CN116566472A - Dynamic discrete topology-oriented world-wide integrated network wide area routing mechanism - Google Patents
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Abstract
The invention relates to a dynamic discrete topology-oriented world-wide integrated network wide area routing mechanism, which comprises the following steps: step 1: constructing a dynamic discrete topology model, and representing a time-varying topology structure of a satellite network segment in the heaven-earth integrated network; step 2: based on a dynamic discrete topology model, a dynamic discrete topology-oriented space-earth integrated network wide area routing mechanism (Dyna-STN) is provided, and a hierarchical architecture is defined in a management plane to realize Dyna-STN, wherein the hierarchical architecture comprises a dynamic discrete topology management plane and a routing management plane; the dynamic discrete topology management plane maintains dynamic binding relations among the satellite entities, the virtual nodes and the time slots, realizes service migration among the satellite entities, and maintains service continuity of the virtual nodes; the routing management plane deploys an OSPF routing information exchange protocol in the virtual coverage network to realize the routing reachable information exchange between satellite-satellite and satellite-ground nodes and establish a routing table.
Description
Technical Field
The invention relates to a routing mechanism, in particular to a dynamic discrete topology-oriented world-wide area routing mechanism of an integrated network, belonging to the technical field of satellite communication.
Background
The number of users and the variety of services of conventional terrestrial wireless communication systems have increased explosively over the past decade. Future networks are expected to possess more resources than current networks to handle the ever-increasing traffic demands. However, the network capacity and coverage of the ground communication system are limited, and in remote areas such as rural areas, mountain areas, islands, etc., the ground communication system alone cannot provide high-speed and reliable wireless access service. Therefore, development of a new network architecture is needed to accommodate diversified services and applications in different scenarios, and to meet the requirements of different service qualities.
In recent years, the focus of 6G network research has been turned to the development of non-terrestrial networks to facilitate worldwide continuous, ubiquitous, high-capacity connectivity and heterogeneous service support. 6G envisages a three-dimensional heterogeneous architecture in which the ground infrastructure is supplemented by non-ground network elements such as drones, aerial platforms and satellites. These network elements not only provide on-demand, cost-effective coverage in densely populated and non-served areas, but also support relay, backhaul, high-speed mobile, and high-throughput hybrid multiple play services.
The rise of Low Earth Orbit (LEO) satellite networks has attracted considerable attention in both academia and industry. An integrated space-time network (STN) is considered a promising 6G network architecture by interconnecting Satellite segments and terrestrial segments. In particular, satellite segments may seamlessly connect remote areas such as rural, ocean and mountain areas, while densely deployed terrestrial segments may provide high-speed access to users in high demand areas. However, the network design and protocol optimization of STNs are affected by some inherent characteristics, which can present challenges. The present invention analyzes some intrinsic characteristics of STN, mainly including:
(1) Isomerism: STN networks include various wireless communication systems employing different access technologies and network devices, such as satellite communication, microwave communication, and mobile communication. These techniques and devices have different transmission rate, bandwidth, latency, and coverage characteristics, resulting in the isomerism of STNs. In order to realize cooperative control, management, data transmission and interconnection, a network protocol and a management strategy with strong adaptability need to be designed. By integrating the advantages of existing wireless communication systems, different protocols can support different functions or applications, enabling STN heterogeneous networks to provide a variety of packet transmissions. In addition, the STN can select a proper network access technology according to the requirement of the user, and better service is provided.
(2) Self-organization: STN components such as satellites, ground stations, etc. are widely distributed and require automatic configuration, management and maintenance. The self-organization gives a certain intelligence and adaptability to the network, so that the topology structure, configuration and resource utilization rate can be automatically adjusted to adapt to different application scenes and network loads. The ad hoc nature of STNs enables them to implement routing and forwarding functions in an infrastructure environment. The STN merges the multi-layer network, and is connected into various mobile devices, so that the anti-damage capability is high. The method is suitable for military communication, emergency service, disaster recovery and other scenes.
(3) Topology time-varying: the spatial network is composed of a constellation of satellites, interconnected by inter-satellite links. The satellite constellation design determines the uniqueness of the satellite network topology. Dynamic changes in the components and topology of the STN, such as changes in satellite orbit and weather conditions, will affect network performance and reliability. Therefore, the time-varying topology requires a certain adaptability and fault tolerance of the network to cope with various network environments and application scenarios. The establishment of the inter-satellite link not only reduces the dependence of the satellite network on the ground network, but also increases the difficulty of system design and manufacturing cost. The high mobility of satellite nodes results in link transients and instability, and therefore requires the design of dynamically changing routing algorithms and link management strategies. Furthermore, achieving efficient link management and path selection is critical to optimizing STN network performance.
In the prior art ospf+ scheme, the scheme adds state leave on the basis of 7 states of an open shortest path first (Open Shortest Path First, OSPF) protocol state machine, and introduces a topology prediction mechanism. The ospf+ protocol decides whether to trigger route convergence by judging whether the neighbor node is temporarily unreachable or unreachable for a long time, thereby reducing the number of route reconvergences caused by the periodic movement of the satellite.
In the prior art Discrete time topology change aggregation (DT-TCA) scheme, DT-TCA exchanges inter-domain route reachability information via border gateway protocol (Border Gateway Protocol, BGP). In addition, the DT-TCA predicts the possible topology change in a certain time period in the future according to the satellite network operation rule, and aggregates the multiple route updates in the time period into one route update, thereby reducing the route update frequency caused by the network topology change and reducing the route jitter.
The above ospf+ and DT-TCA schemes do not fully address the dynamic topology characteristics of satellite networks and therefore have limitations in handling the overhead caused by satellite network topology dynamics.
In the prior art multi-layer satellite routing (Multilayered Satellite Routing, MLSR) scheme, the scheme proposes a routing protocol based on location information for multi-layer satellite IP networks. In this scheme, the forwarding of data packets in the satellite network relies on an MLSR routing table, which is generated by calculation from high orbit satellites grasping the entire network topology. The topology information of the whole network is transmitted from bottom to top by the low orbit satellite, and after the high orbit satellite collects the complete network topology information, the route calculation can be distributed from top to bottom. To reduce the computational complexity of the routing table and the amount of data transmitted, the MLSR groups the low-orbit satellites according to spatial logical positions and simplifies each group into one virtual node.
The above-mentioned MLSR scheme cannot fully cope with the additional overhead caused by the topology dynamics of the satellite network, nor consider the connectivity between the satellite network and the terrestrial network.
Aiming at the problem of network layer fusion of STN different network segments, the invention provides a wide area routing mechanism oriented to dynamic discrete topology, which aims at realizing interconnection and interworking between satellite network segments and ground network segments. The key of realizing the interconnection and intercommunication of the satellite network segments and the ground network segments is to realize the integration of network layers, and the key of the integration of the network layers is to realize the effective exchange of the route reachability information. While conventional routing information exchange protocols such as OSPF, BGP, etc. may achieve this goal in terrestrial networks, these protocols are not suitable for satellite networks. The main reasons are as follows:
(1) Topology dynamics of satellite network: there are significant differences in the topological features of satellite networks and terrestrial networks. The topological structure of the ground network is relatively stable, and the router nodes are mainly concentrated in areas with higher user density and have smaller relation with energy consumption and distance. The topology of the satellite network is dynamic, and the position of the router node is affected by physical parameters such as satellite orbit. In addition, inter-satellite links in satellite networks may be frequently disconnected and reconnected, resulting in frequent link state advertisement exchanges, high routing recalculation overhead, and slow route convergence. Therefore, it is necessary to study and design a routing protocol and a network architecture more suitable for such a specific environment for the dynamic topology structure of the satellite network, so as to improve the performance of the satellite network, reduce the energy consumption, and provide high-quality services for users.
(2) Connectivity of satellite network with terrestrial network: existing research generally improves routing information exchange protocols in terrestrial networks and deploys into satellite networks. For example, the intra-domain routing protocols OSPF+ protocol and DT-TCA scheme, which are applicable to STN, reduce the routing protocol overhead generated by topology changes by improving the standard routing information exchange protocol. However, in a practical scenario, deploying different routing protocols and implementing routing information interactions in different network segments is quite complex.
In order to cope with topology dynamics and star network segment connectivity challenges caused by the isomerism, self-organization and topology time-varying of STN, the invention provides a wide area routing mechanism facing dynamic discrete topology. The mechanism aims at realizing the integration of the network layers of the satellite network segment and the ground network segment so as to improve the performance of a routing protocol and the forwarding performance of a message in the STN.
Disclosure of Invention
The invention aims at the problems existing in the prior art, provides a dynamic discrete topology-oriented world-to-world integrated network wide area routing mechanism, aims at improving the routing protocol performance, the message forwarding performance and the service continuity, and meets the reliability requirement of STN end-to-end data transmission.
