MPLS
IP forwarding is dynamic, robust and scalable, but expensive; “longest prefix match” forwarding
About 50,000 variable-length unique prefixes
Link-layer (e.g. ATM) switching is inexpensive, simple and fast
Cut-through IP flows using labels (e.g. ATM VCI) without going to IP router module
Performed locally at each IP switch
If performed by contiguous group of IP switches, IP flow is cell-switched end-to-end
Soft state; if flow state disappears, packets are routed
Labels are distributed by a dynamic label-distribution protocol
- instruct adjacent upstream node to label IP flow with a VCI
- map input VCI to an output VCI in the switch
Traffic engineering (based on ToS bits, source, destination, ports, etc.) using explicit label-switched paths