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-
-
-The LBX Mini-HOWTO
-
-
-
-----
-
-!!!The LBX Mini-HOWTO
-
-!!Paul D. Smith,
-psmith@baynetworks.comv1.04, 11 December 1997
-
-
-----
-''LBX (Low Bandwidth X) is an X server extension which performs
-compression on the X protocol. It is meant to be used in conjunction
-with X applications and an X server which are separated by a slow
-network connection, to improve display and response time.''
-----
-
-
-
-
-!!1. Introduction
-
-
-
-
-!!2. What's The Status Of LBX?
-
-
-
-
-!!3. Who Can Benefit From LBX?
-
-
-
-
-!!4. Who Doesn't Need LBX?
-
-
-
-
-!!5. How Does LBX Work?
-
-
-
-
-!!6. What Do I Need To Use LBX?
-
-
-
-
-!!7. What Don't I Need To Use LBX?
-
-
-
-
-!!8. How Do I Start LBX?
-
-
-
-
-!!9. Problems
-
-
-
-
-!!10. Documentation
-
-
-
-
-!!11. Alternatives
-
-
-*11.1 dxpc - The Differential X Protocol Compressor
-
-*11.2 Ssh (Secure Shell)
-
-*11.3 Which Is Better?
-
-----
-
-!!1. Introduction
-
-
-''Low-Bandwidth X'' (LBX) attempts to recognize that in this day
-and age, not everyone will be a fast LAN hop or two away from the system
-that they are running their applications on.
-
-
-The X protocol can generate an extraordinary amount of traffic,
-especially for simple-seeming things such as creating new windows. As
-anyone who has tried to use X over a dial-in modem at 28.8 or even
-higher can attest, creating new X windows can involve an excruciating
-wait.
-
-
-LBX is fundamentally a compression and caching scheme designed to
-minimize the amount of X traffic generated between two systems.
-
-
-
-
-
-
-----
-
-!!2. What's The Status Of LBX?
-
-
-As of the X Consortium's release of X11R6.3 in December, 1996, LBX
-is a full extension to the X protocol. For XFree86 folks, that's
-XFree86 version 3.3.
-
-
-
-
-
-
-----
-
-!!3. Who Can Benefit From LBX?
-
-
-If you use a modem to dial into a service provider, then run X
-applications on remote machines with their DISPLAYs set to your local
-machine (or vice versa), LBX will speed up that connection. Also if you
-set DISPLAYs from systems across WANs (other countries, for example) or
-other slow links, LBX can help.
-
-
-
-
-
-
-----
-
-!!4. Who Doesn't Need LBX?
-
-
-LBX is useless, of course, if you're only running applications
-locally, or if you're not running X at all.
-
-
-Also, if you're running on a fast LAN, LBX won't be much help. Some
-people say "if LBX cuts down on network traffic, wouldn't it be good to
-use even on fast LANs?" It might be, if your goal is to reduce network
-traffic. But if your goal is to get better response time LBX probably
-isn't what you want. Although it does introduce caching and
-compression, that comes at a cost on both ends (extra memory for
-caching, and extra CPU for decompression). If your link is fairly
-speedy LBX will probably result in an overall slowdown.
-
-
-
-
-
-
-----
-
-!!5. How Does LBX Work?
-
-
-LBX works by introducing a ''proxy server'' at the client side,
-which performs caching and compression. The X server knows that the
-client is using a proxy server, and decompresses accordingly.
-
-
-Here's a normal setup for remote X clients. In our discussion,
-LOCAL is always the workstation sitting in front of you, whose monitor
-you're looking at, and REMOTE is the remote workstation, where the
-actual application is running.
-
-
-
-
-----
-
-REMOTE LOCAL
-+-----+ +-----+
-| APP |-\ Network +----------+ | |\
-+-----+ \--------------------------->| X SERVER |=>| ||
-+-----+ / (X Protocol) +----------+ +-----+\
-| APP |-/ /_____//
-+-----+
-
-----
-
-
-
-When using LBX, a proxy server (lbxproxy) is introduced on the
-remote side, and the applications talk to that process instead of
-directly to the LOCAL server. That process then performs the caching
-and compression of X requests and forwards them. It looks like this:
-
-
-
-
-----
-
-REMOTE LOCAL
-+-----+
-+-----+ +-------+ Network +----------+ | |\
-| APP |->| PROXY |----------------------------->| X SERVER |=>| ||
-+-----+ +-------+ (LBX/X Protocol) +----------+ +-----+\
-+-----+ / /_____//
-| APP |--/
-+-----+
-
-----
-
-
-
-Details on exactly what caching and compression LBX does is beyond
-the scope of this document.
