I have reviewed this document as part of the security directorate's ongoing effort to review all IETF documents being processed by the IESG. These comments were written primarily for the benefit of the security area directors. Document editors and WG chairs should treat these comments just like any other last call comments. This insipid document describes requirements on an end-to-end session identifier for IP-based multimedia transports. End-to-end identifiers that meet the criteria defined in this document may well raise privacy concerns. The authors do note this and has included a reasonable discussion around potential mitigations etc. in the Security Considerations section. It remains to be seen if actual identifier definitions will be able to mitigate these concerns. An editorial comment: In Section 4.6, should the first use of "restrictive" instead read "permissive"? -- Magnus