[cisco-voip] Echo on IP Phones through PRI

[Erick Bergquist]

DSP Fimware 4.4.708 has issues which can cause echo, etc. Many people on the cisco NetPro forums have ran into echo issues with this DSP firmware.  I don't have the exact bug id's handy, but you can try upgrading to a current 12.4 mainline release if your routers DRAM/flash can take it. 12.4(13a) has 4.4.23 DSP ware. So far, I have not ran into any issues yet with DSP firmware 4.4.21 or higher in 12.4 mainline but YMMV. 

If you can't update the IOS, and I don't believe there is a newer 12.3T release with a newer firmware embedded in it, you can get a standalone DSP firmware image file to put on the router flash that is a newer version from TAC. 

As far as finding out what gateway a call is using, probably the quickest way is to go to the phones web page while the call is connected and look at the stream page for the remote IP address. Other then that, you would need to check out CDR and/or QRT records if they use QRT softkey, etc and go into each gateway. 

----- Original Message ----
From: Matthew Melbourne <matt at melbourne.org.uk>
To: cisco-voip at puck.nether.net
Sent: Wednesday, April 18, 2007 7:50:22 AM
Subject: [cisco-voip] Echo on IP Phones through PRI

We are getting sporadic issues from users on IP phones who are hearing
echo on external calls. From this document is would suggest that echo
on IP Phones is caused by hybrid echo and not any local acoustic echo.

http://www.cisco.com/warp/public/788/voice-qos/echo_ipphone_gateway.html

The MGCP-controlled voice gateways are all running 12.3(14)T7 with DSP
firmware 4.4.708. In CallManager (4.1(3)SR2), echo cancellation is on
for each port, with a "default" echo cancellation coverage of 64ms.
Input gain and output attenuation are set to 0dB.

I have seen suggestions to include the "echo-cancel erl worst-case 3"
command on the voice ports. Can this help in situations of occasional
echo?

Are there any other parameters changes which could help? Could it be a
code/DSP firmware issue? I haven't found a specific echo-related bug
relating to this particular IOS and its embedded DSP firmware.

On occasions, the start of the call is fine but echo comes and goes
during the call.

Is there a quick way of finding out which voice gateway a call is
terminated on (we have 8, and all could be used in a round-robin
fashion for outbound calls).

Cheers,

Matt

-- 
Matthew Melbourne
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