SUMMARY: X-windows over modem link

From: Mark S. Anderson (
Date: Sat Jul 30 1994 - 04:20:09 CDT

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Much too long ago, I wrote:

> Is it possible to operate an X session over 14,400 bps modems? [My
> friend] wants to use a dial-up link running PPP to run a graphics and
> CPU intensive application (ENTEC, for those who know it). The
> application is normally CPU bound, so he thinks that the data transfer
> required for display may not be a big burden.
> Is this fast enough for even the least demanding X session? What are
> your experiences/thoughts on this?


Executive Summary:

The responses went from "it's fine" to "it's too slow to be useful."
The general drift was that it was a little slow, but is tolerable. The
only way to find out if the performance is satisfactory is to try it.
One's satisfaction with the speed of the connection seems to be
dependent to one's expectations, requirements, and especially, the
application. Xterm, emacs (X-mode), etc. are O.K.; graphic-intensive
stuff will be slow, and most likely, unacceptable.


More summary info:

Speed can be improved by:
  - running the window manager locally, rather than on the (remote) host
  - using a protocol that compresses data and is optimized for X
  - having enough local memory
  - having common (frequently used) fonts resident locally
  - 14,400 bps modem should have compression if protocol does not compress

These features are reportedly provided by MIT's X11R6 and NCD's Xremote
(with NCD X-terminal or PC). Xremote is reported to be 10 times faster
than full X over PPP/SLIP. One Xremote-compatible X-server (to run on
the PC terminal) is XVision (from unipress). eXceed's Hummingbird
reportedly also uses compression and does not require PPP.

However, one person uses XVision's XServer for Windows over 14,400bps
line with these results:

  - xmosaic takes 5 min. to get the home page (compared to 15-20 sec.)
  - xv takes 5-7 min to load, and ~5 min. to display a 200k GIF file

Another person, using PC Xware (compression, X-server runs on remote
host) over a 14,400bps line, found that FrameMaker was unusable.

There was quite a bit of detailed information describing experiences
with various configurations (line speed, software, X-server brand,
terminal type, etc.). Because this infomation can not be adequately
expressed in a summary, I have attached the text of the replies to this

A big "Thank-you" to all who responded.

Mark Anderson
The MITRE Corporation
7525 Colshire Drive, MS W747 voice: (703) 883-6439
McLean, VA 22102 FAX: (703) 883-1905

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From: (Daniel R. Bidwell)

I have been running X via 9600 baud for years with an NCD X terminal
and now use a 14.4 modem with a Sparc 1. I love it. I use PPP with
the Sparc 1.

Daniel R. Bidwell	|
Andrews University	Computer Science & Information Systems Department

------------------------------------------------------------------------- From: (Gary Smith)

I use MacX over a 14400bps modem through PPP. I run some pretty intensive graphics display (3D modeling) and it seems to be in the acceptably slow range. I've also used an NCD B&W Xterminal with NCD's Xremote (PPP/SLIP) which was much faster because of the B&W only.

--Gary Smith Dept. of Biostatistics Dana Farber Cancer Institute Boston, MA USA

------------------------------------------------------------------------- From: (Alan Piszcz)

It can be done, I do it daily using either MacX/Exodus. MacTCP and PPP or SLIP. I am using a SUN HOST.

------------------------------------------------------------------------- From: (Sven Heinicke)

you can do it I'm sure, the CPU intensive part will be just as slow locally as it will be over the modem but if your going to be doing any complicated graphics it will be slow. I ran a 19200 baud slip line just for telnet and ftp for a bit and it was noticably slower then normal. Perhaps PPP is better though.

------------------------------------------------------------------------- From: (David N. Edwards)

Well..., NCD used to have a "compressed" (ie proprietary) version of X for use across modems, at least with their 15 b&w terminal. They claimed it did an adequate job for light X usage with 9600 baud modems. Of course, color bitmaps would be slower.

------------------------------------------------------------------------- From: (David J. Knight)

X over 14.4kb works, but is slow. Tolerable by some, not by others.

------------------------------------------------------------------------- From: John Posey <>

PPP is sort of straight forward to setup, but you have to read carefully.

Graphics are really slow, but text is fine. We use US Robotics Courier modems in HST mode with hardware compression turned off. If you could get the new 28,800 modems, the graphics should be fine too :) Note that you must connect the machines directly to the modems (ie, no terminal servers or modem banks allowed).

John Posey, Graduate Student and part time UNIX Systems Programmer InterNet: E&CS, The University of Texas at Dallas Phone (lab) (214) 690-2719 PO Box 830688, MS EC33 Phone (H) (214) 727-5704 Richardson, Texas 75083-0688

------------------------------------------------------------------------- From: (Ron Gilmer)

I've done this a couple of ways and have found it satisfactory...but slow...

