This CucsFabricFcSourceType field classifies what kind of object this FC monitor source reference's sourceDn actually points at — for example a physical port versus a VSAN. For a linking record identifying exactly which object (port, VSAN, or endpoint) is supplying the mirrored traffic for an FC monitoring session, UCS Manager needs to know this category up front because the mechanics of mirroring traffic off a whole VSAN are different from mirroring off a single physical port, even though both are configured through the same reference object. A value of 'fc-port' here would mean the session is mirroring one physical FC port's traffic rather than an entire VSAN's worth of traffic.