Pre-re-routing method based on extended ospf protocol

Abstract

The application discloses a pre-re-routing method based on an extended OSPF protocol, comprising the following steps: extending the OSPF protocol, including extending a link state advertisement (LSA) and optimizing a constrained shortest path first (CSPF) routing algorithm, so as to calculate a transmission route according to a service requirement; using an RSVP-TE protocol to establish a label switched path (LSP) carrying a remaining validity time; based on the remaining validity time of the LSP, triggering a pre-re-routing strategy by comparing the remaining validity time with a remaining transmission time of the service and a preset time threshold, establishing a new LSP before an old LSP is interrupted after triggering, and switching the service transmission to the new LSP; and the preset time threshold is set to be greater than a longest time required for LSP calculation and establishment in a network. The application can solve the problems of diversified QoS requirements in a complex service scenario and service transmission interruption caused by predictable interruption of an inter-satellite link due to relative motion between satellites or a sun eclipse.

Description

Technical Field

[0001] This invention relates to the field of satellite communication network technology, and in particular to a pre-rerouting method based on the extended OSPF protocol. Background Technology

[0002] With the continuous evolution and development of wireless network communication technology, the number of mobile data services and user devices has entered a phase of explosive growth. To meet the resulting communication demands, integrated space-ground information networks have emerged. The components of an integrated space-ground network mainly include space-based networks, airborne access networks, terrestrial networks, and communication links connecting these networks. Compared to terrestrial networks, space-based networks, i.e., satellite networks, have technological advantages such as longer transmission distances, no geographical limitations, and larger transmission capacity. They can provide all-weather, all-area, and all-coverage communication services, ensuring the continuous and stable operation of network services such as regional monitoring, weather forecasting, and emergency rescue. Therefore, satellite networks have gradually become one of the most core components of integrated space-ground information networks.

[0003] Currently, satellite network communication technology is maturing, but the routing protocols and algorithms used in current satellite networks cannot meet the increasingly diverse Quality of Service (QoS) and service robustness requirements. The Open Shortest Path First (OSPF) protocol, widely used in satellite networks, employs Dijkstra's algorithm for route calculation. This algorithm primarily focuses on the shortest path in the topology, neglecting other network constraints. Therefore, when faced with differentiated QoS requirements from various services, OSPF alone cannot achieve route classification and calculation for different services. Furthermore, due to the high dynamism of satellite constellations, the high-speed relative motion of satellite nodes and natural factors such as solar interference can cause predictable interruptions in inter-satellite links.

[0004] To address this issue, the industry commonly employs a method of pre-establishing backup paths for critical nodes or links to protect service transmission. This approach is known as the Fast Rerouting (FRR) strategy. For example, the paper "Enhanced Bit Repair IP FastReroute Mechanism for Rapid Network Recovery" (Applied Sciences, 2021, 11(7):3133) proposes an IP-based Fast Rerouting strategy. This strategy can ensure service transmission by establishing backup paths for critical IP services or critical nodes. Its advantage lies in effectively avoiding service transmission interruptions caused by inter-satellite link failures. However, this strategy cannot provide comprehensive protection for all nodes or links in the entire satellite network. Furthermore, under the Multiprotocol Label Switching (MPLS) protocol architecture, the establishment and maintenance of Label Switched Paths (LSPs) consume significant bandwidth resources and signaling overhead, making this strategy prone to wasting satellite network resources. Therefore, for the problem of predictable inter-satellite link interruptions, there is an urgent need for a resource-efficient mechanism to address service transmission protection in the event of predictable interruptions in all inter-satellite links across the network.

[0005] Chinese invention patent CN103746915A discloses a differentiated services-based routing method. Specifically, it relates to QoS and routing technologies in the communications field. This method improves the OSPF routing protocol, collects network topology and QoS parameter information, and combines this with the characteristics of service QoS requirements to select routes using different strategies. However, this method primarily focuses on differentiated services QoS routing, without considering link lifetime or proposing a proactive defensive rerouting mechanism for predictable link interruptions in satellite network scenarios.

[0006] Chinese invention patent CN119109861A discloses an adaptive link construction method and system based on OSPF and oriented towards service QoS requirements. It integrates QoS parameters by extending OSPF LSA messages and uses the SPF algorithm to dynamically adjust weights according to service requirements to calculate the optimal path. However, this method does not consider link interruption time as an LSA extension parameter, nor does it introduce the RSVP-TE protocol to establish LSPs carrying lifetimes, lacking a systematic design for a pre-rerouting strategy before link interruption.

