Expedited resource negotiation in SIP

A method of operating a communication terminal as an answering terminal, to set up a communication session with another communication terminal operating as an originating terminal, the method comprising:

• receiving from the originating terminal an offer message communicating media capabilities available at the originating terminal and corresponding numbers of media streams;
• selecting at least one media capability based on the communicated media capabilities available at the originating terminal and corresponding numbers of media streams;
• reserving the selected at least one media capability so that no other answering terminal can obtain access to the reserved at least one media capability until such reserved at least one media capability are released;
• and
• sending from the answering terminal to the originating terminal, an answer message communicating the selected at least one media capability.

A communication terminal operable as an originating communication terminal, the communication terminal comprising a processor and a session initiation protocol (SIP) user agent, the SIP user agent configured to:

• send to an answering communication terminal an offer message communicating media capabilities available at the originating communication terminal and corresponding numbers of media streams;
• receive from the answering communication terminal an answer message communicating at least one selected media capability in accordance with the respective corresponding number of media streams communicated in the offer message;
• reserve the communicated media capabilities available at the originating communication terminal before sending the offer message so that no other answering communication terminal can obtain access to the reserved media capabilities until such reserved media capabilities are released;
• and
• release from reservation at the originating communication terminal any unselected media capability on receipt of the answer message communicating the selected at least one media capability.