update on alpha 200 4/166 networking problems

From: Charlie <jui_at_greisen.physics.utah.edu>
Date: Fri, 3 Feb 1995 17:43:32 -0700 (MST)

This is a follow up to my postings about poor NFS/FTP/PING performance.
We have done additional investigation and uncovered some new facts.

Let me start by describing our network setup:


=======================thick=net=================================
                           ||
                     /------------\
     thin wire-------| repeater |----thin-net----{3100}
              | \------------/
              | | |-----...
            {RS6000-1} |-----...
              |
            {NCD x-terminal}
              |
            {NCD x-terminal}
              |
            {5000}
              |
            {NCD x-terminal}
              |
            {ALPHA}
              |
            {MAC}
              |
              |
            {RS6000-2}


  The original symptoms are that I had NFS trouble accessing large files
over NFS on a volume physically located on the 3100, while I had no problems
communicating with the 5000. I finally got hold of the layout of our net
layout above, and started various ping tests. The tests include some of
the nodes shown above, but also involve a news-server located in another
department (some bridges in between) and another RS6000 which is connected
indirectly to the thick-net shown.

the result is as follows:

          originator target percent packet loss
----------------------------------------------------------------------
             ALPHA 3100 1.4
             ALPHA RS6000-1 0.0
             ALPHA RS6000-2 0.0
             ALPHA 5000 0.0
             ALPHA news-server 0.9
             ALPHA RS6000-3 0.8

             3100 5000 0.0
             3100 RS6000-1 0.3
             3100 ALPHA 1.0
             3100 RS6000-2 0.0
             3100 news-server 0.3
             3100 RS6000-3 0.5

             5000 3100 0.0
             5000 RS6000-1 0.0
             5000 ALPHA 0.0
             5000 RS6000-2 0.0
             5000 news-server 0.1
             5000 RS6000-3 0.2

The only consistent pattern is that any communication across the repeater
(it is NOT a bridge) involving my ALPHA encounters a packet loss rate
of about 1%, while communications within the same thin-wire involving my
ALPHA seems OK. There is no evidence that this problem occurs where other
nodes on this thin-wire are involved.

Does this mean I have a hardware problem on my ALPHA?

thanks

Charlie Jui
Dept. of Physics
U. of Utah
Received on Fri Feb 03 1995 - 19:43:51 NZDT

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