[0007] Therefore, there is an urgent need for a pre-rerouting method based on the extended OSPF protocol to address the diverse QoS requirements in complex business scenarios and the problem of predictable interruptions in inter-satellite links due to factors such as relative motion between satellites or solar interference, which can lead to service transmission interruptions. Summary of the Invention

[0008] To address the problems existing in the prior art, the present invention aims to provide a pre-rerouting method based on the extended OSPF protocol, which solves the problems of diverse QoS requirements in complex service scenarios and the problem of predictable interruptions in inter-satellite links due to factors such as relative motion between satellites or solar interference, thus causing service transmission interruptions.

[0009] To achieve the above-mentioned objectives, this invention provides a pre-rerouting method based on the extended OSPF protocol, comprising the following steps:

[0010] Step S1: Extend the OSPF protocol, including extending Link State Advertisement (LSA) and optimizing the Constrained Shortest Path First (CSPF) routing algorithm, to calculate transmission routes according to service requirements;

[0011] Step S2: Establish a Label Switching Path (LSP) carrying the remaining validity time using the RSVP-TE protocol;

[0012] Step S3: Based on the remaining valid time of the LSP, the pre-rerouting policy is triggered by comparing it with the remaining service transmission time and a preset time threshold. After triggering, a new LSP is established before the old LSP is interrupted, and the service transmission is switched to the new LSP.

[0013] The preset time threshold is set to be greater than the maximum time required for LSP calculation and establishment in the network.

[0014] According to one technical solution of the present invention, the extension of the OSPF protocol in step S1 includes:

[0015] Step S11: Add the link interruption time field and the link remaining available bandwidth field to the LSA;

[0016] The value of the link interruption time field is obtained by the node from the link establishment planning table.

[0017] According to one technical solution of the present invention, the optimized CSPF routing algorithm in step S1 includes:

[0018] Step S12: When the controller receives a new service transmission instruction, it triggers the routing calculation process;

[0019] Step S13: Calculate the link metric value using the link bandwidth-based metric calculation method, and select links in ascending order of metric value using the Shortest Path First (SPF) algorithm.

[0020] Step S14: Check whether the remaining effective bandwidth of the selected link meets the service transmission requirements. If it does, continue to step S15; otherwise, return to step S13.

[0021] Step S15: Check if the selected link can reach the destination node. If it can, continue to step S16; otherwise, return to step S13.

[0022] Step S16: Use a new metric calculation formula that includes the remaining effective time of the link, and add the remaining effective time of the link as a weighting factor into the calculation of the new metric.

[0023] Step S17: Use the SPF algorithm to select links in ascending order of the new metric value. The link with the smallest new metric value is the one with the longest duration that can meet the bandwidth requirements of the service transmission.

[0024] According to one technical solution of the present invention, the new metric calculation formula in step S16 introduces a scaling factor a and a scaling factor b, wherein scaling factor a is associated with the weight of the link bandwidth and scaling factor b is associated with the weight of the remaining effective time of the link. By adjusting scaling factor a and scaling factor b, a customized routing selection strategy can be adopted according to different service requirements.

[0025] According to one technical solution of the present invention, when the service needs to prioritize the remaining available bandwidth on the transmission path rather than the remaining effective time, the scaling factor a is increased and the scaling factor b is decreased.

[0026] When the service’s demand for the remaining valid time of the transmission path exceeds its demand for the remaining available bandwidth, increase the scaling factor b and decrease the scaling factor a.

[0027] According to a technical solution of the present invention, step S3, which involves comparing the remaining transmission time of the service with a preset time threshold to trigger a pre-rerouting strategy, specifically includes:

[0028] Step S31: The timer in the controller monitors the remaining valid time of each LSP;

[0029] Step S32: Determine whether the remaining valid time of the LSP is less than the remaining transmission time of the service. If yes, continue to step S33; otherwise, continue monitoring.

[0030] Step S33: Determine whether the remaining valid time of the LSP is less than the preset time threshold T. If so, trigger the pre-rerouting policy; otherwise, continue monitoring.

[0031] According to one technical solution of the present invention, the pre-rerouting strategy includes:

[0032] Step S34: The controller obtains the required bandwidth of the original service and the remaining time required for service transmission;

[0033] Step S35: The controller recalculates the optimal route in the current network using the optimized CSPF routing algorithm;

[0034] Step S36: The controller and the nodes along the route use the RSVP-TE protocol to reserve bandwidth resources and allocate labels for the establishment of the new LSP.

[0035] Step S37: Determine whether the new LSP has been successfully established. If it has been successfully established, continue to step S38; otherwise, return to step S34.

