Port Based Capacity Extensions (PBCEs): Improving SDNs Flow Table Scalability

Software-defined networks (SDNs) come with great promises regarding flexible operation of networks. A key component within SDN-switches is the flow table which holds the rules that determine how data streams are handled. The flow table, however, is a scarce resource with a rather limited rule capacity. To soften this well-known hassle, we propose a novel delegation mechanism for OpenFlow-based SDNs called Port Based Capacity Extension (PBCE). PBCE provides the possibility to delegate flows from a switch with many flow table entries to another less loaded neighboring switch without breaking control plane transparency, i.e., without interfering with existing SDN applications. To do so, PBCE uses flow rule aggregation based on ingress ports and a small number of special rules for both switches. In this paper, we present the PBCE delegation middleware along with a prototypical implementation and first promising performance results that demonstrate the feasibility of the approach.