Comments
SIP was designed to solve only a few problems and to work with a broad spectrum of existing and future IP telephony protocols. To this end SIP provides four basic functions. SIP allows for the establishment of user location (i.e. translating from a user's name to their current network address). SIP provides for feature negotiation so that all of the participants in a session can agree on the features to be supported among them. SIP is a mechanism for call management - for example adding, dropping, or transferring participants. And finally SIP allows for changing features of a session while it is in progress. All of the other key functions are done with other protocols.
Yes this does indeed mean that SIP is not a session description protocol, and that SIP does not do conference control. SIP is not a resource reservation protocol and it has nothing to do with quality of service (QoS). SIP can work in a framework with other protocols to make sure these roles are played out - but SIP does not do them. SIP can function with SOAP, HTTP, XML, VXML , WSDL, UDDI, SDP and an alphabet soup of others. Everyone has a role to play!
Posted by gsmxprt
Please read this
http://portal.acm.org/citation.cfm?id=507679
Posted by johnwesley
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