IPIPGW SIP to SIP codec negotiation problem.

Unanswered Question
Jan 25th, 2008


I have a strange problem with an IPIPGW configured for SIP-SIP.

My setup is as follows:

CCM-----SIP---IPIPGW(2801 IVS image) ----SIP------SP huawei x3000 softswitch

If i configure a codec class as follows

voice class codec 2

codec preference 1 g729br8

codec preference 2 g729r8

for both dial-peers, call works ok as the gateway negotiates g729 on both sides.

If i configured a codec class as follows

voice class codec 1

codec preference 1 g729br8

codec preference 2 g729r8

codec preference 3 g711alaw

I get one way audio as the CCM side is negotiated as g729 and SP softswitch side negotiated as g711. (no transcoding configured). SIP debugs shows the following:

923840618: Jan 25 18:16:20: //6193775/72A534369041/SIP/Info/sipSPICompareRespMediaInfo: No Comparsion needed as 18x response SDP is either absent or ignored

923840619: Jan 25 18:16:20: //6193775/72A534369041/SIP/Info/sipSPIDoMediaNegotiation: Number of m-lines = 1

923840620: Jan 25 18:16:20: //6193775/72A534369041/SIP/Info/sipSPIDoAudioNegotiation: Codec (g711alaw) Negotiation Successful on Static Payload for m-line 1

923840621: Jan 25 18:16:20: //6193775/72A534369041/SIP/Info/sipSPIDoPtimeNegotiation: One ptime attribute found - value:20

why does SIP sipSPIDoAudioNegotiation select g711alaw and my codec class prefers g729.

I need this step so that i can carry voice as g729 to g729 and fax as g711 to g711 without transcoding. I don't have enough resources to transcode all voice calls.

thanks in advance

I have this problem too.
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Paolo Bevilacqua Fri, 01/25/2008 - 11:28


for IP-to-IP calls, just configure "codec transparent" under DP, and let the endpoints negotiate.

Hope this helps, please rate post if it does!

solomonthuo Sat, 01/26/2008 - 01:54


codec transparent doesn't work for SIP to SIP as per documentation. I also configured it but once the user picks up the call disconnects.


Paolo Bevilacqua Sat, 01/26/2008 - 02:41

Well, then point me to the documentation, because I have it configured for sip to sip, and it works fine.

solomonthuo Tue, 01/29/2008 - 00:55


i was referring to the following document

"Cisco Multiservice IP-to-IP Gateway Application Guide"

Cisco IOS Release 12.4(11)XJ2

pg 27.

Paolo Bevilacqua Tue, 01/29/2008 - 02:16


I shall contact cisco documentation team, because that is what I use, and it makes sense to me.


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