Analysis of flows reduction scheme by adopting two MPLS tags in software-defined network

摘要

A switch in a software-defined network (SDN) uses a flow table for packet forwarding. The flow table consists of flow entries decided by a controller. As user requests with a variety of data types have been dramatically increasing, a controller's CPU is overloaded to process those requests. The users may not obtain real-time data. Furthermore, the control plane might be overflowed by OpenFlow messages that correspond to the requests. The number of requests can be reduced by a scheme to keep permanent flow entries in the switch. A huge number of permanent flow entries to support the forwarding function degrade other functions. This paper proposes a scheme to reduce the number of permanent flow entries and the number of OpenFlow messages generated by the controller. The proposed scheme divides switches in the network into several regional groups. It re-designs a flow table that is incorporated with a concept of two multiprotocol label switching tags to guide packets from sources to destinations. One tag guides the packets from a source switch to an edge switch in the destination group. The other tag guides the packets from the edge switch to another switch in the local group. Performance evaluation shows 74% reductions of the number of permanent flow entries, compared to a conventional scheme that keeps permanent flow entries without inquiry to the controller. Moreover, 81% of the number of OpenFlow messages is reduced, compared to another scheme that inquires the controller every time once a request arrives at the switch.