WO2021022944A1 - 针对具有栈深约束的路径计算方法及装置 - Google Patents

针对具有栈深约束的路径计算方法及装置 Download PDF

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WO2021022944A1
WO2021022944A1 PCT/CN2020/099017 CN2020099017W WO2021022944A1 WO 2021022944 A1 WO2021022944 A1 WO 2021022944A1 CN 2020099017 W CN2020099017 W CN 2020099017W WO 2021022944 A1 WO2021022944 A1 WO 2021022944A1
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path
stack
calculation
algorithm
stack depth
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PCT/CN2020/099017
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French (fr)
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张天祥
陆钱春
李锋
刘万慧
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南京中兴软件有限责任公司
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/50—Routing or path finding of packets in data switching networks using label swapping, e.g. multi-protocol label switch [MPLS]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/12—Shortest path evaluation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/34—Source routing

Definitions

  • the embodiments of the present invention relate to the field of communication technology, and in particular to a method and device for path calculation with stack depth constraints.
  • SR Segment Routing
  • MPLS Multi-Protocol Label Switching, Multi-Protocol Label Switching
  • the control plane is implemented based on the IGP routing protocol extension
  • the forwarding layer is implemented based on the MPLS forwarding network
  • the corresponding segment identifier is presented as a label at the forwarding layer.
  • SR-TE SR Traffic Engineering
  • the SDN controller is responsible for calculating the forwarding path of the tunnel and sending the label stack list corresponding to the path to the ingress forwarding device , The forwarding device sequentially performs routing and forwarding according to the label stack list.
  • the technical problem to be solved by the embodiment of the present invention is to solve the optimal path calculation problem with MSD constraints, and to provide a method and device for path calculation with stack depth constraints.
  • the method for calculating a path with a stack depth constraint includes: calculating a first path based on a stack depth constraint value using a first preset algorithm; if the depth of the label stack list corresponding to the first path is less than or If it is equal to the stack depth constraint value, output the first path.
  • the stack depth constraint value can be input into the first preset algorithm as the calculation constraint condition, and the label list stack depth is less than or equal to the first preset algorithm of the stack depth constraint value.
  • the device for calculating a path with a stack depth constraint includes: a first algorithm module configured to calculate the first path based on the stack depth constraint value and using a first preset algorithm; if the first path corresponds to If the depth of the label stack list is less than or equal to the stack depth constraint value, the first path is output.
  • the stack depth constraint value can be input into the first preset algorithm as the calculation constraint condition, and the label list stack depth is less than or equal to the first preset algorithm of the stack depth constraint value.
  • the segment routing path label processing device includes: a memory, a processor, and a computer program stored in the memory and capable of running on the processor, the computer program being executed by the processor When implementing the steps of the method described above.
  • the path with the stack depth constraint can be calculated by Bellman algorithm first, and if the first path that meets the stack depth constraint value condition is obtained, then the first path is output;
  • the first path that meets the stack depth constraint value condition is first calculated by the basic algorithm without considering the stack depth constraint value for path calculation, and the calculated label stack list of the second path is compressed to obtain the stack depth constraint value condition Path, which greatly improves the success rate of calculating paths with stack depth constraints.
  • a computer program is stored on the computer storage medium, and when the computer program is executed by a processor, the steps of the path calculation method with stack depth constraint as described above are implemented.
  • the path with the stack depth constraint can be calculated by Bellman algorithm. If the first path that meets the stack depth constraint value condition is obtained, the first path is output; if the stack depth constraint is not obtained For the first path of the value condition, the basic algorithm is used to first calculate the path calculation without considering the stack depth constraint value, and the calculated label stack list of the second path is compressed to obtain the path that meets the stack depth constraint value. It greatly improves the success rate of calculating paths with stack depth constraints.
  • Fig. 1 is a flowchart of a path calculation method with stack depth constraints according to an embodiment of the present invention
  • FIG. 2 is a detailed flowchart of a path calculation method with stack depth constraints according to an embodiment of the present invention
  • FIG. 3 is a schematic structural diagram of a path calculation device with stack depth constraints according to an embodiment of the present invention.
  • FIG. 4 is a schematic structural diagram of a path calculation device with stack depth constraints according to an embodiment of the present invention.
  • Fig. 5 is a network topology structure diagram according to an embodiment of the present invention.
  • the forwarding devices produced by major communication equipment manufacturers are limited in their support for the label stack list stack depth, that is, when the stack depth exceeds MSD (Maximum Stack Depth), routing and forwarding will fail, which greatly affects SR Technology and promotion of SR-TE. Therefore, it is necessary to use the characteristics of the SR technology to design a new label path calculation method according to the interaction characteristics of the forwarding layer and the controller to ensure the optimal path while satisfying the MSD constraints.
  • MSD Maximum Stack Depth
  • the method for path calculation with stack depth constraints includes:
  • S101 Calculate the first path by using the first preset algorithm based on the stack depth constraint value
  • the path calculation method of this application can be used to calculate an optimal path with MSD (Maximum Stack Depth, maximum stack depth), and the MSD in this application can be understood as a stack depth constraint value.
  • MSD Maximum Stack Depth, maximum stack depth
  • the stack depth and the constraint value can be used as calculation conditions and input into the first preset algorithm to calculate the first path.
  • the first path whose label stack list depth is less than or equal to the MSD can be directly settled through the first preset algorithm.