In order to achieve the above purpose, the technical scheme of the invention is as follows, a dynamic discrete topology-oriented world-to-world integration network wide area routing mechanism, the method comprises the following steps:
step 1: and constructing a dynamic discrete topology model, and representing a time-varying topology structure of a satellite network segment in the STN.
Step 2: based on a dynamic discrete topology model, a dynamic discrete topology-oriented space-earth integrated network wide area routing mechanism (dynamic discrete topology oriented wide-area routing mechanism for satellite-terrestrial integrated networks, dyna-STN) is provided. The present invention defines a hierarchical architecture in the management plane to implement Dyna-STN, the hierarchical architecture comprising a dynamic discrete topology management plane and a routing management plane.
In the scheme, the dynamic discrete topology management plane maintains dynamic binding relations among the satellite entities, the virtual nodes and the time slots, so that service migration among the satellite entities is realized, and service continuity of the virtual nodes is maintained. In addition, the invention also provides a data plane connectivity test scheme to ensure that the data plane can normally run after the service migration is completed. The routing management plane deploys an OSPF protocol in the virtual overlay network to realize the routing reachable information exchange between satellite-satellite and satellite-ground nodes and establish a routing table. In addition, the invention provides a message forwarding method facing the virtual overlay network, so as to ensure the correct and efficient forwarding of the data packet in the virtual overlay network.
Further, the dynamic discrete topology model construction process described in step 1 is described as follows:
the dynamic discrete topology model provided by the invention divides the orbit space of satellite operation into a plurality of service cubes. The projection of each service cube onto the earth is a fixed-size grid, called the service cell. There is a one-to-one correspondence between service cubes, service cells and satellite entities.
Further, the Dyna-STN implementation procedure described in step 2 is described as follows:
in order to realize Dyna-STN, the invention constructs a virtual coverage network composed of fixed virtual nodes to shield the topological dynamic property of LEO satellite network. The dynamic discrete topology management plane maintains dynamic binding relation among the virtual nodes, the satellite entities and the time slots, and the routing management plane deploys a routing information exchange protocol in the virtual coverage network to realize reliable transmission of data packets among the terminal devices.
Further, in step 2, the dynamic discrete topology management plane maintains a dynamic binding relationship among the satellite entities, the virtual nodes and the time slots, so as to realize service migration among the satellite entities, maintain service continuity of the virtual nodes, and ensure that the data plane can normally run after service migration is completed through a data plane connectivity test scheme;
The dynamic binding and service migration process is implemented as follows:
set the mark as SID 0 Is identified as SID, into a service cube 1 Is about to leave the virtual node VID 0 The signaling interactions involved in the dynamic binding and service migration process are described as follows:
step 501: satellite node SID 0 Entering a service cube, triggering a mapping inquiry function, and sending a mapping inquiry message to a SID/VID mapping server in a dynamic discrete topology management plane, wherein the message comprises the SID of a current satellite entity 0 To identify the node by the SID/VID mapping server;
step 502: after receiving the mapping inquiry message, the SID/VID mapping server inquires whether a VID corresponding to the current SID exists in the current time slot and the service cube, and if so, the SID/VID mapping relation item is issued to the SID through a response message 0 The method comprises the steps of carrying out a first treatment on the surface of the Otherwise, the SID/VID server distributes a new VID, establishes a mapping relation with the current SID, and then sends the new VID to the satellite node SID 0 A response message is sent informing the VID allocated to the response message,
step 503: satellite node SID 0 After receiving the response message of the SID/VID mapping server, binding the carried VID with the SID of the user, and storing the mapping relation locally so that the mapping relation can be used by the subsequent message forwarding operation. Meanwhile, the new SID/VID mapping relation is stored in the SID of the satellite node 0 Is used to store the data in the local cache of the computer system,
step 504: the SID/VID mapping server, upon identifying a VID serving a virtual node 0 Is SID 1 Thereafter, the SID is transmitted to the satellite node 1 Transmitting a handover command message indicating it to migrate its router state to the satellite node SID 0 The handover command message includes the current satellite node SID 0 SID and VID of (C) so that satellite node SID 1 It is possible to identify to which node its router state needs to be migrated,
step 505: at satellite node SID 1 Transmitting a confirmation message to the SID/VID mapping server to indicate that the handover command message has been received, wherein the confirmation message contains the SID of the satellite node 1 So that the SID/VID mapping server can accurately identify the source of the validation message,
step 506: satellite node SID 1 After receiving the handover command message, the SID is sent to the satellite node 0 Sending a migration request message to inform the mobile station to migrate the router state to the SID of the satellite node 0 Subsequently, a timer with time T is set, and the SID of the satellite node is set 1 A timer is started after the migration request message is sent,
step 507: satellite node SID 0 Receiving SIDs from satellite nodes 1 After the migration request message of (2), suspending the router state on the control plane, so as to perform state migration operation,
Step 508: satellite node SID 0 To satellite node SID 1 Transmitting a migration confirmation message to inform it that it is ready to receive its router state, at which time the satellite node SID 0 Ready to take over the previous satellite node SID 1 Is provided for the service of (a),
if satellite node SID 1 Receipt of SID from satellite node within timeout time T 0 The confirmation message of (1) indicates that the confirmation message is successfully sent, and the SID of the satellite node 1 The timer may be stopped, the router state migration operation continued,
if satellite node SID 1 Failure to receive SID from satellite node within timeout time T 0 If the confirmation message of (a) is received, triggering a timeout timer, and the SID of the satellite node 1 The relocation request message will be resent, and in order to avoid unlimited retransmission of the relocation request message, the maximum retransmission number N may be set. Satellite node SID every time a timeout timer is triggered 1 The number of relocation request messages sent will be checked. If the maximum number of retransmissions N is reached, the satellite node SID 1 Migration operations may be suspended and exceptions reported.
Step 509: satellite node SID 1 Synchronizing its current router state (including routing tables and configuration files) to satellite node SIDs on the control plane 0 ，
Step 510: satellite node SID 0 Receiving satellite node SID 1 After the router status file is sent, the routing table and configuration file thereof on the control plane are updated so that the router status file can be correctly forwarded to the virtual node VID 0 Is a data packet of a (c),
step 511: satellite node SID 0 The router is restarted. At this time, the satellite node SID 0 Can be a virtual node VID 0 The device can work normally and can be used for the automatic control of the electric motor,
step 512: satellite node SID 0 To satellite node SID 1 A message is sent to complete the migration,
step 513: satellite node SID 1 Receiving satellite node SID 0 After the transmitted migration completion message, the router state is cleared, and the self and virtual node VID are released 0 Is used for the binding relation of (a),
step 514: satellite node SID 1 Transmitting a release message to the SID/VID mapping server to delete the SID in the mapping server 1 With VID 0 Is used for the mapping relation entry of (a),
step 515: SID/VID mapping server receives satellite node SID 1 After releasing SID/VID mapping relation message, deleting SID in its database 1 With VID 0 SID/VID mapping relation between the two nodes, and the SID/VID mapping server maintains a virtual node VID 0 To be queried in the future when needed,
the SID/VID dynamic binding and service migration process has been completed so far. SID (SID) 0 The satellite node has successfully replaced the SID 1 Service of satellite node, virtual node VID 0 Is not affected by the traffic of (a). It should be noted that, for simplicity of description, only migration procedures involving two satellite nodes and one virtual node are introduced in the present embodiment. In practical applications, multiple satellite nodes and virtual nodes may be involved, as well as more complex signaling interactions. In the service migration process, the communication reliability between satellite nodes can be ensured to a certain extent by introducing a timeout mechanism, and the migration failure risk caused by network transmission abnormality is reduced.
The invention provides a signaling flow for implementing dynamic binding and service migration between satellite entities, and network elements implementing the flow include a satellite identifier/virtual identifier (Satellite Identifier/Virtual Identifier, SID/VID) mapping server and satellite entities in a dynamic discrete topology management plane. In addition, the invention provides a service migration scheme for control plane/data plane separation, so as to minimize downtime of the virtual nodes and maintain service continuity of the STN.
Further, in step 2, the routing management plane deploys an OSPF routing information exchange protocol in the virtual overlay network to realize the reachable routing information exchange between satellite-satellite and satellite-ground nodes, and establishes a routing table;
Through a message forwarding method facing to the virtual overlay network, the correct and efficient forwarding of the data packet in the virtual overlay network is ensured;
the detailed process of deploying the OSPF routing information exchange protocol is described as follows:
(1) Initializing an OSPF protocol: first, the virtual nodes need to initialize the OSPF protocol in order to establish neighbor relationships and exchange routing information with other virtual nodes in the virtual overlay network, which are uniquely identified by VIDs in the virtual overlay network,
(2) Establishing a neighbor relation: after the initialization of the OSPF protocol is completed, the virtual node discovers the neighbor node and establishes the neighbor relation by sending a Hello message, the Hello message contains important information such as VID of the virtual node, the virtual node which receives the Hello message checks whether the message meets the condition of establishing the neighbor relation, if the message meets the condition, the two parties establish the neighbor relation and begin exchanging routing information, and in order to reduce network overhead, the invention uses a strategy based on distance to select candidate neighbors.
