I have see AH used in network segmentation. I.e. systems is group A are configured with rules to require all communication be over AH. Systems in group B (which have no AH and no appropriate certificates configured) can't chat with group A. The benefit of using AH vs. ESP in this case is twofold. First, AH is less CPU intensive, and when one considers enabling it on all/many workstations and servers in a company, that can add up to a lot of CPU cycles. Second, since AH only signs, not encrypts, products like network analyzers, IDS/IPS, etc can still perform their functions. Outside of some manual deployments, the only commercial product I know that offers AH based network segmentation is Microsoft's NAP: http://www.microsoft.com/nap Regards, Adam Stasiniewicz -----Original Message----- From: Jack Kohn [mailto:kohn.jack@gmail.com] Sent: Friday, November 13, 2009 6:23 PM To: nanog@nanog.org Subject: AH is pretty useless and perhaps should be deprecated Hi, Interesting discussion on the utility of Authentication Header (AH) in IPSecME WG. http://www.ietf.org/mail-archive/web/ipsec/current/msg05026.html Post explaining that AH even though protecting the source and destination IP addresses is really not good enough. http://www.ietf.org/mail-archive/web/ipsec/current/msg05056.html What do folks feel? Do they see themselves using AH in the future? IMO, ESP and WESP are good enough and we dont need to support AH any more .. Jack