  • the stack depth constraint value can be input into the first preset algorithm as the calculation constraint condition, and the label stack depth list can be directly calculated to be less than or equal to the first value of the stack depth constraint.
  • Path which greatly improves the success rate of calculating paths with stack depth constraints.
  • the method further includes: S103: when the first preset algorithm cannot output the first path, the second preset algorithm is used to calculate without considering the stack The second path of the deep constraint value is compressed, and the label stack list corresponding to the second path is compressed so that the depth of the compressed label stack list is less than or equal to the stack depth constraint value, and the path corresponding to the compressed label stack list is output.
  • the first path whose label list depth is less than or equal to MSD may not be directly calculated through the first preset algorithm.
  • the second preset algorithm can be used to first calculate the path that does not consider the MSD and obtain the second path, and then the label stack of the second path The list is compressed to obtain a path whose label stack list depth is less than or equal to MSD.
  • compressing the label stack list corresponding to the second path includes: replacing at least part of the link labels in the label list with corresponding node labels to reduce the depth of the label stack list.
  • all link labels in the label list can be replaced with corresponding node labels, or part of the link labels in the label list can be replaced with corresponding node labels. As a result, the depth of the tag list can be reduced.
  • the second path from node 1 to node 4 is: 1->2->5->3->4, the corresponding The label list is ⁇ "1->2", “2->5", “5->3", “3->4" ⁇ , and the stack depth is 4, which does not meet the MSD constraint requirements.
  • the label list of the second path is compressed, and the link label in the label list is replaced with the corresponding node label.
  • the label stack list is ⁇ "5", "4" ⁇ , and the stack depth is 2, which meets the MSD constraint requirements.
  • the explanation is that the complete path of the request is divided into two parts, one part is the shortest path 1->2->5 from the starting node 1 to node 5, and the other part is the shortest path 5->4->3 from node 5 to node 4 .
  • the method may further include:
  • the first path or the second path is calculated.
  • preparing path calculation resources includes:
  • path caching can be performed based on the link weight of the forwarding device level.
  • the forwarding device reports to each IGP of the controller through the protocol.
  • the controller performs path cache calculation for the IGP domain. Therefore, when performing path calculation, the shortest path between two nodes can be directly read from the cache, which improves the efficiency of path calculation.
  • the first preset algorithm is Bellman's algorithm
  • the second preset algorithm is Dijkstra's algorithm or Floyed's algorithm.
  • the Bellman algorithm is used to calculate the optimal path with MSD constraints. As a shortest path algorithm, the Bellman algorithm naturally adapts to the path calculation under the maximum hop number constraint, which is also not available in other path algorithms .
  • the depth of the label stack list calculated by Bellman is equal to the total number of all links in the path. At this time, all the labels in the label stack list are the Adj-SID of the link. When the label list stack depth is less than or equal to MSD, the path calculation is considered successful, the result is returned, and the algorithm ends.
  • S11 The forwarding layer network topology status report.
  • the forwarding layer will have multiple IGP domains. Each IGP domain corresponds to the topology shown in Figure 4. When the device is working, the topology of each IGP domain needs to be changed through the communication protocol. Report to the controller;
  • S12 The controller initializes the bandwidth resource, records the link information initialized by S11 to the bandwidth management, initializes the bandwidth resource information for each link, records the maximum, used, and unused bandwidth resources, and calculates the road time Provide reference for link feasibility judgment;
  • the controller caches the entire network path for each IGP domain. After steps S11 and S12, the controller has a grasp of global network information. For each IGP domain, the controller calculates the shortest distance between all nodes in the domain. Path and store, and this step will be triggered whenever the controller restarts or the topology changes;
  • step S14 Use the Bellman algorithm to calculate the optimal path with the maximum stack depth constraint.
  • the algorithm is called, and the bandwidth management module is used to calculate the path. If the path calculation is successful, proceed directly to step S17 to return the path calculation result; otherwise, proceed to step S15;
  • step S15 This step first uses the common path calculation method to obtain an optimal path that does not meet the MSD constraints. On the basis of the established path, the strict LEA algorithm is used to compress the path; if the compression is successful, go directly to step S17 and return As a result, otherwise go to step S16;
  • step S16 In this step, a common path calculation method is first used to obtain an optimal path that does not satisfy the MSD constraint. On the basis of the established path, the loose LEA algorithm is used to compress the path; then step S17 is entered.
  • the device for path calculation with stack depth constraints includes: a first algorithm module.
  • the first algorithm module is set to calculate the first path by using the first preset algorithm based on the stack depth constraint value. If the depth of the label stack list corresponding to the first path is less than or equal to the stack depth constraint value, the first path is output.
  • the stack depth constraint value can be input into the first preset algorithm as the calculation constraint condition, and the label list stack depth can be directly calculated to be less than or equal to the first preset algorithm of the stack depth constraint value.
  • the device further includes: a second algorithm module.
  • the second algorithm module may be configured to use the second preset algorithm to calculate the second path without considering the stack depth constraint value when the first calculation module cannot output the first path, and compress the label stack list corresponding to the second path, Make the depth of the compressed label stack list less than or equal to the stack depth constraint value, and output the path corresponding to the compressed label stack list.
  • the first path with the label stack list depth less than or equal to MSD can be directly settled through the first preset algorithm, but it may also be impossible to use the first preset algorithm Directly calculate the first path whose label list depth is less than or equal to MSD.
