Path switching: reduced-state flow handling in SDN using path information

The advent of virtualization, containerization and the Internet of Things (IoT) is leading to an explosive growth in the number of endpoints. Ideally with Software Defined Networking (SDN), one would like to customize packet handling for each of these endpoints or applications. However this typically leads to a large growth in forwarding state. This growth is avoided in current networks by using aggregation which trades off fine-grained control of micro-flows for reduced forwarding state. It is worthwhile to ask whether the benefits of micro-flow control can be retained without a large growth in forwarding state and without using aggregation. In this paper we describe an incrementally deployable SDN-friendly packet forwarding mechanism called Path Switching that achieves this by compactly encoding a packet's path through the network in the packet's existing address fields. Path Switching provides the same reduction in forwarding state as source routing while retaining the benefits and use of fixed size packet headers and existing protocols. We have extended Open vSwitch (OVS) to transparently support Path Switching as well as an inline service component for folding middlebox services into OVS. The extensions include advanced failover mechanisms like fast reroute. These extensions require no protocol changes as Path Switching leaves header formats unchanged.