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+ EQL Driver: Serial IP Load Balancing HOWTO
+ Simon "Guru Aleph-Null" Janes, simon@ncm.com
+ v1.1, February 27, 1995
+
+ This is the manual for the EQL device driver. EQL is a software device
+ that lets you load-balance IP serial links (SLIP or uncompressed PPP)
+ to increase your bandwidth. It will not reduce your latency (i.e. ping
+ times) except in the case where you already have lots of traffic on
+ your link, in which it will help them out. This driver has been tested
+ with the 1.1.75 kernel, and is known to have patched cleanly with
+ 1.1.86. Some testing with 1.1.92 has been done with the v1.1 patch
+ which was only created to patch cleanly in the very latest kernel
+ source trees. (Yes, it worked fine.)
+
+ 1. Introduction
+
+ Which is worse? A huge fee for a 56K leased line or two phone lines?
+ It's probably the former. If you find yourself craving more bandwidth,
+ and have a ISP that is flexible, it is now possible to bind modems
+ together to work as one point-to-point link to increase your
+ bandwidth. All without having to have a special black box on either
+ side.
+
+
+ The eql driver has only been tested with the Livingston PortMaster-2e
+ terminal server. I do not know if other terminal servers support load-
+ balancing, but I do know that the PortMaster does it, and does it
+ almost as well as the eql driver seems to do it (-- Unfortunately, in
+ my testing so far, the Livingston PortMaster 2e's load-balancing is a
+ good 1 to 2 KB/s slower than the test machine working with a 28.8 Kbps
+ and 14.4 Kbps connection. However, I am not sure that it really is
+ the PortMaster, or if it's Linux's TCP drivers. I'm told that Linux's
+ TCP implementation is pretty fast though.--)
+
+
+ I suggest to ISPs out there that it would probably be fair to charge
+ a load-balancing client 75% of the cost of the second line and 50% of
+ the cost of the third line etc...
+
+
+ Hey, we can all dream you know...
+
+
+ 2. Kernel Configuration
+
+ Here I describe the general steps of getting a kernel up and working
+ with the eql driver. From patching, building, to installing.
+
+
+ 2.1. Patching The Kernel
+
+ If you do not have or cannot get a copy of the kernel with the eql
+ driver folded into it, get your copy of the driver from
+ ftp://slaughter.ncm.com/pub/Linux/LOAD_BALANCING/eql-1.1.tar.gz.
+ Unpack this archive someplace obvious like /usr/local/src/. It will
+ create the following files:
+
+
+
+ ______________________________________________________________________
+ -rw-r--r-- guru/ncm 198 Jan 19 18:53 1995 eql-1.1/NO-WARRANTY
+ -rw-r--r-- guru/ncm 30620 Feb 27 21:40 1995 eql-1.1/eql-1.1.patch
+ -rwxr-xr-x guru/ncm 16111 Jan 12 22:29 1995 eql-1.1/eql_enslave
+ -rw-r--r-- guru/ncm 2195 Jan 10 21:48 1995 eql-1.1/eql_enslave.c
+ ______________________________________________________________________
+
+ Unpack a recent kernel (something after 1.1.92) someplace convenient
+ like say /usr/src/linux-1.1.92.eql. Use symbolic links to point
+ /usr/src/linux to this development directory.
+
+
+ Apply the patch by running the commands:
+
+
+ ______________________________________________________________________
+ cd /usr/src
+ patch </usr/local/src/eql-1.1/eql-1.1.patch
+ ______________________________________________________________________
+
+
+
+
+
+ 2.2. Building The Kernel
+
+ After patching the kernel, run make config and configure the kernel
+ for your hardware.
+
+
+ After configuration, make and install according to your habit.
+
+
+ 3. Network Configuration
+
+ So far, I have only used the eql device with the DSLIP SLIP connection
+ manager by Matt Dillon (-- "The man who sold his soul to code so much
+ so quickly."--) . How you configure it for other "connection"
+ managers is up to you. Most other connection managers that I've seen
+ don't do a very good job when it comes to handling more than one
+ connection.
+
+
+ 3.1. /etc/rc.d/rc.inet1
+
+ In rc.inet1, ifconfig the eql device to the IP address you usually use
+ for your machine, and the MTU you prefer for your SLIP lines. One
+ could argue that MTU should be roughly half the usual size for two
+ modems, one-third for three, one-fourth for four, etc... But going
+ too far below 296 is probably overkill. Here is an example ifconfig
+ command that sets up the eql device:
+
+
+
+ ______________________________________________________________________
+ ifconfig eql 198.67.33.239 mtu 1006
+ ______________________________________________________________________
+
+
+
+
+
+ Once the eql device is up and running, add a static default route to
+ it in the routing table using the cool new route syntax that makes
+ life so much easier:
+
+
+
+ ______________________________________________________________________
+ route add default eql
+ ______________________________________________________________________
+
+
+ 3.2. Enslaving Devices By Hand
+
+ Enslaving devices by hand requires two utility programs: eql_enslave
+ and eql_emancipate (-- eql_emancipate hasn't been written because when
+ an enslaved device "dies", it is automatically taken out of the queue.