  • the second preset algorithm can be used to first calculate the path that does not consider MSD and obtain the second path, and then the second path The label stack list of the path is compressed to obtain the path whose label stack list depth is less than or equal to MSD.
  • the second algorithm module when the second algorithm module compresses the label stack list corresponding to the second path, it is specifically set to replace at least part of the link labels in the label list with corresponding node labels to reduce the label stack. List depth.
  • all link labels in the label list can be replaced with corresponding node labels, or part of the link labels in the label list can be replaced with corresponding node labels. As a result, the depth of the tag list can be reduced.
  • the second path from node 1 to node 4 is: 1->2->5->3->4, the corresponding The label list is ⁇ "1->2", “2->5", “5->3", “3->4" ⁇ , and the stack depth is 4, which does not meet the MSD constraint requirements.
  • the label list of the second path is compressed, and the link label in the label list is replaced with the corresponding node label.
  • the label stack list is ⁇ "5", "4" ⁇ , and the stack depth is 2, which meets the MSD constraint requirements.
  • the explanation is that the complete path of the request is divided into two parts, one part is the shortest path 1->2->5 from the starting node 1 to node 5, and the other part is the shortest path 5->4->3 from node 5 to node 4 .
  • the device may further include: a resource preparation module, which is configured to prepare path calculation resources before performing the first path calculation; Computing resources to perform the calculation of the first path or the second path.
  • a resource preparation module which is configured to prepare path calculation resources before performing the first path calculation
  • Computing resources to perform the calculation of the first path or the second path.
  • the resource preparation module may include: a topology loading module and a path caching module
  • the topology loading module can be set to report network topology information to the controller
  • the path cache module may be configured to perform path cache calculation based on network topology information to obtain path calculation resources.
  • path caching can be performed based on the link weight of the forwarding device level.
  • the forwarding device reports to each IGP of the controller through the protocol.
  • the controller performs path cache calculation for the IGP domain. Therefore, when performing path calculation, the shortest path between two nodes can be directly read from the cache, which improves the efficiency of path calculation.
  • the first preset algorithm may be the Bellman algorithm
  • the second preset algorithm may be the Dijkstra algorithm or the Floyed algorithm.
  • the Bellman algorithm is used to calculate the optimal path with MSD constraints. As a shortest path algorithm, the Bellman algorithm naturally adapts to the path calculation under the maximum hop number constraint, which is also not available in other path algorithms .
  • the depth of the label stack list calculated by Bellman is equal to the total number of all links in the path. At this time, all the labels in the label stack list are the Adj-SID of the link. When the label list stack depth is less than or equal to MSD, the path calculation is considered successful, the result is returned, and the algorithm ends.
  • the segment routing path label processing device includes: a memory, a processor, and a computer program stored in the memory and running on the processor.
  • the computer program is executed by the processor to implement the steps of the above method .
  • the path with the stack depth constraint can be calculated by Bellman algorithm first, and if the first path that meets the stack depth constraint value condition is obtained, then the first path is output;
  • the first path that meets the stack depth constraint value condition is first calculated by the basic algorithm without considering the stack depth constraint value for path calculation, and the calculated label stack list of the second path is compressed to obtain the stack depth constraint value condition Path, which greatly improves the success rate of calculating paths with stack depth constraints.
  • a computer program is stored on the computer storage medium, and when the computer program is executed by a processor, the steps of the above-mentioned path calculation method with stack depth constraints are implemented.
  • the path with the stack depth constraint can be calculated by Bellman algorithm. If the first path that meets the stack depth constraint value condition is obtained, the first path is output; if the stack depth constraint is not obtained For the first path of the value condition, the basic algorithm is used to first calculate the path calculation without considering the stack depth constraint value, and the calculated label stack list of the second path is compressed to obtain the path that meets the stack depth constraint value. It greatly improves the success rate of calculating paths with stack depth constraints.
  • Figure 4 shows a network topology with 10 nodes and 13 links. Each link has its corresponding weight. Let the Adj-SID of link A->B be "A->B", Let the Node-SID of node A be "A”. In order to explain the problem simply, the bandwidth resource information of the link is ignored, but the main flow of the algorithm is not affected.
  • the network topology is considered to be a single IGP domain, and a single IGP domain is used here for the presentation process.
  • the controller Through reporting at the forwarding level, the controller obtains a single IGP network topology, and uses the link weight as the criterion to perform global path caching, as shown in the following table (only some results are listed as examples in the table):
  • the Bellman algorithm in step S14 in Figure 2 can be used to obtain the optimal path as 1->2->5->3->4 or 1->6- >8->3->4, the direct calculation is successful, and the result is returned.
  • the label stack list is ⁇ "1->2", “2->5", "5->3", “ 3->4” ⁇ . It is worth noting that at this time, even if the common path calculation algorithm is used, the optimal path that satisfies the MSD constraint can be obtained.
  • the label compression method proposed in the embodiment of the present invention is to solve the situation that the MSD constraint in the project is relatively small. In fact, the MSD in the actual project is not large.
  • the complete path of the request is divided into two parts, one part is the shortest path 1->2->5 from the starting node 1 to node 5, and the other part is the shortest path 5->4->3 from node 5 to node 4 ,
  • This also makes full use of the characteristics of the Segment Routing technology, that is, the Node-SID is used to guide the routing along the shortest path.
  • the complete path at this time can be uniquely represented, and the path is determined as 1->2->5->3->4 when the forwarding device performs routing and forwarding.
