CN112866103A - Edge-calculation-oriented time-sensitive mobile forwarding network protection method - Google Patents
Edge-calculation-oriented time-sensitive mobile forwarding network protection method Download PDFInfo
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Abstract
The invention relates to a time-sensitive mobile forwarding network protection method facing edge calculation, and belongs to the technical field of communication. The method comprises the following steps: s1: establishing a link priority measurement model; s2: evaluating the reliability of the path; s3: establishing a FRER mechanism based on multi-stage P circles; s4: and selecting a copying and eliminating node and eliminating redundant frames. The invention provides a link priority measurement model to select a reasonable working protection path. The invention also provides an FRER forwarding algorithm based on the multi-stage P-ring, which improves the path reliability and the average recovery time of the network.
Description
Technical Field
The invention belongs to the technical field of communication, and relates to a time-sensitive mobile forwarding network protection method facing edge calculation.
Background
In the future, various 5G network applications appear, and the traditional internet technology and cloud computing cannot meet the requirements of strict low time delay, high bandwidth, high reliability and the like. In order to meet the strict quality of service requirements of more and more delay-sensitive applications at the Edge of a network, Edge Computing (Edge Computing) concepts and technologies have been proposed in recent years, Edge Computing is a micro data center integrating communication, storage and computation, is often deployed at the Edge user side of the internet or networking equipment, is used for a series of time-sensitive tasks such as data storage, analysis and processing, and can better meet the 5G applications with the strict delay requirements in the future. Meanwhile, the hierarchical data processing structure brought by edge calculation reduces the high bandwidth requirement of the data center and the complexity of networking equipment to a certain extent.
5G mobile fronthaul is one of the important components of a 5G mobile communication system, and with application of mimo (passive Multiple Input Multiple output) technology, a fronthaul network connecting an rru (remote Radio unit) and a BBU encounters a transmission capacity bottleneck problem. The 3GPP standard organization further segments BBU functions, places part of real-time processing functions in a distribution unit du (distributed unit), and places part of non-real-time processing functions in a central unit cu (centralized unit) for centralized deployment and clouding. As shown in fig. 1, the RRU is connected to the DU through a fronthaul network, the DU is connected to the CU through a middlhaul network, and the CU is connected to the core network through a backhaul network. The CU/DU flexible partition and deployment mode realizes the on-demand configuration and the efficient utilization of the mobile forwarding network resources, and better adapts to the individual requirements under different scenes. In some application scenarios with high real-time requirements, a CU/DU generally adopts a small cell base station deployment manner, that is, RRUs, antennas, and the like of a radio access portion are integrated with the DU. In consideration of the characteristics and advantages of the edge calculation, when the edge calculation is applied to a 5G mobile communication system, the deployment position can be selected to be at the edge side of the mobile forwarding network, namely, at the CU closer to the edge of the network, so as to better meet the requirements of the time-sensitive application. However, in the mobile fronthaul network architecture based on edge calculation, various service flows and fronthaul flows are transmitted through the mobile fronthaul network and QoS requirements are different, for example, audio and video flows only have a high bandwidth requirement and have strong delay tolerance, real-time control flows have high requirements on delay and reliability and play a crucial role in successful service transmission and normal network operation, and therefore, normal transmission of such time-sensitive flows needs to be protected to guarantee low delay and high reliability requirements. A Time-Sensitive Networking (TSN) provides a highly reliable bounded low-latency streaming service through functional enhancement based on ethernet, and becomes one of the most potential network technologies that currently meet the requirements of these application scenarios.
