Active hierarchical border gateway protocol routing method and system for low-orbit giant satellite base

Abstract

The invention discloses an active hierarchical boundary gateway protocol routing method and system for a low-orbit giant satellite base, and the method comprises the steps: carrying out the time frame and time slot division, predicting the satellite-ground connection switching in a time frame and the throughput of each satellite, and dividing a satellite network into an entrance and exit satellite region, a backbone region and a non-backbone region; iBGP connection is carried out according to satellite partitions, and routing update is carried out under different time slots according to time slot division decisions; in a time slot in which only a hierarchical convergence mechanism is adopted, the satellites in all the partitions transmit and receive UPDATE messages in a hierarchical manner to exchange routing information so as to achieve whole-network convergence; and in a time slot in which an active routing update mechanism is adopted to assist a hierarchical convergence mechanism, the satellite actively updates routing table entries, and transmits and receives a posterior UPDATE message for verification. According to the method, a hierarchical convergence mechanism is adopted, iBGP connection between satellites can be reduced, message overhead can be reduced, the routing convergence speed can be increased, and an active routing updating mechanism is supplemented, so that the routing convergence time can be further shortened, and the satellite network stability can be improved.

Description

Technical Field

[0001] The present invention relates to the field of satellite network routing technology, and in particular to an active hierarchical border gateway protocol routing method and system for low-orbit giant star constellations. Background Art

[0002] The LEO GIGANTUM network is expected to become one of the most important communication infrastructures due to its great potential in providing low-latency, high-reliability and ubiquitous connectivity services. The development of the LEO GIGANTUM network advances the field of satellite communications. Compared with traditional geosynchronous satellites, LEO satellites operate at lower altitudes, providing global coverage and high backhaul capacity. The LEO GIGANTUM network represents a promising technology that can enable seamless global connectivity and advanced applications to meet the needs of massive communications and personalized user experience in 6G.

[0003] The low-orbit satellite network can be regarded as an independent autonomous domain. Its organic integration with different ground autonomous systems requires the inter-domain routing protocol BGP (Border Gateway Protocol). However, the traditional BGP protocol mainly considers the accuracy of reachable routes and is customized for fixed networks. Directly using traditional BGP in low-orbit satellite networks will lead to network instability, excessive routing overhead, slow convergence and other problems.

[0004] Unlike the relatively fixed topology on the ground, the space network topology is highly dynamic. Frequent changes in the space topology will cause frequent updates of BGP neighbor relationships and destination network segment entries. When the physical link between the border routers of the satellite system is switched, that is, the physical link connection with the opposite satellite system is switched from one border router of the opposite system to another border router, the BGP neighbor relationship between the systems changes, the old BGP neighbor relationship is disconnected, and the BGP entity creates a new neighbor relationship by sending a message. When the destination network segment entry increases / decreases or changes, the BGP entity triggers a routing update, and the routing information needs to be re-flooded throughout the network until convergence. For BGP, instability is a key issue. Problems such as unstable inter-domain neighbor relationships, frequent routing updates, and slow routing convergence will all degrade the stability of the low-orbit satellite network and affect the data plane and control plane. Therefore, it is necessary to optimize traditional BGP in combination with the high dynamics of satellite scale, high-speed node movement, and frequent topology changes in the low-orbit giant constellation scenario.

[0005] Traditional BGP generally adopts the iBGP (Internel BGP, Internal Border Gateway Protocol) connection strategy of full connection and route reflector. The full connection strategy connects iBGP peers in pairs, ensuring global routing optimality in small LANs, generally known as full connection optimality. We usually use it as a reference when evaluating BGP routing, but it is not scalable and cannot be deployed in low-orbit satellite networks. The route reflector strategy reduces iBGP connections to a certain extent, but route reflection may reduce the network's robustness to failures, introduce delayed routing convergence, reduce path diversity, use suboptimal routing, and even cause data forwarding loops.

[0006] After searching the existing literature, it was found that Yang Zengyin et al. published an article titled "NTD-BGP, an Inter-Domain Routing Protocol for Space-Ground Integrated Information Network" in the Journal of Tsinghua University (Science and Technology) in 2019. The article is based on the decoupling of the mapping relationship between network topology and inter-domain neighbor relations and routing updates, and proposes an inter-domain neighbor discovery mechanism that is independent of physical topology changes. However, this mechanism will significantly reduce the interaction efficiency between eBGP (Externel BGP, External Border Gateway Protocol) neighbors, especially when the distance between ground stations and satellites is far.