[0036] Step S38: The controller transfers service transmissions to the new LSP;

[0037] Step S39: After the service transmission transfer is completed, delete the old LSP.

[0038] According to one technical solution of the present invention, in the MPLS system, before generating an LSP, the upstream router of the link connection allocates labels and bandwidth resources for the LSP to be generated through the RSVP-TE protocol;

[0039] Whenever a new LSP is established, the router immediately updates the remaining available bandwidth field of the link through the Link Management Protocol (LMP). The update method is: updated remaining available bandwidth = total bandwidth - allocated bandwidth, and then performs LSA flooding across the entire network after the update.

[0040] According to one technical solution of the present invention, the remaining validity time of the LSP is stored on all nodes traversed by the path after the LSP is constructed.

[0041] According to one technical solution of the present invention, the transmission route is calculated based on the effective bandwidth and remaining effective time of the link, and the selected link prioritizes meeting the bandwidth requirements required for service transmission while maximizing the available time of the route.

[0042] The method of maximizing the availability time of the route specifically involves incorporating the remaining effective time of the link as a weighting factor into the calculation of the link metric.

[0043] Using the remaining effective time of the link as a weighting factor includes: first, using the ratio of the maximum effective time of the link to the remaining effective time of the link as the basic weight, and then adjusting the dimensions through a balancing ratio coefficient to ensure that it is numerically balanced with the original cost value; wherein, the maximum effective time of the link is calculated by the node by traversing the effective start time and failure termination time of all planned links from the latest link building plan table.

[0044] According to one aspect of the present invention, a computer-readable storage medium is provided for storing computer instructions, which, when executed by a processor, implement the pre-rerouting method based on the extended OSPF protocol as described in any of the above technical solutions.

[0045] Compared with existing technologies, the pre-rerouting method based on the extended OSPF protocol provided in this invention extends the existing OSPF protocol and proposes a pre-rerouting strategy for predictable inter-satellite link interruptions. This not only meets the diverse QoS requirements of complex service scenarios in routing calculations but also ensures stable and continuous service transmission when predictable inter-satellite link interruptions occur. This invention can improve the service quality and transmission reliability of satellite communication networks.

[0046] By extending LSA and optimizing the CSPF routing algorithm on this basis, we can realize route classification calculation for different services under various QoS requirements and lay the foundation for pre-rerouting strategies.

[0047] By proposing a pre-rerouting strategy, measures are taken in advance when an LSP is about to be interrupted to establish a new LSP and switch service transmission, thereby significantly reducing the service packet loss rate and ensuring high continuity of service transmission. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0049] Figure 1 The schematic diagram illustrates a pre-rerouting method based on the extended OSPF protocol according to an embodiment of the present invention.

[0050] Figure 2 The illustration shows an extended LSA structure according to one embodiment of the present invention, wherein the Effect TimeEnd and Effective bandwidth are extended portions;

[0051] Figure 3 This is a schematic diagram illustrating an optimized CSPF route calculation process according to an embodiment of the present invention.

[0052] Figure 4 The diagram illustrates a pre-rerouting strategy flowchart according to one embodiment of the present invention. Detailed Implementation

[0053] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other. The following embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent application. It should be pointed out that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application.

[0055] like Figure 1 As shown, an embodiment of the present invention provides a method for pre-rerouting based on the extended OSPF protocol, which includes the following steps:

[0056] Step S1: Extend the OSPF protocol, including extending Link State Advertisement (LSA) and optimizing the Limited Shortest Path First (CSPF) routing algorithm, to calculate transmission routes according to service requirements;

[0057] Step S2: Establish a Label Switching Path (LSP) carrying the remaining validity time using the RSVP-TE protocol;

[0058] Step S3: Based on the remaining valid time of the LSP, the pre-rerouting policy is triggered by comparing it with the remaining service transmission time and a preset time threshold. After triggering, a new LSP is established before the old LSP is interrupted, and the service transmission is switched to the new LSP.

[0059] This embodiment relates to the specific implementation process of a pre-rerouting method based on the extended OSPF protocol.

[0060] First, addressing the issue of unmet differentiated QoS requirements for various services in satellite networks, this invention extends the OSPF protocol by adding LSA entries and optimizes the CSPF routing algorithm to ultimately achieve the function of calculating different routes based on the differentiated QoS requirements of different services. Currently, the main link-state information stored in an LSA includes the following: LSA Sequence Number, LSA Generation Time, LSA Type, Advertising Router ID, Link Data, Neighbor ID on the other side of the link, and Tos Metric. To facilitate optimization of the CSPF routing algorithm's calculation process, this invention extends the LSA to store more link-state information. The extended LSA format is as follows: Figure 2 As shown.