1)I used a PC from home to tie into our server at work and ran PC Xremote. This program utilized the server to run the Window Manager and all applications under the WM's control, the PC just handled the display. PC Xremote uses a propriety communications protocol over the 14,400 modem and also does it's own compression.

There was a delay that became irriatating at times (especially with the mouse), but overall the perfromance was acceptable. I did end up using a window manager that was a little simpler and compact - "twm". I found that the less bells and whistles in the WM the better the performance.

2)I now use a SPARCstation at home (and like it MUCH better). I'm tied in over a Telebit T3000 using ppp. I run (obviously) a local window manager and just run the X applications I need from the server over the modem.

I've been happy with could be a little faster :>)

------------------------------------------------------------------------- From: "A. Bryan Curnutt" <bryan@Stoner.COM>

> Is it possible to operate an X session over 14,400 bps modems?

Yes, it's possible. I've done it using PPP. It requires patience.

-- Bryan Curnutt Stoner Associates, Inc. (713)626-9568 voice (713)622-7832 fax

------------------------------------------------------------------------- From: Bill Heiser <heiser@TDWR.ED.RAY.COM>

You can do it but it is really too slow to be useful. For example if you run an XTERM, every character typed will be delayed significantly.

-- Bill Heiser work-> home-> ------------------------------------------------------------------------- From: (David B. Brown)

I use the PD software dp-2.3 for Solaris 1.X and dp-3.1 for Solaris 2.X and regularly run X applications over a 14.4 dialup line. X applications like xrn, xarchie, and xgopher run at an acceptable rate. Things like mailtool are a little slow but then mailtool can be slow even across the local ethernet. You can get the dp stuff from if you don't already have it.

------------------------------------------------------------------------- From: (metal bird dip wing of fire)

I have an SS-1 at home with a Telebit 3000 modem, and I run X applications regularly from remote sites (usually xterm's emacs's). It's not blindingly fast at 14.4K, but it works well enough for me. (In other words, no, it's generally not slow as molasses.)

-|-|-|-|-|-|-/\-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|-|- Joe Turner < > The Concorde Group, Ltd. Cambridge MA 617/491-0400 \/ System Administrator not officially speaking for CGL

------------------------------------------------------------------------- From: jlarivee@s1.f011.DPW.COM (Jerry Larivee)

> Is this fast enough for even the least demanding X session? > What are your experiences/thoughts on this?

I can't say for sure, but this may be a rare area where you'll get better results with X running on a PC then on a UNIX box. I'll explain.

I've used a product called eXceed/eXsess from Hummingbird Ltd. to get X windows access over a dialup line under Microsoft Windows. This product has an advantage over straight PPP between UNIX boxes because the communication protocol eXsess uses a compression algorithm that is optimized for X protocol traffic. There are other products that offer the same features, but we evalutated a few and choose eXceed. I don't know if you can find simillar products for UNIX.

I found the performance running on a 25MHz 386DX, no FPU, 8MB RAM, ISA video card, and 9600 baud (V.32) modem, with compression disabled (MNP 5 conflicts with the built in compression, V.42bis does not have this problem) very reasonable, but I didn't do alot of graphics work. My video is fairly slow, and that may have impacted my performance. One note, using Microsoft Windows (or some other local window manager) as the window manager, is a big win over using a native X window manager running on the remote machine; it saves alot of bandwidth.

Jerry Larivee System Programmer (212) 450-4836 Davis Polk and Wardwell New York, NY

------------------------------------------------------------------------- From: (Upkar Singh Kohli)

ExceedW from HummingBird works great... 14,400 with compression works great. No separate protocols needed, like PPP.

------------------------------------------------------------------------- From: (John Malick)

14,400 bps modem's will do you just find... Since the modems hopefully support v.42bis and such protocols for up to 4:1 compression you will see fairly decent throughput speeds well over 14,400 bps between modems..

Make sure that your DTE interface speeds are set as high as the modem and serial ports support, ie. 38,400 bps. Otherwise you will be sending data to the modem slower than the modems are capable of sending across the phone line and thus the modems will be sitting idle doing nothing but sleeping while they could be sending precious data...

_________________________________________________________ | | | John Malick | | Voice (717) 757-5700 | | E-Mail | | | | Address Soft Systems Engineering | | 3528 Concord Road | | York, PA. 17402 | |_______________________________________________________|

------------------------------------------------------------------------- From: (Aaron Dailey x4989)

We have people here doing just that - running X over a 14.4k modem to a PC running PC Xware (an x server for the PC). I've seen it perform - for text based applications, e.g. emacs in X mode, or xterms, etc it's fine. It was really (unusably) slow on the one graphics program we use much of, Frame. You might at least try it.