[0007] After searching the existing literature, it was found that Jinhu Zang et al. published an article titled "A Border Gateway Protocol LRA-BGP for Integrated Satellite-terrestrial Networks" in the 2022 International Conference on Electrical, Mechanical and Computer Engineering (ICEMCE) in 2022. The article proposed a lightweight border gateway protocol (LRA-BGP) suitable for small-scale networks. The border satellites deployed with LRA-BGP will not publish historical routing information to each other after the neighbor relationship is reestablished. The communicating parties realize routing updates by activating backup routing information.

[0008] In summary, these works are a good start as an exploration of BGP optimization, but they all have limitations: (1) In terms of protocol scalability, these works only focus on adaptation under small-scale low-orbit constellations, and do not consider reducing the number of iBGP connections in the low-orbit giant star scenario; (2) In terms of protocol dynamic adaptability, most works lack methods to deal with frequent satellite-ground switching, resulting in network instability; (3) In terms of protocol routing overhead, these works bring additional message overhead and computing cost, and cannot adapt to the low-orbit giant star scenario. Summary of the invention

[0009] Purpose of the invention: In view of the limitations of the prior art, the present invention proposes an active hierarchical border gateway protocol routing method and system for low-orbit giant constellations, so as to achieve fast routing convergence and take into account both protocol overhead and routing stability in the low-orbit giant constellation scenario.

[0010] Technical solution: To achieve the above purpose, the present invention adopts the following technical solution:

[0011] An active hierarchical border gateway protocol routing method for low-orbit giant stars includes the following steps:

[0012] Divide the time frame and time slot, predict the satellite-to-ground connection switching and the throughput of each satellite within a time frame, divide the time frame into several time slots and divide the satellite network into entry and exit satellite areas, backbone areas and non-backbone areas;

[0013] iBGP connections are made based on satellite partitions, and a mechanism for routing updates in different time slots is determined based on time slot division, and a reference table for distributing active routing updates is distributed;

[0014] In the time slot where only the hierarchical convergence mechanism is used, each sub-area satellite hierarchically sends and receives UPDATE messages to exchange routing information to achieve full network convergence. The newly added path attribute iBGP_PATH in the UPDATE message helps hierarchical routing transmission to achieve intra-domain loop prevention.

[0015] In the time slots where the active routing update mechanism is used to assist the hierarchical convergence mechanism, the satellite actively updates the routing table entries and sends and receives a posteriori UPDATE messages for verification.

[0016] Preferably, the satellite network division comprises:

[0017] Within a time frame, satellites involved in satellite-to-ground connection switching are classified as entry and exit satellites, satellites with throughput exceeding a preset threshold are classified as IGP hotspot satellites, and a preset number of backbone satellites are screened out, and the remaining satellites are classified as non-backbone satellites.

[0018] Preferably, the iBGP connection according to the satellite partition includes:

[0019] At the beginning of the time frame, the entry and exit satellites use iBGP connections to connect to the two backbone area satellites that are physically closest; a full connection strategy is used in the backbone area; and non-backbone area satellites are connected to at least one backbone area satellite.

[0020] Preferably, the mechanism for performing route update in different time slots according to the time slot division decision includes:

[0021] The decision hop count is preset according to the constellation scale. If the calculated hop count between the old and new exit / entry satellites is less than the decision hop count, the active routing update mechanism is used to assist the hierarchical convergence mechanism for routing convergence. If the calculated hop count between the old and new exit / entry satellites is greater than or equal to the decision hop count, only the hierarchical convergence mechanism is used for fast routing update.

[0022] The time when the active routing update mechanism is adopted and the old and new exit / entry satellite Router_id pairs are recorded in sequence, where Router_id defaults to the satellite's loopback address, and is distributed to the exit and entry satellites and backbone area satellites at the beginning of the time frame as a reference table entry for active routing updates.

[0023] Preferably, the UPDATE message adds a new path attribute iBGP_PATH to help select the best path and filter the specified route. The path attribute iBGP_PATH displays the ordered sequence of routers Router_id passed during route propagation and is saved in network byte order. The hierarchical convergence mechanism uses the path attribute AS_PATH of traditional BGP to implement inter-domain loop prevention and uses the newly added iBGP_PATH to implement intra-domain loop prevention. When forwarding the UPDATE message, the router first checks whether the Router_id of the local router is in the iBGP_PATH attribute of the message. If so, the message will be discarded. Otherwise, the Router_id of the local router will be added to the iBGP_PATH attribute of the message.