[0061] In the field of satellite communication networks, the traditional OSPF protocol can only perform route calculations based on the shortest path in the topology, failing to differentiate the varying requirements of different types of services for latency, bandwidth, and transmission duration. This invention extends LSAs to carry key QoS parameters such as remaining available bandwidth and expected link downtime, thus providing an information foundation for subsequent CSPF route optimization. This technique allows each node in the network to obtain a two-dimensional "time-bandwidth" state view of the entire network after LSA flooding, a prerequisite for refined route calculation. Compared to existing technologies that only focus on path hop count or single static bandwidth constraints, this invention introduces a time dimension, enabling routing decisions to anticipate future link downtime and thus mitigating potential link loss risks during the path calculation phase.

[0062] The meanings of the parameters for each entry in the extended LSA are as follows:

[0063] LS Age: Used to record the cumulative duration of an LSA since its generation. The unit is seconds. The system periodically refreshes the LS Age value of all LSAs in the Link State Database (LSDB), and LSAs exceeding their valid lifespan will be removed from the LSDB.

[0064] Options: Optional function field reserved by the protocol; the use of this field is not involved in this invention.

[0065] LS Type: Used to indicate the type of LSA. In this invention, the LS Type is Router LSA.

[0066] Advertising Router: The router ID that generated this LSA;

[0067] Link State ID: For the LSA extended in this invention, the value of this field is the same as that of the Advertising Router field, both of which represent the router ID that generated the LSA;

[0068] LS Sequence Number: The sequence number of the LSA;

[0069] Checksum: The checksum of all information except the LS Age entry;

[0070] Length: The total length of the entire LSA message;

[0071] Number of links: The number of link-state information entries contained in this LSA;

[0072] Type: The type of link. This invention mainly focuses on the point-to-point (P2P) link type, so the value of this entry is 1;

[0073] TOS 0 metric: The total metric for this link;

[0074] Link ID: The neighbor ID of the router that generated this LSA on the other side of the link represented by this LSA;

[0075] Link Data: In this invention, the port ID is filled in;

[0076] Effect Time End: The duration of the link interruption is obtained by the node from the link establishment plan table;

[0077] Effective bandwidth: The remaining available bandwidth of this link;

[0078] The Effect Time End and Effective bandwidth are fields added in this invention. The Effect Time End field is obtained by the node from the link establishment planning table (Note: The link establishment planning table is a data table pre-calculated and stored during the operation of the satellite network, recording the planned establishment and disconnection times of each inter-satellite link; satellite nodes can know in advance when a link will be interrupted by querying this table), providing a time boundary for link failure in routing calculations. The Effective bandwidth field dynamically reflects the remaining transmission capacity of the link after carrying existing LSP services, avoiding the resource overload problem caused by not considering allocated bandwidth in traditional routing algorithms. By integrating the above two fields into the standard OSPF LSA message for flooding, all routers in the domain can establish a global topology view including link lifetime and real-time bandwidth status, laying the foundation for subsequent CSPF optimization calculations.

[0079] In this invention, after adding the Effective Time End to the LSA, the remaining effective time of the link can be obtained by subtracting the current system time from the link disconnection time during route calculation. Furthermore, the initial value of the Effective bandwidth entry is Total bandwidth. In the MPLS architecture, before generating an LSP, the upstream router of the link connection needs to allocate labels and bandwidth resources for the LSP to be generated via the RSVP-TE protocol. Whenever a new LSP is established, the router needs to immediately update the Effective bandwidth entry via the Link State Protocol (LMP), i.e., Effective bandwidth = Total bandwidth - Utilized bandwidth (allocated bandwidth). After this operation, the router then floods the LSA across the entire network.

[0080] After the flooding operation, the LSDB of each node has collected the parameters required for route calculation. At this time, the present invention optimizes the CSPF routing algorithm based on the added link state information. Figure 3 The optimized CSPF route calculation process is demonstrated, and its specific steps are as follows:

[0081] Step 1: The controller triggers the routing calculation process when it receives a new service transmission instruction from the management layer;

[0082] Step 2: Calculate the link metric using a link bandwidth-based metric calculation method (such as Formula 2), and use the SPF algorithm to select links in ascending order of metric values;

[0083] Step 3: Check whether the remaining available bandwidth of the selected link meets the transmission requirements of the service. If it does, continue to Step 4; otherwise, return to Step 2.

