SIP Provides Presence - “Who’s Who”

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Transcoding is the process of conversion between the switched and packet environments. However, Asynchronous Transcoding is to be avoided. According to Intel, “The term “asynchronous transcoding” refers to a situation when, for example, one endpoint is talking G.711 to another endpoint talking G.723 (two different encodings).”

Here is an example of SIP [Session Initiation Protocol] used for instant messaging. The function of a Presence Server is to manage access, connections, directory (who’s who), billing and tracking and other management functions. Here is an example of SIP used for enhanced, multi-user, multi-media conferencing. Note internet access or VXML [Voice eXtensible Markup Language] applications can be directed based on an Exception-triggered instant conference such as a disaster. SIP is the real-time communication protocol for VoIP [Voice over IP].

SIP has been expanded to support video and instant-messaging applications. SIP is designed to perform basic call-control tasks, such as session call set up and tear down and signaling for features such as call hold, caller ID, conferencing and call transferring. However with SIP, the intelligence for call setup and features resides on the SIP device or user agent, such as an IP phone or a PC with voice or instant-messaging software. In contrast, traditional telephony or H.323-based telephony uses a model of intelligent, centralized phone switches with dumb phones with SS7 [Signaling System 7] in PSTN [Public Switched Telephone Network] telephone switching and H.323 or Media Gateway Control Protocol in IP telephony providing call control/routing. For more, go to sipforum.org.

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[tags]voip,techtionary,sip,pstn,vxml,ss7[/tags]