[Comtec Announce] IP Voice: Service Alert: 12/11/2010 - One-way Audio

[David Croft]

This is an update to previously a issued Service Alert on Friday 12th
November 2010.

Issue: Inbound calls from the PSTN were regularly experiencing one way
audio on the inbound direction (from the PSTN).

Status: The carrier has issued the below Post Incident Report.

Incident Summary

On Friday the 12h of November 2010 several of our customers reported
one-way transmission on calls to 0207 xxxxxxx and 0208 xxxxxxx. The
first customer report was received at 12:50. An incident was raised at
13:35, the issue diagnosed and service was restored at 13:53.
One way transmission was experienced where our customers could not
hear the other PSTN-connected party.   The fault was localised to a
VXSM card in the Reading MGX Media Gateway.

12th November 2010

11:58  VXSM Card 1 in the Reading MGX AP922 experienced a DSP issue
and initiated a failover to it’s resilient partner card 2. Following
this failure, various customers reported intermittent one way
transmission.

13:35 Incident raised to investigate the issue

13:53 Service was restored when all 3 routes terminated on the
affected card pair was effectively busied out to live traffic.

The affected cards are currently out of service whilst our vendor
investigates the initial DSP failure and the subsequent one-way
transmission problem. Logs have been provided and test calls made to
provide further traces to enable the investigation.

Observations

The key observations are yet to be defined, as we are awaiting
feedback from our vendors.

Key Actions

The following actions have been identified as part of this incident review.

AP01 Identify the reason that the VXSM card went out of service (DSP issue)
Due 19/11/10

AP02 Identify the reason that one-way transmission occurred when the
VXSM card failed over.
Due 19/11/10

AP03 Review what alarms were generated when the card went out of
service, and what actions were taken in response to these.
Due 16/11/10

Next Steps: The carrier has advised they will release a further report
during the week commencing the 6th of December. If you would like this
to be made available to yourselves please raise a Technical Support
ticket and we will pass on this report when it has been made available
to us.

Regards,

Comtec

--
David Croft
Lead Network Engineer

Comtec Enterprises Ltd
Comtec House
46a Albert Road North
Reigate Industrial Estate
Reigate
Surrey RH2 9EL

Tel: 0845 899 1400
Fax: 0845 899 1401
www.comtec.com

For urgent operational issues please always contact noc at comtec.com or
0845 899 1423 and not any named individual.