OpenFlow MPLS and the open source label switched router

Multiprotocol Label Switching (MPLS) [3] is a protocol widely used in commercial operator networks to forward packets by matching link-specific labels in the packet header to outgoing links rather than through standard IP longest prefix matching. However, in existing networks, MPLS is implemented by full IP routers, since the MPLS control plane protocols such as LDP [8] utilize IP routing to set up the label switched paths, even though the MPLS data plane does not require IP routing. OpenFlow 1.0 is an interface for controlling a routing or switching box by inserting flow specifications into the box's flow table [1]. While OpenFlow 1.0 does not support MPLS
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, MPLS label-based forwarding seems conceptually a good match with OpenFlow's flow-based routing paradigm. In this paper we describe the design and implementation of an experimental extension of OpenFlow 1.0 to support MPLS. The extension allows an OpenFlow switch without IP routing capability to forward MPLS on the data plane. We also describe the implementation of a prototype open source MPLS label switched router, based on the NetFPGA hardware platform [4], utilizing OpenFlow MPLS. The prototype is capable of forwarding data plane packets at line speed without IP forwarding, though IP forwarding is still used on the control plane. We provide some performance measurements comparing the prototype to software routers. The measurements indicate that the prototype is an appropriate tool for achieving line speed forwarding in testbeds and other experimental networks where flexibility is a key attribute, as a substitute for software routers.