[cisco-voip] no audio for 10 seconds

Wed Nov 2 12:25:34 EDT 2011

Only reported on the 9971.  No consistency to the issue.

We've tried a selective firmware update to 9-2-2 without success.
We have checked for possible delays in call setup with MGCP, Q.931 and SIP with no clues or even momentary delays in the setup.
We have exhausted tweak options for the QSIG integration (timers, etc.)
We have attempted to recreate the issue without success even with a phone known to experience the issue.

Unfortunately we don't have the tools available to determine if we're experiencing troubles with the RTP stream initialization, especially seeing as the issue is intermittent.

The one thing which stands out to me is that we have two other locations with the 9971 and they are not experiencing these issues.  Only difference here is the PBX integration with QSIG.  This site is also the only one with PVDM3.

To: Wellnitz, Erick A.
Cc: cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] no audio for 10 seconds

Hi Erick,

Based on history you're a pretty enterprising.  Any insight on what you've checked so far?

Is it only reported on 9971's? Is there any other consistency in the reports thus far?

One of my favorite approaches to get a bit of insight on this type of issue is CMR data.  Look at CMR's for "simple" calls - direct call, connection, duration hangup; no mute/transfer/hold/park/etc.  If you're using fixed packet rate audio codec (not ilbc) then the packets sent/received should be linearly proportional to call duration barring a few special situations.

Assuming 20packets per second are the number of packets received appropriate for the duration of the call?

If the packet counts are correct then it's an audio cut through issue on the gateway or audio rendering issue inside the phone.
gateway concerns: call going into connected state, any progress indicators exchanged (affect audio cut through timing)

If the packet counts are off then there is a network issue.

/wes

On Nov 2, 2011, at 11:46 AM, Wellnitz, Erick A. wrote:

All, especially you really smart guys at Cisco...

We're at a loss for where to continue looking for a potential cause on a very intermittent issue.

Mixed 9971 and 7975 environment with shared lines.  Inbound calls come into our old (and temporary) Siemens PBX.  Cross a QSIG trunk group to Cisco 3945 with PVDM3-192

Caller on our Cisco side places a call.  They hear ringback.  Call connects without audio for about 10 seconds.

We couldn't find anything similar to this in bug toolkit.

9971 firmware: 9-2-1
CUCM Ver: 8.0.3.21900

SR 619601919

We have a  laundry list of issues with the 9971 model but this is currently the most urgent.

ERICK A. WELLNITZ
Network Engineer
Katten Muchin Rosenman LLP
525 W. Monroe Street / Chicago, IL 60661-3693
p / (312) 577-8041
erick.wellnitz at kattenlaw.com<mailto:erick.wellnitz at kattenlaw.com> / www.kattenlaw.com<http://www.kattenlaw.com/>

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