Research On Service Continuity Guarantee Mechanism In Satellite Optical Network

With the development of science and society,satellite networks with high coverage capability have been gradually incorporated into the new generation of basic communication networks.Compared with the traditional microwave transmission method,satellite laser communication has the characteristics of high speed and strong anti-interference.Satellite laser networking has become a research hotspot at home and abroad.At present,satellite laser communication usually adopts the separation of transceiver equipment.In the complex and harsh space environment,both transmitting and receiving equipment may fail,which will form a special unidirectional link failure scenario.If there is a unidirectional transmission link between satellites,the unidirectional link cannot be included in the calculation of routing protocols.This not only affects service transmission through the unidirectional link,but also reduces link utilization.In addition,satellite network topology changes frequently,and the interruption of links between satellites will lead to the failure of service transmission path,thus affecting the continuous service transmission.Therefore,based on the network management and control architecture of spatial laser network,this paper proposes the unidirectional link utilization strategy to deal with unidirectional link faults and the pre-rerouting strategy adapted to the dynamic topology of network.The main work of this paper is as follows:The standard OSPF protocol applies only to bidirectional links.When a unidirectional link fails,OSPF cannot identify it and calculates routes by using it.After the study of unidirectional fault and OSPF protocol,this paper proposes an extended state machine adapted to unidirectional link based on the standard state machine of OSPF protocol,and adds two kinds of unidirectional neighbor states:UnidSnd and UnidRcv.Two types of Unidirectional notification messages,Unidirectional and NonUnidirectional,are proposed to complete the information notification of Unidirectional links.At the same time,the structure and processing flow of Hello messages are also adapted to unidirectional links,so as to realize the utilization of OSPF on unidirectional links,and ensure the transmission of services on unidirectional links while improving the utilization of links.Although the real-time motion of satellite results in the dynamic change of network topology,the change is regular.Therefore,the ground management can generate the corresponding link establishment planning table and use it to guide the satellite to adjust the port pointing at each time.In this paper,a pre-reroute strategy is proposed to obtain the link connectivity information between satellites by using the link establishment planning table,so as to calculate the lifetime of each service transmission path.Before the original service path is about to be interrupted,the service traffic is transferred to the new calculated path in advance to realize continuous service transmission and reduce the service data loss caused by the regular motion of the satellite.Based on the relevant design of the network management and control architecture of space laser network,this paper realizes the development of several functional modules such as network management,routing and data forwarding.Use of CPU development board and FPGA board simulation satellite nodes to build a network,test and verify various function or strategies,and verify the performance of the pre-rerouting strategy through OMNeT++ network simulation software,which proves the innovation and applicability of the two strategies,and it has a certain role in promoting the research and development of the follow-up satellite optical network service continuity assurance.