(3) Exchanging link state information: the invention introduces link state prediction and adopts a layered link state notification strategy to reduce the generation and propagation of LSA messages.
(4) Constructing and updating a routing table: when a virtual node receives LSA messages from other nodes and updates a local link state database, the virtual node needs to run Dijkstra algorithm to calculate the shortest path to the other virtual nodes, then establishes or updates a routing table according to the calculation result, in the routing table, each table item contains information such as VID of the destination, router ID of the next-hop virtual node, path cost and the like,
(5) Maintaining a routing table: in the network operation process, if the link state changes, the virtual node needs to resend the LSA message to inform other nodes, the node receiving the LSA message needs to update the local link state database, rerun the Dijkstra algorithm to calculate the shortest path, and then update the routing table.
Through the steps, the route information exchange between the virtual nodes and the construction of the route table can be effectively realized. And the OSPF protocol is adopted as a routing information exchange mechanism, so that the forwarding efficiency and accuracy of the data packet in the virtual overlay network are ensured. In addition, the routing management plane is also responsible for the correct routing of the data packet, and the present invention describes in detail the message forwarding method in the virtual overlay network in embodiment 6.
Further, service migration between the satellite nodes in step 2 is implemented by a novel data plane/control plane separation service migration method, and the specific process is described as follows:
service migration is required between the satellite nodes A and B, and the specific process is described as follows.
Step 601: establishing a tunnel between the satellite node A and the satellite node B for receiving and transmitting the routing message after the control plane migration and before the link migration is completed, ensuring the continuous operation of the control plane in the service migration process,
step 602: the copy router image, the migration control plane mainly comprises the copy router image (routing protocol binary file and network configuration file) and the memory (including the state of all running processes),
step 603: memory copying, which is divided into two rounds, 1) pre-copying, in the first round of copying, copying all pages in the memory to a target control plane, 2) suspending-copying, in the second round of copying, only copying the last round of modified pages, at this stage, the control plane is in a stop state, the pre-copying step reduces the number of pages to be transmitted in the stop and copy stages, thereby reducing the stop time of the control plane,
Step 604: cloning a data plane, wherein the data plane is generated by a control plane, so that a new data plane is generated by directly utilizing the migrated control plane, and it is noted that a certain time is required for generating the data plane, and the data plane of the satellite node A can still forward data traffic in the process of generating the data plane, but the control plane can not send or receive routing messages any more, which means that the control plane is in a stop state. To solve this problem, after the control plane migration is completed, all routing messages sent to satellite node a are rerouted to the control plane of satellite node B through the established tunnel, and to avoid introducing any additional downtime in the control plane, it is necessary to establish a tunnel before the control plane migration (step 601).
Step 605: asynchronous link migration, theoretically, all links can migrate from satellite node a to satellite node B at the end of cloning of the data plane at the same time, however, performing accurate synchronous link migration on all links is challenging and can significantly increase the complexity of the system (because of the need to implement the synchronization mechanism), at which point the data plane of satellite node a can still forward data traffic, thus requiring no new data plane to work immediately, each link on the old data plane can be independent of the other links, implementing asynchronous migration,
Step 606: verifying and activating the new data plane, after the asynchronous link migration is completed, the correctness of the new data plane needs to be verified and activated, the verification process comprises checking whether the FIB entry and the ACL of the new data plane are consistent with the original data plane and whether the link state is normal, after the verification is passed, activating the new data plane and starting normal message forwarding,
step 607: the tunnel is disconnected, after the new data plane is activated and starts to work normally, the tunnel between the satellite node A and the satellite node B can be disconnected, at this time, the service migration process is completed, the satellite node B takes over the service of the satellite node A and ensures the continuity of the service,
further, the data plane connectivity test scheme described in step 2, the detailed procedure is described as follows:
(1) Testing basic connectivity: ICMP request packets are sent from the new data plane to the neighboring nodes using Ping or other similar network diagnostic tools. If an ICMP response packet is received, the basic connectivity is indicated to be good. It is noted that this step only tests the basic communication capabilities between the new data plane and the neighboring nodes.
(2) Testing end-to-end connectivity: paths from the new data plane to other nodes in the network are checked using Traceroute or similar tools. This may help determine if the new data plane is able to forward traffic normally and if there are potential routing problems.
(3) And (3) verifying and forwarding functions: and verifying the forwarding function of the new data plane by sending the test traffic. This includes verifying the correctness of their FIB and ACL. Network monitoring tools may be used to check whether the data packet is forwarded according to the intended route.
(4) Checking the link layer protocol: verify whether the new data plane properly supports link layer protocols (e.g., ethernet, PPP, etc.). The normal operation of the link layer protocol can be ensured by checking parameters such as interface state, speed, duplex setting and the like.
(5) Test control plane protocol: it is checked whether the communication between the new data plane and the control plane is normal. This includes verifying that adjacencies of control plane protocols (e.g., OSPF, BGP, etc.) are properly established and that the routing tables are updated correctly.
(6) Monitoring performance indexes: performance metrics such as delay, throughput, and packet loss rate for the new data plane are collected and analyzed. This helps determine whether the new data plane is able to meet service requirements and performance criteria.
(7) Troubleshooting: if a problem is found during the test, troubleshooting is required to solve the problem. Possible causes include hardware failures, software configuration errors, routing table inconsistencies, etc. And according to the nature of the problem, adopting corresponding measures to repair.
Further, the correct and efficient forwarding of the data packet in the virtual overlay network in the step 2 is realized by a message forwarding method facing to the virtual overlay network, and the detailed process is described as follows:
assume that Host1 wishes to establish communication with Host 2. As shown in fig. 7, the method for forwarding a message provided by the present invention is described below.
Step 701: the Host1 resolves through the DNS server to obtain the IP address of the Host 2.
Step 702: the Host1 constructs a data packet into a normal IP data packet with the IP address acquired from the DNS server as a destination SID and with the IP address allocated to the Host1 by the network as a source SID, and forwards the data packet to the ingress virtual node.
Step 703: the ingress virtual node obtains the VID associated with the destination SID by querying the local SID/VID mapping cache. And if the local buffer memory fails to provide the corresponding mapping relation, sending a mapping inquiry message to the SID/VID mapping resolver. In the process, the ingress virtual node updates its local SID/VID mapping cache as needed.
Step 704: the SID/VID mapping parser processes the mapping query message from the ingress virtual node and looks up the corresponding mapping relationship.
Step 705: the SID/VID mapping resolver sends the mapping relationship to the ingress virtual node.
Step 706: the ingress virtual node adds a Dyna-STN header to the original packet. The Dyna-STN header contains the source VID, destination VID, and other necessary fields. In this way, the data packet is encapsulated in the Dyna-STN header for forwarding in the virtual overlay network.
Step 707: the encapsulated packet is routed in the virtual overlay network according to the VID information in the Dyna-STN header. And the virtual node searches the next-hop virtual node in the routing table according to the destination VID of the data packet. Once the next hop virtual node is found, it forwards the packet to that virtual node. This process continues until the packet reaches the virtual node where the destination VID is located.
Step 708: the data packet arrives at the egress virtual node of the network where the target host is located. The egress virtual node examines the Dyna-STN header of the packet to obtain the source VID and the destination VID. The egress virtual node determines the destination host for the packet based on the destination VID. Next, the egress virtual node deletes the Dyna-STN header from the data packet to recover the data packet.
Step 709: the egress virtual node forwards the decapsulated original data packet to the target Host2.
Compared with the prior art, the invention has the following advantages,
(1) In order to solve the problem of route oscillation caused by satellite network topology dynamics, a virtual coverage network oriented to dynamic discrete topology is constructed by a dynamic discrete topology management plane. Compared with the prior art, the virtual overlay network eliminates the additional overhead brought by topology dynamics to the satellite network, and enables the routing information exchange protocol to be available in the satellite network.
(2) The invention provides a service migration scheme for separating a control plane from a data plane, which reduces the time required by state synchronization among satellite entities, thereby ensuring the service continuity of STN. With the expansion of the satellite network scale, the dynamic discrete topology management plane can effectively manage the dynamic binding relationship between the satellite entity and the virtual node, and ensures the expandability of the STN.
(3) The invention realizes the interconnection and intercommunication between the satellite network and the ground network through the route management plane. The connectivity problem of the satellite network and the ground network is solved while the dynamic characteristics of the satellite network topology are considered. The route management plane exchanges route reachability information and constructs a route table by deploying an OSPF protocol between the virtual node and the ground node so as to improve the performance of the route protocol and the forwarding performance of the message.
