SDP is a format for describing multimedia sessions to allow participants to join. It describes session name and purpose, times active, media types, formats and addresses. SDP specifies the protocol version, origin, session name, connection data, timing, media descriptions and attributes. It is used to establish multimedia sessions across different transport protocols and applications like SIP, SAP, RTSP and HTTP.

1. SDP
(Session Description
Protocol)

2. SDP is purely a format for session
description. It does not incorporate a
transport protocol and it is intended to use
different transport protocols as SIP, SAP,
RTSP, HTTP.
SDP

3. ● Session Initiation
● Streaming Media
● Email and the WWW
● Multicast Session Announcement
Example of SDP Usage

4. In general, SDP must convey sufficient
information to enable applications to join a
session and to announce the resources to
be used to any non-participants that may
need to know.
SDP

5. ● Session name and purpose
● Times the session is active
● The media comprising the session
● Information needed to receive those
media(addresses, ports,formats , etc.)
SDP

6. ● "application/sdp"
● ISO 10646 character set in UTF-8
encoding.
● <type>=<value>
SDP Specification

7. ● Session Description
● Time Description
● Media description
SDP description order

8. v= (protocol version)
o= (originator and session identifier)
s= (session name)
i=* (session information)
u=* (URI of description)
e=* (email address)
p=* (phone number)
c=* (connection information -- not required if included in
all media)
b=* (zero or more bandwidth information lines)
z=* (time zone adjustments)
k=* (encryption key)
a=* (zero or more session attribute lines)
Session Description

9. t= (time the session is active)
r=* (zero or more repeat times)
Time Description

10. m= (media name and transport address)
i=* (media title)
c=* (connection information -- optional if included at
session level)
b=* (zero or more bandwidth information lines)
k=* (encryption key)
a=* (zero or more media attribute lines)
Media Description

11. ● Protocol version (“v=”)
v=0
● Origin (“o=”)
o=<username> <sess-id> <sess-version> <nettype>
<addrtype> <unicast-address>
● Session name (“s”)
s=<session name>
● Session information (“i=”)
i=<session description>

12. ● URI (“u=”)
u=<uri>
● Email and Phone (“e=” and “p=”)
e=<email-address> (e=j.doe@example.com (Jane Doe))
p=<phone-number> (p=+1 617 555-6011)
● Connection Data (“c=”)
c=<nettype> <addrtype> <connection-address>
(c=IN IP4 224.2.36.42/127)
● Bandwidth (“b=”)
b=<bwtype>:<bandwidth>

13. ● Timing (“t=”)
t=<start-time> <stop-time>
● Repeat time (“r=”)
r=<repeat interval> <active duration> <offsets from
start-time>
t=3034423619 3042462419
r=604800 3600 0 90000
● Encription Keys (“k=”)
k=<method>
k=<method>:<encryption key>
k=base64:<encoded encryption key>

14. ● Attributes (“a=”)
a=<attribute>:<value>
● Media Description
m=<media> <port> <proto> <fmt>
m=video 49170/2 RTP/AVP 31

15. a=cat:<category>
a=keywds:<keywords>
a=tool:<name and version of tool>
a=ptime:<packet time>
a=maxptime:<maximum packet time>
a=rtpmap:<payload type> <encoding
name>/<clock rate> [/<encoding
parameters>]
SDP Attributes

16. a=recvonly
a=sendrecv
a=sendonly
a=inactive
a=orient:<orientation>
a=type:<conference type>
a=charset:<character set>
SDP Attributes

17. a=sdplang:<language tag>
a=framerate:<frame rate>
a=quality:<quality>
SDP Attributes

18. [Offer]
v=0
o=alice 2890844526 2890844526 IN IP4 host.atlanta.
example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
m=audio 49170 RTP/AVP 0 8 97
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:97 iLBC/8000
m=video 51372 RTP/AVP 31 32
a=rtpmap:31 H261/90000
a=rtpmap:32 MPV/90000
Audio and Video
[Answer]
v=0
o=bob 2808844564 2808844564 IN IP4
host.biloxi.example.com
s=
c=IN IP4 host.biloxi.example.com
t=0 0
m=audio 49172 RTP/AVP 0 8
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
m=video 0 RTP/AVP 31
a=rtpmap:31 H261/90000

19. [Second-Offer]
v=0
o=alice 2890844526 2890844527 IN IP4
host.atlanta.example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
m=audio 51372 RTP/AVP 0
a=rtpmap:0 PCMU/8000
m=video 0 RTP/AVP 31
a=rtpmap:31 H261/90000
Audio and Video
[Second-Answer]
v=0
o=bob 2808844564 2808844565 IN IP4
host.biloxi.example.com
s=
c=IN IP4 host.biloxi.example.com
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
m=video 0 RTP/AVP 31
a=rtpmap:31 H261/90000

