Session Initiation Protocol (SIP)-Specific Event Notification," RFC 3265, 2002. Petrack, S., and L. Conroy, "The PINT Service Protocol: Extensions to SIP and SDP for IP Access to Telephone Call Services," RFC 2848, 2000. Rosenberg, J., and H. Schulzrinne, "A Session Initiation Protocol (SIP) Event Package for Conference State," IETF Internet-Draft, Work in Progress, June 2002. SIP Request Messages [8] Rosenberg, J., and H. Schulzrinne, "An INVITE Initiated Dialog Event Package for the Session Initiation Protocol (SIP)," IETF Internet-Draft, Work in Progress, March 2003. Mahy, R., "A Message Summary and Message Waiting Indication Event Package for the Session Initiation Protocol (SIP)," IETF Internet-Draft, Work in progress, March 2003. Rosenberg, J., "A Presence Event Package for the Session Initiation Protocol (SIP)," IETF Internet-Draft, Work in Progress, January 2003. Rosenberg, J., "A Session Initiation Protocol (SIP) Event Package for Registrations," IETF Internet-Draft, October 2002. Rosenberg, J., "A Watcher Information Event Template-Package for the Session Initiation Protocol (SIP)," IETF Internet-Draft, Work in Progress, January 2003. Campbell, B., et al., "Session Initiation Protocol (SIP) Extension for Instant Messaging," RFC 3428, 2002. Crocker, D., et al., "Common Presence and Instant Messaging (CPIM)," IETF Internet- Draft, Work in Progress, August 2002. [15] Sparks, R., "Establishing jabber Messaging Sessions with the Session Initiation Protocol," IETF Internet-Draft, Work in Progress, October 2002. [16] Donovan, S., "The SIP INFO Method," RFC 2976, 2000. Rosenberg, J., and H. Schulzrinne, "Reliability of Provisional Responses in Session Initia- tion Protocol (SIP)," RFC 3262, 2002. Rosenberg, J., "The Session Initiation Protocol (SIP) UPDATE Method," RFC 3311, 2002. [19] Schulzrinne, H., and A. Vaha-Sipila, "The tel URI for Telephone Calls," IETF Internet- Draft, February 2003. [20] Hoffman, P., L. Masinter, and J. Zawinski, "The mailto URL Scheme," RFC 2368, 1998. [21] Fielding, R., et al., "Hyp