This read-create OCTET STRING (up to 300 bytes) on the port identified by ifIndex in tnExprPortTable records an identifier for the remote port this port is understood to be connected to, e.g. a far-end site/port label learned or configured for the fiber link. Operators and the topology-discovery function use it to confirm the physical fiber plant matches the intended network design, catching a fiber patched to the wrong far-end port.