On a point-to-point circuit with a fully initialized adjacency to a peer IS, the value of this object is the circuit ID negotiated during adjacency initialization. On a point to point circuit without such an adjacency, the value is the concatenation of the local system ID and the one-byte isisCircLevelIDOctet for this circuit, i.e., the value that would be proposed for the circuit ID. On other circuit types, the value returned is the zero- length OCTET STRING.