A method, Bridge, and system in a Provider Backbone Bridge Network (PBBN) for enabling frames from a Higher Layer Entity attached alternatively to a Provider Instance Port (PIP) on an I-Component of a Backbone Edge Bridge or to a Customer Backbone Port on a B-Component of the Backbone Edge Bridge, to reach an intended entity in the PBBN. A Multiplexed Service Access Point (SAP) of a Service Instance Multiplex Entity handles the frames of the Higher Layer Entity, and is assigned a Service Instance ID (I-SID) value that is universally recognized to identify Layer 2 Control Protocols. The Service Instance Multiplex Entity utilizes the Multiplexed SAP to transfer frames between the PIP or the Customer Backbone Port and the entity in the PBBN.