SIP (Session Initiation Protocol)

SIP is a relatively new Internet standard. It is a simple, low-level protocol for initiating interactive communication sessions between users. These sessions can involve two or more users. Such sessions include voice, video, chat, interactive games, and virtual reality.

SIP by itself is not specific to mobile phones, but it is a key foundation for several phone-related standards, including most new Push-To-Talk technologies.

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