eql.txt
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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
- 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. :)