ments on transcoding, which have wider scope than the hearing impaired. 11.1.2 Conferencing Design Team This design team is working on issues relating to tightly coupled multiparty con- ferencing. The work SO far has produced a requirements [2], framework [3], and call control [4] documents that are SIPPING working group items. The frame- work includes voice, video, IM, and collaboration. Other items include the defi- nition of the isfocus feature tag [5] and the conference event package [6]. The design team is also working on areas relating to standardizing XML messages for conference and media mixing policy. This will allow an intelligent end point or automata to set up and configure a multimedia conferencing ses- sion. The media policy manipulation will allow an end point to control their view and mixing of the overall conference. This work will be standardized in the new XCON (centralized conferencing) IETF working group. However, Future Directions intelligent SIP end points and clients will likely support these extensions and protocols. 11.1.3 Application Interaction Design Team This design team is developing a framework for application interaction using SIP. It will cover areas such as dual-tone multifrequency (DTMF) and stimulus (button pressing) transport and integration with SIP signaling. 11.1.4 Emergency Calling Design Team This design team is developing requirements for SIP support of emergency call- ing (911 in the United States and 112 in other parts of the world). 11.2 Other SIP Work Areas Some other important work areas relating to SIP are discussed in the following sections. 11.2.1 Emergency Preparedness The IETF Internet Emergency Preparedness (IEPREP) working group has been working on requirements on how to make sure that the Internet functions prop- erly and can provide reliable communications for emergency personnel in the event of an emergency or disaster. There is a document of requirements for SIP [7] that may produce some SIP extensions and conventions. 11.2.2 Globally Routable Contact UR