[0084] Step 4: Check if the selected link can reach the destination node. If it can, continue to Step 5; if it cannot, return to Step 2.

[0085] Step 5: Use a new metric calculation method that includes the remaining valid time of the link (such as formulas (1) and (3)) to add the remaining valid time of the link to the calculation of the new metric;

[0086] Step 6: Use the SPF algorithm to select links in ascending order of metric value. The link with the smallest metric value is the one that can meet the bandwidth requirements of the service transmission and has the longest duration.

[0087] Step 7: The optimized CSPF route calculation process ends.

[0088] Steps 1 to 7 above constitute the core calculation flow of the optimized CSPF routing algorithm of this invention. This flow improves upon the traditional CSPF algorithm: the traditional CSPF algorithm typically calculates the shortest path only on a subset of topologies that satisfy a single constraint (such as available bandwidth), while this invention expands path selection from a single bandwidth constraint to a dual optimization of "bandwidth + time" by introducing a link remaining effective time weight in the metric calculation. Specifically, steps 3 and 4 constitute the first stage of feasibility screening, ensuring that the selected links meet the basic transmission conditions for services in terms of bandwidth and connectivity; steps 5 and 6 constitute the second stage of optimization selection, prioritizing the link with the longest remaining effective time among the candidate links that meet the basic conditions. The purpose of this two-stage design is: the first stage of screening can quickly eliminate links that do not meet the hard bandwidth constraint or have topology breaks, narrowing the scope of subsequent optimization calculations; after introducing the time weight in the second stage, the calculated path is the path expected to maintain connectivity for the longest time among all paths that meet the bandwidth requirements, thereby significantly improving the stability and continuity of service transmission.

[0089] Routing is calculated based on the effective bandwidth and impact time of a link. The selected link must prioritize meeting the bandwidth requirements of service transmission while maximizing the available time of the route. Based on this, this invention incorporates effective time as a weighting factor into the metric calculation. Specifically, the ratio of the maximum effective time of a link to its remaining effective duration is used as the basic weight. Then, a balancing coefficient is applied to adjust the dimensions to ensure numerical balance with the original cost value. The maximum effective time of a link is calculated by traversing the start and end times of all planned links when the node receives the latest link establishment plan. Therefore, the optimized link metric calculation formula can be expressed as follows:

[0090] (1)

[0091] (2)

[0092] (3).

[0093] Depending on the specific business requirements, some services may require routing algorithms to obtain paths with fewer hops, while others require paths with longer validity periods. Therefore, this invention adds scale factors a and b to the new metric formula in formula (1). By adjusting scale factors a and b, the routing algorithm can be customized according to different business requirements, thereby selecting a path that meets the user's needs. Furthermore, the methods for obtaining the old metric value and the remaining validity period parameter are shown in formulas (2) and (3). In this invention, the main factor affecting the old metric value is the remaining available bandwidth of the link. Scale factor a is associated with the weight of the link bandwidth, and scale factor b is associated with the weight of the remaining validity period of the link. For example, the initial values ​​of scale factors a and b are selected as 50 (setting them to 50 is a relatively balanced choice, and the values ​​of a and b can be adjusted according to different types of business requirements). When a business needs to prioritize the remaining available bandwidth on the transmission path rather than the remaining validity period, factor a can be increased, and factor b can be decreased. Conversely, when the service's demand for the remaining valid time of the transmission path exceeds its demand for the remaining available bandwidth, factor b should be increased and factor a should be decreased. This adjustment ensures that the routing algorithm's metric matches the specific needs of the service, meeting the multi-QoS requirements of complex service scenarios in satellite networks.

[0094] The design of the aforementioned scaling factors a and b provides flexible, customizable routing strategies for services with different QoS requirements. For bandwidth-sensitive services (such as high-definition video backhaul), factor a can be increased and factor b decreased, causing the routing algorithm to prioritize links with sufficient remaining available bandwidth. For duration-sensitive services (such as long-duration telemetry data transmission), factor b can be increased and factor a decreased, causing the routing algorithm to prioritize paths with longer lifetimes. By dynamically adjusting the relative values ​​of a and b, a smooth transition can be achieved between the two optimization dimensions of bandwidth and time, avoiding the limitations of traditional fixed-weight schemes that cannot flexibly adapt to different service types. Thus, multiple QoS requirements in complex service scenarios in satellite networks can be met within a unified routing framework.