Drawings
FIG. 1 is a schematic diagram of a wide area routing mechanism for a dynamic discrete topology oriented hierarchical architecture provided by the present invention;
FIG. 2 is a schematic diagram of a service cube and a service cell in a dynamic discrete model provided by the present invention;
fig. 3 is a topology diagram of an LEO satellite network in a virtual overlay network and an heaven and earth integrated network provided by the present invention;
FIG. 4 is a schematic diagram of the present invention for establishing dynamic binding between a virtual node and a satellite entity;
FIG. 5 is a signaling flow diagram of dynamic binding and service migration of satellite identifiers/virtual identifiers between satellite entities provided by the present invention;
FIG. 6 is a step diagram of a control plane/data plane separated service migration scheme provided by the present invention;
fig. 7 is a schematic diagram of a packet forwarding method in a virtual overlay network according to the present invention.
Detailed Description
In order to enhance the understanding of the present invention, the present embodiment will be described in detail with reference to the accompanying drawings.
Example 1: referring to fig. 1, a dynamic discrete topology oriented world-wide integrated network wide area routing mechanism.
The core idea of implementing a dynamic discrete topology oriented world-wide integrated network wide area routing mechanism is to define a hierarchical architecture in the management plane to implement the proposed Dyna-STN. The hierarchical architecture includes a dynamic discrete topology management plane and a route management plane, as shown in fig. 1.
In a dynamic discrete topology management plane, the present invention builds a dynamic discrete topology model to describe the time-varying topology of the LEO satellite network in the STN. The Dyna-STN superimposes a virtual overlay network composed of fixed virtual nodes on the satellite network, shielding the dynamics of the satellite network topology. The dynamic discrete topology management plane is responsible for maintaining dynamic binding relations between the virtual nodes and the satellite entities in different time slots. In the dynamic discrete topology management plane, the present invention also provides a novel control plane/data plane separated service migration scheme to maintain the service continuity of the virtual nodes.
In the route management plane, the invention deploys an OSPF protocol in a virtual overlay network composed of virtual nodes to realize the exchange of route reachability information between satellite-satellite and satellite-ground network nodes. The Dyna-STN realizes STN routing table construction and data packet forwarding through a routing management plane, and realizes network layer fusion of a satellite network segment and a ground network segment. In particular, in the Dyna-STN scheme provided by the invention, the forwarding and processing of the data packet depend on the virtual node, and the maintenance and updating of the SID/VID mapping relation of the virtual node depend on a dynamic discrete topology management plane. Furthermore, in order to enable packets in the STN to be forwarded and processed correctly, the present invention contemplates interactions between the dynamic discrete topology management plane and the routing management plane in terms of:
(1) Node state switching: the dynamic discrete topology management plane monitors the node positions and connection states in the satellite network in real time and passes these information to the route management plane. And the routing management plane calculates an optimal routing path according to the information, and ensures that the data packet is forwarded along the optimal routing path.
(2) Topology prediction and update: the dynamic discrete topology management plane predicts topology changes in the satellite network, such as satellite orbit changes, inter-satellite link disconnects and reconnects, and communicates these predicted information to the route management plane. The routing management plane adjusts the routing table accordingly, and reduces the influence of topology change on network performance.
(3) And (3) routing strategy adjustment: the routing management plane adjusts the routing policy according to the real-time topology information acquired from the dynamic discrete topology management plane. For example, a stable link or a link with a lower latency is preferred to improve network performance.
(4) Collaboration across network partitions: when there are multiple different network partitions between the satellite network and the ground network, the dynamic discrete topology management plane and the route management plane need to cooperatively process the route information exchange between the partitions. This is achieved by introducing virtual nodes between network partitions in a dynamic discrete topology management plane, while the routing management plane adjusts the routing policies across the partitions according to the state of these virtual nodes.
(5) Load balancing and congestion control: the dynamic discrete topology management plane monitors the load conditions in the network and passes this information to the routing management plane. The latter performs load balancing according to real-time network load conditions and performs congestion control when congestion occurs so as to ensure correct forwarding of data packets.
In the Dyna-STN provided by the invention, the dynamic discrete topology management plane and the routing management plane work cooperatively, so that the performance of the terminal equipment in the STN in terms of routing protocol performance, message forwarding performance and service continuity is improved. Hereinafter, the present invention will specifically describe the implementation procedure of Dyna-STN in connection with example 2, example 3, example 4, example 5 and example 6.
Example 2: dynamic discrete topology management plane
In order to solve the problem of route oscillation caused by dynamic satellite network topology, the dynamic discrete topology management plane constructs a virtual overlay network facing the dynamic discrete topology, eliminates the additional overhead brought by the topology dynamics to the satellite network, and enables a route information exchange protocol to be available in the satellite network. The specific implementation steps of embodiment 2 include:
(1) Dynamic discrete topology modeling
The invention provides a dynamic discrete topology model, which has the following design ideas: 1) The satellite nodes need to communicate with neighboring satellite nodes. In the dynamic discrete topology model, the whole space of satellite operation is divided into a plurality of service cubes, and satellite nodes only communicate with adjacent nodes in the same service cube; 2) The satellite nodes need to communicate with the ground subscribers. The dynamic discrete topology model divides the ground area into several serving cells, and one satellite node communicates with only ground subscribers within the same serving cell. To improve message forwarding performance, the partitioning of the service cubes and the service cells may be dynamically adjusted to accommodate different network conditions. The projection of the service cube on the earth surface is the service unit, and a one-to-one correspondence exists among the service cube, the service unit and the satellite nodes, as shown in fig. 2 and 3.
(2) Construction of virtual overlay networks
According to the network planning, the dynamic discrete topology model deploys a fixed virtual node for each service cube and service cell. When a satellite entity enters a service cube, then the satellite entity serves virtual nodes in the service cube. The virtual nodes are alternately operated by a plurality of satellite entities on the same orbit to realize uninterrupted service. A virtual overlay network consisting of a plurality of virtual nodes is superimposed over the satellite nodes to mask the dynamics of the satellite network topology. Such virtual node-based virtual overlay networks can be maintained if enough satellites are deployed in the same orbit. The topology of the satellite network changes at each time slot, while the topology of the virtual overlay network remains unchanged. In addition, when two satellite entities are handed over, it is also necessary to migrate the data and status of the previous satellite entity to the next satellite entity. To this end, the present invention also provides an efficient service migration scheme, which is described in detail in embodiment 5.
(3) SID/VID dynamic binding and maintenance
The Dyna-STN assigns each satellite entity a unique satellite identifier (Satellite Identifier, SID) that enables it to be uniquely identified within the STN. Similarly, virtual nodes are uniquely identified in the STN by virtual identifiers (Virtual Identifier, VID). The dynamic discrete topology management plane is responsible for maintaining dynamic binding relationships between virtual nodes, satellite entities and timeslots. When a satellite entity enters or leaves a certain service cube, the SID/VID mapping server updates the binding relationship between the virtual node and the satellite entity as required. In order to improve the efficiency of dynamic binding and mapping maintenance, embodiment 4 provides a signaling flow for SID/VID dynamic binding and service migration.
Example 3: route management plane
The dynamic discrete topology management plane abstracts the satellite network into a static network similar to a ground network by maintaining a dynamic binding relationship between the virtual nodes and the satellite entities, thereby eliminating the influence of topology dynamics on the satellite network. The route management plane is responsible for exchanging route reachable information between virtual nodes to ensure correct and efficient transmission of data packets in the virtual overlay network. The functions of the route management plane mainly comprise route table construction and data packet forwarding. The invention realizes the route information interaction between the virtual nodes through the OSPF protocol, and constructs the route table. The detailed procedure is described below:
(1) Initializing an OSPF protocol: first, the virtual nodes need to initialize the OSPF protocol in order to establish neighbor relationships with other virtual nodes in the virtual overlay network and exchange routing information. The virtual nodes are uniquely identified in the virtual overlay network by the VID.
(2) Establishing a neighbor relation: after the initialization of the OSPF protocol is completed, the virtual node discovers the neighbor nodes and establishes the neighbor relation by sending a Hello message, wherein the Hello message contains important information such as VID and the like of the virtual node. The virtual node that received the Hello message checks whether the message satisfies the condition for establishing a neighbor relation. If the condition is satisfied, the two parties establish a neighbor relation and begin exchanging routing information. To reduce network overhead, the present invention uses a distance-based policy to select candidate neighbors.
(3) Exchanging link state information: the virtual nodes exchange link state information by sending link state advertisement (Link State Advertisement, LSA) messages between them. The LSA message contains VID, link information, link overhead, etc. information of the virtual node. The nodes receiving the LSA messages will store these information in a local link state database and forward the LSA messages to other neighboring nodes to ensure that the nodes in the entire network obtain the latest link state information. In order to reduce network overhead, the invention introduces link state prediction and adopts a layered link state notification strategy to reduce the generation and propagation of LSA messages.
(4) Constructing and updating a routing table: when one virtual node receives LSA messages from other nodes and updates the local link state database, dijkstra algorithm needs to be run to calculate the shortest path to other virtual nodes. Then, the virtual node establishes or updates the routing table according to the calculation result. In the routing table, each entry contains information such as VID of the destination, router ID of the virtual node of the next hop, path cost, etc.
