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.

Background: SIP currently provides no standard way to indicate that an invite via diversion from the original terminating user (e.g., via busy response or an unconditional call forward) is the result of diversion rather than a new origination, making it impossible in the absence of proprietary signaling to distinguish between the two cases. This draft adds an orig-cdiv signal to the P-Served-User header to indicate an invite resulting from a diversion, allowing an application server to take different actions in the two cases.

Security evaluation: The addition of a new actionable signal is properly noted as the main security consideration of this change, along with a reminder that the P-Served-User header must be implemented as a privileged channel within a single trust domain and not transited into a domain from an untrusted entity.

Other comments: As a reviewer new to SIP, I found the document very easy to follow. The introduction contained basic background about the use case, a clear explanation of the problem, and a high-level overview of the proposed solution. The normative section of the document was very clearly illustrated by the later examples section, containing two typical use-cases with clear diagrams. This is a model internet draft.