VVX400 InValid SDP Answer Received

[Anonymous]

Hello,

We're using a VVX400 running 5.0.1.4068.

It sends an INVITE containing the following SDP:

v=0
o=- 1401728954 1401728954 IN IP4 10.100.0.29
s=Polycom IP Phone
c=IN IP4 10.100.0.29
t=0 0
a=sendrecv
m=audio 2264 RTP/AVP 9 18 110 0 8 127
a=rtpmap:9 G722/8000
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=rtpmap:110 iLBC/8000
a=fmtp:110 mode=30
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:127 telephone-event/8000

It receives back an OK containing the following:

v=0
o=NetSapiens_Nms 31775 31775 IN IP4 [removed]
s=pjmedia
c=IN IP4 [removed]
t=0 0
m=audio 24712 RTP/AVP 110 127
c=IN IP4 [removed]
a=rtpmap:110 ILBC/8000
a=fmtp:110 mode=30
a=rtpmap:127 telephone-event/8000
a=fmtp:127 0-15
a=rtcp:2348 IN IP4 192.168.1.72
a=ptime:20
a=maxptime:120

The phone returns an ACK, and then immediately a BYE. Checking the syslog, I see the following line:

CStateInviteClient::OnEvResponse InValid SDP Answer Received

after the ACK, and before the BYE.

I can't see what's invalid about the SDP received back. The only thing I can see that I suspect could be the cause, is that the INVITE contains "iLBC" and the response contains "ILBC", so the case doesn't match. Checking RFC 4566, values in attribute lines are not supposed to be case sensitive however.

Can you see anything invalid about the response SDP?

[SteffenBaierUK]

Hello Squigley,

welcome back to the Polycom Community.

It may be the a=fmtp:110 mode=30 as I found a similar case (VOIP-48109) in our database.

You may want to look at the voIpProt.SDP.iLBC.13_33kbps.includeMode and maybe the voice.codecPref.x Parameters.

If all of the above fails please log this with support and mention above internal reference.

Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.

Best Regards

Steffen Baier

Polycom Global Services

[Anonymous]

Hi Steffen,

I checked the documentation for 5.0.1 which we're running on this phone: http://downloads.polycom.com/voice/voip/uc/UC_Software_ReleaseNotes_UCS_5_0_1.pdf

which says:

sip added voIpProt.SDP.offer.iLBC.13_33Kbps.includeMode   See Administrators  Guide for SIP 3.2.0  for details.

I check that: http://supportdocs.polycom.com/PolycomService/support/global/documents/support/setup_maintenance/pro...

After reading the documentation, I added the parameter: voIpProt.SDP.iLBC.13_33kbps.includeMode to our config, and set it 0, but upon updating the phone, syslog says:

Unknown parameter "voIpProt.SDP.iLBC.13_33kbps.includeMode" found, ignoring.

I thought perhaps it was a case issue, but changing the k to a K to match the Admin Guide, it still says:

Unknown parameter "voIpProt.SDP.iLBC.13_33Kbps.includeMode" found, ignoring.

(and as expected there's no change to the SDP, it still includes the mode). It appears that even though it's in the release notes, this variable wasn't added to 5.0.1.

[SteffenBaierUK]

Hello Squigley,

I suggest you continue the troubleshooting via an official SR on our end.

Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.

Best Regards

Steffen Baier

Polycom Global Services