Hi, 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. The call completion feature defined in this specification allows the caller of a failed call to be notified when the callee becomes available to receive a call. The Security Considerations section mentions 'SPIT' but nowhere does the document define the term. What does it mean? The SC section also mentions a "DoD" attack -- is the US Department of Defence actually going to attack something? Or does DoD mean something else? It's never defined. Was this perhaps a typo of "DoS", Denial of Service? If so, I recommend you fix the typo but also expand the acronym for those not necessarily familiar with the term "DoS". -derek -- Derek Atkins 617-623-3745 derek at ihtfp.com www.ihtfp.com Computer and Internet Security Consultant