The Cisco Session Initiation Protocol (SIP) Calls MIB module is designed to provide protocol-specific information on SIP calls which are currently active. SIP is an application-layer signalling protocol for creating, modifying and terminating multimedia sessions with one or more participants. SIP is defined in RFC 3261 (June 2002). The endpoints in a SIP communication are called user agents. A user agent is an application which contains both a User Agent Client (UAC) and a User Agent Server (UAS). A UAC is an application that initiates a SIP request. A UAS is an application that contacts the user when a SIP request is received and that returns a response on behalf of the user. This MIB module provides information on SIP calls and the user agents initiating these calls. Also, it provides a way to manage media forking of SIP calls.