!!! Overview[1]
[{$pagename}] ([SIP]) is a communications [protocol] for signaling, for the purpose of controlling multimedia communication sessions. 

The most common applications of [{$pagename}] are in Internet telephony for voice and video calls, private IP telephone systems, as well as instant messaging over [Internet Protocol] ([IP]) networks.

The [protocol] defines the messages that are sent between [endpoints], which govern establishment, termination and other essential elements of a call. 

[{$pagename}] can be used for creating, modifying and terminating sessions consisting of one or several media streams. [{$pagename}] is designed to be independent (although not agnostic) of the underlying transport layer, and can be used with [UDP], [TCP], and [SCTP]; [{$pagename}] can also be secured using [TLS] over the latter two. [{$pagename}] is a text-based [protocol], incorporating many elements of the [Hypertext Transfer Protocol] ([HTTP]) and the [Simple Mail Transfer Protocol] ([SMTP]).

By itself, [{$pagename}] only provides signaling; it is used in conjunction with other protocols that specify the media format and protocol to be used to subsequently communicate the media. Although [{$pagename}] can carry arbitrary data, [{$pagename}] is typically used to carry a [Session Description Protocol] ([SDP]) message specifying the codec and the use of either the [Real-time Transport Protocol] ([RTP]) or Secure Real-time Transport Protocol (SRTP) for media communication.

!! More Information
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* [#1] - [Session_Initiation_Protocol|Wikipedia:Session_Initiation_Protocol|target='_blank'] - based on information obtained 2017-05-06-