local Area Networks". T. - Pusateri. June 1993. - - o RFC 1390 "Transmission of IP and ARP over FDDI Networks". D. Katz. - January 1993. - - o RFC 1583 "OSPF Version 2". John Moy. March 1994. - - o RFC 1584 "Multicast Extensions to OSPF". John Moy. March 1994. - - o RFC 1585 "MOSPF: Analysis and Experience". John Moy. March 1994. - - o RFC 1812 "Requirements for IP version 4 Routers". Fred Baker, - Editor. June 1995 - - o RFC 2117 "Protocol Independent Multicast-Sparse Mode (PIM-SM): - Protocol Specification". D. Estrin, D. Farinacci, A. Helmy, D. - Thaler; S. Deering, M. Handley, V. Jacobson, C. Liu, P. Sharma, and - L. Wei. July 1997. - - o RFC 2189 "Core Based Trees (CBT version 2) Multicast Routing". A. - Ballardie. September 1997. - - o RFC 2201 "Core Based Trees (CBT) Multicast Routing Architecture". - A. Ballardie. September 1997. - - - - 10.2. Internet Drafts. - - - o "Introduction to IP Multicast Routing". draft-ietf-mboned-intro- - multicast- 03.txt. T. Maufer, C. Semeria. July 1997. - - o "Administratively Scoped IP Multicast". draft-ietf-mboned-admin-ip- - space-03.txt. D. Meyer. June 10, 1997. - - 10.3. Web pages. - - - o Linux Multicast Homepage. - - - o Linux Multicast FAQ. - - o Multicast and MBONE on Linux. - - - o Christian Daudt's MBONE-Linux Page. - - - o Reliable Multicast Links - - - o Multicast Transport Protocols - - 10.4. Books. - - o "TCP/IP Illustrated: Volume 1 The Protocols". Stevens, W. Richard. - Addison Wesley Publishing Company, Reading MA, 1994 - - o "TCP/IP Illustrated: Volume 2, The Implementation". Wright, Gary - and W. Richard Stevens. Addison Wesley Publishing Company, Reading - MA, 1995 - - o "UNIX Network Programming Volume 1. Networking APIs: Sockets and - XTI". Stevens, W. Richard. Second Edition, Prentice Hall, Inc. - 1998. - - o "Internetworking with TCP/IP Volume 1 Principles, Protocols, and - Architecture". Comer, Douglas E. Second Edition, Prentice Hall, - Inc. Englewood Cliffs, New Jersey, 1991 @@ -6920,15 +3246,3 @@ HOWTO.html - -10.3. Redundant networking - - IP Address Takeover (IPAT). When a network adapter card fails, its IP - address should be taken by a working network card in the same node or - in another node. MAC Address Takeover: when an IP takeover occurs, it - should be made sure that all the nodes in the network update their ARP - caches (the mapping between IP and MAC addresses). - - See the High-Availability HOWTO for more details: - http://metalab.unc.edu/pub/Linux/ALPHA/linux-ha/High-Availability- - HOWTO.html diff --git a/LDP/guide/docbook/Linux-Networking/Sources.xml b/LDP/guide/docbook/Linux-Networking/Sources.xml index bfa0aeef..9130ab96 100644 --- a/LDP/guide/docbook/Linux-Networking/Sources.xml +++ b/LDP/guide/docbook/Linux-Networking/Sources.xml @@ -441,4 +441,113 @@ Leased line Mini HOWTO 61. ftp://ftp.us.kde.org/pub/kde/unstable/apps/network/ 62. http://www.linux-mag.com/2000-04/networknirvana_01.html + A good page providing comparisons between reliable multicast protocols + is + + . + + A very good and up-to-date site, with lots of interesting links + (Internet drafts, RFCs, papers, links to other sites) is: + + . + + is also a good source of + information on the subject. + + Katia Obraczka's "Multicast Transport Protocols: A Survey and + Taxonomy" article gives short descriptions for each protocol and tries + to classify them according to different features. You can read it in + the IEEE Communications magazine, January 1998, vol. 36, No. 1. + + + + 10. References. + + 10.1. RFCs. + + + o RFC 1112 "Host Extensions for IP Multicasting". Steve Deering. + August 1989. + + o RFC 2236 "Internet Group Management Protocol, version 2". W. + Fenner. November 1997. + + o RFC 1458 "Requirements for Multicast Protocols". Braudes, R and + Zabele, S. May 1993. + + o RFC 1469 "IP Multicast over Token-Ring Local Area Networks". T. + Pusateri. June 1993. + + o RFC 1390 "Transmission of IP and ARP over FDDI Networks". D. Katz. + January 1993. + + o RFC 1583 "OSPF Version 2". John Moy. March 1994. + + o RFC 1584 "Multicast Extensions to OSPF". John Moy. March 1994. + + o RFC 1585 "MOSPF: Analysis and Experience". John Moy. March 1994. + + o RFC 1812 "Requirements for IP version 4 Routers". Fred Baker, + Editor. June 1995 + + o RFC 2117 "Protocol Independent Multicast-Sparse Mode (PIM-SM): + Protocol Specification". D. Estrin, D. Farinacci, A. Helmy, D. + Thaler; S. Deering, M. Handley, V. Jacobson, C. Liu, P. Sharma, and + L. Wei. July 1997. + + o RFC 2189 "Core Based Trees (CBT version 2) Multicast Routing". A. + Ballardie. September 1997. + + o RFC 2201 "Core Based Trees (CBT) Multicast Routing Architecture". + A. Ballardie. September 1997. + + + + 10.2. Internet Drafts. + + + o "Introduction to IP Multicast Routing". draft-ietf-mboned-intro- + multicast- 03.txt. T. Maufer, C. Semeria. July 1997. + + o "Administratively Scoped IP Multicast". draft-ietf-mboned-admin-ip- + space-03.txt. D. Meyer. June 10, 1997. + + 10.3. Web pages. + + + o Linux Multicast Homepage. + + + o Linux Multicast FAQ. + + o Multicast and MBONE on Linux. + + + o Christian Daudt's MBONE-Linux Page. + + + o Reliable Multicast Links + + + o Multicast Transport Protocols + + 10.4. Books. + + o "TCP/IP Illustrated: Volume 1 The Protocols". Stevens, W. Richard. + Addison Wesley Publishing Company, Reading MA, 1994 + + o "TCP/IP Illustrated: Volume 2, The Implementation". Wright, Gary + and W. Richard Stevens. Addison Wesley Publishing Company, Reading + MA, 1995 + + o "UNIX Network Programming Volume 1. Networking APIs: Sockets and + XTI". Stevens, W. Richard. Second Edition, Prentice Hall, Inc. + 1998. + + o "Internetworking with TCP/IP Volume 1 Principles, Protocols, and + Architecture". Comer, Douglas E. Second Edition, Prentice Hall, + Inc. Englewood Cliffs, New Jersey, 1991 +