(5) Maintaining a routing table: in the network operation process, if the link state changes, the virtual node needs to resend the LSA message to inform other nodes. The nodes receiving the LSA message need to update the local link state database, re-run the Dijkstra algorithm to calculate the shortest path, and then update the routing table.
Through the steps, the route information exchange between the virtual nodes and the construction of the route table can be effectively realized. And the OSPF protocol is adopted as a routing information exchange mechanism, so that the forwarding efficiency and accuracy of the data packet in the virtual overlay network are ensured. In addition, the routing management plane is also responsible for the correct routing of the data packet, and the present invention describes in detail the message forwarding method in the virtual overlay network in embodiment 6.
Example 4: signaling flow for SID/VID dynamic binding and service migration
In the dynamic discrete topology model, as a satellite entity moves in a service cube of a virtual node, services need to be provided to the corresponding virtual node. To ensure that the virtual node can continue to provide service, the subsequent satellite needs to enter the service cube before the previous satellite leaves, synchronizing the relevant data and status information between the two satellite entities. Therefore, the present invention designs SID/VID dynamic binding and service migration signaling flow.
The key network elements involved in dynamic binding and service migration are the satellite nodes and SID/VID mapping servers. The SID/VID mapping server is located in a dynamic discrete topology management plane, maintaining the mapping relationship between all satellite entities, virtual nodes and timeslots, as shown in table 1. In addition, each satellite entity maintains some key information including current SID/VID binding relationships, local SID/VID mapping buffers, routing information bases, lists of available virtual nodes, and three-dimensional coordinate sets of virtual nodes.
| Satellite identifier/virtual identifier/time slot | 1 | 2 | … | T |
| SID 0 | VID 0 | VID 1 | … | VID n |
| SID 1 | VID n | VID 0 | … | VID n-1 |
| … | … | … | … | … |
| SID n | VID 1 | VID 2 | … | VID 0 |
Table 1SID/VID mapping server maintained mapping table
The satellite entities are deployed on the space orbit at fixed distance intervals, three-dimensional coordinates of the satellite entities are acquired by a satellite-borne sensor in each time slot, and whether the current time slot enters a new service cube is judged. After the satellite entity confirms that the service cube enters a new service cube, a query message is sent to a SID/VID mapping server in the dynamic discrete topology management plane, the VID corresponding to the SID of the satellite entity in the current time slot is obtained, and the query message carries the SID of the current satellite entity. After the SID/VID mapping server processes the query message sent by the satellite entity, a response message is sent to the satellite entity, and a new SID/VID mapping relation table item is issued. The satellite node binds the queried VID to its SID and performs service migration with the satellite entity previously leaving the service cube, as shown in fig. 4.
Each satellite node maintains a local SID/VID mapping cache for storing recently bound SID/VID mappings. When a satellite node needs to bind a new SID/VID, it first searches the local cache to determine if the virtual node has been bound. If the corresponding mapping relation is found in the local cache, the satellite node can directly bind by using the mapping relation; otherwise, the satellite node needs to send a query message to the SID/VID mapping server to acquire the VID corresponding to the destination SID. After receiving response message from SID/VID mapping server, satellite entity saves new mapping relation in local buffer memory, and uses the mapping relation. The size and the validity period of the local cache can be configured according to actual requirements so as to balance the relation between query efficiency and cache resources.
To ensure the efficiency and accuracy of SID/VID dynamic binding and service migration, a series of signaling interactions will be performed between satellite entities. The signaling flow of SID/VID dynamic binding and service migration provided by the invention is shown in FIG. 5. Assume that the identification is SID 0 Into the service cube, identified as SID 1 Is about to leave the virtual node VID 0 The signaling interactions involved in the dynamic binding and service migration process are described as follows:
step 501: satellite node SID 0 And entering a service cube, triggering a mapping query function, and sending a mapping query message to a SID/VID mapping server in the dynamic discrete topology management plane. The message contains the current satellite entity SID 0 To identify the node.
Step 502: after receiving the mapping inquiry message, the SID/VID mapping server inquires whether VID corresponding to the current SID exists in the current time slot and the service cube. If so, issuing SID/VID mapping relation entry to SID by response message 0 The method comprises the steps of carrying out a first treatment on the surface of the Otherwise, the SID/VID server distributes a new VID, establishes a mapping relation with the current SID, and then sends the new VID to the satellite node SID 0 And sending a response message to inform the VID allocated to the response message.
Step 503: satellite node SID 0 After receiving the response message of the SID/VID mapping server, binding the carried VID with the SID of the user, and storing the mapping relation locally so that the mapping relation can be used by the subsequent message forwarding operation. At the same time, new SIDsThe VID mapping relation is stored in the SID of the satellite node 0 Is included in the cache.
Step 504: the SID/VID mapping server, upon identifying a VID serving a virtual node 0 Is SID 1 Thereafter, the SID is transmitted to the satellite node 1 Transmitting a handover command message indicating it to migrate its router state to the satellite node SID 0 . The handover command message contains the current SID of the satellite node 0 SID and VID of (C) so that satellite node SID 1 It is possible to identify to which node its router state needs to be migrated.
Step 505: at satellite node SID 1 And sending an acknowledgement message to the SID/VID mapping server to indicate that the handover command message has been received. The confirmation message contains the SID of the satellite node 1 So that the SID/VID mapping server can accurately identify the source of the validation message.
Step 506: satellite node SID 1 After receiving the handover command message, the SID is sent to the satellite node 0 Sending a migration request message to inform the mobile station to migrate the router state to the SID of the satellite node 0 . Subsequently, a timer with time T is set, and the SID of the satellite node is set 1 And starting a timer after the migration request message is sent.
Step 507: satellite node SID 0 Receiving SIDs from satellite nodes 1 After the migration request message, the router state is suspended on the control plane, so that the state migration operation can be performed.
Step 508: satellite node SID 0 To satellite node SID 1 A migration confirmation message is sent to inform it that it is ready to receive its router state. At this time, the satellite node SID 0 Ready to take over the previous satellite node SID 1 Is a service of (a).
If satellite node SID 1 Receipt of SID from satellite node within timeout time T 0 The confirmation message of (1) indicates that the confirmation message is successfully sent, and the SID of the satellite node 1 The timer may be stopped and the router state migration operation may continue.
If satellite node SID 1 In the superNo SID received from satellite node within time T 0 If the confirmation message of (a) is received, triggering a timeout timer, and the SID of the satellite node 1 The relocation request message will be resent. In order to avoid unlimited retransmission of the migration request message, the maximum retransmission times N may be set. Satellite node SID every time a timeout timer is triggered 1 The number of relocation request messages sent will be checked. If the maximum number of retransmissions N is reached, the satellite node SID 1 Migration operations may be suspended and exceptions reported.
Step 509: satellite node SID 1 Synchronizing its current router state (including routing tables and configuration files) to satellite node SIDs on the control plane 0 。
Step 510: satellite node SID 0 Receiving satellite node SID 1 After the router status file is sent, the routing table and configuration file thereof on the control plane are updated so that the router status file can be correctly forwarded to the virtual node VID 0 Is a data packet of a data.
Step 511: satellite node SID 0 The router is restarted. At this time, the satellite node SID 0 Can be a virtual node VID 0 And normally works.
Step 512: satellite node SID 0 To satellite node SID 1 And sending a migration completion message.
Step 513: satellite node SID 1 Receiving satellite node SID 0 After the transmitted migration completion message, the router state is cleared, and the self and virtual node VID are released 0 Is a binding relationship of (a).
Step 514: satellite node SID 1 Transmitting a release message to the SID/VID mapping server to delete the SID in the mapping server 1 With VID 0 Is described.
Step 515: SID/VID mapping server receives satellite node SID 1 After releasing SID/VID mapping relation message, deleting SID in its database 1 With VID 0 SID/VID mapping relation between them. At the same time, the SID/VID mapping server maintains a virtual node VID 0 To be required in the futureCan be queried when needed.
The SID/VID dynamic binding and service migration process has been completed so far. SID (SID) 0 The satellite node has successfully replaced the SID 1 Service of satellite node, virtual node VID 0 Is not affected by the traffic of (a). It should be noted that, for simplicity of description, only migration procedures involving two satellite nodes and one virtual node are introduced in the present embodiment. In practical applications, multiple satellite nodes and virtual nodes may be involved, as well as more complex signaling interactions. In the service migration process, the communication reliability between satellite nodes can be ensured to a certain extent by introducing a timeout mechanism, and the migration failure risk caused by network transmission abnormality is reduced.
The dynamic SID/VID binding and service migration signaling flow provided by the invention can ensure that service continuity is ensured when a satellite entity moves on a space orbit. Meanwhile, by distributing different VIDs and maintaining the mapping relation between the satellite entity and the virtual node, the effective management of the dynamic discrete topology is realized. In the signaling interaction process, the state of the virtual node is temporarily suspended, so that a short downtime is caused. To this end, the present invention provides a control plane/data plane separated service migration scheme to minimize downtime of virtual nodes and to ensure that STNs provide services without interruption. Embodiment 5 describes the service migration process in detail.
