An Acronym for Authentication Header
An Authentication Header is part of the IPsec? protocol. IPSec is used to authenticate data passing between two hosts on the Internet. The Authentication Header provides only authentication - no encryption. A more detailed analysis is available at http://www.freeswan.org/freeswan_trees/freeswan-1.99/doc/ipsec.html#AH.ipsec.
Authentication Header is specified in RFC:2042
4 pages link to AH: