What is the function of the IP Authentication Header (AH)?

The IP Authentication Header (AH) is designed primarily to provide data integrity and origin authentication for IP packets. This ensures that the data has not been altered during transmission and confirms the identity of the sender. The AH achieves these objectives by using hashing algorithms to create a message digest that is included in the packet. If the data was modified in transit, the message digest would not match upon receipt, indicating tampering.

Moreover, the origin authentication aspect of the AH allows the receiver to verify that the packet indeed came from the claimed sender and not an impersonator. This is critical in maintaining the security of communications over potentially insecure networks, such as the internet.

While encryption is associated with providing confidentiality (which is not a function of AH as it does not encrypt the data), and IP address allocation management is outside the scope of AH's functionality, the primary focus on data integrity and origin authentication distinctly identifies the correct choice regarding the role of the IP Authentication Header.