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 document is ready for publication as a Proposed Standard RFC, but has a nit that should be considered before publication. Nit: (This was part of my early review of -00) The claim in 1.1 about not requiring persistent storage is contradicted by the definition of the protocol. At the very least, there is the need to persist the most recent (index,PC) seen.