SDP

SDP is intended for describing multimedia sessions for the purposes of session announcement, session invitation, and other forms of multimedia session initiation. SDP is used from VOIP signalling protocols like SIP, H.323 and some minor VOIP protocols to transfer media setup information about a multi media client from A to B.

• SDP is used by SAP - the Service Announcement Protocol.
• SDP is used by SIP

IETF RFCs

• RFC 4566: Session Description Protocol
• obsolete RFC2327: Session Description Protocol
• RFC 3388: Grouping of Media Lines in the Session Description Protocol (SDP)
• obsolete RFC 3266: Support for IPv6 in Session Description Protocol (SDP)
• IANA SDP parameters: http://www.iana.org/assignments/sdp-parameters

Fields

Optionalitemsaremarkedwitha`*'.

Session description

v=(protocolversion)
o=(owner/creatorandsessionidentifier).
s=(sessionname)
i=*(sessioninformation)
u=*(URIofdescription)
e=*(emailaddress)
p=*(phonenumber)
c=*(connectioninformation-notrequiredifincludedinallmedia)
b=*(bandwidthinformation)
Oneormoretimedescriptions(seebelow)
z=*(timezoneadjustments)
k=*(encryptionkey)
a=*(zeroormoresessionattributelines)
Zeroormoremediadescriptions(seebelow)

Time description

t=(timethesessionisactive)
r=*(zeroormorerepeattimes)

Media description

m=(medianameandtransportaddress)
i=*(mediatitle)
c=*(connectioninformation-optionalifincludedatsession-level)
b=*(bandwidthinformation)
k=*(encryptionkey)
a=*(zeroormoremediaattributelines)

RTP Payload Type Numbers

RTP payload type numbers appear in the m= and rtpmap lines of the SDP, but these numbers are not defined in the SDP RFCs, there is more information here: RTP.