What does Authentication Header (AH) provide in IPsec?

• A. Integrity protection for packet headers and data as well as user authentication
• B. Confidentiality of the payload only
• C. Encryption for the entire IP packet
• D. Anti-spoofing only

Answer: (A)

Authentication Header provides integrity and authenticity for the entire IP packet—both the header and the payload—and it also offers anti-replay protection. It does not provide confidentiality or encryption of the payload. So the statement that best matches AH is that it ensures integrity for headers and data and authenticates the sender. The other options describe confidentiality or encryption (which AH does not do) or only anti-spoofing (which misses the integrity and anti-replay protections AH provides).