AH

The IPSec protocol that provides integrity and authentication but not confidentiality.

AH is an IPsec protocol that provides connectionless integrity, data origin authentication, and optional replay protection by signing the packet, including portions of the IP header, but it does not encrypt the payload. Because it authenticates header fields, AH breaks when traffic passes through NAT, which rewrites addresses. For the exam, contrast AH with ESP: ESP supplies confidentiality through encryption and is far more commonly deployed, so AH alone is rarely chosen when privacy of the data is required.