[0095] Based on the extended OSPF protocol and CSPF routing algorithm described above, by adding the remaining valid time and remaining available bandwidth of the link to the metric value of the route calculation, the calculated route and the established LSP also have corresponding valid time. However, due to the high dynamism of satellites, the valid time of the LSP may still not be able to 100% meet the transmission duration of the service. In this case, it is possible that the service transmission may not be completed before the LSP is interrupted. Therefore, based on this, the present invention proposes a pre-rerouting strategy. The steps of the pre-rerouting strategy are as follows: Figure 4 As shown, the specific process is as follows:

[0096] Step 1: The timer in the controller monitors the remaining valid time of each LSP;

[0097] Step 2: Determine if the remaining validity time of the LSP is less than the remaining transmission time of the service. If yes, continue to Step 3; otherwise, continue monitoring.

[0098] Step 3: Determine if the remaining valid time of the LSP is less than the time threshold T. If yes, continue to step 4; otherwise, continue monitoring.

[0099] Step 4: The controller triggers the pre-rerouting policy;

[0100] Step 5: The controller obtains the bandwidth requirements of the original service and the remaining time required for service transmission;

[0101] Step 6: The controller recalculates the optimal route in the current network using the optimized CSPF algorithm;

[0102] Step 7: The controller and the nodes along the route use the RSVP-TE protocol to reserve bandwidth resources and allocate labels for the construction of LSP;

[0103] Step 8: Determine if the LSP has been successfully established. If it has been successfully established, continue to Step 9; otherwise, return to Step 5.

[0104] Step 9: The controller transfers service transmissions to the new LSP;

[0105] Step 10: After the service transmission transfer is completed, delete the old LSP;

[0106] Step 11: The entire pre-rerouting policy process is complete.

[0107] Once an LSP is built, its remaining validity period is stored on all nodes along the path. The controller monitors the remaining validity period of each LSP. When the remaining validity period of an LSP is less than the remaining transmission time required for service transmission on that path, and less than a predetermined time threshold T, the pre-routing mechanism is triggered. Nodes will pre-calculate a new route based on the extended CSPF algorithm according to service requirements and automatically build a new LSP. After the new LSP is successfully established, service transmission is transferred to the new LSP, and the old LSP is deleted. In this way, even if an LSP is interrupted, the continuity of service transmission is guaranteed.

[0108] The aforementioned pre-rerouting strategy enables lossless service handover in scenarios where inter-satellite links are predictably interrupted. Steps 1 to 3 constitute a dual threshold judgment mechanism: the first judgment (whether the remaining valid time of the LSP is less than the remaining transmission time of the service) ensures that the rerouting process is only initiated when the current LSP cannot support the complete transmission of the service, avoiding unnecessary path switching; the second judgment (whether it is less than the preset time threshold T) ensures that sufficient time margin is reserved before the link is interrupted to complete the establishment of the new LSP. Since pre-rerouting is triggered by comparing the remaining valid time of the LSP with the remaining transmission time of the service and the preset time threshold, the old LSP cannot become invalid before the pre-rerouting mechanism is triggered and the new LSP is established. Therefore, the time threshold must be greater than the maximum time required for LSP calculation and establishment in the network. The time required for LSP recalculation and establishment depends on factors such as satellite computing power performance, network protocol, and constellation size. Therefore, the setting of the time threshold varies with the specific scenario. For example, in the established simulation scenario, the maximum time required for LSP recalculation and establishment is 12 seconds. Therefore, 13 seconds can be set as the time threshold.

[0109] Steps 6 through 10 constitute an atomic path switching closed loop: the controller first calculates the new path using the same optimized CSPF algorithm as during initial path establishment, ensuring that the new path also meets service QoS requirements; then, it completes bandwidth reservation and label allocation for the new LSP via the RSVP-TE protocol; service switching is only performed after confirming the successful establishment of the new LSP; finally, the old LSP is deleted to release resources. This "Make-Before-Break" switching mode, compared to traditional "reconnect after disconnection" or "local backup path" schemes, can fundamentally avoid service interruption and data packet loss, ensuring continuous service transmission.

[0110] Therefore, the pre-routing strategy, a predictive protection mechanism, can automatically calculate and establish a new path before the service transmission path is interrupted due to predictable link failures. This reduces the impact of predictable factors such as network topology changes or natural phenomena like solar outages on service transmission, thus ensuring stable service transmission. Simultaneously, by optimizing the time threshold T in the mechanism, the wasted time of available link availability can be minimized.

[0111] In some embodiments of the present invention, the extension of the OSPF protocol in step S1 specifically includes adding a link outage time field and a link remaining available bandwidth field to the LSA.

