2.6. Integrity Check Value (ICV)

This is a variable-length field that contains the Integrity Check Value (ICV) for this packet. The field must be an integral multiple of 32 bits (IPv4 or IPv6) in length. The details of ICV processing are described in Section 3.3.3, "Integrity Check Value Calculation", and Section 3.4.4, "Integrity Check Value Verification". This field may include explicit padding, if required to ensure that the length of the AH header is an integral multiple of 32 bits (IPv4) or 64 bits (IPv6). All implementations MUST support such padding and MUST insert only enough padding to satisfy the IPv4/IPv6 alignment requirements. Details of how to compute the required padding length are provided below in Section 3.3.3.2, "Padding". The integrity algorithm specification MUST specify the length of the ICV and the comparison rules and processing steps for validation.