Abstract: A transport interface (10) provides add drop multiplex functionality and termination requirements for the transportation of network traffic. The transport interface (10) includes high speed units (12), broadband interfaces (16), and SONET formatters (18). Each high speed unit (12), broadband interface (16), and SONET formatter has redundant protection pairs (A and B). The high speed units (12), broadband interfaces (16), and SONET formatters (18) communicate with each other by in-band datalinks (40). The redundant protection pairs (A and B) communicate with one another by protection pair datalinks (42). The in-band datalinks (40) and the protection pair datalinks (42) provide protection switching within the transport interface (10) in the event of component failure. The in-band datalinks (40) are generated out of available or consumed bytes within either a section overhead (32) or a line overhead (34) of SONET OC-N frame (30).