An important performance of network traffic transmission is the reliability of the path, where protection and restoration of the path is an important means to guarantee this performance. In a conventional optical network and an MPLS network, protection switching is a common method for path protection, that is, a pre-calculated redundant backup path is used for path switching when a main link of the network fails or fails, so as to ensure fast recovery of important services and minimize an average recovery delay caused by a path failure, but this approach inevitably increases consumption of network bandwidth resources. The industry uses PRP (parallel reduction protocol) and HSR (High-availability Seamless reduction) protocols[3]Frame seamless redundancy transmission between two independent sub-networks is realized, but the situation that a large amount of bandwidth is occupied exists. On the basis, 802.1CB[4]Frame Replication and Elimination (FRER) mechanisms in the standard forward replicated frames on redundant paths, delete the replicated frames at a destination node, and realize seamless redundant transmission of delay sensitive data. However, the 802.1CB standard does not specify the computation and configuration process of redundant paths, and common practice includes solving two disjoint parallel paths using a shortest path method, or solving two intersecting paths with a common link, as in document [5 ]]The Shared Backup Path Protection (SBPP) method in (1) is difficult for NP to solve in the multi-service Shared Path solution in large networks. Because two parallel forwarding paths generated by the FRER mechanism form a ring path at the copying and eliminating nodes, the solution problem of the two parallel disjoint paths can be converted into the solution of one ring path, which is combined with the P circle in the optical network[6]The (Preconfigured cycle, P-cycle) protection method is compatible. For example, document [7 ]]The P-ring protection method is used for realizing dynamic service protection in the power communication network, and the redundancy rate and the blocking rate of the system are reduced. Document [8]A P-Ball protection method is provided by using integer linear programming on the basis of P circles so as to solve the problem of double protection in a networkA link failure problem. Document [9 ]]And solving the optimal protection combination of the P circle set by using a genetic algorithm so as to solve the problems of frequency spectrum fragments and resource redundancy in the elastic optical network. Document [10 ]]The P-ring protection is combined with the network coding direction, and an intelligent P-ring protection method is provided to realize self-adaptive protection under different link failure conditions. However, the current P-turn construction method based on the heuristic algorithm considers that an end-to-end available backup path is provided from a source node and a destination node, and cannot provide a more detailed and reliable link-level protection process.
Disclosure of Invention
In view of this, an object of the present invention is to provide a method for protecting an edge-oriented time-sensitive mobile forwarding network, in which a working path to be protected is selected through a constructed link priority model, and segment-by-segment careful backup path protection is provided for a working link through multi-stage P-turn cascade, so that the network reliability is ensured, and at the same time, the extra bandwidth consumption of a frame replication and elimination mechanism is reduced as much as possible, and the average recovery time of frames is reduced.
In order to achieve the purpose, the invention provides the following technical scheme:
an edge-computing-oriented time-sensitive mobile forwarding network protection method comprises the following steps:
s1: establishing a link priority measurement model;
s2: evaluating the reliability of the path;
s3: establishing a FRER mechanism based on multi-stage P circles;
s4: and selecting a copying and eliminating node and eliminating redundant frames.
Optionally, the S1 specifically includes: selecting a working path with high priority for protection by constructing a link priority measurement model; the link priority factor comprises the link criticality of a static factor, and the normal working probability and the link idle rate of a link in a dynamic factor; the three factors are considered comprehensively, and the following link priority measurement model is given as a basis for selecting the working path, as shown in the following formula (1):
wherein, Pd(lwp) Priority information indicating a link, the larger the value, the better; cd(lwp) For link criticality, PijIs the set of the best paths between nodes i and j, mp lwpFor the number of shortest paths through links on the working path, Cd(lwp) The larger the value, the better; wR(lwp) Probability of link working properly, pijAs probability of link failure, WR(lwp) The larger the value, the better; fR(lwp) For link idle, b (l)wp) For the total bandwidth of the link, bu (l)wp) The difference between the currently used bandwidth of the link and the bandwidth of the link is the residual bandwidth, FR(lwp) Representing the degree of idleness of the current link, the larger the value, the better.
Optionally, the S2 specifically includes:
the frame is successfully forwarded on the path on the premise that all the passing links can work normally, and the reliability of the path is evaluated by considering the failure probability of the links and the residual bandwidth of the links;
the failure of the path has two conditions, namely, the failure of the working path and the normal work of the protection path; secondly, the working path and the protection path simultaneously have faults;
and comprehensively evaluating the reliability of the path by considering the condition of the residual bandwidth of the link, as shown in the following formula (2),
wherein, γijThe link bandwidth utilization rate is represented by the ratio of the link bandwidth utilization rate to the total link bandwidth, and the smaller the current link bandwidth utilization rate is, the smaller the fault probability of the link is; p is a radical ofijFor the probability of each link failing, the smaller the value, the better; r1As a working path P1Path reliability in the event of a link failure, R2Backup path P for P turns2And the reliability of the path when the link failure occurs, wherein the value range of the reliability of the path is between 0 and 1; v1And V2Are respectively a path P1And path P2A set of points on; in order to reduce the failure probability on the P-circle backup path, when the P-circle backup link is constructed, the path reliability of the backup link is evaluated, so that the path with the highest reliability is selected as the P-circle backup link.