-
-
-
-
-
-
-----
-
-!!6. What Do I Need To Use LBX?
-
-
-You need an X server on your LOCAL system which has the LBX
-extension compiled in. Unless you explicitly told it not to when
-building it, X11R6.3 servers automatically enable LBX. Also, all
-XFree86 3.3 servers have LBX enabled by default.
-
-
-You can use the xdpyinfo command to see if your server has the LBX
-extension: run xdpyinfo and look at the list just under "number of
-extensions"; you should see "LBX" listed there.
-
-
-Next, you need to get an lbxproxy program compiled for the REMOTE
-system. This is the tricky part. If the remote system is not the same
-type as your local system, the lbxproxy on your local system will
-do you no good, of course.
-
-
-There is unfortunately no "broken out" distribution of lbxproxy, so
-you will have to either (a) get and build most, if not all, of X11R6.3
-for the remote system, or (b) find someplace to get a pre-compiled
-lbxproxy binary for your system. The latter is much simpler of
-course.
-
-
-The lbxproxy is simply a single executable. There are no
-configuration files, resource files, etc. associated with it.
-
-
-
-
-
-
-----
-
-!!7. What Don't I Need To Use LBX?
-
-
-The REMOTE system __does not__ need a new X server (as always, the
-REMOTE system doesn't need ''any'' X server running).
-
-
-The application you want to run __does not__ need to be linked with any
-special version of X, or any special libraries; I regularly use
-commercial X11R5 apps over LBX with no trouble.
-
-
-You __do not__ need root or other privileged access on the REMOTE
-system; the lbxproxy process runs under your normal access
-permissions. Further, you can run it right from your home directory: it
-does not have to be installed anywhere.
-
-
-
-
-
-
-----
-
-!!8. How Do I Start LBX?
-
-
-OK,
here it is... after all that it's actually quite simple.
-Replace LOCAL and REMOTE below with the hostnames of your local
-workstation and remote system, respectively (don't get them mixed up!)
-
-
-On LOCAL:
-
-
-
-
-
-# Start your X server.
-
-#
-
-# Tell your X server that the remote system is allowed access.
-Using the host-list method, type xhost +REMOTE. If you use
-xauth you may need to do more than this; see the ''xauth(1)'' man
-page for more information.
-You should consult the
-Remote X Apps Mini-HOWTO if you're not familiar with remote X access permission
-setup.
-#
-
-
-
-On REMOTE:
-
-
-
-
-
-# Start lbxproxy and tell it to forward to the LOCAL X server,
-like this:
-
-
-$ lbxproxy -display LOCAL:0 :1 &
-
-
-This tells lbxproxy to use display :1 on
-the REMOTE system; if that system has >1 display already you can use
-:2 or whatever instead.
-
-#
-
-# Set your DISPLAY environment variable to point to the display
-that lbxproxy is providing, instead of the normal display:
-
-
-$ DISPLAY=:1
-$ export DISPLAY
-
-
-Or, if you use csh or clones:
-
-
-% setenv DISPLAY :1
-
-
-
-#
-
-# If you're using xauth you will need to ensure that your
-cookie is available locally. See the
-Remote X Apps Mini-HOWTO for more information on this.
-
-#
-
-# Start your X applications!
-#
-
-
-
-That's it; all X apps that are started up pointing to :1 will use
-LBX. Of course, there's no reason you couldn't also start X apps
-pointing to LOCAL:0 and have both running at the same time.
-
-
-
-
-
-
-----
-
-!!9. Problems
-
-
-Here are some common problems:
-
-
-
-
-; __Q)__:
-
-lbxproxy exits with an "access denied" error.
-
-
-
-; __A)__:
-
-This means the LOCAL system isn't accepting connections from
-the REMOTE system due to permissions errors. See the
-Remote X Apps Mini-HOWTO for details on these issues.
