The Session Description Protocol (SDP)
On Internet Multicast backbone (Mbone) a session directory tool is used to advertise multimedia conferences and communicate the conference addresses and conference tool-specific information required for participation and this is done by SDP. SDP describes multimedia sessions for the purpose of session announcement, session invitation and other forms of multimedia session initiation.[para] The SDP communicates the existence of a session and conveys sufficient information to enable participation in the session and such messages are sent by periodically multicasting an announcement packet to a well-known multicast address and port using SAP (session announcement protocol). The messages are sent in the form of UDP packets with a SAP header and a text payload which is the SDP session description.
Session Description Protocol (SDP) is a format for describing streaming media initialization parameters in an ASCII string. The IETF published the original specification as an IETF Proposed Standard in April 1998, and subsequently published a revised specification as an IETF Proposed Standard as RFC 4566 in July 2006.
SDP is intended for describing multimedia communication sessions for the purposes of session announcement, session invitation, and other forms of multimedia session initiation. SDP does not provide the content of the media form itself but simply provides a negotiation between two end points to allow them to agree on a media type and format. This allows SDP to support upcoming media types and formats, enabling systems based on this technology to be forward compatible.
SDP started off as a component of the Session Announcement Protocol (SAP), but found other uses in conjunction with RTP, RTSP, SIP and just as a standalone format for describing multicast sessions.
There are five terms related to SDP:
1. Conference: It is a set of two or more communicating users along with the software they are using.
2. Session : Session is the multimedia sender and receiver and the flowing stream of data.
3. Session Announcement: A session announcement is a mechanism by which a session description is conveyed to users in a proactive fashion, i.e., the session description was not explicitly requested by the user.
4. Session Advertisement : same as session announcement
5. Session Description : A well defined format for conveying sufficient information to discover and participate in a multimedia session.
The Session Description Protocol (SDP) describes multimedia sessions for the purpose of session announcement, session invitation and other forms of multimedia session initiation.
Session directories assist the advertisement of conference sessions and communicate the relevant conference setup information to prospective participants. SDP is designed to convey such information to recipients. SDP is purely a format for session description - it does not incorporate a transport protocol, and is intended to use different transport protocols as appropriate including the Session Announcement Protocol (SAP) , Session Initiation Protocol (SIP) , Real-Time Streaming Protocol (RTSP) , electronic mail using the MIME extensions, and the Hypertext Transport Protocol (HTTP) .
SDP is intended to be general purpose so that it can be used for a wider range of network environments and applications than just multicast session directories. However, it is not intended to support negotiation of session content or media encodings.
On Internet Multicast backbone (Mbone) a session directory tool is used to advertise multimedia conferences and communicate the conference addresses and conference tool-specific information necessary for participation. The SDP does this. It communicates the existence of a session and conveys sufficient information to enable participation in the session.
Many of the SDP messages are sent by periodically multicasting an announcement packet to a well-known multicast address and port using SAP (session announcement protocol). These messages are UDP packets with a SAP header and a text payload. The text payload is the SDP session description. Messages can also be sent using email or the WWW (World Wide Web).
The SDP text messages include:
* Session name and purpose
* Time the session is active
* Media comprising the session
* Information to receive the media
Protocol Structure - SDP (Session Description Protocol)
SDP messages are text messages using the ISO 10646 character set in UTF-8 encoding. SDP Session description (optional fields has an *) is:
v= (protocol version)
o= (owner/creator 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=* (bandwidth information)
One or more time descriptions (see below)
z=* (time zone adjustments)
k=* (encryption key)
a=* (zero or more session attribute lines)
Zero or more media descriptions (see below)
Time description
t= (time the session is active)
r=* (zero or more repeat times)
Media description
m= (media name and transport address)
i=* (media title)
c=* (connection information - optional if included at session-level)
b=* (bandwidth information)
k=* (encryption key)
a=* (zero or more media attribute lines)
On Internet Multicast backbone (Mbone) a session directory tool is used to advertise multimedia conferences and communicate the conference addresses and conference tool-specific information required for participation and this is done by SDP. SDP describes multimedia sessions for the purpose of session announcement, session invitation and other forms of multimedia session initiation.[para] The SDP communicates the existence of a session and conveys sufficient information to enable participation in the session and such messages are sent by periodically multicasting an announcement packet to a well-known multicast address and port using SAP (session announcement protocol). The messages are sent in the form of UDP packets with a SAP header and a text payload which is the SDP session description.
