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

[Bob Penfield]

There may be an answer in both the 180 and 200 OK, but they must be the same.

>From RFC 3261 section 13.2.1

      o  If the initial offer is in an INVITE, the answer MUST be in a
         reliable non-failure message from UAS back to UAC which is
         correlated to that INVITE.  For this specification, that is
         only the final 2xx response to that INVITE.  That same exact
         answer MAY also be placed in any provisional responses sent
         prior to the answer.  The UAC MUST treat the first session
         description it receives as the answer, and MUST ignore any
         session descriptions in subsequent responses to the initial
         INVITE.

cheers,
(-:bob
________________________________
From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of hari prasad
Sent: Wednesday, May 20, 2009 3:34 AM
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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