[SIPForum-discussion] SDP in 180 Ringing & 200 OK

[prasanna c]

+ Answer can in both 180 & 200 OK.
+ RFC recommends that the UAC use the SDP in 180 (which is received ahead of 200) and ignore the subsequent answers.

Date: Wed, 20 May 2009 13:03:33 +0530
From: siphari at gmail.com
To: discussion at sipforum.org
Subject: [SIPForum-discussion] SDP in 180 Ringing & 200 OK

Hello All,
I have a basic doubt regarding the SDP  Answer, in a Offer/Answer model.
Can there be a ANSWER in both 180 and 200 OK?
If so, is that mandatory to have the same SDP in both the response?


I have the following two Answers in one of my scenario:

180 Ringing:
v=0
o=- 3654100372 1235990184 IN IP4 192.168.13.13
s=SDP Data
c=IN IP4 192.168.13.13

t=0 0
m=audio 46608 RTP/AVP 18 8 96
a=rtpmap:96 telephone-event/8000
a=ptime:20
a=sqn:0
a=cdsc:1 image udptl t38
a=cpar:a=T38FaxVersion:0
a=cpar:a=T38MaxBitRate:14400
a=cpar:a=T38FaxRateManagement:transferredTCF

a=cpar:a=T38FaxMaxBuffer:336
a=cpar:a=T38FaxMaxDatagram:176
a=cpar:a=T38FaxUdpEC:t38UDPRedundancy

200 OK:

v=0
o=- 3805400806 1235990190 IN IP4 192.168.13.25

s=SDP Data
c=IN IP4 192.168.13.25
t=0 0
m=audio 52138 RTP/AVP 18 8 96
a=rtpmap:96 telephone-event/8000
a=ptime:20
a=sqn:0
a=cdsc:1 image udptl t38
a=cpar:a=T38FaxVersion:0

a=cpar:a=T38MaxBitRate:14400
a=cpar:a=T38FaxRateManagement:transferredTCF
a=cpar:a=T38FaxMaxBuffer:336
a=cpar:a=T38FaxMaxDatagram:176
a=cpar:a=T38FaxUdpEC:t38UDPRedundancy

Here the Owner, Connection and Audio Port were all different.

Is this RFC complaint?
Should the UAC consider only the SDP in 200 OK?

Thanks in Advance.
Kind Regards,
Hari Prasad V


 

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