  • the embodiment of the present invention integrates three path calculation schemes based on stack depth constraints, which greatly improves the path calculation success rate.
  • the method and device for path calculation with stack depth constraint provided by the embodiments of the present invention have the following beneficial effects: the stack depth constraint value can be input into the first preset algorithm as the calculation constraint condition and directly calculated
  • the first path whose label list stack depth is less than or equal to the stack depth constraint value improves the efficiency and success rate of calculating the path with the stack depth constraint value.

Abstract

本发明实施例中提出了一种针对具有栈深约束的路径计算方法及装置，计算方法包括：基于栈深约束值，采用第一预设算法计算第一路径；若所述第一路径对应的标签栈列表的深度小于或等于所述栈深约束值，则输出所述第一路径。根据本发明实施例中的计算方法，可以通过将栈深约束值输入第一预设算法，作为计算约束条件，直接计算得到标签列表栈深度小于等于栈深约束值的第一路径，提高了计算具有栈深约束值的路径的效率和成功率。

Description

针对具有栈深约束的路径计算方法及装置 技术领域
本发明实施例涉及通信技术领域，尤其是涉及一种针对具有栈深约束的路径计算方法及装置。
背景技术
SR(Segment Routing，分段路由)是一种新型的MPLS(Multi-Protocol Label Switching，多协议标签交换)技术。其中，控制平面基于IGP路由协议扩展实现，转发层面基于MPLS转发网络实现，对应的Segment标识在转发层面呈现为标签。SR-TE(SR Traffic Engineering)是使用SR作为控制信令的一种新型的MPLS隧道技术，SDN控制器负责计算隧道的转发路径，并将与路径对应的标签栈列表下发给入节点转发设备，转发设备依次根据标签栈列表进行路由转发。
当前，各大通信设备厂商生产的转发设备对标签栈列表栈深支持程度受到限制，即当栈深超过MSD(Maximum Stack Depth)时，会导致路由转发失败，这在很大程度上影响了SR技术以及SR-TE的推广。
针对相关技术中存在的上述问题，目前尚未提出有效的解决方案。
发明内容
本发明实施例要解决的技术问题是解决带有MSD约束的最优路径计算问题，提供一种针对具有栈深约束的路径计算方法及装置。
根据本发明实施例的针对具有栈深约束的路径计算方法，包括：基于栈深约束值，采用第一预设算法计算第一路径；若所述第一路径对应的标签栈列表的深度小于或等于所述栈深约束值，则输出所述第一路径。
根据本发明实施例的针对具有栈深约束的路径计算方法，可以通过将栈深约束值输入第一预设算法，作为计算约束条件，直接计算得到标签列表栈深度小于等于栈深约束值的第一路径，从而极大提高了计算具有栈深 约束值的路径的效率和成功率。
根据本发明实施例的针对具有栈深约束的路径计算装置，包括：第一算法模块，设置为基于栈深约束值，采用第一预设算法计算第一路径；若所述第一路径对应的标签栈列表的深度小于或等于所述栈深约束值，则输出所述第一路径。
根据本发明实施例的针对具有栈深约束的路径计算装置，可以通过将栈深约束值输入第一预设算法，作为计算约束条件，直接计算得到标签列表栈深度小于等于栈深约束值的第一路径，从而极大提高了计算具有栈深约束值的路径的效率和成功率。
根据本发明实施例的分段路由路径标签处理装置，包括：存储器、处理器及存储在所述存储器上并可在所述处理器上运行的计算机程序，所述计算机程序被所述处理器执行时实现如上述所述的方法的步骤。
根据本发明实施例的分段路由路径标签处理装置，首先可以通过Bellman算法计算具有栈深约束的路径，若得到符合栈深约束值条件的第一路径，则输出第一路径；若得不到符合栈深约束值条件的第一路径，则通过基本算法先计算不考虑栈深约束值进行路径计算，并对计算得到的第二路径的标签栈列表进行压缩，得到符合栈深约束值条件的路径，从而极大提高了计算具有栈深约束值的路径成功率。
根据本发明实施例的计算机存储介质，所述计算机存储介质上存储有计算机程序，所述计算机程序被处理器执行时实现如上述所述的针对具有栈深约束的路径计算方法的步骤。