+ I haven't found a good reason to write it yet... other than for
+ completeness, but that isn't a good motivator is it?--)
+
+
+ The syntax for enslaving a device is "eql_enslave <master-name>
+ <slave-name> <estimated-bps>". Here are some example enslavings:
+
+
+
+ ______________________________________________________________________
+ eql_enslave eql sl0 28800
+ eql_enslave eql ppp0 14400
+ eql_enslave eql sl1 57600
+ ______________________________________________________________________
+
+
+
+
+
+ When you want to free a device from its life of slavery, you can
+ either down the device with ifconfig (eql will automatically bury the
+ dead slave and remove it from its queue) or use eql_emancipate to free
+ it. (-- Or just ifconfig it down, and the eql driver will take it out
+ for you.--)
+
+
+
+ ______________________________________________________________________
+ eql_emancipate eql sl0
+ eql_emancipate eql ppp0
+ eql_emancipate eql sl1
+ ______________________________________________________________________
+
+
+
+
+
+ 3.3. DSLIP Configuration for the eql Device
+
+ The general idea is to bring up and keep up as many SLIP connections
+ as you need, automatically.
+
+
+ 3.3.1. /etc/slip/runslip.conf
+
+ Here is an example runslip.conf:
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ ______________________________________________________________________
+ name sl-line-1
+ enabled
+ baud 38400
+ mtu 576
+ ducmd -e /etc/slip/dialout/cua2-288.xp -t 9
+ command eql_enslave eql $interface 28800
+ address 198.67.33.239
+ line /dev/cua2
+
+ name sl-line-2
+ enabled
+ baud 38400
+ mtu 576
+ ducmd -e /etc/slip/dialout/cua3-288.xp -t 9
+ command eql_enslave eql $interface 28800
+ address 198.67.33.239
+ line /dev/cua3
+ ______________________________________________________________________
+
+
+
+
+
+ 3.4. Using PPP and the eql Device
+
+ I have not yet done any load-balancing testing for PPP devices, mainly
+ because I don't have a PPP-connection manager like SLIP has with
+ DSLIP. I did find a good tip from LinuxNET:Billy for PPP performance:
+ make sure you have asyncmap set to something so that control
+ characters are not escaped.
+
+
+ I tried to fix up a PPP script/system for redialing lost PPP
+ connections for use with the eql driver the weekend of Feb 25-26 '95
+ (Hereafter known as the 8-hour PPP Hate Festival). Perhaps later this
+ year.
+
+
+ 4. About the Slave Scheduler Algorithm
+
+ The slave scheduler probably could be replaced with a dozen other
+ things and push traffic much faster. The formula in the current set
+ up of the driver was tuned to handle slaves with wildly different
+ bits-per-second "priorities".
+
+
+ All testing I have done was with two 28.8 V.FC modems, one connecting
+ at 28800 bps or slower, and the other connecting at 14400 bps all the
+ time.
+
+
+ One version of the scheduler was able to push 5.3 K/s through the
+ 28800 and 14400 connections, but when the priorities on the links were
+ very wide apart (57600 vs. 14400) the "faster" modem received all
+ traffic and the "slower" modem starved.
+
+
+ 5. Testers' Reports
+
+ Some people have experimented with the eql device with newer
+ kernels (than 1.1.75). I have since updated the driver to patch
+ cleanly in newer kernels because of the removal of the old "slave-
+ balancing" driver config option.
+
+
+ o icee from LinuxNET patched 1.1.86 without any rejects and was able
+ to boot the kernel and enslave a couple of ISDN PPP links.
+
+ 5.1. Randolph Bentson's Test Report
+
+
+
+
+
+
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+ From bentson@grieg.seaslug.org Wed Feb 8 19:08:09 1995
+ Date: Tue, 7 Feb 95 22:57 PST
+ From: Randolph Bentson <bentson@grieg.seaslug.org>
+ To: guru@ncm.com
+ Subject: EQL driver tests
+
+
+ I have been checking out your eql driver. (Nice work, that!)
+ Although you may already done this performance testing, here
+ are some data I've discovered.
+
+ Randolph Bentson
+ bentson@grieg.seaslug.org
+
+ ---------------------------------------------------------
+
+
+ A pseudo-device driver, EQL, written by Simon Janes, can be used
+ to bundle multiple SLIP connections into what appears to be a
+ single connection. This allows one to improve dial-up network
+ connectivity gradually, without having to buy expensive DSU/CSU
+ hardware and services.
+
+ I have done some testing of this software, with two goals in
+ mind: first, to ensure it actually works as described and
+ second, as a method of exercising my device driver.
+
+ The following performance measurements were derived from a set
+ of SLIP connections run between two Linux systems (1.1.84) using
+ a 486DX2/66 with a Cyclom-8Ys and a 486SLC/40 with a Cyclom-16Y.
+ (Ports 0,1,2,3 were used. A later configuration will distribute
+ port selection across the different Cirrus chips on the boards.)