Optionally, the S3 specifically includes:
after a working path is found by using a link priority model, P-turn link protection needs to be carried out on the working path; the key of the FRER mechanism based on the multi-level P circle is the construction of the multi-level P circle, and the protection of the working link by the backup link section by section is realized; the single P circle construction adopts a shortest path construction method, namely, a secondary shortest path is calculated between two nodes of each working link, and if a plurality of shortest paths exist, one with the highest path reliability is considered to be configured as a P circle backup link; if the shortest path is not found, a P-turn backup link does not need to be configured; however, the segment-by-segment link protection method may generate a redundant link, that is, a common link may exist in the minimum backup P-ring of the adjacent working links, and the ring formation process needs to be improved; in addition, if the links in the P circle are all in fault, the whole FRER transmission is blocked, and a new P circle protection working link needs to be reconstructed; compared with the P-ring construction method, the multi-stage P-ring construction method comprises the following steps:
using a shortest path algorithm to carry out segment-by-segment P-circle protection on links on a working path;
combining the constructed P circles, if the minimum P circle of the adjacent working links has a public link, combining the P circles into a new P circle, and simultaneously protecting the two sections of working links;
the length of the P-turn backup link is initially selected as the shortest path, if the backup link fails, the length of the P-turn link needs to be enlarged, and the shortest path without failure is calculated again.
Optionally, the S4 specifically includes:
firstly, selecting a source node and a destination node as a copying position and an eliminating position of a frame respectively;
secondly, considering the configuration situation of a P-ring backup link in the network, if a working link which is not configured with the P-ring is identified, namely the shortest path between the working links is not found, adding the starting node and the end node of the current link as the elimination and the duplication positions of the frame respectively;
a large number of frames are accumulated at a port of a destination switch, which causes network congestion and increase of packet loss rate, so that redundant frames need to be processed in time; the elimination of the redundant frame is realized by adding redundant control bytes at the head part of the frame, the added redundant control bytes comprise a replication node identifier, a serial number identifier, a path identifier and a switch identifier, and the steps for controlling the redundant frame are as follows:
1) the source node numbers frames in sequence and adds serial number identification;
2) after the replication node replicates the frame, adding a replication node identifier and a path identifier, wherein 0 is a working path and 1 is a backup path;
3) verifying whether the current link has a P-turn backup link, if so, turning to the step 4), otherwise, identifying the frame replication node identifier and the sequence number at the initial node, discarding the replication frame, and repeating the step 2 at the tail node);
4) verifying whether the switch node is a destination node, if so, turning to the step 5), otherwise, modifying the switch identifier as the self identifier, continuing to forward to the next node, and turning to the step 3);
5) the destination node eliminates the duplicate node identification and the serial number of the node identification frame, and discards the frame which arrives after the two identifications are the same.
The invention has the beneficial effects that:
(1) a link priority metric model is proposed to select a reasonable working protection path.
(2) A FRER forwarding algorithm based on multi-level P-ring is provided, so that the reliability of the network is improved and the bandwidth consumption is reduced.
(3) The method for eliminating redundant frames and the selection principle of the copying and eliminating nodes are provided.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.
Drawings
For the purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a schematic diagram of a mobile network;
FIG. 2 is a schematic diagram of the FRER mechanism;
FIG. 3 is a schematic diagram of a multi-stage P-turn construction;
FIG. 4 is a COST-239 network topology;
FIG. 5 is a comparison of path reliability under different loads;
FIG. 6 is a comparison of bandwidth consumption rates at different loads;
fig. 7 is a comparison of average recovery times at different loads.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.
Wherein the showings are for the purpose of illustrating the invention only and not for the purpose of limiting the same, and in which there is shown by way of illustration only and not in the drawings in which there is no intention to limit the invention thereto; to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not an indication or suggestion that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes, and are not to be construed as limiting the present invention, and the specific meaning of the terms may be understood by those skilled in the art according to specific situations.