根据本发明实施例的计算机存储介质，首先可以通过Bellman算法计算具有栈深约束的路径，若得到符合栈深约束值条件的第一路径，则输出第一路径；若得不到符合栈深约束值条件的第一路径，则通过基本算法先计算不考虑栈深约束值进行路径计算，并对计算得到的第二路径的标签栈列表进行压缩，得到符合栈深约束值条件的路径，从而极大提高了计算具有栈深约束值的路径成功率。
附图说明
图1是根据本发明实施例的针对具有栈深约束的路径计算方法流程图；
图2是根据本发明实施例的针对具有栈深约束的路径计算方法的详细流程图；
图3是根据本发明实施例的针对具有栈深约束的路径计算装置的结构示意图；
图4是根据本发明实施例的针对具有栈深约束的路径计算装置的结构示意图；
图5是根据本发明实施例的网络拓扑结构图。
具体实施方式
为更进一步阐述本发明为达成预定目的所采取的技术手段及功效，以下结合附图及较佳实施例，对本发明进行详细说明如后。
当前，各大通信设备厂商生产的转发设备对标签栈列表栈深支持程度受到限制，即当栈深超过MSD(Maximum Stack Depth)时，会导致路由转发失败，这在很大程度上影响了SR技术以及SR-TE的推广。因此，需要利用SR技术的特点，根据转发层面与控制器的交互特性，设计新的标签路径计算方法，在满足MSD约束的同时保证最优路径。
如图1所示，根据本发明实施例的针对具有栈深约束的路径计算方法，包括：
S101：基于栈深约束值，采用第一预设算法计算第一路径；
需要说明的是，本申请的路径计算方法可以用于针对具有MSD(Maximum Stack Depth，最大栈深)的最优路径的计算，本申请中的MSD可以理解为栈深约束值。在进行路径计算时，可以将栈深与约束值作为计 算条件输入第一预设算法，计算出第一路径。
S102：若第一路径对应的标签栈列表的深度小于或等于栈深约束值，则输出第一路径；
需要说明的是，通过将MSD输入第一预设算法，作为计算约束条件，可以通过第一预设算法直接结算得到标签栈列表深度小于或等于MSD的第一路径。
根据本发明实施例的针对具有栈深约束的路径计算方法，可以通过将栈深约束值输入第一预设算法，作为计算约束条件，直接计算得到标签栈深列表小于等于栈深约束的第一路径，从而极大提高了计算具有栈深约束值的路径成功率。
在本发明的一些实施例中，如图1所示，所述方法还包括：S103：在所述第一预设算法无法输出所述第一路径时，采用第二预设算法计算不考虑栈深约束值的第二路径，并对第二路径对应的标签栈列表进行压缩，使压缩后的标签栈列表的深度小于等于栈深约束值，并输出压缩后的标签栈列表对应的路径。
需要说明的是，通过第一预设算法可能无法直接计算得到标签列表深度小于或等于MSD的第一路径。当通过第一预设算法无法直接计算得到标签栈列表的深度小于或等于MSD时，可以通过第二预设算法先计算不考虑MSD的路径并得到第二路径，随后对第二路径的标签栈列表进行压缩，得到标签栈列表深度小于等于MSD的路径。
根据本发明的一些实施例，对第二路径对应的标签栈列表进行压缩，包括：将标签列表中的至少部分链路标签替换为相应的节点标签，以降低标签栈列表深度。
也就是说，可以将标签列表中的全部链路标签替换为相应的节点标签， 也可以是将标签列表中的部分链路标签替换为相应的节点标签。由此，可以降低标签列表深度。
如图4所示，若MSD为2，假设通过第二预设算法计算不考虑MSD得到节点1到节点4的第二路径为：1->2->5->3->4，对应的标签列表为{“1->2”，“2->5”，“5->3”，“3->4”}，栈深为4，不满足MSD约束要求。对第二路径的标签列表进行压缩，将标签列表中的链路标签替换为相应的节点标签得到标签栈列表为{“5”，“4”}，栈深为2，满足MSD约束要求。解释为，请求的完整路径分为了两部分，一部分是起始节点1到节点5的最短路径1->2->5，另一部分是节点5到节点4的最短路径5->4->3。
在本发明的一些实施例，方法还可以包括：
在进行第一路径计算之前，准备路径计算资源；
基于路径计算资源，进行第一路径或第二路径的计算。
可以理解的是，通过在计算路径之前，预先准备路径计算资源，可以提高路径计算效率。
可选地，准备路径计算资源包括：
向控制器上报网络拓扑信息；
基于网络拓扑信息进行路径缓存计算以得到路径准备资源。
例如，如图2所示，在进行路径计算之前，首先可以基于转发设备层面链路权值进行路径缓存，当控制器第一次启动或者重启时，转发设备通过协议上报给控制器每个IGP域的网络拓扑信息，控制器对IGP域进行路径缓存计算。由此，当进行路径计算时，可以直接从缓存中读取两节点之间的最短路径，提高了路径计算效率。
在本发明的一些实施例，第一预设算法为贝尔曼(Bellman)算法，第二预设算法为迪杰斯特拉(Dijkstra)算法或弗洛伊德(Floyed)算法。
需要说明的是，使用Bellman算法计算带有MSD约束的最优路径，Bellman算法作为最短路径算法的一种，与最大跳数约束下的算路天然适配，这也是其它路径算法所不具备的。使用Bellman计算得到的标签栈列表深度等于路径中所有链路条数总数，此时标签栈列表中所有标签都为链路的Adj-SID。当标签列表栈深小于等于MSD时，认为路经计算成功，返回结果，算法到此结束。
