This Recommendation specifies the security negotiation mechanism for ITU-T H.225.0 call signalling message exchanges. The main goals include the following.

1) Secure selection of the security mechanism. Otherwise, the procedure of negotiation is vulnerable to certain attacks such as malicious manipulation or bidding-down attacks. The entire registration, admission and status (RAS) message shall be protected during the negotiation procedure.

2) Involved [ITU-T H.323] entities shall determine mutually agreed security protocols without requiring additional round trips.

3) Entities involved in the negotiation procedure shall be aware of the result of the negotiation, such as success or failure.

4) The negotiation procedure should not cause any additional burden to the involved entities.