Research On Key Technologies Of SDN-Oriented IoT Service Middleware

The Internet of Things(IoT)services refer to providing users with ubiq-uitous,real-time,secure,and intelligent services in the IoT scenario.In re-cent years,with the popularity of smart devices and the advancement of sens-ing technology,IoT devices and services have increased explosivly.Faced with massive data,heterogeneous networks,and diverse service requirements,how to design and implement IoT services has become an urgent issue.Pub-lish/subscribe middleware is often used to build the communication infrastruc-ture of IoT services.It aims to build an IoT platform to unify message formats and interconnect heterogeneous networks to lower-layer networks,provide a unified abstraction to upper-layer applications,and deliver events efficiently for IoT services.The emerging Software-Defined Networking(SDN)brings greater programmability and flexibility to the network due to its logically cen-tralized controller and separation of control and forwarding.SDN can be used to solve the hard issue of Quality of Service(QoS)guarantee in delivering events between publishers and subscribers for IoT services.The combination of pub-lish/subscribe middleware and SDN forms a SDN-oriented publish/subscribe middleware,which further promotes the arrival of the IoT era.The research work and contributions of this thesis are as follows:(1)To address the issue of how to use SDN and publish/subscribe middle-ware to provide IoT services,this paper proposes an SDN-like publish/subscribe middleware architecture and implementation framework,and elaborates how to use this architecture to implement SDN-like topic-oriented publish/subscribe middleware prototype as IoT communication infrastructure.This paper also de-scribes how to use the programmability of SDN to encode the priority of event topic and authorization policy by the SDN controller into the matching fields of the flow entries of SDN switches to implement differentiated IoT services and user access control,improving the efficiency and security of event delivery in IoT.(2)In view of the hard problem of QoS guarantee in IoT services,a cross-layer QoS enabled control framework is designed to improve the QoS of deliv-ering events in SDN-like publish/subscribe middleware for IoT services.The cross-layer means controlling QoS at different management layers.One layer is at the control layer,which uses the characteristics of SDN centralized control to improve the QoS in the autonomous domain of the SDN controller from a local perspective,and the other layer is at the global management layer to im-prove the QoS of the global network from the perspective of administrator.The two application scenarios of differentiated services and access control verify the rationality of the design of the cross-layer QoS enabled control framework.(3)To solve the issue of the real-time delivery of massive delay-sensitive data in IoT services,a topic-oriented Steiner tree multicast routing algorithm with improved shortest paths is designed to construct publish/subscribe over-lay networks for multiple topics,which can minimize the total link delay of event transmission and reduce the number of flow entries in SDN switches,improving the efficiency of event delivery and forming a fast multicast rout-ing.A topic-oriented bucket-based multicast forwarding algorithm considering the subscription coverage relationships between topics is also designed to im-prove the efficiency of event forwarding,reducing the number of flow table entries of switches and improving the matching ability of the switches.These two algorithms and the SDN-like design together compose the topic-oriented bucket-based fast multicast routing in IoT.(4)Aiming at the characteristics of diversified and customized user re-quirements in IoT services,this paper proposes how to use an SDN-like pub-lish/subscribe middleware architecture and configure priority queues in the out ports of SDN switches to provide differentiated IoT services.It also designs a two-layer queue management mechanism based on user requirements to ensure the reliability of differentiated services from two perspectives.One is the local queue bandwidth adjustment algorithm for a single switch in SDN controllers.The other is the global QoS control policy for all switches on the path from a publisher to a subscriber in administrator.In this way,this paper uses the char-acteristics of SDN centralized control to obtain the entire network topology,dynamically configure the delay constraints of switches,and allocate queue bandwidth more reasonably from a system view,guaranteeing the reliability of differentiated services in IoT.