当采用Bellman无法计算得到标签列表栈深小于等于MSD时，首先可以选用普通路径算法，如Dijkstra算法或Floyed算法等计算出一条不考虑MSD约束的最优路径，然后，使用严格LEA算法对该条路径进行压缩，思路为使用Node-SID来代替批量的Adj-SID。值得注意的是，利用Node-SID来引导路由转发路径时，当全网路径缓存中查询到两点之间最短路径只有一条时，才会使用Node-SID来代替批量的Adj-SID，这样可以保证标签栈列表中的Node-SID和Adj-SID元素可以表示唯一一条完整的起始节点到终节点的路径。当标签栈深小于等于MSD时，认为路径计算成功，返回结果，算法至此结束。
或者，首先使用普通路径算法如Dijkstra、Floyed等计算出一条不考虑MSD约束的最优路径，同样使用Node-SID来批量代替的Adj-SID，与上述方法不同的是，利用Node-SID来引导转发路径时，当全网路径缓存中查询到两点之间存在多条等价最短路径时，即ECMP场景，也会使用Node-SID来代替批量的Adj-SID，此时，与严格LEA相反，标签栈列表中的Node-SID和Adj-SID元素不能做到表示唯一一条完整的起始节点到终节点的路径。当标签栈深小于等于MSD时，认为路径计算成功，返回结果，若标签栈深大于MSD，路径计算失败，返回失败结果。
需要说明的是，根据本发明实施例中的针对具有栈深约束的路径计算 方法可以应用于SDN(Software Defined Network，软件定义网络)控制器进行SR(Segment Routing)标签路径计算，有效的压缩Segment Routing路径标签。具体步骤如图2所示：
S11：转发层网络拓扑状态上报，转发层会有多个IGP域，每个IGP域都对应有如图4所示的拓扑结构，当设备工作时，需要通过通信协议将每个IGP域的拓扑结构上报给控制器；
S12：控制器进行带宽资源的初始化，将S11初始化的链路信息，记录到带宽管理，为每条链路初始化带宽资源信息，记录好最大、已用、未用的带宽资源，并算路时链路可行性判断提供参考；
S13：控制器针对每个IGP域进行全网路径缓存，经过步骤S11和S12，控制器对全局的网络信息有了掌握，针对每个IGP域，控制器会计算出该域内所有节点之间的最短路径并进行存储，每当控制器重启或者拓扑变化时，该步骤都会被触发；
S14：使用Bellman算法进行带有最大栈深约束下的最优路径计算，当有算路请求到达时，调用该算法，结合带宽管理模块进行算路。若算路成功则直接进行步骤S17返回算路结果，否则进入步骤S15；
S15：该步骤首先使用普通算路方法，得到一条不满足MSD约束的最优路径，在该既定路径的基础上，使用严格LEA算法对该路径进行压缩；若压缩成功，则直接进入步骤S17返回结果，否则进入步骤S16；
S16：该步骤首先使用普通算路方法，得到一条不满足MSD约束的最优路径，在该既定路径的基础上，使用松散LEA算法对该路径进行压缩；之后进入步骤S17。
如图3和图4所示，根据本发明实施例的针对具有栈深约束的路径计 算装置，包括：第一算法模块。
具体而言，第一算法模块设置为基于栈深约束值，采用第一预设算法计算第一路径。若第一路径对应的标签栈列表的深度小于或等于栈深约束值，则输出第一路径。
根据本发明实施例的针对具有栈深约束的路径计算装置，可以通过将栈深约束值输入第一预设算法，作为计算约束条件，直接计算得到标签列表栈深小于等于栈深约束值的第一路径，从而极大提高了计算具有栈深约束值的路径的效率和成功率。
在本发明的一些实施例中，装置还包括：第二算法模块。第二算法模块可以设置为在第一算模块无法输出第一路径时，采用第二预设算法计算不考虑栈深约束值的第二路径，并对第二路径对应的标签栈列表进行压缩，使压缩后的标签栈列表的深度小于等于栈深约束值，并输出压缩后的标签栈列表对应的路径。
需要说明的是，通过将MSD输入第一预设算法，可以通过第一预设算法直接结算得到标签栈列表深度小于或等于MSD的第一路径，但也可能是，通过第一预设算法无法直接计算得到标签列表深度小于或等于MSD的第一路径。
也就是说，当通过第一预设算法无法直接计算得到标签栈列表的深度小于或等于MSD时，可以通过第二预设算法先计算不考虑MSD的路径并得到第二路径，随后对第二路径的标签栈列表进行压缩，得到标签栈列表深度小于等于MSD的路径。
根据本发明的一些实施例，第二算法模块对第二路径对应的标签栈列表进行压缩时，具体设置为：将标签列表中的至少部分链路标签替换为相应的节点标签，以降低标签栈列表深度。
也就是说，可以将标签列表中的全部链路标签替换为相应的节点标签，也可以是将标签列表中的部分链路标签替换为相应的节点标签。由此，可以降低标签列表深度。
如图4所示，若MSD为2，假设通过第二预设算法计算不考虑MSD得到节点1到节点4的第二路径为：1->2->5->3->4，对应的标签列表为{“1->2”，“2->5”，“5->3”，“3->4”}，栈深为4，不满足MSD约束要求。对第二路径的标签列表进行压缩，将标签列表中的链路标签替换为相应的节点标签得到标签栈列表为{“5”，“4”}，栈深为2，满足MSD约束要求。解释为，请求的完整路径分为了两部分，一部分是起始节点1到节点5的最短路径1->2->5，另一部分是节点5到节点4的最短路径5->4->3。
如图3和图4所示，在本发明的一些实施例，装置还可以包括：资源准备模块，资源准备模块设置为在进行第一路径计算之前，准备路径计算资源；由此，可以基于路径计算资源，进行第一路径或第二路径的计算。
可以理解的是，通过在计算路径之前，预先准备路径计算资源，可以提高路径计算效率。
如图3和图4所示，根据本发明的一些实施例，资源准备模块可以包括：拓扑加载模块和路径缓存模块
