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 summary of the review is Ready with nits. (Section 3, nit) In the paragraph that includes "However, nonrandom SPI and restricting their possible values MAY lead to privacy and security concerns" , it would be nice to add something like "(see below for more details)". When I first read that paragraph, I was about to comment that it's unclear what the privacy/security concerns are, but then it was explained a few paragraphs below. (Section 4) Am I understanding correctly, that the last paragraph is giving the option of resetting the Sequence Number when rekeying? Does IPSec try to prevent eavesdroppers from determining when rekeying happens? (I really don't know that much about IPSec.) If it does, then resetting the SN could leak that information, if not then there's nothing to leak.