Application Servers, SIP Proxies, and SoftSwitches (a.k.a. Media Gateway Controllers) act as SIP [2] User Agents to control the media processing capabilities of media servers. The SIP Request URI identifies the desired service and provides a context for the media server to interpret the SIP message. This document describes a standard SIP addressing mechanism to address specific services. Because of SIP's flexibility, the existing protocol accommodates these services. This document proposes a standard URI scheme for important media services such as announcements and conferencing.