Shadow MACs

Abstract

While SDN promises fine-grained, dynamic control of the network, in practice limited switch TCAM rule space restricts most forwarding to be coarse-grained. As an alternative, we demonstrate that using destination MAC addresses as opaque forwarding labels allows an SDN controller to leverage large MAC (L2) forwarding tables to manage a plethora of fine-grained paths. In this shadow MAC model, the SDN controller can install MAC rewrite rules at the network edge to guide traffic on to intelligently selected paths to balance traffic, avoid failed links, or route flows through middleboxes. Further, by decoupling the network edge from the core, we address many other problems with SDN, including consistent network updates, fast rerouting, and multipathing with end-to-end control.