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List:       dxpc
Subject:    HBX?  High latency X for Satellite Networking
From:       bduncan () beachnet ! org (Bill Duncan)
Date:       1997-07-28 18:25:22
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This is not strictly about dxpc, but I thought that readers here might know
more about this technology, and whether there is code available anywhere
which might help.

The problem I am working on is not really related to low bandwidth, but
has more to do with latencies in a wide area network and synchronous
request/replies.  I've tried dxpc in this environment where a link to London
is about 150ms in each direction, and it does not really help in window
startup times.

There was a paper in the X proceedings called "HBX -- High Bandwidth X for
Satellite Networking" which describes the problem.  I've been trying to
reach the authors to see if there is code available or any further info
without success.  The paper (in PS format) can be reached on the net from:

  http://www.wins.hrl.com/people/ygz/papers/xtech96.html

The following are some results produced with an awk script on the output
of a modified version of xmond.  The application running is a third-party
Motif-based product.  Note the average turnaround time of 0.29 seconds.
These are round-trip times.  Also note that if I can "spoof"
some of the top request/replies, I can cut latencies for creating windows
down considerably.

Synchronous Request/Reply Transactions
======================================

    Seconds  Count  Request                uS  Per     % of total time
----------------------------------------------------------
  24.890375    110  AllocColor            226276.1   18.7%
  23.015011     89  GetInputFocus         258595.6   17.3%
  12.807337     53  InternAtom            241647.9    9.6%
  10.473151     22  GetGeometry           476052.3    7.9%
  10.000684     22  QueryColors           454576.5    7.5%
   9.971028     38  GetProperty           262395.5    7.5%
   9.936836     28  AllocNamedColor       354887.0    7.5%
   9.287785     33  GetSelectionOwner     281448.0    7.0%
   9.182274     19  QueryFont             483277.6    6.9%
   2.077667      6  GetKeyboardMapping    346277.8    1.6%
   2.041262      4  GrabPointer           510315.5    1.5%
   2.002960      9  GetModifierMapping    222551.1    1.5%
   1.560358      6  QueryTree             260059.7    1.2%
   1.456062      4  TranslateCoordinates  364015.5    1.1%
   1.171661      4  GrabKeyboard          292915.2    0.9%
   1.101117      5  LookupColor           220223.4    0.8%
    .881283      4  GetWindowAttributes   220320.8    0.7%
    .669997      3  QueryExtension        223332.3    0.5%
    .658753      3  QueryBestSize         219584.3    0.5%
----------------------------------------------------------
 133.185601sec 462                        288280.5  100.0%


Has anyone else tried anything like this?  I know that the X protocol is
really the wrong thing to run on a WAN, but the alternatives are uglier.
(One alternative which I'm hoping to beat, is Citrix, which is another
MS company.)

-- 
Bill Duncan, VE3IED  | BeachNet  -->  http://www.beachnet.org
bduncan@BeachNet.org |   - Network/System Administration
bduncan@ve3ied.uucp  |   - Web Design, Hosting Services
+1 416 693-5960      |   - System Analysis/Design/Programming

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