[0024] Preferably, the hierarchical convergence mechanism stipulates that the backbone area adopts the principle of intra-domain horizontal splitting, that is, the routes learned by the backbone area satellite from its iBGP neighbors will not be transmitted to its other iBGP neighbors; the non-backbone area breaks the horizontal splitting rule, and uses the newly added path attribute iBGP_PATH to prevent routing loops and reduce the number of iBGP connections of non-backbone area satellites; UPDATE messages can only be transmitted from the backbone area to the non-backbone area, and the entry and exit satellite areas and the backbone area can transmit UPDATE messages to each other.

[0025] Preferably, the satellite actively updates the routing table entries and sends and receives a posteriori UPDATE messages for verification, including:

[0026] Retrieve the old exit / entry satellite network segment entry of the backbone area satellite BGP routing table, actively update the old exit / entry satellite Router_id in the entry to the new exit / entry satellite Router_id, and save the temporary entry until the new exit / entry satellite network segment under the time slot fails and is removed;

[0027] Add a new route entry of the new exit / entry satellite network segment-new exit / entry satellite Router_id to the backbone area satellite BGP routing table;

[0028] The control entry and exit satellite area sends UPDATE a posteriori messages to the backbone area to verify the active routing update entries. When the update is correct, the process of sending the UPDATE a posteriori messages does not affect the convergence time of the entire network; when an update error occurs, the corresponding routing entry will be corrected to the routing information of the UPDATE a posteriori message and continue to be transmitted through the hierarchical convergence mechanism.

[0029] An active hierarchical border gateway protocol routing system for low-orbit giant stars, comprising:

[0030] A prediction module is used to divide the time frame and time slot, predict the satellite-to-ground connection switching and the throughput of each satellite within a time frame, and divide the satellite network into the entry and exit satellite area, the backbone area and the non-backbone area;

[0031] A decision module is used to make iBGP connections according to satellite partitions, decide the mechanism for performing routing updates in different time slots according to time slot division, and distribute reference tables for active routing updates;

[0032] A hierarchical convergence mechanism implementation module is used for hierarchical transmission and reception of UPDATE messages by satellites in each zone to exchange routing information in a time slot when the hierarchical convergence mechanism is adopted, so as to achieve convergence of the entire network. A newly added path attribute iBGP_PATH in the UPDATE message helps hierarchical transmission of routing to achieve intra-domain loop prevention.

[0033] The active routing update mechanism implementation module is used for actively updating routing table entries by the satellite in the time slot when the active routing update mechanism is used to assist the hierarchical convergence mechanism, and sending and receiving a posteriori UPDATE messages for verification.

[0034] A computer system comprises a memory, a processor and a computer program / instruction stored in the memory and executable on the processor, wherein when the computer program / instruction is executed by the processor, the steps of an active hierarchical border gateway protocol routing method for low-orbiting giant stars are implemented.

[0035] A computer program product includes a computer program / instruction, wherein when the computer program / instruction is executed by a processor, the steps of the active hierarchical border gateway protocol routing method for low-orbit superstar constellations are implemented.

[0036] Beneficial effects: The active hierarchical border gateway protocol routing method and system for low-orbit giant stars provided by the present invention introduces a new intra-domain routing loop prevention and routing transmission mechanism based on the traditional border gateway protocol. Different from the iBGP connection strategies such as full connection and route reflector of traditional BGP, the present invention adopts a hierarchical convergence mechanism based on the innovative path attribute iBGP_PATH; and different from the traditional BGP to achieve routing updates by continuously revoking / re-declaring routing prefixes, the present invention introduces an active routing update mechanism based on satellite-to-ground switching prediction to assist the hierarchical convergence mechanism. Compared with the prior art, the active hierarchical border gateway protocol routing method for low-orbit giant stars proposed by the present invention takes into account both protocol overhead and routing stability, accelerates the routing convergence speed of the network, and improves the adaptability to the large-scale and high dynamics of low-orbit giant stars. At the same time, the present invention also ensures backward compatibility with standard BGP routers. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a framework diagram of a routing system according to an embodiment of the present invention;

[0038] Figure 2 It is a schematic diagram of updating the BGP routing table by the active routing update mechanism in an embodiment of the present invention;

[0039] Figure 3 is a flow chart of a routing method according to an embodiment of the present invention;

[0040] Figure 4 It is a comparison chart of experimental results of the routing method of the embodiment of the present invention. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the embodiments of the present invention are described in detail below in conjunction with the accompanying drawings: This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given. It should be understood that the specific examples described here are only used to explain the present invention, but the protection scope of the present invention is not limited to the following embodiments.

