| With the continuous development of network technology and the popularization of 5G,a variety of new services such as automatic driving,virtual reality(VR),Internet of Things(Io T)and so on have sprung up,which put forward higher requirements to the network.As a new Network architecture,Software Defined Networking(SDN)has the advantages of separation of forwarding and control,centralized control and programmability,which can better adapt to the development of Network technology.Application services can submit various requests to the controller through the northbound interfaces.The controller sends forwarding policies that meet users’ requirements to the switch,and collects status information about the switch through the southbound interfaces.Supported by the key special sub-project of the National Key Research and Development Program of China named "Broadband Communication and Novel Network"-Research on the network virtualization architecture and verification(2020YFB1805601),This thesis mainly studies the design of delay guarantee mechanism for SDN services with low delay requirement.The first two chapters of this thesis summarize the SDN architecture and its research organization at home and abroad,introduce the basic development process of SDN southbound interface protocol OpenFlow,the working mechanism of packet matching forwarding and the message types of OpenFlow,and then introduce the research status of delay measurement technology in traditional network and SDN respectively.Finally,the current delay guarantee mechanism and its advantages and disadvantages are introduced.The main research issues and contributions of this thesis include the following two parts:(1)An active/passive delay measurement mechanism based on OpenFlow protocol extensions is designed.This thesis analyzes the shortcomings of the current SDN network delay measurement mechanism,which does not take the types of switches into consideration and the measurement process requires a large number of flow entries to be installed,so a combined active and passive measurement mechanism based on OpenFlow protocol extensions is designed.Its main features include: 1.This mechanism considers the situation that the switch is an input-queuing switch,and extends the interaction information between the controller and the switch in the OpenFlow protocol.When the measurement command is issued,the information of the input port is carried to support more accurate delay measurement;2.Combining active measurement with passive measurement,on the one hand,reduces the communication overhead for measurement,on the other hand,more comprehensively covers the transmission path between nodes.3.Source routing methods are used in active measurements,saving more storage resources.In this thesis,a network model,node models and process domain models are built in OPNET software to simulate and validate the combined active/passive delay measurement mechanism.(2)A delay guarantee mechanism based on link staining is designed.This thesis adds a link staining mechanism for delay assurance based on the delay measurement results in Chapter3.The mechanism first colors the service by calculating the delay sufficiency of the service,and then colors the link according to the proportion of services in different colors on the link.When a new service arrives,a different colored path is chosen for it depending on the volume of service.This mechanism not only selects the path that meets the delay requirements when the service arrives,but also considers the delay impact of new arrivals during the service transmission.A rerouting mechanism is also added to further improve the level of service delay satisfaction.In this thesis,the simulation of the delay guarantee mechanism is completed in the NSFNET network topology.The simulation results show that the delay guarantee mechanism based on link staining proposed in this thesis achieves a higher degree of service satisfaction,which verifies the effectiveness of the mechanism. |