As shown in fig. 2, the FRER mechanism prevents link failure from interrupting data transmission by transmitting frames and their copies in parallel on disjoint paths, i.e., using a seamless redundancy transmission manner, so that the construction and calculation of two paths are an important issue. Because the FRER mechanism respectively copies and eliminates frames at a source node and a destination node and respectively and simultaneously transmits the characteristics of the same frames by using two paths, and the characteristics are matched with the P-circle construction process, the invention adopts a P-circle calculation-based mode to construct the two paths of the FRER, firstly constructs a link priority measurement model, selects a working path needing protection, and then constructs a P-circle backup link to protect the working path. Compared with the conventional network link protection method, the multi-stage P-ring structure protection method has the following different characteristics and requirements.
How to choose the critical working path and provide the targeted link protection for it. Therefore, the priority measurement model of the link is established, and the working path with higher priority is selected for priority link protection, so that the limited path resources can be more effectively used.
In the case of a multi-link failure on a working path, the conventional P-turn protection may provide 1:1 or 1: the backup links of N protect, but cannot guarantee the timely recovery of each failed link. Therefore, a finer granularity P-ring protection mechanism needs to be designed.
When a plurality of links fail within the P-turn, the transmission of both the frame and the duplicate frame will be blocked. In this case, the backup P-turn link with the failed link needs to be expanded.
FRER mechanism-FRER-MPC based on multi-stage P-ring
1.1 Link priority metric model
Because the path resources are limited, the link backup protection can not be carried out on all paths, so the method selects the working path with high priority for protection by constructing a link priority measurement model. The link priority factors mainly comprise link criticality of static factors, and link normal working probability and link idle rate in dynamic factors. The invention comprehensively considers the three factors and provides the following link priority measurement model as the basis for selecting the working path, as shown in the following formula (1):
wherein, Pd(lwp) Indicating the priority information of the link, the larger the value, the better. Cd(lwp) For link criticality, PijIs the set of the best paths between nodes i and j, mp lwpFor the number of shortest paths through links on the working path, Cd(lwp) The larger the value, the better. WR(lwp) Probability of link working properly, pijAs probability of link failure, WR(lwp) The larger the value, the better. FR(lwp) For link idle, b (l)wp) For the total bandwidth of the link, bu (l)wp) The difference between the currently used bandwidth of the link and the bandwidth of the link is the residual bandwidth, FR(lwp) Representing the degree of idleness of the current link, the larger the value, the better.
1.2 Path reliability assessment
The invention considers the failure probability of the link and the residual bandwidth of the link to evaluate the reliability of the path. The failure of the path mainly has two kinds, firstly, the working path has failure and the protection path works normally; secondly, the working path and the protection path simultaneously have faults. Further, the invention considers the condition of link residual bandwidth, and carries out comprehensive evaluation on the reliability of the path, as shown in the following formula (2),
wherein, γijThe link bandwidth utilization rate is represented by the ratio of the link utilization bandwidth to the total link bandwidth, and the smaller the current link bandwidth utilization rate is, the smaller the failure probability of the link is. p is a radical ofijThe smaller the value, the better the probability of failure of each link. R1As a working path P1Path reliability in the event of a link failure, R2Backup path P for P turns2And the path reliability when the link failure occurs is in a range of 0 to 1. V1And V2Are respectively a path P1And path P2Set of points above. In order to reduce the probability of failure on the P-turn backup path, when the P-turn backup link is constructed, the path reliability of the backup link can be evaluated, so that the path with the highest reliability is selected as the P-turn backup link.
