The hash value is the Base64 encoding of the SHA-1 checksum. A routing node discards packets that fail a header checksum test. UDP checksum computation is optional for IPv4. Reliability is addressed through error detection using a weak checksum algorithm. An IP packet has no data checksum or any other footer after the data section. The packet payload is not included in the checksum. A pseudo-header that mimics the IPv6 header for computation of the checksum is shown below. This algorithm is then called the Fletcher-64 checksum. This algorithm is then called the Fletcher-16 checksum. This algorithm is then called the Fletcher-32 checksum. This field is the IP checksum of outer header. The sum is then bitwise complemented and inserted as the checksum field. The indexed value is the checksum digit. More checksum algorithm options are planned for the future. The data stream can contain an optional checksum.