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High availability is crucial for industrial Ethernet networks as well as Ethernet-based control systems such as automation networks and substation automation systems (SAS). Since standard Ethernet does not support fault tolerance capability, the high availability of Ethernet networks can be increased by using redundancy protocols. Various redundanc...
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... a failure-free case, RSTP blocks the redundant link between Ethernet SW1 and SW4 to avoid the switching SW2 and loop, SW3 fails, as shown RSTP in activates Figure 16a. corresponding The source blocked node connecting ports in SW1 to SW1 and SW4 sends to traffic enable frames the to blocked link between them, as shown in Figure 16b. Therefore, RSTP suffers switchover delay in a the destination node connecting to SW3 through the path, SW1-SW2-SW3. When the link between case of network failure. SW2 and SW3 fails, RSTP activates corresponding blocked ports in SW1 and SW4 to enable the blocked link between 4.1.2. Redundancy them, as Performance shown in Figure under SwitchBox 16b. Therefore, ‐ Based HSR RSTP suffers switchover delay in a case of network failure. 4.1.2. Redundancy Performance under SwitchBox-Based HSR and sends them over its trunk ports connecting to SwitchBoxes SW2 and SW4. SW2 and SW4 look up We their consider MAC table an HSR and send network the frames with four over HSR another SwitchBoxes, trunk port when as shown they in receive Figure them 17. for In a the failure-free first case, time. when SwitchBox receiving SW3 unicast receives frames two copies sent by of a each source frame node, from SwitchBox two links connected SW1 looks to it, up looks its MAC up its table and sends MAC them table and over then its trunk forwards ports the connecting first copy to to SwitchBoxes the destination SW2 node and and SW4. discards SW2 the and duplicate. SW4 look up their The MAC process table of and forwarding send the the frames unicast over frames another in a trunk failure port ‐ free when case is they shown receive in Figure them 17a. for the first time. When the link between SwitchBoxes SW2 and SW3 fails, only one copy of each frame is lost, SwitchBox SW3 receives two copies of each frame from two links connected to it, looks up its MAC while the other copy still reaches the destination SwitchBox SW3 without a switchover delay, table and then forwards the first copy to the destination node and discards the duplicate. The process as shown in Figure 17b. SwitchBox SW3 looks up its MAC table and forwards the copy to the of forwarding the unicast frames in a failure-free case is shown in Figure 17a. When the link between SwitchBoxes SW2 and SW3 fails, only one copy of each frame is lost, while the other copy still reaches the destination SwitchBox SW3 without a switchover delay, as shown in This section describes the traffic performance analysis of SwitchBox-based HSR compared to the standard HSR. Since the standard HSR is mainly applied in ring topologies, we consider a sample network in the ring topology to analyze, evaluate and compare with respect to traffic performance. To analyze and evaluate traffic performance, network traffic was chosen as a performance metric. Network traffic is defined as the total number of frame copies that travel on links and that are received by nodes in the network. ‚ Network unicast traffic: Network unicast traffic is the total number of unicast frame copies that are delivered on links and received by nodes when a source node sends unicast frames to a destination node in the network. ‚ Network broadcast traffic: Network broadcast traffic is the total number of broadcast frame copies that are delivered on links and received by nodes when a source node sends broadcast frames to the other nodes in the network. We consider a sample network consisting of eight DANH rings; each DANH ring includes four DANH nodes, as shown in Figure 18. QuadBoxes are used to connect DANH rings under the standard HSR, whereas SwitchBoxes are used to connect DANH rings under SwitchBox-based HSR. To avoid single points of failure in the network, two QuadBoxes/SwitchBoxes are used to connect to two rings. 4.2.1. Notations In this paper, we use some parameters for network traffic performance analysis. These parameters are denoted and described in Table ...
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... the example network in Figure 18, the number of links of each SwitchBox ring is equal to 8, whereas the number of links of each DANH ring is equal to 5, excluding one link between two SwitchBoxes in the DANH ring. Network unicast traffic nt is calculated as ...
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... the sample network in Figure 18, the number of links of each QuadBox ring is equal to 8, whereas the number of links of each DANH ring is equal to 6. Network unicast traffic is calculated ...
