NCoS:A Framework For Realizing Network Coding Over Software-defined Network

Network coding is a novel transmission for achieving theoretical upper bound of multicast capacity.Different from traditional store-add-forward model of packet switch,network coding uses store-encode-and-forward model that allows intermediate nodes to encode the received packets together before sending them out.Network coding can save bandwidth as well as balance load effectively.However,implementing network coding in traditional wired network needs to add coding function and support multipath multicast routing in routers,which is impossible for routers with closed architecture.Software-defined network(SDN)is an new network architecture that decouples network element's control plane and data plane.It uses a logical centralized controller and defines a unified API for accessing data plane,which can easily add new proto-cols and functions into network and move the big stone which hinder innovation of the traditional network.This article studies the key technologies for implementing net-work coding on SDN and proposes a NCoS,a framework for realizing network coding over SDN through extending switch and controller functions.NCoS can be used as an experimental platform for network coding algorithms' deployment and testing in re-al network.During the design,this article has carefully discussed and solved several problems caused by the particularity of network coding,and proposed a method for fast OpenFlow extension.NCoS have implemented basic functions of deterministic network coding and random network coding in switch and provided functions of mul-tipath multicast routing,an algorithm for finding code vector for deterministic network coding and several functions to support network coding application,such as multicast group management,flow information management,buffer management.Users can use this functions to compose their own network coding applications.This article also takes advantage of the logical centralized control of SDN and proposes a optimization scheme for deterministic linear network encoding,which reduces the overhead of coding func-tion in switch.