MPLS Label Distribution

This chapter introduces the concepts and applications of Multiprotocol Label Switching (MPLS) label distribution and MPLS signaling. The chapter also gives the opportunity to exercise and expand one's working knowledge with both hands-on exercises and vendor examples. MPLS switches must be trained; they must learn all the rules and circumstances under which to apply. Two methods are used to make switches that are “trained” for these purposes. One method uses hard programming and is similar to how a router is programmed for static routing. Static programming eliminates the ability to dynamically reroute or manage traffic. Modern networks change on a dynamic basis. Two modes are used to load cross-connect tables: independent control and ordered control. Finding a transport vehicle with which to build these complex tables is of the utmost concern to network designers. Label Distribution Protocol was created by design engineers and the MPLS workgroup as a means of addressing such transport needs. This protocol works much like a telephone call—when labels are bound, they remain bound until a command appears to tear down the call. The chapter compares various aspects of these protocols and examines the trade-offs in each.