This is a one-byte identifier used in protocol packets to identify a circuit; values do not need to be unique except on LANs where this Intermediate System is the Designated Intermediate System. This octet combines with the router's System ID to form the LAN circuit ID whenever this router is acting as DIS on a segment, and because it only needs to be unique among the circuits where this router actually holds the DIS role, an admin can safely reuse the same octet elsewhere. For example, a router acting as DIS on two different LAN segments simultaneously would need distinct values, say 1 and 2, on those two circuits to form unambiguous pseudonode LSP IDs for each segment.