Session Description Protocol (SDP) is a signaling protocol used to
describe multimedia sessions over the internet. It is an IETF (Internet
Engineering Task Force) standard, and its primary purpose is to describe the
format and content of a session. It is commonly used in conjunction with
other signaling protocols, such as SIP (Session Initiation Protocol) and
H.323, to establish and manage multimedia sessions.
SDP allows participants in a multimedia session to exchange information
about the session, including media types, codecs, bandwidth, and other
parameters necessary for the establishment and maintenance of the session.
This information is carried in a text-based format and is commonly
transmitted as part of the signaling message used to establish the
session.
SDP is used by a variety of signaling protocols to describe multimedia
sessions. SIP, for example, uses SDP to negotiate the parameters of a
session, including the type of media to be used, the codec used for
compression, and the transport protocol to be used for delivery. Similarly,
H.323 uses SDP to describe the media streams and negotiate the codecs and
other parameters used in a session.
SDP also provides a mechanism for describing the media streams themselves.
This includes information about the media type (audio, video, or text), the
codec used, and the transport protocol used to deliver the media stream.
Other information, such as the media format, resolution, and bit rate, can
also be included in the SDP message.
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In addition to describing multimedia sessions, SDP can also be used to
negotiate security mechanisms for the session. This includes authentication
and encryption parameters that can be used to protect the confidentiality
and integrity of the session.
Overall, SDP is a powerful and flexible signaling protocol used to describe
multimedia sessions over the internet. It is widely used in conjunction with
other signaling protocols to establish and manage sessions, and provides a
mechanism for negotiating a wide range of parameters, including media type,
codecs, and security mechanisms. As multimedia communications continue to
grow in importance, SDP is likely to remain a key component of the signaling
protocols used to establish and manage these sessions.