-
-
-As a simple trouble-shooting measure, try running a simple X app
-like xclock on REMOTE and have it display on the local
-system without using lbxproxy:
-
-
-
-
-
-$ xclock -display LOCAL:
-
-
-
-
-If that doesn't work, it's xhost or some other basic X
-problem, not LBX.
-
-
-
-
-----
-
-!!10. Documentation
-
-
-The only documentation available in a standard X distribution may be
-the ''lbxproxy(1)'' man page.
-
-
-If you have access to the X source tree, then very interesting
-information on LBX is available there:
-
-
-
-
-
-*xc/doc/specs/Xext/lbx.mif (Framemaker MIF)
-*
-
-*xc/doc/hardcopy/Xext/lbx.PS.Z (Compressed Postscript)
-*
-
-*xc/doc/hardcopy/Xext/lbxTOC.html (HTML)
-*
-
-
-
-More detailed discussion of specific LBX algorithms is available here:
-
-
-
-
-
-*xc/doc/specs/Xext/lbxalg.mif (Framemaker MIF)
-*
-
-*xc/doc/specs/Xext/lbxalg.PS.Z (Compressed Postscript)
-*
-
-
-
-If you don't have access to the X11 source, you can obtain these
-files from
-the X Consortium's FTP site.
-
-
-
-
-
-
-----
-
-!!11. Alternatives
-
-
-If you don't like lbxproxy for some reason: you're not
-satisfied with the performance, it doesn't work for you, you don't want
-to hassle with creating an lbxproxy for the remote host, or you simply
-are interested in trying other options, there is at least one other
-package for X protocol compression (anyone have others?)
-
-
-
-
-!!11.1 dxpc - The Differential X Protocol Compressor
-
-
-
-
-
-
-*Original Author:
-Brian Pane <brianp@cnet.com>
-*
-
-*Current Maintainer:
-Zachary Vonler <lightborn@mail.utexas.edu>
-*
-
-
-
-
-dxpc works in essentially the same way as LBX. However, to
-avoid having to implement an X extension and modify the X server code,
-dxpc uses __two__ proxies: one that runs on the REMOTE host, like
-lbxproxy, and one that runs on the LOCAL host.
-
-
-The REMOTE host proxy communicates between the X clients and the
-LOCAL host proxy, and the LOCAL host proxy communicates between
-the X server and the REMOTE host proxy.
-
-
-So, to ''both'' the X clients and the X server, it looks like X
-protocol as usual.
-
-
-
-
-!Advantages
-
-
-
-
-
-* Since it's a completely separate application that does not
-require any X internals, it's ''much'' simpler to compile and
-install.
-
-*
-
-* It's maintained separately, so you don't have to wait for the
-OSF to release new X versions for enhancements or fixes.
-
-*
-
-* It provides more and better compression information and
-statistics than lbxproxy.
-*
-
-
-
-
-
-!Disadvantages
-
-
-
-
-
-* It is not a standard part of X; you must obtain and build it
-separately.
-
-*
-
-* It is slightly more complex to set up, since it requires a
-LOCAL-side proxy as well as the REMOTE proxy.
-*
-
-
-
-
-
-!Where Can I Get dxpc?
-
-
-The source for dxpc is available at
-ftp.x.org.
-
-
-There is a WWW homepage for dxpc that gives a lot of good
-information, including pointers to the dxpc mailing list, access to the
-source code, and a number of pre-built binaries for various platforms:
-
-
-
-http://ccwf.cc.utexas.edu/~zvonler/dxpc/
-
-
-
-!!11.2 Ssh (Secure Shell)
-
-
-
-
-Ken Chase <lbxhowto@sizone.org>
-notes that
-ssh can
-be used for compression. Although its main purpose is to provide
-security, it also compresses the data it sends.
-
-
-Thus, if you run X over a ssh link you will automatically obtain
-some amount of compression.
-
-
-
-
-!!11.3 Which Is Better?
-
-
-
-I don't know. Both LBX and dxpc are certainly better at raw
-compression than ssh. Of course, ssh provides the added
-advantage of security. And of course, there's no reason you can't use
-both ssh and one of the other two, to get good compression and
-security.
-
-
-It shouldn't be hard to run some benchmarking against these options
-and get both subjective and statistical measurings of performance. But
-I haven't done this, and I don't know of anyone who has
.
-
-
-
-----
+Describe [HowToLBX]
here.
