Expedited resource negotiation in SIP

摘要

A method of expediting resource negotiation in a modified Session Initiation Protocol (SIP) reduces the number of messages exchanged for resource negotiation, thereby reducing the latencies involved in session setup. The method entails sending an INVITE message having a modified SIP header containing an indication that the originator's terminal seeks a fast session setup. The INVITE message further contains a list of all codecs available at the originator's terminal and how many each type of media component are required. These codecs can be provided in an order of preference. The answerer selects the codecs for the requested media types from the list of available codecs without engaging in a back-and-forth resource negotiation for the codecs. The result is that the session can be set up with fewer messages which provides quicker session setup than in the prior art.

主权项

1. A method of operating a communication terminal as an originating terminal to originate a communication session with another communication terminal operating as an answering terminal, the method comprising:
sending to the answering terminal an offer message communicating media capabilities available at the originating terminal and corresponding numbers of media streams; receiving from the answering terminal an answer message communicating at least one media capability selected from the media capabilities communicated in the offer message in accordance with the respective corresponding number of media streams communicated in the offer message; reserving the communicated media capabilities available at the originating terminal before sending the offer message so that no other answering terminal can obtain access to the reserved media capabilities until such reserved media capabilities are released; and releasing from reservation at the originating terminal any unselected media capability on receipt of the answer message communicating the selected at least one media capability.