The Session Initiation Protocol Core (SIPCore) working group is chartered to maintain and continue the development of the SIP protocol, currently defined as proposed standard RFCs 3261, 3262, 3263, 3264, and 6665. The SIPCore working group will concentrate on specifications that update or replace the core SIP specifications named above as well as specifications pertaining to small, self-contained SIP protocol extensions. The process and requirements for new SIP extensions are documented in RFC5727, "Change Process for the Session Initiation Protocol". Throughout its work, the group will strive to maintain the basic model and architecture defined by SIP. In particular: 1. Services and features are provided end-to-end whenever possible. 2. Reuse of existing Internet protocols and architectures and integrating with other Internet applications is crucial. 3. Standards-track extensions and new features must be generally applicable, and not applicable only to a specific set of session types. 4. Simpler solutions that solve a given problem should be favored over more complex solutions. The primary source of change requirements to the core SIP specifications (enumerated above) will be a) interoperability problems that stem from ambiguous, or under-defined specification, and b) requirements from other working groups in the ART Area. The primary source of new protocol extensions is the DISPATCH working group, which will generally make the determination regarding whether new SIP-related work warrants a new working group or belongs in an existing one.