This document registers new disposition-types for the Content- Disposition header field that apply to the application/3gpp-ims+xml body (part) used by 3GPP. The applicability of these content- disposition values are limited to 3GPP IMS. The application/ 3gpp-ims+xml body (part) has the following three distinct uses: (1) for redirecting the emergency session to use a different domain (e.g. using a Circuit Switched call), (2) for delivering user profile specific information from the SIP registrar to an Application Server, and (3) for causing a UAC to attempt to re-register with the IMS.