+ Once a link was established, I timed a binary ftp transfer of
+ 289284 bytes of data. If there were no overhead (packet headers,
+ inter-character and inter-packet delays, etc.) the transfers
+ would take the following times:
+
+ bits/sec seconds
+ 345600 8.3
+ 234600 12.3
+ 172800 16.7
+ 153600 18.8
+ 76800 37.6
+ 57600 50.2
+ 38400 75.3
+ 28800 100.4
+ 19200 150.6
+ 9600 301.3
+
+ A single line running at the lower speeds and with large packets
+ comes to within 2% of this. Performance is limited for the higher
+ speeds (as predicted by the Cirrus databook) to an aggregate of
+ about 160 kbits/sec. The next round of testing will distribute
+ the load across two or more Cirrus chips.
+
+ The good news is that one gets nearly the full advantage of the
+ second, third, and fourth line's bandwidth. (The bad news is
+ that the connection establishment seemed fragile for the higher
+ speeds. Once established, the connection seemed robust enough.)
+
+ #lines speed mtu seconds theory actual %of
+ kbit/sec duration speed speed max
+ 3 115200 900 _ 345600
+ 3 115200 400 18.1 345600 159825 46
+ 2 115200 900 _ 230400
+ 2 115200 600 18.1 230400 159825 69
+ 2 115200 400 19.3 230400 149888 65
+ 4 57600 900 _ 234600
+ 4 57600 600 _ 234600
+ 4 57600 400 _ 234600
+ 3 57600 600 20.9 172800 138413 80
+ 3 57600 900 21.2 172800 136455 78
+ 3 115200 600 21.7 345600 133311 38
+ 3 57600 400 22.5 172800 128571 74
+ 4 38400 900 25.2 153600 114795 74
+ 4 38400 600 26.4 153600 109577 71
+ 4 38400 400 27.3 153600 105965 68
+ 2 57600 900 29.1 115200 99410.3 86
+ 1 115200 900 30.7 115200 94229.3 81
+ 2 57600 600 30.2 115200 95789.4 83
+ 3 38400 900 30.3 115200 95473.3 82
+ 3 38400 600 31.2 115200 92719.2 80
+ 1 115200 600 31.3 115200 92423 80
+ 2 57600 400 32.3 115200 89561.6 77
+ 1 115200 400 32.8 115200 88196.3 76
+ 3 38400 400 33.5 115200 86353.4 74
+ 2 38400 900 43.7 76800 66197.7 86
+ 2 38400 600 44 76800 65746.4 85
+ 2 38400 400 47.2 76800 61289 79
+ 4 19200 900 50.8 76800 56945.7 74
+ 4 19200 400 53.2 76800 54376.7 70
+ 4 19200 600 53.7 76800 53870.4 70
+ 1 57600 900 54.6 57600 52982.4 91
+ 1 57600 600 56.2 57600 51474 89
+ 3 19200 900 60.5 57600 47815.5 83
+ 1 57600 400 60.2 57600 48053.8 83
+ 3 19200 600 62 57600 46658.7 81
+ 3 19200 400 64.7 57600 44711.6 77
+ 1 38400 900 79.4 38400 36433.8 94
+ 1 38400 600 82.4 38400 35107.3 91
+ 2 19200 900 84.4 38400 34275.4 89
+ 1 38400 400 86.8 38400 33327.6 86
+ 2 19200 600 87.6 38400 33023.3 85
+ 2 19200 400 91.2 38400 31719.7 82
+ 4 9600 900 94.7 38400 30547.4 79
+ 4 9600 400 106 38400 27290.9 71
+ 4 9600 600 110 38400 26298.5 68
+ 3 9600 900 118 28800 24515.6 85
+ 3 9600 600 120 28800 24107 83
+ 3 9600 400 131 28800 22082.7 76
+ 1 19200 900 155 19200 18663.5 97
+ 1 19200 600 161 19200 17968 93
+ 1 19200 400 170 19200 17016.7 88
+ 2 9600 600 176 19200 16436.6 85
+ 2 9600 900 180 19200 16071.3 83
+ 2 9600 400 181 19200 15982.5 83
+ 1 9600 900 305 9600 9484.72 98
+ 1 9600 600 314 9600 9212.87 95
+ 1 9600 400 332 9600 8713.37 90
+
+
+
+
+
+ 5.2. Anthony Healy's Report
+
+
+
+
+
+
+
+ Date: Mon, 13 Feb 1995 16:17:29 +1100 (EST)
+ From: Antony Healey <ahealey@st.nepean.uws.edu.au>
+ To: Simon Janes <guru@ncm.com>
+ Subject: Re: Load Balancing
+
+ Hi Simon,
+ I've installed your patch and it works great. I have trialed
+ it over twin SL/IP lines, just over null modems, but I was
+ able to data at over 48Kb/s [ISDN link -Simon]. I managed a
+ transfer of up to 7.5 Kbyte/s on one go, but averaged around
+ 6.4 Kbyte/s, which I think is pretty cool. :)
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