In some cases it may be advantageous for adjacent nodes to exchange some extra information beyond the Interest and ContentObject messages themselves, for the purpose of making the overall operation more efficient. We call these link messages, and describe them here.

SequenceNumber

SequenceNumber ::= BLOB

The SequenceNumber message may be included in a series of messages. The primary use of this message is when unreliable datagrams are being used as a transport. The BLOB is interpreted as a binary number in network byte order (i.e., big endian). Typically, one SequenceNumber message would be included in each datagram, with the value being advanced by one. This allows the receiving side to detect gaps in the sequence, an indication of missing or reordered packets.

The starting value is chosen by the sending side. The sending side may choose to restart the sequence at a different point. To minimize confusion, the new origin should differ from the last-used sequence number by a value of at least 255.

The minimum BLOB size is one byte, and the maximum is 6 bytes.