[0042] like Figure 1As shown, an active hierarchical border gateway protocol routing method for low-orbit giant stars disclosed in an embodiment of the present invention first performs time frame and time slot division, predicts satellite-ground connection switching and the throughput of each satellite within a time frame, and divides the satellite network into an entry and exit satellite area, a backbone area, and a non-backbone area; then, iBGP connection is performed according to the satellite partition, and a mechanism for performing route update in different time slots is determined according to the time slot division, and a reference table for active route update is distributed; in a time slot where only a hierarchical convergence mechanism is adopted, each partitioned satellite hierarchically sends and receives UPDATE messages to exchange routing information to achieve full network convergence, and a path attribute iBGP_PATH is added to the UPDATE message to help hierarchical route transmission to achieve intra-domain loop prevention; in a time slot where an active route update mechanism is adopted to assist the hierarchical convergence mechanism, the satellite actively updates the routing table entries, and sends and receives a posteriori UPDATE messages for verification.

[0043] In specific implementation, the snapshot technology based on the existing virtual topology can be used to predict the satellite-to-ground connection switching and the throughput of each satellite in each time frame.

[0044] Figure 3 The following is a flow chart showing the execution of the method described in this embodiment within a time frame. Figure 1 and Figure 3 , the detailed steps of the method described in this embodiment are as follows:

[0045] Step S1, divide the time into several time frames, predict the satellite-to-ground connection switching and the throughput of each satellite in a time frame, divide the time frame into several time slots and divide the satellite network into several areas.

[0046] Specifically, in this step, within a time frame, satellites involved in satellite-to-ground connection switching are divided into entry-exit satellites, high-throughput satellites are divided into IGP (Interior Gateway Protocol) hotspot satellites, and an appropriate number of backbone satellites are selected from them, and the remaining satellites are divided into non-backbone satellites; within a time frame, the time slots of satellite-to-ground connection switching and the new and old entry-exit satellites are saved accordingly.

[0047] Step S2, iBGP connection is performed according to satellite partition, a mechanism for performing route updates in different time slots is determined according to time slot division, and a reference table for active route updates is distributed.

[0048] Specifically, in this step, different iBGP connection methods are set according to the satellite division of the entry and exit satellite area, backbone area and non-backbone area. At the beginning of the time frame, the entry and exit satellite uses iBGP connection to connect to the two backbone area satellites with the closest physical distance. A full connection strategy is adopted in the backbone area to connect all backbone area satellites in pairs. Non-backbone area satellites are connected to at least one backbone area satellite, and additional iBGP connections in the non-backbone area can be introduced according to demand to enhance network robustness.

[0049] The number of decision hops is preset according to the constellation scale. Taking the export satellite as an example, if the calculated number of hops between the old / new export satellites is less than the decision hops, the active routing update mechanism is used to assist the hierarchical convergence mechanism for routing convergence; if the calculated number of hops between the old / new export satellites is greater than or equal to the decision hops, only the hierarchical convergence mechanism is used for rapid routing update; for the entry satellite, the number of hops between the old / new entry satellites is calculated, and the rest is the same.

[0050] The time t when the active routing update mechanism is adopted and the old / new export satellite Router_id pair are recorded in sequence through calculation and screening, where Router_id defaults to the loopback address of the satellite and is distributed to the entry and exit satellites and backbone area satellites at the beginning of the time frame as a reference table entry for active routing update as shown in Table 1.

[0051] Table 1 Reference entries for active routing updates

[0052]

[0053] Step S3, determining the routing update mechanism of the current time slot. When only the hierarchical convergence mechanism is used in the time slot, each subarea satellite hierarchically sends and receives UPDATE messages to exchange routing information to achieve full network convergence.

[0054] In this embodiment, the UPDATE message contains several path attributes to help select the best path and filter the specified route. The hierarchical convergence mechanism introduces an innovative path attribute iBGP_PATH. The path attribute iBGP_PATH is an optional attribute of the UPDATE message and can be set to delivery / non-delivery as needed. The path attribute iBGP_PATH shows the ordered sequence of routers Router_id passed during route propagation and is saved in network byte order.