1.3 multistage P-loop based FRER mechanism
Through the above-mentioned section analysis, after the working path is found by using the link priority model, P-turn link protection needs to be performed on the working path. The key of the FRER mechanism based on the multi-level P circle is the construction of the multi-level P circle, and the protection of the working link by the backup link section by section is realized. The single P circle construction adopts a shortest path construction method, namely, a secondary shortest path is calculated between two nodes of each working link, and if a plurality of shortest paths exist, one with the highest path reliability is considered to be configured as a P circle backup link; if the shortest path is not found, the backup link of the P circle does not need to be configured. However, the segment-by-segment link protection method may generate redundant links, that is, a common link may exist in the minimum backup P-turn of the adjacent working links, so that the looping process needs to be improved. In addition, if the links in the P-turn are all in failure, the whole FRER transmission will be blocked, so that a new P-turn protection working link needs to be reconstructed. Therefore, compared with the traditional P-ring construction method, the multi-stage P-ring construction method is mainly embodied in the following three different steps:
using a shortest path algorithm to carry out segment-by-segment P-circle protection on links on a working path;
and combining the constructed P circles, and combining the P circles into a new P circle if the minimum P circle of the adjacent working links has a public link, and simultaneously protecting the two sections of working links.
The length of the P-turn backup link is initially selected as the shortest path, if the backup link fails, the length of the P-turn link needs to be enlarged, and the shortest path without failure is calculated again.
In the following, an example is given of the FRER mechanism based on multi-stage P-turns, and as shown in fig. 3, it is assumed that S, D are respectively the source and destination nodes, and one of the calculated working paths is (S, a)1,A2,A3D), the basic P-turn construction method is to calculate a backup path (S, A) which is not intersected with the working path4,A5,A6D), then constituting a basic P-turn, denoted P0. The multilevel P-circle construction method respectively protects the working links section by P-circle, and the minimum P-circle containing the corresponding working links is obtained by calculation1、P2、P3、P4Taking into account the circle P3And P4Links which are dual P turns and intersect on one turn (common link A)2A5) Therefore, the two are combined, and the new P circle is marked as P5So that the intersecting links become circle P5And the prior probability of the P circle is improved. Further, assume P-turn backup link (S, a)4) Failure causes the circle P1Failure, at which point P should be enlarged1The length of the loop and calculating a new protective loop (S, A)7,A4,A1S), is denoted as P1'. The general procedure of the FRER mechanism based on multi-level P-turns is therefore: the frames are sent from the source node S and redundant frames are generated and dividedRespectively pass through the selected working path (S, A)1,A2,A3D) and multi-stage P-turn backup paths (S, A)4,A1,A5,A3,A6And D), then forwarding to the destination node D hop by hop, and finally performing redundancy processing on the received frame and the copy thereof at the destination node to realize parallel seamless redundancy transmission of the frame.
The reliability analysis of the path is carried out simply for the basic P circle and the multi-level P circle constructed by the heuristic algorithm, and if the reliability of each link is P and the value is 0.8, the circle P is P0Reliability R (P)0)＝1-(1-p4)20.65, circle P1And P2Has a reliability of R (P)1)＝R(P2)＝1-(1-p)(1-p2) 0.93, circle P5Reliability R (P)5)＝1-(1-p2)20.87, circle P1Reliability of R (P)1')＝1-(1-p)(1-p3) 0.90, the reliability R (P) of the initial multi-stage P-turnM)＝R(P1)×R(P2)×R(P5) Reliability R (P) of P-turn in multiple stages with P-turn length extended 0.75M')＝R(P1')×R(P2)×R(P5) 0.73. Therefore, it can be seen from the simple analysis of the present example that the multi-level P-turn path reliability is higher than the basic P-turn path reliability and decreases as the P-turn length increases.
1.4 method for selecting copying and eliminating node and eliminating redundant frame
The FRER mechanism achieves the goal of reliable transmission by transmitting frames and their copies in parallel on the working path and the redundant path. The key ideas of this mechanism include the duplication of frames, the parallel transmission of the same frames, and the elimination of redundant frames. After the working path is calculated and selected, and the P-turn backup link calculation parallel transmission path is constructed, the positions of the copying and eliminating nodes and the redundant frames are selected. The invention discloses a method for selecting a copying and eliminating node, which comprises the following steps:
firstly, selecting a source node and a destination node as a copying position and an eliminating position of a frame respectively;
secondly, considering the configuration situation of the P circle backup link in the network, if the working link without the P circle is identified, that is, the next shortest path between the working links is not found, the starting node and the ending node of the current link are added to be respectively used as the elimination position and the copying position of the frame.
