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