Example 5: data plane/control plane separated service migration scheme
In order to ensure that virtual nodes in the virtual overlay network can provide uninterrupted service, the dynamic discrete topology management plane is also responsible for handling service migration between satellite nodes. The invention provides a novel service migration scheme with separated data plane and control plane, which is inspired by network virtualization real-time router migration and aims at reducing downtime of virtual nodes.
In network function virtualization, a virtual network is overlaid on an underlying network, where the underlying network is composed of network nodes and network links, similar to the dynamic discrete topology oriented virtual overlay network provided by the present invention. The invention introduces the concept of a virtual router based on VROOM technology. Virtual routers provide the network virtualization infrastructure and execute on routers (physical substrates). Virtual routers, like virtual machines, can migrate from one physical substrate to another without disrupting traffic or altering the logical topology. The virtual router migration is essentially to copy the virtual router image onto a new physical substrate and stop all current processes before copying information, which is a direct extension of the existing virtual machine migration method. However, the delays and interruptions caused by the data traffic and routing protocols required to complete these steps are unacceptable.
To ensure that the proposed service migration scheme is available in the STN, it must be ensured that the message forwarding function of the data plane is not interrupted during the migration process. Due to the retransmission mechanism designed in the routing protocol, the control plane can tolerate short breaks. Nevertheless, the control plane after migration in the new satellite node must be quickly restarted to ensure that protocol adjacencies with other satellite nodes are not lost.
In the satellite node service migration scheme provided by the invention, splitting the data/control plane and implementing asynchronous migration is considered to minimize virtual node downtime. The inventive solution introduces a software defined network (software defined networking, SDN) architecture that decouples the data plane and the control plane. The control plane of the virtual node is stored in the SDN controller, while the data plane is associated with the physical substrate (satellite node). The data plane state mainly includes forwarding information base (forwarding information base, FIB) entries and access control lists (access control list, ACL). A data plane hypervisor is introduced between the data plane and the control plane, allowing the control plane to migrate between different data planes. The separation of the data plane and the control plane allows the control plane to migrate during service migration, while the data plane operates normally. In addition, to achieve service and link migration for satellite nodes, dynamic binding of FIB of virtual router to underlying interfaces needs to be supported. After migration is complete, the binding needs to be dynamically re-established for the new physical floor. The process of service migration includes router service migration and link migration, as shown in fig. 6. The invention assumes that service migration is required between satellite nodes a and B, and the specific process is described below.
Step 601: and establishing a tunnel. A tunnel is established between the satellite node A and the satellite node B for receiving and transmitting the routing message after the control plane migration and before the link migration is completed. The establishment of the tunnel ensures continuous operation of the control plane during service migration.
Step 602: the router image is replicated. The migration control plane mainly includes the copy router image (routing protocol binary and network configuration files) and memory (including the state of all running processes).
Step 603: and (5) copying the memory. The memory copy is performed in two rounds. 1) Pre-copy. In the first round of copying, all pages in the memory are copied to the target control plane. 2) Pause-copy. In the second round of copying, only the page that was modified in the previous round is copied. At this stage, the control plane is in a shutdown state. The pre-copy step reduces the number of pages that need to be transferred during the stop and copy phases, thereby reducing downtime of the control plane.
Step 604: the data plane is cloned. The data plane may be generated by the control plane, thus generating a new data plane directly with the migrated control plane. It is noted that the generation of the data plane requires a certain time. During the data plane generation process, the data plane of the satellite node a can still forward data traffic, but its control plane can no longer send or receive routing messages, which means that the control plane is in a down state. To solve this problem, after the control plane migration is completed, all routing messages sent to satellite node a are rerouted to the control plane of satellite node B through the established tunnel. To avoid introducing any additional downtime in the control plane, a tunnel needs to be established before the control plane is migrated (step 601).
Step 605: asynchronous link migration. Theoretically, at the end of the data plane cloning, all links can migrate simultaneously from satellite node a to satellite node B. However, performing accurate synchronous link migration on all links is challenging and can significantly increase the complexity of the system (because of the need to implement a synchronization mechanism). At this point, the data plane of satellite node a may still forward data traffic, and thus does not need to work immediately. Each link on the old data plane may implement asynchronous migration independently of the other links.
Step 606: the new data plane is validated and activated. After the asynchronous link migration is completed, the correctness of the new data plane needs to be verified and activated. The validation process includes checking whether FIB entries and ACLs of the new data plane are consistent with the original data plane and whether the link state is normal. After the verification is passed, the new data plane is activated and normal message forwarding is started.
Step 607: the tunnel is disconnected. After the new data plane is activated and starts to work properly, the tunnel between satellite node a and satellite node B may be disconnected. At this time, the service migration process is completed, and the satellite node B takes over the service of the satellite node a and ensures continuity of the service.
In addition, in the asynchronous link migration process of step 605, the present invention adopts a more intelligent link migration policy to ensure important link priority migration and improve the efficiency of the migration process. The steps of the intelligent link migration strategy are described as follows:
1) Analyzing link properties: attribute information of the links is collected, including load conditions, priorities, expected migration times, etc. Such information may be obtained from sources such as link statistics, service level agreements, and the like.
2) Ordering links: and sorting the links according to the collected link attribute information. A weight algorithm may be used to assign a weight value to each link and then rank the links by weight value. The weight algorithm can be adjusted according to actual requirements and scenes so as to meet different priority and performance requirements.
3) Migration links one by one: and migrating the links one by one according to the ordered link sequence. During the migration process, the data plane of the source node is kept in an active state so that data traffic can still be forwarded during the migration process. Meanwhile, the progress and state of the link migration are monitored to ensure smooth progress of the link migration.
4) Updating the link state: and after the link migration is completed, updating the link state information. This may include notifying neighboring nodes, updating routing tables and link state databases, etc.
5) Monitoring a migration process: in the whole migration process, performance indexes of link migration, such as migration time, data loss rate and the like, are monitored. And according to the indexes, the migration strategy is adjusted and optimized to improve the migration efficiency and reduce the influence.
6) And (3) finishing migration: after all links are migrated, the data plane service of the source node is closed gracefully, and resources are released.
In addition, the invention adds some extra steps and consideration on the basis of the service migration scheme, so that the service migration scheme is more perfect and robust. The invention provides a scheme for testing connectivity of a new data plane so as to ensure normal operation of the data plane. The detailed steps for testing connectivity of a new data plane are described below:
1) Testing basic connectivity: ICMP request packets are sent from the new data plane to the neighboring nodes using Ping or other similar network diagnostic tools. If an ICMP response packet is received, the basic connectivity is indicated to be good. It is noted that this step only tests the basic communication capabilities between the new data plane and the neighboring nodes.
2) Testing end-to-end connectivity: paths from the new data plane to other nodes in the network are checked using Traceroute or similar tools. This may help determine if the new data plane is able to forward traffic normally and if there are potential routing problems.
3) And (3) verifying and forwarding functions: and verifying the forwarding function of the new data plane by sending the test traffic. This includes verifying the correctness of their FIB and ACL. Network monitoring tools may be used to check whether the data packet is forwarded according to the intended route.
4) Checking the link layer protocol: verify whether the new data plane properly supports link layer protocols (e.g., ethernet, PPP, etc.). The normal operation of the link layer protocol can be ensured by checking parameters such as interface state, speed, duplex setting and the like.
5) Test control plane protocol: it is checked whether the communication between the new data plane and the control plane is normal. This includes verifying that adjacencies of control plane protocols (e.g., OSPF, BGP, etc.) are properly established and that the routing tables are updated correctly.
6) Monitoring performance indexes: performance metrics such as delay, throughput, and packet loss rate for the new data plane are collected and analyzed. This helps determine whether the new data plane is able to meet service requirements and performance criteria.
7) Troubleshooting: if a problem is found during the test, troubleshooting is required to solve the problem. Possible causes include hardware failures, software configuration errors, routing table inconsistencies, etc. And according to the nature of the problem, adopting corresponding measures to repair.
Through the above steps, the new data plane connectivity test scheme of embodiment 5 can ensure the normal operation of the data plane in the migration process, thereby providing more stable and efficient network services for users.
Example 6: message forwarding method for virtual overlay network
In order to ensure the correct and efficient transmission of data packets in a dynamic discrete topology network, the invention provides an innovative message forwarding method. Compared with the prior art, the invention enables the data transmission between the source host and the target host to be more efficient and accurate by redesigning the data package format and the route in the virtual overlay network.
The main network element involved in message forwarding comprises: the system comprises a source host, an entry virtual node, a SID/VID mapping parser, a virtual node, an exit virtual node and a destination host.
