Research On Resilience Technology In Software Defined Networks

With the rapid development of the Internet,the network has penetrated into every aspect of people's life.The research of network resilience technology has also received increasing attention.The Software-Defined Networking(SDN)paradigm supports deploying traffic flows dynamically by a centralized controller to SDN switches.In particular,the controller configures forwarding rules in SDN switches to route traffic flows.With the characteristics of flexible structure,centralized configuration,and rapid deployment of network services,it is possible to study the network resilience technology well.This thesis mainly studies the flow entry compressing problem in a single link failure scenario in SDN.Flow entry sharing and flow entry multiplexing are proposed.These two methods are considered to minimize the total number of flow entries while guaranteeing traffic survivability against a single link failure.In the method of flow entry sharing,we introduce two cases of flow entry sharing:(1)sharing between backup flow entries;(2)sharing between working flow entry and backup flow entry.In this way,the number of flow entries is greatly reduced.In this way,the total number of flow entries can be reduced greatly.To this end,we consider the limited size of Ternary Content Addressable Memory(TCAM)in SDN switches,and employ flow entry sharing in SDN protection.We first present the problem as an Integer Linear Programming(ILP)model,and then design a greedy based heuristic algorithm named Flow Entry Sharing Protection(FESP).Extensive simulation results show that compared with the previous SDN protection algorithms,FESP significantly reduces the total number of flow entries.In the method of flow entry multiplexing,we first give the definition of multiplexing segment.We multiplex traffic flows traversing through the same multiplexing segment into an aggregated flow with the label of VLAN ID.Thus,multiple flow entries are merged into one multiplexed flow entry.In this way,the total number of flow entries can be reduced greatly.We also extend the method to SDN protection,and reduce the number of backup flow entries.We formulate this problem as an ILP model.Since this problem is NP-hard,we design a polynomial algorithm using the Markov approximation technique.Theoretical analysis indicates that the polynomial algorithm generates near-optimal solution.The extensive emulation results show that compared with the benchmark algorithms,the proposed Markov approximation based algorithm reduces the total number of flow entries significantly.