An end-to-end session identifier in SIP-based multimedia communication networks refers to the ability for endpoints, intermediate devices, and management and monitoring system to identify and correlate SIP messages and dialogs of the same higher-level end-to-end "communication session" across multiple SIP devices, hops, and administrative domains. Unfortunately, there are a number of factors that contribute to the fact that the current dialog identifiers defined in SIP are not suitable for end-to-end session identification. Perhaps the most important factor worth describing is that in real-world deployments of Back-to-Back User Agents (B2BUAs) devices like Session Border Controllers (SBC) often change the call identifiers (e.g., the From-tag and To-tag that are used in conjunction with the Call-ID header to make the dialog-id) as the session signaling passes through. An end-to-end session identifier should allow the possibility to identify the communication session from the point of origin, passing through any number of intermediaries, to the ultimate point of termination. It should have the same aim as the From-tag, To-tag and Call-ID conjunction, but should not be mangled by intermediaries. A SIP end-to-end session identifier has been considered as possible solution of different use cases like troubleshooting, billing, session tracking, session recording, media and signaling correlation, and so forth. Some of these requirements come from other working groups within the RAI area (e.g., SIPRec). Moreover, other standards organizations have identified the need for SIP and H.323 to carry the same "session ID" value so that it is possible to identify a call end-to end even when performing inter working between protocols. This group will focus on a document that will specify a SIP identifier that has the same aim as the From-tag, To-tag and Call-ID conjunction, but is less likely to be mangled by intermediaries. In doing this work, the group will pay attention to the privacy implications of a "session ID", for example considering the possibility to make it intractable for nodes to correlate "session IDs" generated by the same user for different sessions.