The ground network data message format includes: original IP header and payload. In the present invention we introduce a new encapsulation format, the Dyna-STN header. The Dyna-STN header contains the source VID, destination VID, and other necessary fields. By adding a Dynabeads-STN header, the data packet can be routed correctly in the virtual overlay network.
The format of the datagram containing the original IP header is described as follows:
| Source SID | Destination SID | Payload |
The format of the datagram containing the Dyna-STN header is described as follows:
| source VID | Destination VID | Source SID | Destination SID | Payload |
Assume that Host1 wishes to establish communication with Host 2. As shown in fig. 7, the method for forwarding a message provided by the present invention is described as follows:
step 701: the Host1 resolves through the DNS server to obtain the IP address of the Host 2.
Step 702: the Host1 constructs a data packet into a normal IP data packet with the IP address acquired from the DNS server as a destination SID and with the IP address allocated to the Host1 by the network as a source SID, and forwards the data packet to the ingress virtual node.
Step 703: the ingress virtual node obtains the VID associated with the destination SID by querying the local SID/VID mapping cache. And if the local buffer memory fails to provide the corresponding mapping relation, sending a mapping inquiry message to the SID/VID mapping resolver. In the process, the ingress virtual node updates its local SID/VID mapping cache as needed.
Step 704: the SID/VID mapping parser processes the mapping query message from the ingress virtual node and looks up the corresponding mapping relationship.
Step 705: the SID/VID mapping resolver sends the mapping relationship to the ingress virtual node.
Step 706: the ingress virtual node adds a Dyna-STN header to the original packet. The Dyna-STN header contains the source VID, destination VID, and other necessary fields. In this way, the data packet is encapsulated in the Dyna-STN header for forwarding in the virtual overlay network.
Step 707: the encapsulated packet is routed in the virtual overlay network according to the VID information in the Dyna-STN header. And the virtual node searches the next-hop virtual node in the routing table according to the destination VID of the data packet. Once the next hop virtual node is found, it forwards the packet to that virtual node. This process continues until the packet reaches the virtual node where the destination VID is located.
Step 708: the data packet arrives at the egress virtual node of the network where the target host is located. The egress virtual node examines the Dyna-STN header of the packet to obtain the source VID and the destination VID. The egress virtual node determines the destination host for the packet based on the destination VID. Next, the egress virtual node deletes the Dyna-STN header from the data packet to recover the data packet.
Step 709: the egress virtual node forwards the decapsulated original data packet to the target Host2.
According to the message forwarding method for the virtual overlay network, which is provided by the embodiment, by redesigning the message encapsulation format and the route in the virtual overlay network, the high efficiency and the accuracy of data transmission between the source host and the target host are ensured.
It should be noted that the above-mentioned embodiments are not intended to limit the scope of the present invention, and equivalent changes or substitutions made on the basis of the above-mentioned technical solutions fall within the scope of the present invention as defined in the claims.
Claims (8)
1. A dynamic discrete topology oriented world-wide integrated network wide area routing mechanism, the method comprising the steps of:
step 1: constructing a dynamic discrete topology model, and representing a time-varying topology structure of a satellite network segment in the heaven-earth integrated network;
step 2: based on a dynamic discrete topology model, a dynamic discrete topology-oriented world-wide integrated network wide area routing mechanism (dynamic discrete topology oriented wide-area routing mechanism for satellite-terrestrial integrated networks, dyna-STN) is provided, and a hierarchical architecture is defined in a management plane to realize Dyna-STN, wherein the hierarchical architecture comprises a dynamic discrete topology management plane and a routing management plane.
2. The dynamic discrete topology-oriented world-wide-area network routing mechanism of claim 1, wherein the dynamic discrete topology model construction process in step 1 is as follows: the dynamic discrete topological model divides the orbit space of the satellite operation into a plurality of service cubes, the projection of each service cube on the earth is a grid with a fixed size, the grid is called a service cell, and a one-to-one correspondence exists among the service cubes, the service cells and the satellite entities.
3. The dynamic discrete topology-oriented world-wide-area network routing mechanism of claim 1, wherein the Dyna-STN implementation procedure in step 2 is described as follows: constructing a virtual overlay network composed of fixed virtual nodes to shield the topology dynamic property of the LEO satellite network, maintaining a dynamic binding relation among the virtual nodes, the satellite entities and the time slots by a dynamic discrete topology management plane, realizing service migration among the satellite entities, deploying an OSPF (open shortest path first) routing information exchange protocol in the virtual overlay network by a routing management plane, establishing a routing table and responsible for forwarding data messages, and realizing reliable transmission of data packets among terminal devices; periodic interactions between the dynamic discrete topology management plane and the routing management plane include node state switching, topology prediction and updating, routing policy adjustment, cross-network partition collaboration, and load balancing and congestion control.
4. The space-earth integrated network wide area routing mechanism for dynamic discrete topology according to claim 3, wherein in step 2, the dynamic discrete topology management plane maintains dynamic binding relations among satellite entities, virtual nodes and time slots, service migration among satellite entities is realized, service continuity of the virtual nodes is maintained, and through a data plane connectivity test scheme, normal operation of a data plane after service migration is completed is ensured;
The dynamic binding and service migration process is implemented as follows:
set the mark as SID 0 Is identified as SID, into a service cube 1 Is about to leave the virtual node VID 0 The signaling interactions involved in the dynamic binding and service migration process are described as follows:
step 501: satellite node SID 0 Entering a service cube, triggering a mapping inquiry function, and sending a mapping inquiry message to a SID/VID mapping server in a dynamic discrete topology management plane, wherein the message comprises the SID of a current satellite entity 0 To identify the node by the SID/VID mapping server;
step 502: after receiving the mapping inquiry message, the SID/VID mapping server inquires whether a VID corresponding to the current SID exists in the current time slot and the service cube, and if so, the SID/VID mapping relation item is issued to the SID through a response message 0 The method comprises the steps of carrying out a first treatment on the surface of the Otherwise, the SID/VID server distributes a new VID, establishes a mapping relation with the current SID, and then sends the new VID to the satellite node SID 0 A response message is sent informing the VID allocated to the response message,
step 503: satellite node SID 0 After receiving the response message of the SID/VID mapping server, binding the carried VID with the SID of the user, and storing the mapping relation locally so that the mapping relation can be used by the subsequent message forwarding operation, and simultaneously, storing the new SID/VID mapping relation in the SID of the satellite node 0 Is used to store the data in the local cache of the computer system,
step 504: the SID/VID mapping server, upon identifying a VID serving a virtual node 0 Is SID 1 Thereafter, the SID is transmitted to the satellite node 1 Transmitting a handover command message indicating it to migrate its router state to the satellite node SID 0 The handover command message includes the current satellite node SID 0 SID and VID of (C) so that satellite node SID 1 It is possible to identify to which node its router state needs to be migrated,
step 505: at satellite node SID 1 Transmitting a confirmation message to the SID/VID mapping server to indicate that the handover command message has been received, wherein the confirmation message contains the SID of the satellite node 1 So that the SID/VID mapping server can accurately identify the source of the validation message,
step 506: satellite node SID 1 After receiving the handover command message, the SID is sent to the satellite node 0 Sending a migration request message to inform the mobile station to migrate the router state to the SID of the satellite node 0 Subsequently, a timer with time T is set, and the SID of the satellite node is set 1 A timer is started after the migration request message is sent,
step 507: satellite node SID 0 Receiving SIDs from satellite nodes 1 After the migration request message of (2), suspending the router state on the control plane, so as to perform state migration operation,
Step 508: satellite node SID 0 To satellite node SID 1 Transmitting a migration confirmation message to inform it that it is ready to receive its router state, at which time the satellite node SID 0 Ready to take over the previous satellite node SID 1 Is provided for the service of (a),
if satellite node SID 1 Receiving from the satellite node within the timeout period TPoint SID 0 The confirmation message of (1) indicates that the confirmation message is successfully sent, and the SID of the satellite node 1 The timer may be stopped, the router state migration operation continued,
if satellite node SID 1 Failure to receive SID from satellite node within timeout time T 0 If the confirmation message of (a) is received, triggering a timeout timer, and the SID of the satellite node 1 To resend the relocation request message, a maximum number of retransmissions N may be set, in order to avoid unlimited retransmissions of the relocation request message, whenever a timeout timer is triggered, the satellite node SID 1 The number of transmitted relocation request messages will be checked, if the maximum number of retransmissions N is reached, the satellite node SID 1 The migration operation may be suspended and an abnormal situation reported,
step 509: satellite node SID 1 Synchronizing its current router state (including routing tables and configuration files) to satellite node SIDs on the control plane 0 ，
Step 510: satellite node SID 0 Receiving satellite node SID 1 After the router status file is sent, the routing table and configuration file thereof on the control plane are updated so that the router status file can be correctly forwarded to the virtual node VID 0 Is a data packet of a (c),
step 511: satellite node SID 0 Restarting the router, at this point, the satellite node SID 0 Can be a virtual node VID 0 The device can work normally and can be used for the automatic control of the electric motor,
step 512: satellite node SID 0 To satellite node SID 1 A message is sent to complete the migration,
step 513: satellite node SID 1 Receiving satellite node SID 0 After the transmitted migration completion message, the router state is cleared, and the self and virtual node VID are released 0 Is used for the binding relation of (a),
step 514: satellite node SID 1 Transmitting a release message to the SID/VID mapping server to delete the SID in the mapping server 1 With VID 0 Is used for the mapping relation entry of (a),
step 515: SID/VID mapping server receives satellite node SID 1 Is to release SID/VID mapping relationAfter the message is tied, the SID is deleted from its database 1 With VID 0 SID/VID mapping relation between the two nodes, and the SID/VID mapping server maintains a virtual node VID 0 To be queried in the future when needed,
the SID/VID dynamic binding and service migration process has been completed so far.
