Change the definition to the following, adding a NOTE to align wih IEEE P802.1AE-Rev as follows (and as already included in the successfully balloted P802.1Xck, and this maintenance request has been submitted to complete the audit trail):
A 16-bit identifier that uniquely identifies each of a systems transmit SCs that uses the same MAC address as a component of its SCI.
NOTE-The Port Identifier is not constrained to correspond to any other identifier, index, or port number, and there can be more than one SC for a physical port, identifying frames transmitted by separate virtual ports, and more than one SC for a physical or virtual port if that port uses different SCs to transmit frames of different priorities.