sdp 简单介绍

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Session Description Protocol

Purpose and Content

l The purpose of SDP is to convey information about media streams in multimedia sessions to help participants join or gather info of a particular session

l SDP includes51Testing软件测试网 z1a1r-`5u4a

-Session name and purpose51Testing软件测试网e&qBP'p]L

-Time(s) the session is active

-The media comprising the session

-Information to receive those media (addresses, ports, formats and so on)

Format51Testing软件测试网Z-KZ-n,b

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l SDP is a short structured textual description51Testing软件测试网.]-q4[AB

l It conveys the name and purpose of the session, the media, protocols,codecformats, timing and transport information

l A tentative participant checks these information and decides whether to join a session and how and when to join a session if it decides to do so51Testing软件测试网%{4{4E(P7k#Ps:ce

l The format has entries in the form. of<type>=<value>, where the<type>defines a unique session parameter, and the<value>provides a specific value for that parameter.51Testing软件测试网*Z gE^6ZKT

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Session Description Parameters -1

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Session description(* denotes optional )

v= (protocol version)51Testing软件测试网
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o= (owner/creator and session identifier)

s= (session name)51Testing软件测试网,DK*eh6[

i=* (session information)

u=* (URI of description)51Testing软件测试网CK-Mb@k

e=* (email address)51Testing软件测试网EpS;\C%ST

p=* (phone number)51Testing软件测试网5Y"R`!wS C$@
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c=* (connection information -not required if included in all media)51Testing软件测试网l;R'W L%Y!H1VN`

b=* (bandwidth information)

One or more time descriptions (see next slide)

z=* (time zone adjustments)51Testing软件测试网U4pxGd

k=* (encryption key)51Testing软件测试网,? Rh?w{m

a=* (zero or more session attribute lines)51Testing软件测试网.g*V5~%HH

Zero or more media descriptions (see next slide)

Session Description Parameters -251Testing软件测试网"`5[{Ke~y

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l Time description(* denotes optional )51Testing软件测试网i1d m/V6O/|A a

t= (time the session is active)51Testing软件测试网0R
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r=* (zero or more repeat times)51Testing软件测试网{FMWJ:kt

l Media description(* denotes optional )

m= (media name and transport address)

i=* (media title)51Testing软件测试网)P}?7X8^V

c=* (connection information -optional if included at session-level)

b=* (bandwidth information)

k=* (encryption key)

a=* (zero or more media attribute lines)

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An Example

Below is an example session description, taken from RFC 2327:51Testing软件测试网8p?7r4[TV+X

v=051Testing软件测试网4p@X XC&n7A8MN

o=mhandley2890844526 2890842807 IN IP4 126.16.64.4

s=SDP Seminar51Testing软件测试网)zT"@u9T_^

i=A Seminar on the session description protocol51Testing软件测试网(?$j0_0J&{;qR

u=http://www.cs.ucl.ac.uk/staff/M.Handley/sdp.03.ps

e=mjh@isi.edu(Mark Handley)51Testing软件测试网+OHKw N&i/m*E

c=IN IP4 224.2.17.12/127

t=2873397496 287340469651Testing软件测试网!z BjS1SIN m

a=recvonly51Testing软件测试网*WX@/J6C2S([#M!NrbDu,U

m=audio 49170 RTP/AVP 051Testing软件测试网4_*l-a0C._%Q2l!y

m=video 51372 RTP/AVP 31

m=application 32416udp wb51Testing软件测试网5I/}-}N0S
zG5\

a=orient:portrait

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This presentation is only a rough introduction. For better understanding go through the document of RFC 2327

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