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Re: ATM Question
From: "Thomas P. Brisco" <brisco () globix net>
Date: Fri, 6 Oct 2000 09:07:41 -0400 (EDT)



        We were seeing something similar yesterday (and yup -
it's still there today).  We also noted that if you turn on the
record-route options, then your problem will disappear (I suspect
packet options may cause delivery to be ok - though while the RR
option helps, DF doesnt, but "timestamp" will).  We're not seeing
packet loss in any other scenario.  I noticed, suspiciously, that
there is always a very "hockey toothed" (every other packet) pattern
in the lossage (load balancing onto a botched circuit?).

        Things I've played with:
        * size          50%     (tried 800, 1200, 2500)
        * DF            50%
        * RR            100%
        * pattern       seems to be generally 50%
        * timestamp     100%
        * TOS           50%
        
        We've opened up a case with cisco ... seems pretty
bizarre, but could it be the ATM switch?
        As long as we're not using the source address of
the ATM network - things are fine (e.g. sourcing off of
the loopback, going one hop back, etc).

                                                - Tom

On Fri, 6 Oct 2000, Richard Inhand wrote:

Date: Fri, 6 Oct 2000 04:50:10 -0700 (PDT)
From: Richard Inhand <chapinhand () yahoo com>
To: nanog () merit edu
Subject: ATM Question


I'm currently looking into a weird problem at an ATM
peering point on the West Coast, when I ping from my
peer router to any of my peers I get some but not
total packet loss, when I ping from one router back or
use the loopback interface as source things are fine.
Whereas, with all my other ATM peering point routers,
for example at MAE-EAST I can ping my peers cleanly
from the same router. This isn't (to my knowledge)
affecting traffic just wondering why this strange
phenomenon should occur only in the one place.

Any body else had any similar problems?

Richard Hand


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