[0055] In this step, the hierarchical convergence mechanism uses the traditional BGP path attribute AS_PATH to implement inter-domain loop prevention, and uses the newly added iBGP_PATH to implement intra-domain loop prevention. When the router forwards the UPDATE message, it first checks whether the iBGP_PATH attribute of the message contains the local router's Router_id. If so, the message will be discarded. Otherwise, the local router's Router_id will be added to the iBGP_PATH attribute of the message, that is, its loopback address will be added to the beginning of the sequence.

[0056] The backbone area adopts the principle of intra-domain split horizon, that is, the routes learned by the backbone satellite from its iBGP neighbors will not be transmitted to its other iBGP neighbors. The non-backbone area breaks the split horizon rule and uses the newly added path attribute iBGP_PATH to prevent routing loops and reduce the number of iBGP connections of non-backbone satellites.

[0057] The hierarchical convergence mechanism stipulates that UPDATE messages can only be transmitted from the backbone area to the non-backbone area, and the entry and exit satellite areas and the backbone area can transmit UPDATE messages to each other. The above route filtering rules are implemented by modifying the standard BGP filter.

[0058] Step S4: When the active routing update mechanism is used to assist the hierarchical convergence mechanism in this time slot, the satellite actively updates the routing table entries and sends and receives a posteriori UPDATE messages for verification.

[0059] The NEXT_HOP attribute is a necessary attribute of the UPDATE message, indicating the border router leaving / entering an autonomous domain. In this embodiment, the next_hop_self function is enabled for the entry and exit satellite areas, and the NEXT_HOP attribute of the BGP routing table will record the loopback address of the border satellite. When the satellite-to-ground connection switch occurs, taking the exit satellite as an example, the relevant BGP routing entry is updated through routing, and its NEXT_HOP attribute is converted from the Router_id of the old exit satellite to the Router_id of the new exit satellite; the same is true for the entry satellite.

[0060] When the clock system of the backbone satellite detects that the current time t matches a time t0 in the active routing update reference table, the active routing update mechanism will be triggered, such as Figure 2 shown.

[0061] Specifically, in this step, the active routing update mechanism retrieves the old export satellite network segment p of the backbone area satellite BGP routing table. past entry, change the old export satellite loopback address Router_id in the entry past Actively updated to the new export satellite loopback address Router_id new , save the temporary entry until the new exit satellite network segment p under this time slotnew Invalidation removed.

[0062] The active routing update mechanism adds a new export satellite network segment to the backbone area satellite BGP routing table. new - New export satellite loopback address Router_id new The routing entry.

[0063] The active routing update mechanism controls the entry and exit satellite areas to send UPDATE a posteriori messages to the backbone area to verify the active routing update entries. Specifically, when the backbone area receives the message, it searches for the destination network segment in the message. If its NEXT_HOP attribute is consistent with its own BGP routing table, the active routing update result is correct. If not, the corresponding network segment entry in the BGP routing table is updated. When the update is correct, the process of sending the UPDATE a posteriori message does not affect the convergence time of the entire network; when an update error occurs, the corresponding routing entry will be corrected to the routing information of the UPDATE a posteriori message and continue to be transmitted through the hierarchical convergence mechanism;

[0064] In this embodiment, the active routing update mechanism is an aid and supplement to the hierarchical convergence mechanism, and the hierarchical convergence mechanism is used for all cross-region routing information transmission.

[0065] Based on the above, the optimization aspects of the border gateway protocol in the low-orbit giant star constellation of the present invention can be summarized as follows: (1) Scalability: ensuring the scalability of the protocol in the low-orbit giant star constellation, especially minimizing the number of iBGP connections in the satellite network; (2) Dynamic adaptability: adapting to the highly dynamic ground-satellite link switching, improving the convergence speed and maintaining network stability under frequent ground-satellite link changes; (3) Routing overhead: BGP message overhead and computing load, ensuring the above two characteristics while minimizing the additional overhead and computing cost.

[0066] To verify the effect of the present invention, the embodiments of the present invention were tested on a self-developed high-fidelity and high-efficiency satellite Internet system-level simulation platform, comparing the traditional full-connection strategy, route reflector and the method of the present invention, and comparing the performance of the three in terms of iBGP connection number, message overhead, average convergence time and packet loss rate. The experimental results are as follows: Figure 4 As shown, the embodiments of the present invention can effectively reduce the number of iBGP connections and BGP message overhead under different satellite scales, while accelerating the routing convergence speed, and have a significant effect on reducing data forwarding packet loss.