拓扑加载模块可以设置为向控制器上报网络拓扑信息；
路径缓存模块可以设置为基于网络拓扑信息进行路径缓存计算以得到路径计算资源。
例如，如图2所示，在进行路径计算之前，首先可以基于转发设备层面链路权值进行路径缓存，当控制器第一次启动或者重启时，转发设备通过协议上报给控制器每个IGP域的网络拓扑信息，控制器对IGP域进行路径缓存计算。由此，当进行路径计算时，可以直接从缓存中读取两节点之 间的最短路径，提高了路径计算效率。
在本发明的一些实施例，第一预设算法可以为Bellman算法，第二预设算法可以为Dijkstra算法或Floyed算法。
需要说明的是，使用Bellman算法计算带有MSD约束的最优路径，Bellman算法作为最短路径算法的一种，与最大跳数约束下的算路天然适配，这也是其它路径算法所不具备的。使用Bellman计算得到的标签栈列表深度等于路径中所有链路条数总数，此时标签栈列表中所有标签都为链路的Adj-SID。当标签列表栈深小于等于MSD时，认为路经计算成功，返回结果，算法到此结束。
当采用Bellman无法计算得到标签列表栈深小于等于MSD时，首先可以选用普通路径算法，如Dijkstra算法或Floyed算法等计算出一条不考虑MSD约束的最优路径，然后，使用严格LEA算法对该条路径进行压缩，思路为使用Node-SID来代替批量的Adj-SID。值得注意的是，利用Node-SID来引导路由转发路径时，当全网路径缓存中查询到两点之间最短路径只有一条时，才会使用Node-SID来代替批量的Adj-SID，这样可以保证标签栈列表中的Node-SID和Adj-SID元素可以表示唯一一条完整的起始节点到终节点的路径。当标签栈深小于等于MSD时，认为路径计算成功，返回结果，算法至此结束。
或者，首先使用普通路径算法如Dijkstra、Floyed等计算出一条不考虑MSD约束的最优路径，同样使用Node-SID来批量代替的Adj-SID，与上述方法不同的是，利用Node-SID来引导转发路径时，当全网路径缓存中查询到两点之间存在多条等价最短路径时，即ECMP场景，也会使用Node-SID来代替批量的Adj-SID，此时，与严格LEA相反，标签栈列表中的Node-SID和Adj-SID元素不能做到表示唯一一条完整的起始节点到 终节点的路径。当标签栈深小于等于MSD时，认为路径计算成功，返回结果，若标签栈深大于MSD，路径计算失败，返回失败结果。
根据本发明实施例的分段路由路径标签处理装置，包括：存储器、处理器及存储在存储器上并可在处理器上运行的计算机程序，计算机程序被处理器执行时实现如上述的方法的步骤。
根据本发明实施例的分段路由路径标签处理装置，首先可以通过Bellman算法计算具有栈深约束的路径，若得到符合栈深约束值条件的第一路径，则输出第一路径；若得不到符合栈深约束值条件的第一路径，则通过基本算法先计算不考虑栈深约束值进行路径计算，并对计算得到的第二路径的标签栈列表进行压缩，得到符合栈深约束值条件的路径，从而极大提高了计算具有栈深约束值的路径成功率。
根据本发明实施例的计算机存储介质，计算机存储介质上存储有计算机程序，计算机程序被处理器执行时实现如上述的针对具有栈深约束的路径计算方法的步骤。
根据本发明实施例的计算机存储介质，首先可以通过Bellman算法计算具有栈深约束的路径，若得到符合栈深约束值条件的第一路径，则输出第一路径；若得不到符合栈深约束值条件的第一路径，则通过基本算法先计算不考虑栈深约束值进行路径计算，并对计算得到的第二路径的标签栈列表进行压缩，得到符合栈深约束值条件的路径，从而极大提高了计算具有栈深约束值的路径成功率。
下面以具体的实施例详细描述根据本发明的针对具有栈深约束的路径计算方法：
如图4所示为一个具有10个节点、13条链路的网络拓扑，每条链路有它对应的权值，令链路A->B的Adj-SID为“A->B”，令节点A的Node-SID为“A”，为了简单说明问题，忽略了链路的带宽资源信息，但不影响算法的主流程。认为该网络拓扑为单个IGP域，这里以单个IGP域进行展示流程。
通过转发层面上报，控制器获得了单个IGP网络拓扑，以链路权值为准则，进行全局路径缓存，如下表所示(表中只列出了部分结果作为示例)：
Figure PCTCN2020099017-appb-000001
假设当前有一个算路请求，起点为节点1，终点为节点4，当该请求携带的最大栈深约束为一下几种情况时，分别讨论：
(1)最大栈深约束MSD＝4时：此时使用图2中的步骤S14中的Bellman算法可得到最优路径为1->2->5->3->4或者1->6->8->3->4，直接算路成功，返回结果，假设为前者，此时标签栈列表为{“1->2”,“2->5”，“5->3”，“3->4”}。值得注意的是，此时即使是使用普通算路算法，也可以得到满足MSD约束的最优路径。而本发明实施例中提出的标签压缩方法就是为了解决工程中MSD约束比较小的情况，事实上，实际工程中MSD都不大。
(2)最大栈深约束MSD＝3时：此时使用图2中步骤S14中的Bellman算法可得到跳数为3时的最优路径：1->6->7->4，算路成功，返回结果，此时标签栈列表为{“1->6”,“6->7”,“7->4”}；而使用普通算路算法得到的最 优路径还是1->2->5->3->4或者1->6->8->3->4，此时跳数为4大于MSD，算路失败。
