Subject: [Sipping] SDP lines in SIP Service Quality Reporting Event

From: Marc Petit-Huguenin <[email-masked]>
Date: Fri, 11 Feb 2005 05:27:46 -0800

About draft-johnston-sipping-rtcp-summary-06:

With this version, the c=, m= and a= lines of the SDP are copied in the 
report event. But as the m= line can list more than one codec, how do we 
know which one was used?

Also when used on an endpoint that supports ICE, the IP address in the 
m= line and the port in the m= line are not used. Does it means that the 
a=candidate line should also be added in the event report? If it is the 
case then we have the same problem than above, we do not know which IP 
address/port was used.

One solution to this problem could be to insert in the event report a 
stripped version of the m=, c= and a= lines that contain only what was 
used for the duration of the event, e.g. with the following SDP:

c=IN IP4 10.1.28.1
m=audio 5002 RTP/AVP 0 18 101
a=rtpmap:0 PCMU/8000
a=rtpmap:18 G729/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
a=candidate:0 0.6 asd9f8f8== 9asfhfvva9==affahnz 192.0.34.166 35534
a=candidate:0 0.4 xcyca87sbb f99fhaz0ftrafdgl99d 24.4.99.114 16002

The event report for G.711 through a TURN server then contains:

c=IN IP4 10.1.28.1
m=audio 5002 RTP/AVP 0
a=rtpmap:0 PCMU/8000
a=candidate:0 0.6 asd9f8f8== 9asfhfvva9==affahnz 192.0.34.166 35534

Then the next report for G.711 through a STUN address contains:

c=IN IP4 10.1.28.1
m=audio 5002 RTP/AVP 0
a=rtpmap:0 PCMU/8000
a=candidate:0 0.4 xcyca87sbb f99fhaz0ftrafdgl99d 24.4.99.114 16002

Later the endpoint decides to switch to G.729:

c=IN IP4 10.1.28.1
m=audio 5002 RTP/AVP 18
a=rtpmap:18 G729/8000
a=candidate:0 0.4 xcyca87sbb f99fhaz0ftrafdgl99d 24.4.99.114 16002

Problem is, sending DTMF also change the codec, but I guess that 
endpoint can have a local policy that prevent to send an Event Report in 
this case:

c=IN IP4 10.1.28.1
m=audio 5002 RTP/AVP 101
a=rtpmap:101 telephone-event/8000
a=candidate:0 0.4 xcyca87sbb f99fhaz0ftrafdgl99d 24.4.99.114 16002
a=fmtp:101 0-15

-- 
Marc Petit-Huguenin
Home: [email-masked]
Work: [email-masked]

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