[0067] Based on the same inventive concept, an embodiment of the present invention also discloses an active hierarchical border gateway protocol routing system for low-orbit giant stars, including: a prediction module, used for performing time frame and time slot division, predicting satellite-to-ground connection switching and the throughput of each satellite within a time frame, and dividing the satellite network into entry and exit satellite areas, backbone areas, and non-backbone areas; a decision module, used for performing iBGP connection according to satellite partitions, deciding the mechanism for performing route update in different time slots according to time slot division, and distributing reference tables for active route update; a hierarchical convergence mechanism implementation module, used for hierarchical sending and receiving UPDATE messages by satellites in each partition to exchange routing information in a time slot using a hierarchical convergence mechanism to achieve full network convergence, and a newly added path attribute iBGP_PATH in the UPDATE message helps hierarchical routing transmission to achieve intra-domain anti-loop; an active route update mechanism implementation module, used for actively updating routing table entries by satellites in a time slot using an active route update mechanism to assist the hierarchical convergence mechanism, and sending and receiving a posteriori UPDATE messages for verification.

[0068] Based on the same inventive concept, an embodiment of the present invention also discloses a computer system, including a memory, a processor, and a computer program / instruction stored in the memory and executable on the processor. When the computer program / instruction is executed by the processor, the steps of the active hierarchical border gateway protocol routing method for low-orbit superstar constellations are implemented.

[0069] Based on the same inventive concept, an embodiment of the present invention also discloses a computer program product, including a computer program / instruction, which, when executed by a processor, implements the steps of the active hierarchical border gateway protocol routing method for low-orbit superstar constellations.

[0070] The program / instruction code for implementing the method of the present invention can be written in any combination of one or more programming languages. These programs / instruction codes can be provided to a processor or controller of a general-purpose computer, a special-purpose computer or other programmable data processing device, so that the program / instruction code, when executed by the processor or controller, enables the steps of the method of the present invention to be implemented. The program / instruction code can be executed completely on the machine, partially on the machine, partially on the machine as an independent software package and partially on a remote machine or completely on a remote machine or server. The parts not described in detail in the present invention are all known technologies of those skilled in the art.

[0071] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An active hierarchical border gateway protocol routing method for low-orbit giant stars, characterized in that: The following steps are involved: Divide the time frame and time slot, predict the satellite-to-ground connection switching and the throughput of each satellite within a time frame, and divide the satellite network into entry and exit satellite areas, backbone areas, and non-backbone areas; iBGP connections are made based on satellite partitions, and a mechanism for routing updates in different time slots is determined based on time slot division, and a reference table for distributing active routing updates is distributed; In the time slot where only the hierarchical convergence mechanism is used, each sub-area satellite hierarchically sends and receives UPDATE messages to exchange routing information to achieve full network convergence. The newly added path attribute iBGP_PATH in the UPDATE message helps hierarchical routing transmission to achieve intra-domain loop prevention. In the time slots where the active routing update mechanism is used to assist the hierarchical convergence mechanism, the satellite actively updates the routing table entries and sends and receives a posteriori UPDATE messages for verification.

2. The active hierarchical border gateway protocol routing method for low-orbit giant stars according to claim 1 is characterized in that: The satellite network division includes: Within a time frame, satellites involved in satellite-to-ground connection switching are classified as entry and exit satellites, satellites with throughput exceeding a preset threshold are classified as IGP hotspot satellites, and a preset number of backbone satellites are screened out, and the remaining satellites are classified as non-backbone satellites.

3. The active hierarchical border gateway protocol routing method for low-orbit giant stars according to claim 1 is characterized in that: The iBGP connection according to the satellite partition includes: At the beginning of the time frame, the entry and exit satellites use iBGP connections to connect to the two backbone area satellites that are physically closest; a full connection strategy is used in the backbone area; and non-backbone area satellites are connected to at least one backbone area satellite.

