SDP Offer/Response Example

v=0	Version of SDP (0)
o=	Origin - not used by SIP
c=IN IP4 130.237.212.6	Connection INternet, IPv4, address=130.237.212.6
t=	Time - not used by SIP
m=video 4004 RTP/AVP 14 26	Media Video, port=4004, type=RTP/AVP profile, profiles: 14 and 26
a=rtpmap:14 MPA/90000	Attribute for profile 14, codec=MPA, sampling rate=90000
a=rtpmap:26 JBEG/90000	Attribute for profile 26, codec=JBEG, sampling rate=90000
m=audio 4006 RTP/AVP 0 4	Media Audio, port=4006, type=RTP/AVP profile, profiles: 0 and 4
a=rtpmap:0 PCMU/8000	Attribute for profile 0, codec=PCMU (PCM µlaw), sampling rate=8000
a=rtpmap:4 GSM/8000	Attribute for profile 4, codec=GSM, sampling rate=8000

If the RTCP port is not the next port number, then an rtcp-attribute can be specified in the form [RFC 3605] (this might be useful in conjunction with a NAT):

"a=rtcp:" port [nettype addrtype connection-address] <CRLF>

Slide Notes

C. Huitema, "Real Time Control Protocol (RTCP) attribute in Session Description Protocol (SDP)", IETF RFC 3605, October 2003 http://www.ietf.org/rfc/rfc3605.txt Links to an external site.

Transcript

[slide195] So for example, here's an example of why SDP really isn't the kind of negotiating protocol you would think. It's an offer and you either accept it or you reject it. So it's an offer response. So in this case, one entity say: I can take this kind of video, I can take µ-law encoded audio, I can take JBEG encoded video, I can take RTP in µ-law or GSM encoding and they send it off to the other party.