Further, the accumulation of a large number of frames at the destination switch port will cause network congestion and increase of packet loss rate, so that the redundant frames need to be processed in time. The invention realizes the elimination of redundant frames by adding redundant control bytes at the head of a frame, wherein the added redundant control bytes comprise a copy node identifier (duplication), a Sequence number identifier (Sequence), a path identifier (path) and a switch identifier (switch), and the steps for controlling the redundant frames are as follows:
the source node numbers frames in sequence and adds serial number identification;
after the replication node replicates the frame, adding a replication node identifier and a path identifier, wherein 0 is a working path and 1 is a backup path;
verifying whether the current link has a P-turn backup link, if so, turning to the step 4), otherwise, identifying the frame replication node identifier and the sequence number at the initial node, discarding the replication frame, and repeating the step 2 at the tail node);
verifying whether the switch node is a destination node, if so, turning to the step 5), otherwise, modifying the switch identifier as the self identifier, continuing to forward to the next node, and turning to the step 3);
the destination node eliminates the duplicate node identification and the serial number of the node identification frame, and discards the frame which arrives after the two identifications are the same.
1.5 Forwarding Algorithm based on FRER-MPC
The FRER mechanism achieves seamless high-reliability transmission of delay-sensitive data streams using both redundant frames and redundant paths, where the computation of two forwarding paths for frames and their duplicates is an important step of the mechanism. Algorithm 1 is a forwarding algorithm based on FRER-MPC and is used to solve the problem of computing two paths. The algorithm mainly comprises the following steps:
firstly, selecting a working path needing protection, namely a first forwarding path of a frame, by using a link priority model;
then, the working path is protected section by calculating and configuring a multi-level P-turn backup path;
then, adjacent P circles with a public link are combined, so that bandwidth waste is reduced;
and finally, calculating a second forwarding path of the duplicated frame through a plurality of cascaded P-turn paths.
FRER-MPC mechanism performance evaluation
The invention carries out quantitative comparison and analysis of indexes of a FRER-MPC mechanism based on a multi-stage P-ring structure, a shortest path forwarding SPS mechanism based on a minimum hop count and a link priority and a FRER-PC mechanism based on a single P-ring structure combination, wherein the performance evaluation indexes comprise path reliability, bandwidth consumption rate and average recovery time.
2.1 evaluation index
(1) Path reliability
The average reliability of the path refers to the probability product of successfully forwarding the frame under the condition that the link does not fail, and is a key parameter for reflecting the performance of the selected path, and the higher the reliability value is, the higher the success rate of frame forwarding is.
(2) Rate of bandwidth consumption
The bandwidth consumption rate reflects the overhead condition of the frame in the multipath forwarding process, and the calculation formula is the ratio of the bandwidth consumed during the frame forwarding to the total effective bandwidth resource of the network, wherein the total effective bandwidth of the network is the sum of the working bandwidths of the working path and the protection path.
(3) Average recovery time
The average recovery time reflects the reliable ability of the protection mechanism to recover from frame transmission after a link failure. The shorter the average recovery time, the more reliable the protection mechanism. The average recovery time in the present invention is defined as the difference between the receiving time of the first frame after the occurrence of the link failure and the receiving time of the last frame before the occurrence of the link failure, and the detection time of the link failure is ignored here.
2.2 simulation setup
As shown in FIG. 4, the experiment employs a European COST-239 including 11 nodes and 26 links[11]Network topology, link bandwidth set to 1Gbit/s, assuming link failure probability obeys 0,0.1]Uniformly distributed in the middle. The frame arrival process obeys Poisson distribution, the number of frames is 50000, and the size obeys even distribution from 64 bytes to 500 bytes. The length K of the P circle is the total number of the working link and the backup link, and the values are 3 and 4.
2.3 simulation results and analysis
FIG. 5 shows the path reliability of the three mechanisms FRER-MPC, FRER-PC and SPS as a function of load. The average reliability of all three schemes gradually decreases as the load increases. The path reliability of the SPS scheme is the lowest, because the shortest path selected based on the shortest hop count does not have a backup path, the failure probability of each link on the path determines the reliability of the whole forwarding path. The FRER-PC mechanism combines the shortest paths two by two to form a P-ring backup link of a working path, thereby greatly improving the reliability of the path. On the basis, the FRER-MPC mechanism configures P circles section by section for the link. Meanwhile, when the length K of the P circles is different, the reliability of the path forwarded by the frame is also changed. When the length of the P-turn increases, the path reliability begins to decrease, because the increase of the length of the P-turn increases the hop count of the backup link of the P-turn and decreases the path reliability, thereby affecting the reliability of the transmission path of the whole frame. When the working path and the backup path simultaneously fail, the method sacrifices certain path reliability performance through the expansion and reconfiguration of the range of the P circle, but solves the problem of multi-link failure in the network, and has more flexibility.
