This transport-typed field records which underlying network transport — Ethernet, native Fibre Channel, or FCoE — applies to this FC monitoring session's source port. Because this FC monitoring session's source port models the physical FC port whose traffic is being mirrored/copied for an FC monitoring session, the transport value determines which physical port types and cabling are valid for this specific connection, and mismatches here are a common root cause of an uplink that won't come up. For an FC-oriented object like this one the value is typically 'fc', meaning it rides over native Fibre Channel rather than being encapsulated in Ethernet frames.