Traffic Retention Technology Under Network Mobility

Satellite communication systems can achieve global coverage,which is a huge advantage over terrestrial communication systems.Therefore,satellite networks will play an important role in future global networking.Low Earth Orbit（LEO）satellite network has the advantages of low communication delay and low networking cost compared with satellite networks in other orbits due to its low orbit height,and has become one of the key research of future satellite networks in many countries including China.However,the topology of LEO satellite networks is highly dynamic,and access devices exist in the form of mobile private networks,which increases the frequency of access devices handover among access points,interrupts services repeatedly,and ultimately degrades user experience.Compared with the traditional network architecture,Software Defined Networking（SDN）has a global view of the network and the ability to centrally control the forwarding equipment,and can respond more quickly and effectively in the face of handover events.Therefore,thesis mainly studies the traffic retention technology in the LEO satellite network under SDN architecture.In order to avoid the traffic interruption caused by the handover action triggered by the dynamic change of the LEO satellite network topology,thesis first designs a satellite network architecture based on a virtual layered network.In this architecture,virtual access points are introduced,each virtual access point has a static fixed footprint on the ground and is dynamically mapped to a physical satellite,which can provide stable access services to ground equipment.Then,aiming at the situation that the access equipment exists in the form of a mobile private network,thesis designs the addressing and communication strategy of locator identifier separation.This strategy enables the traffic communication to only perceive the identities but network locations of the two communicating parties.The access device only changes its network location after the handover and keeps the identities unchanged,thus keeping the traffic volume before the handover alive.Based on the proposed satellite network architecture and locator identifier separation strategy above,thesis implements a traffic retention system based on ONOS,which includes four modules: virtual and real satellite management,proxy neighbor discovery,private network access management,and active routing.The first three modules can support the basic traffic communication capabilities between mobile private networks,and when the private network switches its access point,it can help it shorten the offline time under the premise of keeping the traffic alive.The active routing module is a supplement to the system’s routing capabilities.On the basis of implementing the QoS policy based on traffic class distinction,this module implements a routing algorithm that meets the traffic bandwidth and a routing algorithm that meets the penalized bandwidth.The former allows traffic to be routed to the shortest path in turn,while the latter allows traffic volume to be distributed over different paths.In order to reduce the complexity of simulation,thesis expands the ability of Mininet,and uses it to complete the test of private network handover among access points and the test of non-uniformly distributed traffic routing.The simulation results show that the traffic retention system implemented in thesis can keep its traffic alive after the private network handovered,and the cooperative handover can significantly shorten its offline gap;in the active routing module,compared with the application of single routing algorithm that meets the traffic bandwidth,a mixture application of two methods can achieve a higher proportion of delay-sensitive traffic in all traffic that are routed to the shortest paths based on hop count.