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List:       sip-implementors
Subject:    Re: [Sip-implementors] SDP answer with c=0.0.0.0 and a=sendrecv behavior
From:       "Shanbhag, Somesh (Nokia - IN/Bangalore)" <somesh.shanbhag () nokia ! com>
Date:       2017-07-11 3:33:52
Message-ID: HE1PR0701MB26357BCFD1483DCC8494D07BEEAE0 () HE1PR0701MB2635 ! eurprd07 ! prod ! outlook ! com
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<<<<<< v=0o=- 8 1 IN IP4 192.168.95.142s=-c=IN IP4 0.0.0.0t=0 0a=sendrecvm=audio \
24208 RTP/AVP 8 0 96c=IN IP4 0.0.0.0a=rtpmap:8 PCMA/8000a=rtpmap:0 \
PCMU/8000a=rtpmap:96 telephone-event/8000a=fmtp:96 0-15a=maxptime:40 >>>>>

May be the B2BUA is not handling the connection IP as 0.0.0.0 when you explicitly \
specify a=sendrecv (although by default it is always sendrecv). What will happen if \
you send a=sendrecv attribute in successful case you have listed? You can try that \
out too!

Br,
Somesh
> --)

-----Original Message-----
From: sip-implementors-bounces@lists.cs.columbia.edu \
[mailto:sip-implementors-bounces@lists.cs.columbia.edu] On Behalf Of Sourav Dhar \
                Chaudhuri
Sent: Friday, July 07, 2017 8:47 PM
To: Paul Kyzivat <pkyzivat@alum.mit.edu>; Sip-implementors \
                <sip-implementors@lists.cs.columbia.edu>
Subject: [Sip-implementors] SDP answer with c=0.0.0.0 and a=sendrecv behavior

Hi,
There is a B2B sitting between  A (Caller) and B ( callee)

1)     A  has sent INVITE without SDP towards B
2)    B has responded  200OK with SDP offer for INVITE to  A. Refer below the SDP \
offer v=0o=- 16408314 16408314 IN IP4 ABC.DEF.GH.IJs=-c=IN IP4 192.168.119.69t=0 \
0a=sendrecvm=audio 3866 RTP/AVP 8 0 18 96c=IN IP4 \
192.168.119.69b=RR:0b=RS:0a=rtpmap:8 PCMA/8000a=rtpmap:0 PCMU/8000a=rtpmap:18 \
G729/8000a=fmtp:18 annexb=noa=rtpmap:96 telephone-event/8000a=fmtp:96 \
0-15a=maxptime:40


3)    Then A has sent ACK with SDP answer.
v=0o=- 8 1 IN IP4 192.168.95.142s=-c=IN IP4 0.0.0.0t=0 0a=sendrecvm=audio 24208 \
RTP/AVP 8 0 96c=IN IP4 0.0.0.0a=rtpmap:8 PCMA/8000a=rtpmap:0 PCMU/8000a=rtpmap:96 \
telephone-event/8000a=fmtp:96 0-15a=maxptime:40 Now this ACK is not passed to B by \
the B2B sitting between them.Is the SDP answer is valid? As it can be seen in \
connection line 0.0.0.0 but media attribute is sendrecv. Is sendrecv possible here?


There is another successful  case
1) A  has sent INVITE without SDP towards B
2) B has responded  200OK with SDP offer for INVITE to  A. Refer below the SDP offer
v=0o=- 1498048404 1498048404 IN IP4 192.168.95.97s=Basic Sessionc=IN IP4 \
192.168.95.97t=0 0m=audio 22780 RTP/AVP 18 8 0 96 99a=rtpmap:96 AMR/8000a=fmtp:96 \
octet-align=1a=rtpmap:99 telephone-event/8000a=ptime:20 3)    Then A has sent ACK \
with SDP answer.

v=0o=- 2 1 IN IP4 192.168.95.142s=Basic Sessionc=IN IP4 0.0.0.0t=0 0m=audio 23148 \
RTP/AVP 8 0 99a=rtpmap:99 telephone-event/8000a=ptime:20  This time the  ACK is \
passed successfully to B by the B2B sitting between them. Here it can be seen in SDP \
answer that connection line is 0.0.0.0 but no sendrecv.

Thanks,Sourav
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