Introducing SDN Control in MPLS Networks

MPLS networks have evolved over the last 10-15 years and have become critically important for ISPs. MPLS is primarily used in two ways: to perform traffic engineering in IP networks, providing greater determinism and more efficient usage of network resources; and for enabling MPLS based L2 or L3 enterprise Virtual Private Network (VPN) services, which continues to be one of more profitable services offered by ISPs. MPLS is the preferred solution for such services, mainly because plain-vanilla IP networks are incapable of providing the same services; and older ways of providing these services using ATM or Frame-Relay networks are no longer used. As carriers deploy MPLS they find that (a) even though the MPLS data plane was meant to be simple, vendors support MPLS as an additional feature on complex, energy hogging, expensive core routers; † and (b) the IP/MPLS control plane has become exceedingly complex with a wide variety of protocols tightly intertwined with the associated data-plane mechanisms. We make the observation that in any MPLS network, there are simple data-plane mechanisms of pushing-on, swapping, and popping-off MPLS labels in a label-switchedpath. These mechanisms are controlled by a number of control-plane protocols that help