Session Description Protocol (SDP) is a format for describing streaming media initialization parameters in an ASCII string. The IETF published the original specification as an IETF Proposed Standard in April 1998, and subsequently published a revised specification as an IETF Proposed Standard as RFC 4566 in July 2006.
SDP is intended for describing multimedia communication sessions for the purposes of session announcement, session invitation, and other forms of multimedia session initiation. SDP does not provide the content of the media form itself but simply provides a negotiation between two end points to allow them to agree on a media type and format. This allows SDP to support upcoming media types and formats, enabling systems based on this technology to be forward compatible.
SDP started off as a component of the Session Announcement Protocol (SAP), but found other uses in conjunction with RTP, RTSP, SIP and just as a standalone format for describing multicast sessions.
There are five terms related to SDP:
1. Conference: It is a set of two or more communicating users along with the software they are using.
2. Session : Session is the multimedia sender and receiver and the flowing stream of data.
3. Session Announcement: A session announcement is a mechanism by which a session description is conveyed to users in a proactive fashion, i.e., the session description was not explicitly requested by the user.
4. Session Advertisement : same as session announcement
5. Session Description : A well defined format for conveying sufficient information to discover and participate in a multimedia session.
The Session Description Protocol (SDP) describes multimedia sessions for the purpose of session announcement, session invitation and other forms of multimedia session initiation.
Session directories assist the advertisement of conference sessions and communicate the relevant conference setup information to prospective participants. SDP is designed to convey such information to recipients. SDP is purely a format for session description - it does not incorporate a transport protocol, and is intended to use different transport protocols as appropriate including the Session Announcement Protocol (SAP) , Session Initiation Protocol (SIP) , Real-Time Streaming Protocol (RTSP) , electronic mail using the MIME extensions, and the Hypertext Transport Protocol (HTTP) .
SDP is intended to be general purpose so that it can be used for a wider range of network environments and applications than just multicast session directories. However, it is not intended to support negotiation of session content or media encodings.
On Internet Multicast backbone (Mbone) a session directory tool is used to advertise multimedia conferences and communicate the conference addresses and conference tool-specific information necessary for participation. The SDP does this. It communicates the existence of a session and conveys sufficient information to enable participation in the session.
Many of the SDP messages are sent by periodically multicasting an announcement packet to a well-known multicast address and port using SAP (session announcement protocol). These messages are UDP packets with a SAP header and a text payload. The text payload is the SDP session description. Messages can also be sent using email or the WWW (World Wide Web).
The SDP text messages include:
* Session name and purpose
* Time the session is active
* Media comprising the session
* Information to receive the media
Protocol Structure - SDP (Session Description Protocol)
SDP messages are text messages using the ISO 10646 character set in UTF-8 encoding. SDP Session description (optional fields has an *) is:
v= (protocol version)
o= (owner/creator 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=* (bandwidth information)
One or more time descriptions (see below)
z=* (time zone adjustments)
k=* (encryption key)
a=* (zero or more session attribute lines)
Zero or more media descriptions (see below)
Time description
t= (time the session is active)
r=* (zero or more repeat times)
Media description
m= (media name and transport address)
i=* (media title)
c=* (connection information - optional if included at session-level)
b=* (bandwidth information)
k=* (encryption key)
a=* (zero or more media attribute lines)
