e 37th meeting in December 1996. The new SIP was based on HTTP, but could use both UDP and TCP as transport protocols. It used SDP to describe multimedia The Session Initiation Protocol: SIP Figure 4-2 Session Invitation Protocol Simple Conference Invitation Protocol SCIP and SIPv1 were (SIPv1) (SCIP) merged into SIPv2. Session Initiation Protocol (SIPv2) sessions, and it was text based. It remains the current version of the SIP protocol. SIP development efforts were the province of the Multiparty Multimedia Session Control (MMUSIC) working group, chaired by Joerg Ott and Colin Perkins. The first draft grew out of the feedback received by the authors and discussions in the MMUSIC mailing list. In 1998, Jonathan Rosenberg was added as a co-author of the specification because he had contributed SO much to the discussion, and in the following February (1999), SIP reached the proposed standard level and was published as RFC 2543. As time went by, SIP gained importance in the IETF, resulting in the for- mation of a new SIP working group in September 1999. This working group was originally chaired by Joerg Ott, Jonathan Rosenberg, and Dean Willis. In August 2000, Brian Rosen replaced Rosenberg as co-chair because Rosenburg and Willis changed corporate affiliations to the same company, and diversity was desired among the chairs. Close on the heels of the March 2001 IETF meeting, the SIP working group was split in two. Discussions about the main SIP specification and its fundamental extensions now take place in a group that continues to be called SIP, whereas discussions about applications that use SIP are carried out in a group called SIPPING. This division of labor should help manage the enormous number of contributions related to SIP that the IETF is being asked to consider. Proposed Standard Status As of July 2001, SIP is still not a finished product. Its current status is proposed standard. Further review is needed before it can be awarded the next maturity level of draft standard, and it must have had at least two 