Research On IoT Services Providing Mechanism And Performance Optimization Under SDN

The Internet of Things(IoT)services refer to the user access to the intelligent service process based on information perception,information analysis processing and software definition in the heterogeneous network environment.With the increasing diversity services and the wide range of applications for IoT,new demands for IoT service delivery mechanism are put forward and new challenges for the underlying communicationinfrastructure are also raised.In the background of the higher voice of network innovation,we construct a unified service platform for the Internet of things based on the Software-Defined Networking(SDN)as the infrastructure network.Benefited from the characteristics of programmability,customizability,controllability,which are all owned by SDN,we design a load-balanced routing mechanism to optimize the allocation of resources,aiming at achieving the efficiency of the whole system;we provide differentiated network services for different IoT services by realizing feedback queue management on SDN-configurable switches,aiming at pursuing the personalized service requirements;we build delay constraint minimum cost multicast trees for every topic of publish subscribe/system to cater for the different needs of different IoT services,aiming at improving QoE.Researches and contributions of this thesis are summarized as follows:(1)Referring to the research of IoT service provision mechanism under SDN network environment,we implement a topic based publish/subscribe system as a unified access platform for IoT services.In SDN network,we have developed a prototype system,realized the whole publish/subscribe system,including cluster management(i.e.different event agent are divided into different clusters),topology management(i.e.how to maintain the connection relationship between clusters),topic management(i.e.how to effectively organize and manage topics),strategy management(i.e.how to express and organize strategies),etc.Especially,with regard to topology establishment and maintenance,we take full account of the difference between of SDN and traditional TCP/IP network as infrastructure network,and realize the topology construction and maintenance under SDN.(2)Aiming at IoT data's characteristics of periodicity,redundancy and predictability,we can predict the data distribution within a period of time.According to the global network topology view and the current link utilization,we propose a load-balanced routing algorithm for multi-source-multi-terminal multicast problem,maximizing the residual bandwidth as the optimization goal.In this algorithm,we take full consideration of the topic coverage relationship to calculate event routing gradually so as to minimize the computation cost and the flow table items of switches.(3)In view of the different QoS requirements of IoT data,we provide a differentiated service in the data forwarding plane of the SDN network to meet the diversified Internet of things applications.We divide every egress port of every SDN-configurable switch into multiple priority queues.Every high priority queue should guarantee its upper limit for queuing delay.SDN control plane obtains real-time length information of all the queues by collecting data periodically,and adjusts bandwidth allocated to each queue accordingly.In this way,it ensures high priority queues' upper bound of delay.Finally,given that routing paths of events have been calculated,every event with different delay requirements is distributed to different priority queues along its routing paths so that its total delay is not greater than its delay constraints.(4)Aiming at real-time transmission demand of time-sensitive IoT application,we propose an algorithm to construct delay constraint minimum cost steiner tree as topic overlay network,considering delay and cost as the two variables attached to each edge.To estimate delay,we take queuing delay as the dominant and variable delay suffered on each node,other constituent part(including process delay,transmission delay and propagation delay)as constant.Then,the cost of a link is measured by the utilization of the current link.For every topic,we first construct the minimum Steiner tree and the minimum cost Steiner tree respectively.When the minimum cost path from source node to a terminal node satisfies the delay constraint of this topic,the minimum cost path is added to multicast tree.Otherwise,the minimum delay path is added.In this way,the minimum cost Steiner tree is formed and it satisfies the delay constraint.