[0112] The link interruption time field is identified as "Effect Time End," and its value is obtained by the node from the link establishment planning table. The remaining available bandwidth field is identified as "Effective bandwidth," and its initial value is the total bandwidth of the link, which is dynamically updated during network operation as LSPs are established and deleted.

[0113] By explicitly adding the two fields mentioned above to the standard OSPF Router LSA, the link-state advertisement of the OSPF protocol is extended to adapt to the dynamic characteristics of satellite networks. Compared with existing technologies that only integrate general QoS parameters (such as latency and packet loss rate), this invention introduces the time dimension of "link interruption time" as state information. This enables the link-state database built based on LSA flooding to include not only network topology and conventional QoS information, but also the expected failure time and real-time remaining bandwidth of each link. This gives each node in the network the ability to predict link interruptions and perceive dynamic changes in network bandwidth resources, providing the necessary global information view for implementing pre-rerouting strategies.

[0114] According to one aspect of the present invention, an electronic device is provided, comprising: one or more processors, one or more memories, and one or more computer programs; wherein the processor is connected to the memory, and the one or more computer programs are stored in the memory, and when the electronic device is running, the processor executes the one or more computer programs stored in the memory to cause the electronic device to perform a pre-rerouting method based on the extended OSPF protocol as described in any of the above technical solutions.

[0115] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor.

[0116] The memory can be an internal storage unit of the terminal device, such as a hard drive or RAM. Alternatively, it can be an external storage device, such as a plug-in hard drive, Smart Media Card (SMC), Secure Digital (SD) card, or Flash Card. Furthermore, the memory can include both internal and external storage units. The memory is used to store the computer program and other programs and data required by the terminal device. It can also be used to temporarily store data that has been output or will be output.

[0117] According to one aspect of the present invention, a computer-readable storage medium is provided for storing computer instructions, which, when executed by a processor, implement a pre-rerouting method based on the extended OSPF protocol as described in any of the above technical solutions.

[0118] For example, computer-readable storage media can be read-only memory (ROM), random access memory (RAM), read-only optical disc (CD-ROM), magnetic tape, floppy disk, and optical data storage devices. They can be implemented using computer-executable program code, thus allowing them to be stored in a storage device for execution by a computing device, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Therefore, this invention is not limited to any particular hardware and software combination.

[0119] The method and system based on the extended OSPF protocol proposed in this invention extend the OSPF protocol and propose a pre-rerouting strategy for predictable interruptions of inter-satellite links. This satisfies the diverse QoS requirements of routing calculations in complex service scenarios and enables stable and continuous service transmission when predictable interruptions occur in inter-satellite links.

[0120] The pre-rerouting method based on the extended OSPF protocol provided by this invention has the following beneficial effects:

[0121] By extending the existing OSPF protocol and proposing a pre-rerouting strategy for predictable inter-satellite link interruptions, this invention can not only meet the routing calculation requirements of diverse QoS needs in complex service scenarios, but also achieve stable and continuous service transmission when predictable inter-satellite link interruptions occur. This invention can improve the service quality and service transmission reliability of satellite communication networks.

[0122] By extending LSA and optimizing the CSPF routing algorithm on this basis, we can realize route classification calculation for different services under various QoS requirements and lay the foundation for pre-rerouting strategies.

[0123] By proposing a pre-rerouting strategy, measures are taken in advance when an LSP is about to be interrupted to establish a new LSP and switch service transmission, thereby significantly reducing the service packet loss rate and ensuring high continuity of service transmission.

[0124] The above description is merely one embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A pre-rerouting method based on the extended OSPF protocol, characterized in that, Includes the following steps: Step S1: Extend the OSPF protocol, including extending Link State Advertisement (LSA) and optimizing the Constrained Shortest Path First (CSPF) routing algorithm, to calculate transmission routes according to service requirements; Step S2: Establish a Label Switching Path (LSP) carrying the remaining validity time using the RSVP-TE protocol; Step S3: Based on the remaining valid time of the LSP, the pre-rerouting policy is triggered by comparing it with the remaining service transmission time and a preset time threshold. After triggering, a new LSP is established before the old LSP is interrupted, and the service transmission is switched to the new LSP. The preset time threshold is set to be greater than the maximum time required for LSP calculation and establishment in the network.

2. The pre-rerouting method based on the extended OSPF protocol according to claim 1, characterized in that, The extension of the OSPF protocol in step S1 includes: Step S11: Add the link interruption time field and the link remaining available bandwidth field to the LSA; The value of the link interruption time field is obtained by the node from the link construction planning table.