FIG. 6 shows the bandwidth consumption rate of the three mechanisms FRER-MPC, FRER-PC and SPS as a function of load. As can be seen from the figure, the bandwidth consumption rates of the three schemes are gradually increased as the load increases. The SPS scheme has the lowest bandwidth consumption rate because the backup path is not used to protect the transmission of the frame. In the FRER-PC scheme, a P-turn backup link is configured for a working path, and the same frames are transmitted in parallel, so that the reliability of the path is improved, and the bandwidth consumption of frame transmission is increased. The FRER-MPC mechanism further increases the redundant transmission of frames by way of segment-by-segment link protection, and the bandwidth consumption rate inevitably increases when the length of the P-turn is further extended.
FIG. 7 shows the mean recovery time of the three mechanisms FRER-MPC, FRER-PC and SPS as a function of load. It can be seen from the figure that the frame average recovery time for all three schemes is kept at a certain value as the load increases. The SPS scheme does not use a redundant path to protect frame transmission, and needs to recalculate and configure a new forwarding path when a link failure occurs, so the average recovery time is longest. The FRER-PC scheme transmits the same frame in parallel through P circles of protection paths, and avoids the problem of path recalculation, so that the recovery time after link failure is only influenced by the time delay difference between the working path and the backup path, and because the two paths are both the optimal two paths in the shortest path set and the time delay difference is very small, the average recovery time of the scheme is almost 0. The FRER-MPC scheme is similar to the FRER-PC scheme, and the average recovery time of the SPS scheme is reduced by a parallel protection path mode, but the time delay difference between the backup path and the working path is increased due to the multi-level P-turn backup link, and the time delay difference is further expanded along with the increase of the length of the P-turn, so that the average recovery time after the link failure is increased. The average recovery time performance of the FRER-MPC scheme provided by the invention is between the two, but the path reliability of the network is improved, and the method has better balance and applicability.
The invention mainly provides a multi-level P-ring-based time-sensitive network protection mechanism FRER-MPC, which selects a working path to be protected according to a link priority model, provides segment-by-segment backup link protection by utilizing a multi-level P-ring cascade connection mode, then provides a forwarding algorithm based on the FRER-MPC, and processes redundant frames by adding a redundant control word mode. Simulation results show that the FRER-MPC scheme effectively improves the path reliability of the FRER-PC scheme and reduces the average recovery time of the SPS scheme.
Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.
Claims (5)
1. A time-sensitive mobile forwarding network protection method facing edge calculation is characterized in that: the method comprises the following steps:
s1: establishing a link priority measurement model;
s2: evaluating the reliability of the path;
s3: establishing a FRER mechanism based on multi-stage P circles;
s4: and selecting a copying and eliminating node and eliminating redundant frames.
2. The method for protecting an edge-oriented time-sensitive mobile forwarding network according to claim 1, wherein: the S1 specifically includes: selecting a working path with high priority for protection by constructing a link priority measurement model; the link priority factor comprises the link criticality of a static factor, and the normal working probability and the link idle rate of a link in a dynamic factor; the three factors are considered comprehensively, and the following link priority measurement model is given as a basis for selecting the working path, as shown in the following formula (1):
wherein, Pd(lwp) Priority information indicating a link, the larger the value, the better; cd(lwp) For link criticality, PijIs the set of the best paths between nodes i and j, mp lwpFor the number of shortest paths through links on the working path, Cd(lwp) The larger the value, the better; wR(lwp) Probability of link working properly, pijAs probability of link failure, WR(lwp) The larger the value, the better; fR(lwp) For link idle, b (l)wp) For the total bandwidth of the link, bu (l)wp) The difference between the currently used bandwidth of the link and the bandwidth of the link is the residual bandwidth, FR(lwp) Representing the degree of idleness of the current link, the larger the value, the better.