(3)最大栈深约束MSD＝2时：此时使用图2中步骤S14中的Bellman算法，算路失败，因为在最大跳数约束为2的情况下，无可行路径；接下来使用普通算路算大得到一条不含有跳数约束的最优路径，假设该路径为：1->2->5->3->4，使用严格LEA算法，得到的标签栈列表为{“5”，“4”}，满足MSD约束要求。解释为，请求的完整路径分为了两部分，一部分是起始节点1到节点5的最短路径1->2->5，另一部分是节点5到节点4的最短路径5->4->3，这也是充分利用了Segment Routing技术的特点，即通过Node-SID来引导路由沿着最短路径方向转发。值得注意的是，此时的完整路径是可以唯一表示的，转发设备进行路由转发时候路径确定为1->2->5->3->4。
(4)最大栈深约束MSD＝1时：使用图2中步骤S14中的Bellman算法和步骤S15中的严格LEA算法都不能得到满足要求的标签栈列表。而使用图2中步骤S16中松散LEA算法，得到的标签栈列表为{“4”}，算路成功。解释为，转发设备进行路由转发的时候将从节点1开始沿着到节点4的最短路径进行，值得注意的是，此时节点1到节点4的最短路径有两条：1->2->5->3->4和1->6->8->3->4，所以并不能唯一标示转发路径。
本发明实施例综合了三种基于栈深约束的算路方案，极大提高了算路成功率。
通过具体实施方式的说明，应当可对本发明为达成预定目的所采取的技术手段及功效得以更加深入且具体的了解，然而所附图示仅是提供参考与说明之用，并非用来对本发明加以限制。
工业实用性
如上所述，本发明实施例提供的一种针对具有栈深约束的路径计算方法及装置具有以下有益效果：可以通过将栈深约束值输入第一预设算法，作为计算约束条件，直接计算得到标签列表栈深度小于等于栈深约束值的第一路径，提高了计算具有栈深约束值的路径的效率和成功率。

Claims (12)

  1. 一种针对具有栈深约束的路径计算方法，包括：
    基于栈深约束值，采用第一预设算法计算第一路径；
    若所述第一路径对应的标签栈列表的深度小于或等于所述栈深约束值，则输出所述第一路径。
  2. 根据权利要求1所述的针对具有栈深约束的路径计算方法，其中，所述方法还包括：
    在所述第一预设算法无法输出所述第一路径时，采用第二预设算法计算不考虑所述栈深约束值的第二路径，并对所述第二路径对应的标签栈列表进行压缩，使压缩后的所述标签栈列表的深度小于等于所述栈深约束值，并输出压缩后的所述标签栈列表对应的路径。
  3. 根据权利要求2所述的针对具有栈深约束的路径计算方法，其中，对所述第二路径对应的标签栈列表进行压缩，包括：
    将所述标签列表中的至少部分链路标签替换为相应的节点标签，以降低标签栈列表深度。
  4. 根据权利要求2所述的针对具有栈深约束的路径计算方法，其中，所述方法还包括：
    在进行第一路径计算之前，向控制器上报网络拓扑信息；
    基于所述网络拓扑信息进行路径缓存计算；
    基于所述路径缓存计算数据，进行所述第一路径或所述第二路径的计算。
  5. 根据权利要求2所述的针对具有栈深约束的路径计算方法，其中，
    所述第一预设算法为贝尔曼算法，所述第二预设算法为迪杰斯特拉算法或弗洛伊德算法。
  6. 一种针对具有栈深约束的路径计算装置，包括：
    第一算法模块，设置为基于栈深约束值，采用第一预设算法计算第一路径；
    若所述第一路径对应的标签栈列表的深度小于或等于所述栈深约束值，则输出所述第一路径。
  7. 根据权利要求6所述的针对具有栈深约束的路径计算装置，其中，所述装置还包括：
    第二算法模块，设置为在所述第一算模块无法输出所述第一路径时，采用第二预设算法计算不考虑所述栈深约束值的第二路径，并对所述第二路径对应的标签栈列表进行压缩，使压缩后的所述标签栈列表的深度小于等于所述栈深约束值，并输出压缩后的所述标签栈列表对应的路径。
  8. 根据权利要求7所述的针对具有栈深约束的路径计算装置，其中，所述第二算法模块对所述第二路径对应的标签栈列表进行压缩时，具体设置为：
    将所述标签列表中的至少部分链路标签替换为相应的节点标签，以降低标签栈列表深度。
  9. 根据权利要求7所述的针对具有栈深约束的路径计算装置，其中，所述装置还包括：
    拓扑加载模块，设置为在进行第一路径计算之前，向控制器上报网络拓扑信息；
    路径缓存模块，设置为基于所述网络拓扑信息进行路径缓存计算；
    所述第一算法模块和所述第二算法模块基于所述路径缓存计算数据，进行所述第一路径和所述第二路径的计算。
  10. 根据权利要求7所述的针对具有栈深约束的路径计算装置，其中，
    所述第一预设算法为贝尔曼算法，所述第二预设算法为迪杰斯特拉算法或弗洛伊德算法。
  11. 一种分段路由路径标签处理装置，包括：存储器、处理器及存储在所述存储器上并可在所述处理器上运行的计算机程序，所述计算机程序被所述处理器执行时实现如权利要求1至5中任一项所述的针对具有栈深约束的路径计算方法的步骤。
  12. 一种计算机存储介质，所述计算机存储介质上存储有计算机程序，所述计算机程序被处理器执行时实现如权利要求1至5中任一项所述的针对具有栈深约束的路径计算方法的步骤。
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