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. I find one case which can be a small disadvantage: both sides have to be updated to use tunneling, even if only one side is blocked by NAT. Can we handle this case? Tina Sent from my IPv6 address 2001:0:4137:9e76:20f1:518:f56e:f6a5