3. The method for protecting an edge-oriented time-sensitive mobile forwarding network according to claim 2, wherein: the S2 specifically includes:
the frame is successfully forwarded on the path on the premise that all the passing links can work normally, and the reliability of the path is evaluated by considering the failure probability of the links and the residual bandwidth of the links;
the failure of the path has two conditions, namely, the failure of the working path and the normal work of the protection path; secondly, the working path and the protection path simultaneously have faults;
and comprehensively evaluating the reliability of the path by considering the condition of the residual bandwidth of the link, as shown in the following formula (2),
wherein, γijThe link bandwidth utilization rate is represented by the ratio of the link bandwidth utilization rate to the total link bandwidth, and the smaller the current link bandwidth utilization rate is, the smaller the fault probability of the link is; p is a radical ofijFor the probability of each link failing, the smaller the value, the better; r1As a working path P1Path reliability in the event of a link failure, R2Backup path P for P turns2And the reliability of the path when the link failure occurs, wherein the value range of the reliability of the path is between 0 and 1; v1And V2Are respectively a path P1And path P2A set of points on; in order to reduce the failure probability of the P-turn backup path, the structureAnd when the P-circle backup link is established, evaluating the path reliability of the backup link, so as to select the path with the highest reliability as the P-circle backup link.
4. The method for protecting an edge-oriented time-sensitive mobile forwarding network according to claim 3, wherein: the S3 specifically includes:
after a working path is found by using a link priority model, P-turn link protection needs to be carried out on the working path; the key of the FRER mechanism based on the multi-level P circle is the construction of the multi-level P circle, and the protection of the working link by the backup link section by section is realized; the single P circle construction adopts a shortest path construction method, namely, a secondary shortest path is calculated between two nodes of each working link, and if a plurality of shortest paths exist, one with the highest path reliability is considered to be configured as a P circle backup link; if the shortest path is not found, a P-turn backup link does not need to be configured; however, the segment-by-segment link protection method may generate a redundant link, that is, a common link may exist in the minimum backup P-ring of the adjacent working links, and the ring formation process needs to be improved; in addition, if the links in the P circle are all in fault, the whole FRER transmission is blocked, and a new P circle protection working link needs to be reconstructed; compared with the P-ring construction method, the multi-stage P-ring construction method comprises the following steps:
using a shortest path algorithm to carry out segment-by-segment P-circle protection on links on a working path;
combining the constructed P circles, if the minimum P circle of the adjacent working links has a public link, combining the P circles into a new P circle, and simultaneously protecting the two sections of working links;
the length of the P-turn backup link is initially selected as the shortest path, if the backup link fails, the length of the P-turn link needs to be enlarged, and the shortest path without failure is calculated again.
5. The method of claim 4, wherein the method comprises the following steps: the S4 specifically includes:
firstly, selecting a source node and a destination node as a copying position and an eliminating position of a frame respectively;
secondly, considering the configuration situation of a P-ring backup link in the network, if a working link which is not configured with the P-ring is identified, namely the shortest path between the working links is not found, adding the starting node and the end node of the current link as the elimination and the duplication positions of the frame respectively;
a large number of frames are accumulated at the port of the target switch, which causes network blockage and the increase of packet loss rate, and redundant frames are processed in time;
the elimination of the redundant frame is realized by adding redundant control bytes at the head part of the frame, the added redundant control bytes comprise a replication node identifier, a serial number identifier, a path identifier and a switch identifier, and the steps for controlling the redundant frame are as follows:
1) the source node numbers frames in sequence and adds serial number identification;
2) after the replication node replicates the frame, adding a replication node identifier and a path identifier, wherein 0 is a working path and 1 is a backup path;
3) verifying whether the current link has a P-turn backup link, if so, turning to the step 4), otherwise, identifying the frame replication node identifier and the sequence number at the initial node, discarding the replication frame, and repeating the step 2 at the tail node);
4) verifying whether the switch node is a destination node, if so, turning to the step 5), otherwise, modifying the switch identifier as the self identifier, continuing to forward to the next node, and turning to the step 3);
5) the destination node eliminates the duplicate node identification and the serial number of the node identification frame, and discards the frame which arrives after the two identifications are the same.
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