20. [Offer]
v=0
o=alice 2890844526 2890844526 IN IP4
host.atlanta.example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
m=audio 49170 RTP/AVP 0 97
a=rtpmap:0 PCMU/8000
a=rtpmap:97 iLBC/8000
m=audio 49172 RTP/AVP 98
a=rtpmap:98 telephone-event/8000
a=sendonly
Two Audio Streams
[Answer]
v=0
o=bob 2808844564 2808844564 IN IP4
host.biloxi.example.com
s=
c=IN IP4 host.biloxi.example.com
t=0 0
m=audio 49172 RTP/AVP 97
a=rtpmap:97 iLBC/8000
m=audio 49174 RTP/AVP 98
a=rtpmap:98 telephone-event/8000

21. [Offer]
v=0
o=alice 2890844526 2890844526 IN IP4
host.atlanta.example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
m=audio 49170 RTP/AVP 0 97
a=rtpmap:0 PCMU/8000
a=rtpmap:97 iLBC/8000
Hold and Unhold
[Answer]
v=0
o=bob 2808844564 2808844564 IN IP4
host.biloxi.example.com
s=
c=IN IP4 placeholder.biloxi.example.
com
t=0 0
m=audio 49172 RTP/AVP 97
a=rtpmap:97 iLBC/8000
a=sendonly

22. [Second-Offer]
v=0
o=bob 2808844564 2808844565 IN IP4 host.
biloxi.example.com
s=
c=IN IP4 host.biloxi.example.com
t=0 0
m=audio 49170 RTP/AVP 97
a=rtpmap:97 iLBC/8000
Hold and Unhold
[Second-Answer]
v=0
o=alice 2890844526 2890844527 IN IP4
host.atlanta.example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
m=audio 49178 RTP/AVP 97
a=rtpmap:97 iLBC/8000

23. [Offer]
v=0
o=alice 2890844526 2890844526 IN IP4
host.atlanta.example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
m=audio 49170 RTP/AVP 0 97
a=rtpmap:0 PCMU/8000
a=rtpmap:97 iLBC/8000
m=audio 49172 RTP/AVP 98
a=rtpmap:98 telephone-event/8000
a=sendonly
Hold with two streams
[Answer]
v=0
o=bob 2808844564 2808844564 IN IP4
host.biloxi.example.com
s=
c=IN IP4 host.biloxi.example.com
t=0 0
m=audio 49172 RTP/AVP 97
a=rtpmap:97 iLBC/8000
m=audio 49174 RTP/AVP 98
a=rtpmap:98 telephone-event/8000
a=recvonly

24. [Second-Offer]
v=0
o=bob 2808844564 2808844565 IN IP4
host.biloxi.example.com
s=
c=IN IP4 host.biloxi.example.com
t=0 0
m=audio 49172 RTP/AVP 97
a=rtpmap:97 iLBC/8000
a=sendonly
m=audio 49174 RTP/AVP 98
a=rtpmap:98 telephone-event/8000
a=recvonly
Hold with two streams
[Second-Answer]
v=0
o=alice 2890844526 2890844527 IN IP4
host.atlanta.example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
m=audio 49170 RTP/AVP 0 97
a=rtpmap:0 PCMU/8000
a=rtpmap:97 iLBC/8000
m=audio 49172 RTP/AVP 98
a=rtpmap:98 telephone-event/8000
a=sendonly

25. [Offer]
v=0
o=alice 2890844526 2890844526 IN IP4
host.atlanta.example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
m=audio 49170 RTP/AVP 0
a=rtpmap:0 PCMU/8000
Audio, then Video Added
[Answer]
v=0
o=bob 2808844564 2808844564 IN IP4
host.biloxi.example.com
s=
c=IN IP4 host.biloxi.example.com
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000

26. [Second-Offer]
v=0
o=alice 2890844526 2890844527 IN IP4 host.
atlanta.example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
m=audio 49170 RTP/AVP 0
a=rtpmap:0 PCMU/8000
m=video 49172 RTP/AVP 31
a=rtpmap:31 H261/90000
Audio, then Video Added
[Second-Answer]
v=0
o=bob 2808844564 2808844565 IN IP4
host.biloxi.example.com
s=
c=IN IP4 host.biloxi.example.com
t=0 0
m=audio 49172 RTP/AVP 0
a=rtpmap:0 PCMU/8000
m=video 49168 RTP/AVP 31
a=rtpmap:31 H261/90000