5. The dynamic discrete topology-oriented world-wide-area network routing mechanism of claim 4, wherein service migration between satellite nodes in step 2 is implemented by a novel data plane/control plane separation service migration method, and the specific process is described as follows: the specific process of service migration between the satellite nodes A and B is described as follows:
step 601: establishing a tunnel between the satellite node A and the satellite node B for receiving and transmitting the routing message after the control plane migration and before the link migration is completed, ensuring the continuous operation of the control plane in the service migration process,
step 602: the copy router image, the migration control plane mainly comprises the copy router image (routing protocol binary file and network configuration file) and the memory (including the state of all running processes),
step 603: memory copying, which is divided into two rounds, 1) pre-copying, in the first round of copying, copying all pages in the memory to a target control plane, 2) suspending-copying, in the second round of copying, only copying the last round of modified pages, at this stage, the control plane is in a stop state, the pre-copying step reduces the number of pages to be transmitted in the stop and copy stages, thereby reducing the stop time of the control plane,
Step 604: cloning the data plane, the data plane is generated by the control plane, so that the control plane after migration is directly utilized to generate a new data plane, after the control plane migration is completed, all the routing messages sent to the satellite node A are rerouted to the control plane of the satellite node B through the established tunnel,
step 605: asynchronous link migration, all links can migrate from satellite node a to satellite node B simultaneously at the end of the cloning of the data plane, however, performing accurate synchronous link migration on all links is challenging and can significantly increase the complexity of the system (because of the need to implement the synchronization mechanism), at which time the data plane of satellite node a can still forward data traffic, thus requiring no new data plane to work immediately, each link on the old data plane can be independent of the other links, implementing asynchronous migration,
step 606: verifying and activating the new data plane, after the asynchronous link migration is completed, the correctness of the new data plane needs to be verified and activated, the verification process comprises checking whether the FIB entry and the ACL of the new data plane are consistent with the original data plane and whether the link state is normal, after the verification is passed, activating the new data plane and starting normal message forwarding,
Step 607: and (3) disconnecting the tunnel, and after the new data plane is activated and starts to work normally, disconnecting the tunnel between the satellite node A and the satellite node B, wherein the service migration process is completed, and the satellite node B takes over the service of the satellite node A and ensures the continuity of the service.
6. The dynamic discrete topology-oriented world-wide-area network routing mechanism of claim 4, wherein the data plane connectivity test scheme in step 2 is described as follows:
(1) Testing basic connectivity: using Ping or other similar network diagnostic tools, an ICMP request packet is sent from the new data plane to the neighboring node, and if an ICMP response packet is received, indicating that the basic connectivity is good,
(2) Testing end-to-end connectivity: using Traceroute or similar tools, the path from the new data plane to other nodes in the network is checked, which can help determine if the new data plane is able to forward traffic normally, and if there are potential routing problems,
(3) And (3) verifying and forwarding functions: by sending test traffic, the forwarding function of the new data plane is verified, including verifying the correctness of its FIB and ACL, using network monitoring tools to check whether the data packet is forwarded according to the intended route,
(4) Checking the link layer protocol: verifying whether the new data plane supports the link layer protocol correctly, can ensure that the link layer protocol works properly by checking parameters such as interface status, rate and duplex settings,
(5) Test control plane protocol: checking whether the communication between the new data plane and the control plane is normal, which includes verifying whether the adjacencies of control plane protocols (e.g.ospf, BGP, etc.) are established normally, and whether the routing table is updated correctly,
(6) Monitoring performance indexes: collecting and analyzing performance metrics of the new data plane, including delay, throughput, and packet loss rate, which helps determine whether the new data plane can meet service requirements and performance criteria;
(7) Troubleshooting: if a problem is found in the test process, troubleshooting is needed to solve the problem, and possible reasons include hardware faults, software configuration errors and inconsistent routing tables, and corresponding measures are taken to repair according to the nature of the problem.
7. The dynamic discrete topology-oriented world-wide integrated network wide area routing mechanism of claim 3, wherein in step 2, the routing management plane deploys an OSPF routing information exchange protocol in the virtual overlay network, realizes routing reachable information exchange between satellite-satellite and satellite-ground nodes, and establishes a routing table; through a message forwarding method facing to the virtual overlay network, the correct and efficient forwarding of the data packet in the virtual overlay network is ensured;
The detailed process of deploying the OSPF routing information exchange protocol is described as follows:
(1) Initializing an OSPF protocol: first, the virtual nodes need to initialize the OSPF protocol in order to establish neighbor relationships and exchange routing information with other virtual nodes in the virtual overlay network, which are uniquely identified by VIDs in the virtual overlay network,
(2) Establishing a neighbor relation: after the initialization of the OSPF protocol is completed, the virtual node discovers the neighbor node and establishes the neighbor relation by sending a Hello message, the Hello message contains important information such as VID of the virtual node, the virtual node which receives the Hello message checks whether the message meets the condition of establishing the neighbor relation, if the condition is met, the two parties establish the neighbor relation and begin exchanging routing information,
(3) Exchanging link state information: the virtual nodes exchange link state information by sending link state advertisement (Link State Advertisement, LSA) messages, the LSA messages contain VID, link information, link overhead and other information of the virtual nodes, the nodes receiving the LSA messages store the information in a local link state database and forward the LSA messages to other neighbor nodes, so as to ensure that the nodes in the whole network obtain the latest link state information,
(4) Constructing and updating a routing table: when a virtual node receives LSA messages from other nodes and updates a local link state database, the virtual node needs to run Dijkstra algorithm to calculate the shortest path to the other virtual nodes, then establishes or updates a routing table according to the calculation result, in the routing table, each table item contains information such as VID of the destination, router ID of the next-hop virtual node, path cost and the like,
(5) Maintaining a routing table: in the network operation process, if the link state changes, the virtual node needs to resend the LSA message to inform other nodes, the node receiving the LSA message needs to update the local link state database, rerun the Dijkstra algorithm to calculate the shortest path, and then update the routing table.
8. The dynamic discrete topology-oriented world-wide-area routing mechanism of the integrated network according to claim 7, wherein the correct and efficient forwarding of the data packet in the virtual overlay network in step 2 is implemented by a message forwarding method oriented to the virtual overlay network, and the detailed process is described as follows:
assuming that Host1 wishes to establish communication with Host2, the message forwarding method provided is described as follows:
Step 701: the Host1 resolves through the DNS server, obtains the IP address of the Host2,
step 702: the Host1 constructs a packet into a normal IP packet with the IP address acquired from the DNS server as a destination SID, with the IP address assigned to it by the network in which the Host1 is located as a source SID, and forwards it to the ingress virtual node,
step 703: the portal virtual node obtains the VID associated with the destination SID by querying the local SID/VID mapping cache, and if the local cache fails to provide the corresponding mapping relationship, sends a mapping query message to the SID/VID mapping parser, in the process, the portal virtual node updates its local SID/VID mapping cache as needed,
step 704: the SID/VID mapping parser processes the mapping query message from the ingress virtual node, and looks up the corresponding mapping relationship,
step 705: the SID/VID mapping resolver sends the mapping relationship to the ingress virtual node,
step 706: the ingress virtual node adds a Dyna-STN header to the original packet, which contains the source VID, destination VID, and other necessary fields, so that the packet is encapsulated in the Dyna-STN header for forwarding in the virtual overlay network,
Step 707: the encapsulated data packet is routed in the virtual overlay network according to VID information in the Dyna-STN header, the virtual node searches a next-hop virtual node in a routing table according to the destination VID of the data packet, and once the next-hop virtual node is found, the data packet is forwarded to the virtual node, and the process is continued until the data packet reaches the virtual node where the destination VID is located;
step 708: the data packet arrives at the egress virtual node of the network where the destination host is located, the egress virtual node examines the Dynabar-STN header of the data packet to obtain a source VID and a destination VID, based on the destination VID, the egress virtual node determines the destination host for the data packet, and then the egress virtual node deletes the Dynabar-STN header from the data packet to recover the data packet,
step 709: the egress virtual node forwards the decapsulated original data packet to the target Host2.
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