4. The active hierarchical border gateway protocol routing method for low-orbit giant stars according to claim 1 is characterized in that: The mechanism for performing routing updates in different time slots according to time slot division decisions includes: The decision hop count is preset according to the constellation scale. If the calculated hop count between the old and new exit / entry satellites is less than the decision hop count, the active routing update mechanism is used to assist the hierarchical convergence mechanism for routing convergence. If the calculated hop count between the old and new exit / entry satellites is greater than or equal to the decision hop count, only the hierarchical convergence mechanism is used for fast routing update. The time when the active routing update mechanism is adopted and the old and new exit / entry satellite Router_id pairs are recorded in sequence, where Router_id defaults to the satellite's loopback address, and is distributed to the exit and entry satellites and backbone area satellites at the beginning of the time frame as a reference table entry for active routing updates.

5. The active hierarchical border gateway protocol routing method for low-orbit giant stars according to claim 1, characterized in that: The UPDATE message adds a new path attribute iBGP_PATH to help select the best path and filter the specified route. The path attribute iBGP_PATH shows the ordered sequence of routers Router_id passed during route propagation and is saved in network byte order. The hierarchical convergence mechanism uses the path attribute AS_PATH of traditional BGP to implement inter-domain loop prevention and uses the newly added iBGP_PATH to implement intra-domain loop prevention. When forwarding the UPDATE message, the router first checks whether the iBGP_PATH attribute of the message contains the Router_id of the local router. If so, the message will be discarded. Otherwise, the Router_id of the local router will be added to the iBGP_PATH attribute of the message.

6. The active hierarchical border gateway protocol routing method for low-orbit giant stars according to claim 1, characterized in that: The hierarchical convergence mechanism stipulates that the backbone area adopts the principle of intra-domain horizontal splitting, that is, the routes learned by the backbone area satellite from its iBGP neighbors will not be transmitted to its other iBGP neighbors; the non-backbone area breaks the horizontal splitting rule and uses the newly added path attribute iBGP_PATH to prevent routing loops and reduce the number of iBGP connections of non-backbone area satellites; UPDATE messages can only be transmitted from the backbone area to the non-backbone area, and the entry and exit satellite areas and the backbone area can transmit UPDATE messages to each other.

7. The active hierarchical border gateway protocol routing method for low-orbit giant stars according to claim 1, characterized in that: The satellite actively updates the routing table entries and sends and receives a posteriori UPDATE messages for verification, including: Retrieve the old exit / entry satellite network segment entry of the backbone area satellite BGP routing table, actively update the old exit / entry satellite Router_id in the entry to the new exit / entry satellite Router_id, and save the temporary entry until the new exit / entry satellite network segment under the time slot fails and is removed; Add a new route entry of the new exit / entry satellite network segment-new exit / entry satellite Router_id to the backbone area satellite BGP routing table; The control entry and exit satellite area sends UPDATE a posteriori messages to the backbone area to verify the active routing update entries. When the update is correct, the process of sending the UPDATE a posteriori messages does not affect the convergence time of the entire network; when an update error occurs, the corresponding routing entry will be corrected to the routing information of the UPDATE a posteriori message and continue to be transmitted through the hierarchical convergence mechanism.

8. An active hierarchical border gateway protocol routing system for low-orbit giant stars, characterized in that: include: A prediction module is used to divide the time frame and time slot, predict the satellite-to-ground connection switching and the throughput of each satellite within a time frame, and divide the satellite network into the entry and exit satellite area, the backbone area and the non-backbone area; A decision module is used to make iBGP connections according to satellite partitions, decide the mechanism for performing route updates in different time slots according to time slot division, and distribute reference tables for active route updates; A hierarchical convergence mechanism implementation module is used for hierarchical transmission and reception of UPDATE messages by satellites in each zone to exchange routing information in a time slot when the hierarchical convergence mechanism is adopted, so as to achieve convergence of the entire network. A newly added path attribute iBGP_PATH in the UPDATE message helps hierarchical transmission of routing to achieve intra-domain loop prevention. The active routing update mechanism implementation module is used for actively updating routing table entries by the satellite in the time slot when the active routing update mechanism is used to assist the hierarchical convergence mechanism, and sending and receiving a posteriori UPDATE messages for verification.

9. A computer system comprising a memory, a processor, and a computer program / instruction stored in the memory and executable on the processor, characterized in that: When the computer program / instructions are executed by the processor, the steps of the active hierarchical border gateway protocol routing method for low-orbit superstar constellations according to any one of claims 1-7 are implemented.

10. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by the processor, the steps of the active hierarchical border gateway protocol routing method for low-orbit superstar constellations according to any one of claims 1-7 are implemented.

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