Aaron Dailey Internet: StorageTek Corporation Voice: (303) 673-4989, FAX: (303) 673-2570 Mail: MS0262, 2270 South 88th Street, Louisville, C0 80028

------------------------------------------------------------------------- From: (Bill Hargen)

> Is it possible to operate an X session over 14,400 bps modems?

It all depends on the application. I frequently use mailtool over just such a link and it is OK. It is a bit sluggish, but even the compose window is useable (~1/2 second delay on character display). I have also used Mosaic, but you will want to disable loading images!

Other applications can be completely unuseable. I tried Cadre Teamwork (a CASE tool). It took two minutes to display anything - even module specs which are all text. It must have been using bitmaps for everything.

If you have some sort of Ethernet traffic monitor, you might be able to measure the X windows traffic while this is on the Ethernet and get some idea of what the bandwidth requirement is.

------------------------------------------------------------------------- From:

We had a demo X application called PV-Wave that we tried running over a 256K bandwidth and it was S-L-O-W, Not sure how graphically oriented your app is (moving things, rotating objects, etc) but i am fairly confident that it will be (generally) painfully slow, unless it is mostly text I/O. ------------------------------------------------------------------------- From: Chris Komuves <>

You could do this with our XVision XServer product over PPP, and get OK response (although OK is a relative concept). Our company also markets a version of XVision that works over NCD's XRemote protocol for X compression. This will give up up to three times the speed of PPP (still slow by network standards, but better than PPP). You can also run VT320 sessions and ftp files simultaneous to using multiple X Windows with an optional host end.

-- /======================^=============================^======================\ | Christopher Komuves | Internet: | 2025 Lincoln Highway | | Sales Representative | Phone: (908) 287-2100 x.914 | Suite 209 | | UniPress Software | Fax: (908) 287-4929 | Edison, NJ 08817 | | "What we love we shall grow to resemble" -Bernard of Clairvaux | \===========================================================================/

------------------------------------------------------------------------- From: (Mark Owens)

I tried to run an xterm over slip and was really frustrated by the slooowww response. Any event generated by the clinet has to traverse the SLIP link. This means that mouse events, redraws, menu events (in short lots-o-stuff) within the client window go over this link...really slow and painful. If your friend has to do this for any length of time, you may end up visiting him in an institution :)

------------------------------------------------------------------------- From: (Adam Fox)

You may want to seriosuly look into the newly release X11R6. It is advertised to have a new feature called LBX (Low Bandwidth X), which is supposed to support X over serial lines. Before the release of R6, many vendors supported their own serial adaptations to X for THEIR Xterminals.

While I'm not entirely sure how LBX works, it is probably worth checking into.

-- Adam Fox Systems Programmer Supercomputing Reseach Center Bowie, MD USA

------------------------------------------------------------------------- From: Marco Pineda <>

Slow, even at 14400, although I can live with xterm (barely). I'm trying to get my company to pay for an ISDN connection. I think you just have to try it and see if you can live with it.

************************************************************************* * Be vague... be very vague. | * * "Carpe Cibum" | Marco Pineda * *************************************************************************

------------------------------------------------------------------------- From: (Glenn Satchell - Uniq Professional Services)

This is the setup we have, 14400 bps modem running various PPP implementations. It is ok for a telnet session, but I find running say, mailtool, to be a little slow. If it's graphics intensive then it depends on what he'll put up with.

-- Glenn Satchell | Uniq Professional Services Pty Ltd ACN 056 279 335 | PO Box 70, Paddington, NSW 2021, (Sydney) Australia | Phone 02 360 7434 Pager 016 287 000 Fax 02 331 2572 |

------------------------------------------------------------------------- From: Dave Fetrow <>

If you: use serial-line compression optimized for Xwindows Have enough local memory Run the window manager locally Have common fonts locally

the answer is YES.

PPP may not be the best choice for the link (I just use NCD's Xwindow product for a PC which has the above features) but it shouldn't be too bad; especially if you are only doing text but graphics will probably require patience. A tip: Tektronix 4010 style graphics are probably more efficient if you can get away with it.

X11release6 has this kind of stuff builtin.

------------------------------------------------------------------------- From: Rodney Campbell <>

I suggest that you use a compressed X protocol like (NCD's) XRemote over the serial link rather than run full X over PPP or SLIP. I have been using Xremote (to both NCD X Terminals and PC's running an XRemote compatible X Server [like XVision]) for over a year now (at 9600 and 14.4K) and it is very good. They say that XRemote is about 10 times faster than Full X over PPP/SLIP.

