ATM Output Drops

Unanswered Question
May 31st, 2007

Show tech and show policy map attached. I cannot use the show queueing command to get more details. 2 PVCs - sno-cao and sno-brq are seeing a lot of output drops. The voice calls are suffering heavily. This was all working until last Thursday. No change was done. The problem started on Thursday. One action plan to try and resolve problem is that the IOS was on upgraded on Monday from 12.3(15b) to 12.3(19). The problem is still there even after upgrading.

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Overall Rating: 3 (1 ratings)
Paolo Bevilacqua Sun, 06/03/2007 - 17:46


I think the show queueing commmand is now obsolete and replaces by show service-policy as you already where doing.

Can you check service policy at the time drops occurs ? Does the traffic volume going out on the PVC matches what the ATM SP has contracted to you? Havi you contacted them to knwo fi the made any change at the time the problem started? Are the voice-class counters being incremented when there are voice calls ?

astanislaus Sun, 06/03/2007 - 18:56

The Service Provider says they have made no change.

The SHOW SERVICE POLICY command has proved that no drops occur due to exceeding the policy. This command has been done several times.

We again checked with the carrier to see if they made any changes and if they see any issues and they said NO.

This setup has been working fine for more than a year.

That is why we moved to 3745 and all OK so far.

I somehow still suspect something external to the 7507 (original router) had caused the problem.

Probably the move to 3745 probably has happened around the same time that the external trigger has gone away.

My only concern is why on the 7507 the FAST MEMORY Free is only 128 bytes all the time.

Paolo Bevilacqua Sun, 06/03/2007 - 19:15


In fact, even if the provider had lowered the service parameters, you would not see output drops, but packet loss instead.

The strangest thing is the voice quality issues with a service-policy that was meant to avoid exactly that.

Anyway, 7500/vip/distributed features are very complex systems that are hard to diagnose at times. This is why the TAC has a specialized team for this kind of issues.

Good luck!


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