One-way Audio Issue Observed when SBC Does not Restructure the Retransmitted "200 OK"

Asset ID:	1-72-2118676.1
Update Date:	2017-05-15
Keywords:

Solution Type Problem Resolution Sure

Solution 2118676.1 : One-way Audio Issue Observed when SBC Does not Restructure the Retransmitted "200 OK"

Applies to:

Acme Packet 4600 - Version S-Cx6.4.0 and later
Information in this document applies to any platform.

Symptoms

Customer is facing one-way audio issue intermittently.

Cause

One-way Audio Issue when SBC does not restructure the retransmitted 200 OK. When we looked at wireshark traces, we found one-way audio happens only on calls, where SBC receives a retransmitted 200 OK.

Customer gets a real quick 200 OK retransmitted (in the very same second). SBC does not restructure (modify c in SDP) in this retransmitted 200 OK.

The original 200 OK is restructured (IP for c in SDP) is modified as desired.

The first 200 OK SDP part is:

v=0
o=root 122043687 122043692 IN IP4 aa.aa.aa.aa
s=PBX
c=IN IP4 aa.aa.aa.aa
t=0 0
m=audio 19238 RTP/AVP 8 0 3 18
a=rtpmap:8 PCMA/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:3 GSM/8000
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=ptime:20
a=sendrecv

forwarded on access side with changed c IP:

v=0
o=root 122043687 122043692 IN IP4 bb.bb.bb.bb
s= PBX
c=IN IP4 bb.bb.bb.bb
t=0 0
m=audio 59264 RTP/AVP 8 0 3 18
a=rtpmap:8 PCMA/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:3 GSM/8000
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=ptime:20
a=sendrecv

The retransmitted 200 OK is passed as it is, without any restructuring, which is causing one-way audio.

This behavior was diagnosed and tracked as Defect 22105954.

Solution

A solution for Defect 22105954 has been integrated within SCX640m7p1, SCZ712m5p4, and the SCZ730m1 releases.

References

<BUG:22233013> - ONE-WAY AUDIO ISSUE WHEN SBC DOES NOT RESTRUCTURE THE RETRANSMITTED 200 OK
<NOTE:1589489.1> - How to Capture all Log Files on Acme Packet systems including 3800, 4500, 4600, 6100, 6300
<BUG:22105954> - SBC PASSING SDP WITH IPV4 ADDRESS INTO IMS WHICH IS V6.

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