3. The pre-rerouting method based on the extended OSPF protocol according to claim 2, characterized in that, The optimized CSPF routing algorithm in step S1 includes: Step S12: When the controller receives a new service transmission instruction, it triggers the routing calculation process; Step S13: Calculate the link metric value using the link bandwidth-based metric calculation method, and select links in ascending order of metric value using the Shortest Path First (SPF) algorithm. Step S14: Check whether the remaining effective bandwidth of the selected link meets the service transmission requirements. If it does, continue to step S15; otherwise, return to step S13. Step S15: Check if the selected link can reach the destination node. If it can, continue to step S16; otherwise, return to step S13. Step S16: Use a new metric calculation formula that includes the remaining effective time of the link, and add the remaining effective time of the link as a weighting factor into the calculation of the new metric. Step S17: Use the SPF algorithm to select links in ascending order of the new metric value. The link with the smallest new metric value is the one with the longest duration that can meet the bandwidth requirements of the service transmission.

4. The pre-rerouting method based on the extended OSPF protocol according to claim 3, characterized in that, The new metric calculation formula in step S16 introduces scale factor a and scale factor b, where scale factor a is associated with the weight of link bandwidth and scale factor b is associated with the weight of the remaining effective time of the link. By adjusting scale factor a and scale factor b, a customized routing selection strategy can be developed according to different service requirements.

5. The pre-rerouting method based on the extended OSPF protocol according to claim 4, characterized in that, When the business needs to prioritize the remaining available bandwidth on the transmission path rather than the remaining effective time, increase the scaling factor a and decrease the scaling factor b. When the service’s demand for the remaining valid time of the transmission path exceeds its demand for the remaining available bandwidth, increase the scaling factor b and decrease the scaling factor a.

6. The pre-rerouting method based on the extended OSPF protocol according to claim 1, characterized in that, Step S3, which involves comparing the data with the remaining service transmission time and a preset time threshold to trigger a pre-rerouting strategy, specifically includes: Step S31: The timer in the controller monitors the remaining valid time of each LSP; Step S32: Determine whether the remaining valid time of the LSP is less than the remaining transmission time of the service. If yes, continue to step S33; otherwise, continue monitoring. Step S33: Determine whether the remaining valid time of the LSP is less than the preset time threshold T. If so, trigger the pre-rerouting policy; otherwise, continue monitoring.

7. The pre-rerouting method based on the extended OSPF protocol according to claim 6, characterized in that, The pre-rerouting strategy includes, Step S34: The controller obtains the required bandwidth of the original service and the remaining time required for service transmission; Step S35: The controller recalculates the optimal route in the current network using the optimized CSPF routing algorithm; Step S36: The controller and the nodes along the route use the RSVP-TE protocol to reserve bandwidth resources and allocate labels for the establishment of the new LSP. Step S37: Determine whether the new LSP has been successfully established. If it has been successfully established, continue to step S38; otherwise, return to step S34. Step S38: The controller transfers service transmissions to the new LSP; Step S39: After the service transmission transfer is completed, delete the old LSP.

8. The pre-rerouting method based on the extended OSPF protocol according to claim 2, characterized in that, In the MPLS architecture, before an LSP is generated, the upstream router of the link connection allocates labels and bandwidth resources for the LSP to be generated through the RSVP-TE protocol. Whenever a new LSP is established, the router immediately updates the remaining available bandwidth field of the link through the Link Management Protocol (LMP). The update method is: updated remaining available bandwidth = total bandwidth - allocated bandwidth, and then performs LSA flooding across the entire network after the update.

9. The pre-rerouting method based on the extended OSPF protocol according to claim 1, characterized in that, The remaining validity period of the LSP is stored on all nodes traversed by the path after the LSP is constructed.

10. The pre-rerouting method based on the extended OSPF protocol according to any one of claims 1 to 9, characterized in that, The transmission route is calculated based on the effective bandwidth and remaining effective time of the link. The selected link prioritizes meeting the bandwidth requirements of the service transmission while maximizing the available time of the route. The method of maximizing the availability time of the route specifically involves incorporating the remaining effective time of the link as a weighting factor into the calculation of the link metric. Using the remaining effective time of the link as a weighting factor includes: first, using the ratio of the maximum effective time of the link to the remaining effective time of the link as the basic weight, and then adjusting the dimensions through a balancing ratio coefficient to ensure that it is numerically balanced with the original cost value; wherein, the maximum effective time of the link is calculated by the node by traversing the effective start time and failure termination time of all planned links from the latest link building plan table.

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