Media

Although SIP meets the needs for signaling information, VoIP PBXs still require a method to transmit the media stream. The Real-Time Transport Protocol (RTP) is used in almost every VoIP implementation and was developed specifically for transmitting audio and video traffic across networks. Encryption of the media traffic was later added in the form of Secure Real-Time Transport Protocol (SRTP), which is what Lync Server uses by default to ensure that the media cannot be intercepted and played back.

SRTP only provides a standard for carrying the media traffic that can be of various media codecs. Media codecs are a way of translating audio and video data into bits that can be transmitted across a network. For two users to have an audio conversation, ...

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