Hello,
I
have a question regarding the SDP part of the Invite
request.
suppose user agent "A" wants to talk to user agent "B",
he sends a INVITE
request to B. the SDP part of the invite request is
as follows,
v= 0
o= A 1464112736 1464112736 IN IP4
151.209.33.190
s=Calling
c=IN IP4 pgs-477
t=0 0
m=audio 2074 RTP/AVP 0 3
5
a=rtpmap:0
PCMU/8000
a=rtpmap:3
GSM/4000
a=rtpmap:5
ADPCM/4000
If user agent accepts the request and
agrees to talk to user agent A, he
sends a OK response with SDP as
followed.
v= 0
o= B1464112736 1464112736 IN IP4
151.209.33.194
s=Answering the
call
c=IN IP4 pgs-451
t=0 0
m=audio 2074 RTP/AVP 3 5
a=rtpmap:3
GSM/4000
a=rtpmap:5
ADPCM/4000
now why can’t the user agent A send an
ACK by selecting one of the coders specified in answer AS
mentioned
below ?
v=
0
o= A 1464112736 1464112736 IN IP4
151.209.33.190
s=Calling
c=IN IP4 pgs-477
t=0 0
m=audio 2074 RTP/AVP 3
a=rtpmap:3
GSM/4000
than
analyzing the payload type (PT) header field in the RTP Packet.
Thanks
in advance
Prabha
N