Which term describes the IPsec component that provides authentication for origin and integrity and protection against replay attacks?

Which term describes the IPsec component that provides authentication for origin and integrity and protection against replay attacks?

• A. Authentication Header (AH)
• B. Encapsulation Security Payload (ESP)
• C. TLS
• D. VPN

Answer: (A)

IPsec uses a mechanism specifically designed to verify who sent a packet and that its contents haven’t been altered, while also preventing the reuse of old packets. The Authentication Header provides this by authenticating the origin of the IP packet and ensuring data integrity, using a sequence number to detect and reject replayed packets. It does not encrypt the payload, so it doesn’t offer confidentiality—that role is handled by ESP when encryption is needed. TLS is a separate protocol for securing sessions over TCP, and a VPN is a broader technology that may use IPsec but isn’t a single IPsec component.

IPsec uses a mechanism specifically designed to verify who sent a packet and that its contents haven’t been altered, while also preventing the reuse of old packets. The Authentication Header provides this by authenticating the origin of the IP packet and ensuring data integrity, using a sequence number to detect and reject replayed packets. It does not encrypt the payload, so it doesn’t offer confidentiality—that role is handled by ESP when encryption is needed. TLS is a separate protocol for securing sessions over TCP, and a VPN is a broader technology that may use IPsec but isn’t a single IPsec component.