[Asterisk-Users] FWIW- Cisco 1750 dropped packets and choppy audio

Rich Adamson radamson at routers.com
Thu Jun 10 06:27:49 MST 2004

This email is intended to document an issue for anyone searching the archives.

We had a problem yesterday with _all_ iax2 and sip sessions; no reasonable
conversation could be established due to extremely choppy audio in one
direction only (outbound from * to distant sip phones and distant * boxes).
We were running HEAD from June 8th.

While diagnosing the root cause, we monitored bandwidth utilization at the
asterisk-connected managed-switch as well as at the Cisco 1750 Internet
interface. We observed consistent/even data flows to/from the * box, however
the outbound Cisco interface indicated more inbound traffic than outbound
traffic by a considerable/noticeable amount. Both iax2 and sip sessions were 
impacted exactly the same regardless of the codec being used.

In the haste to identify the root-cause, the Cisco 1750 was rebooted
(Version 12.2(4)T7) and the problem disappeared. A Service-Policy had been
applied to the outbound interface for QoS purposes. Removing the policy
while a poor quality session was in progress had zero impact. Unfortunitly, 
no other Cisco data was gathered before the reboot. We're waiting for
reoccurrence to gather additional doc. We are 100% confident this is a
Cisco issue as opposed to * or any other resource. (Someone, maybe Eric, 
mentioned a Cisco QoS bug previously on this list. Indications are this 
might be the bug that person had mentioned.)

The Cisco had been in use for a couple of years and we've never seen this
issue arise prior to yesterday. The * box had been in semi-production since
late last year and has been stable (given the expected issues associated
with using HEAD as opposed to Stable).

There were no logged messages from the Cisco even though syslog messages are
normally monitored closely.


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