SIP and XXXXX Sample Clauses

SIP and XXXXX. In order not to add additional roundtrips to the call establishment, the key agreement conducted with XXXXX should be contained in the SIP INVITE transaction. The simplest case, when no error occurs, is conducted as illus- trated in figure 11.1. MIKEY usually requires no more than one roundtrip, so the whole key exchange can be included in the INVITE transaction. Figure 11.1: XXXXX in a SIP INVITE transaction An Internet Draft [25] defines how XXXXX should be integrated into the SIP messages, as part of the session description. The MIKEY messages are added as an SDP attribute key-mgmt, either at the session level (in which case it applies to all the streams), or at the media level (if it is specific to protecting only one stream). Several key-mgmt attributes can be included if the initiator wants to offer several alternative ways of exchanging keys. To avoid a downgrade attack, each key agreement message must contain the list of the key agreement meth- ods and protect its integrity. In the case of XXXXX, this is done by adding a GENERAL EXTENSION payload containing this list. Re-keying should be included into RE-INVITE messages. However, this has not yet been implemented.