In fact I am logged in from home right now at my Xterminal running XRemote at 14.4K using Emacs, XTerms, Xarchie, Mosaic etc.

-- Rodney Campbell |Email : Telecom Australia |Snail : PO Box A792, Sydney South 2000, Australia. Information Technology Group| : Level 1, 18-20 Orion Rd, Lane Cove West. Network Systems |Phone : +61 (0)2 911 3123 Fax: +61 2 911 3199 |

------------------------------------------------------------------------- From: spuddy! (Mike Cross) [^^^^^^^^^^^^^^^^ wrong - see below. -ed]

I suggest that your friend talks to NCD they offer dialup X windows support, its not standard (yet?) so I've seen the demo and it looks OK. As you would expect its not as fast as direct graphics and large repaints can take some time, but its good.



------------------------------------------------------------------------- From: (Brett Lymn)

14.4k is barely usable for X - v.42bis is much better but you will have to be patient. On a fast link X may be cpu bound but the equation changes when the link is slow as there is a lot of data going between client and server.

-- Brett Lymn, Computer Systems Administrator, AWA Defence Industries

------------------------------------------------------------------------- From: admin@gilligan.UCSD.EDU (System Administrator)

We've been running XVision's XServer for Windows over a 14,400bps phone connection, and have found that running graphic intensive progs takes far too much time to be considered "efficient". For instance, running Mosaic, it takes about 5 minutes just to get the home page! On the network it takes about 15-20 secs at most! And programs such as XView take about 5-7 minutes just to start, then another 5 or so to display a 200k GIF file...I don't know what your requirements are, but these numbers are way too high for us! Normal cmdtool windows are slow to respond, but they can be "fast enough" for some types of file editing and directory listing, etc. As far as graphics go, I wouldn't count on anything too great!

------------------------------------------------------------------------- From: (George Medakovich)

I used to run DESQview/X over a slip connection at 9600 bps. It was sluggish, but definitely usable.

Now I use X/Remote (NCD) over a tty dialup with a 14400 bps connection (UDS FasTalk) and it is very usable with text-oriented applications (cmdtool, news readers, mailtool, Sybase APT apps, etc.).

George Medakovich First National Bank of Chicago

------------------------------------------------------------------------- From:

we tried PC-Xware, it works with Xremote Protocol. That means the server runs on a local Sun and the remote PC is Display :0.1 (data is compressed by the server).

If You use normal character-based-windows (csh, xmail, ...) it's fine but graphic-applications are very slow.

This week we'lll try X over PPP, but I think it's worse.

-- +-------------------------------------------------------------------+ | Thorsten Schunk | Zentrum fuer Graphische Datenverarbeitung eV | | | Graphisches RechenZentrum | | | Wilhelminenstrasse 7 Tel: 06151/155-315 | | | 64283 Darmstadt Fax: 06151/155-399 | +-------------------------------------------------------------------+

------------------------------------------------------------------------- From: Dan Stromberg - OAC-DCS <>

Yes, it's fast enough for low-demand X.

You may find speed improvements using bswm (window manager that maximizes backing store on the local machine), sxpc (X specific compressions) and/or term (somewhat analogous to slip, but strictly user-level, and I suspect it has protocol prioritization, since it is generally MUCH more "comfortable" than slip doing concurrent telnet and ftp at the same time. It also includes generic compression), all of which are freely redistributable.

I tried xv and xterm over sun's ppp a while back - xv was ridiculous and probably will be regardless of what software you use - but xterm was quite reasonable.

------------------------------------------------------------------------- From: Francois.Banville@Ville.Sherbrooke.Qc.CA

I have a HDS monochrome X terminal at home. It has its server code on EEPROM. It supports PPP and I use a 14400 baud modem to connect it to a Annex III terminal server.

It takes a long time to load the local window manager that I use but, once this is done, I can do some work. I find it acceptable to use our mailtool, many xterm and the like. It is not acceptable for X word-processing or drawing programs. One can do it, but one grow very old very fast. I find it very usefull for home based support work.

-------------------------------------------------------------------------- Francois Banville | voice: (819) 823-5124 Analyste en recherche | fax: (819) 821-5470 et exploitation | Ville de Sherbrooke | email: Francois.Banville@Ville.Sherbrooke.Qc.CA --------------------------------------------------------------------------

Mark Anderson ---------------------------------------------------------- The MITRE Corporation 7525 Colshire Drive, MS W747 voice: (703) 883-6439 McLean, VA 22102 FAX: (703) 883-1905

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