[SIPForum-discussion] RFC 3407 SDP Payload

Irving Barria ibarria at cableonda.com
Tue Aug 7 13:59:42 UTC 2007

Hi Ken,


RTPMAP is necessary when the media does not have a payload-type number
assigned by IANA. In the case of PCMA y PCMU, you're right, RTPMAPs are not
needed. But for the telephone event payload (maybe you're using RFC2833 in
your Codec Profiles) it is required since the number for that payload type
is not standardized and can be chosen dynamically. I'm talking about the
"a=rtpmap:101 telephone-event/8000" line.

The peer in the session should be matching to PCMU in this case, I think.



Irving B.



De: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org]
En nombre de Ken Ryon
Enviado el: Lunes, 06 de Agosto de 2007 09:39 p.m.
Para: discussion at sipforum.org
Asunto: [SIPForum-discussion] RFC 3407 SDP Payload


Can anyone of you find a problem with the following SDP payload from a
Nortel CS2000?

How I read RFC3407, the rtpmap media attribute is not required and my client
(if it is RFC3407 compliant) should be matching up on 0 and 8.  PCMU and
PCMA codecs.

Any thoughts?

o=PVG 0 871293894 IN IP4
p=+1 6135555555 
c=IN IP4
t=0 0
a=cdsc: 1 audio RTP/AVP 0 8 116 18 13 101
a=cpar: a=rtpmap:116 AAL2-G726-32/8000
a=cpar: a=rtpmap:101 telephone-event/8000
a=cpar: a=fmtp:101 0-15
a=cpar: a=ptime:10
a=cpar: a=ptime:20
a=cpar: a=fmtp:18 annexb=yes
a=sqn: 0
m=audio 61862 RTP/AVP 0 8 101
a=fmtp:101 0-15
a=rtpmap:101 telephone-event/8000

-Ken <http://www.linkedin.com/in/kenryon> 

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