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... Simulation 1: Validate Seamless Redundancy In this simulation, we considered an HSR network with six SwitchBoxes, as shown in Figure 23. A source node sent unicast frames to a destination node. During the communications, we assumed that three link failures occurred on the following links: the link between SwitchBoxes SW1 and SW3, the link between SwitchBoxes SW2 and SW4, and the link between SwitchBoxes SW4 and SW6. In the simulation, the source node sent N unicast frames to the destination node ( N = 10, 20, . . . , 100). The number of unicast frames received at the destination nodes was recorded to evaluate the redundancy performance of the SwitchBox-based HSR. 5.1.2. Simulation 2: Validate the Analyzed Traffic Performance We considered the sample network in Figure 18. Simulations were conducted for both unicast and broadcast traffic described and analyzed in Section 4. In these simulations, the source node sent N traffic frames, including unicast and broadcast frames ( N = 10, 20, . . . , 100). Network traffic under the standard HSR and the SwitchBox-based HSR was recorded for comparison with the analyzed network traffic described in Section 4. 5.1.3. Simulation 3: Evaluate and Compare the Traffic Performance The objective of the simulation was to evaluate and compare the traffic performance of the SwitchBox-based HSR with that of the standard HSR. Simulations were conducted for both unicast and broadcast traffic. In these simulations, the source node sent N traffic frames, including unicast and broadcast frames ( N = 10, 20, . . . , 100). Network traffic under the standard HSR and the SwitchBox-based HSR was recorded for evaluation and comparison. Case 1 We considered a sample HSR network consisting of twelve DANH rings; each DANH ring included ten DANH nodes, as shown in Figure 24. Case 2 In that case, we considered a sample HSR network in Figure 25 consisting of twenty DANH rings that are connecting through a QuadBox/SwitchBox ring. Each DANH ring included ten DANH nodes. 5.2.1. Simulation 1 Table 2 shows the network frame statistics in Simulation 1. The simulation results show that there is no lost frame during the communications. In other words, the SwitchBox-based HSR provides seamless redundancy with zero switchover time in a case of failure. 5.2.2. Simulation 2 Table 3 shows the network traffic frames recorded from the simulation for both unicast and broadcast traffic under the standard HSR protocol and the SwitchBox-based HSR. Figure 26a shows the comparison of the analytical unicast traffic performance and Figure 26b shows the comparison of the simulated unicast traffic performance for the SwitchBox-based HSR with the standard HSR. The analytical and simulation results are the same. In this case, the analytical and simulation results show that the SwitchBox-based HSR reduces network unicast traffic by 76% compared with the standard HSR. Figure 27a shows the comparison of the analytical broadcast traffic performance and Figure 27b shows the comparison of the simulated broadcast traffic performance for the SwitchBox-based HSR compared with the standard HSR. The simulation results are similar to the analytical results. In this case, the analytical and simulation results show that the SwitchBox-based HSR reduces network broadcast traffic by up to 49% compared with the standard HSR. 5.2.3. Simulation 3 Table 4 shows network traffic frames recorded in case 1 of the simulation for both unicast and broadcast traffic under the standard HSR protocol and the SwitchBox-based HSR. Table 5 shows the network traffic frames recorded in case 2 of the simulation for both unicast and broadcast traffic under the standard HSR protocol and the SwitchBox-based HSR. Figure 28 shows the comparison of the unicast and broadcast traffic performance for the SwitchBox-based HSR compared to the standard HSR. In this case, the simulation results show that the SwitchBox-based HSR reduced network unicast traffic by 83% and network broadcast traffic by 50% compared to the standard HSR. Figure 29 shows the comparison of the unicast and broadcast traffic performance for the SwitchBox-based HSR compared to the standard HSR. In this case, the simulation results show that the SwitchBox-based HSR reduced network unicast traffic by 89% and network broadcast traffic by 50% compared to the standard HSR. The results of Simulation 1 demonstrate that SwitchBox-based HSR provides seamless redundancy for HSR networks in any topology. Unlike RSTP, which suffers switchover delay, SwitchBox-based HSR provides zero recovery time in case of network failures. The results of Simulation 2 validate the unicast and broadcast traffic performance analyzed in Section 4. The simulation results shows that the simulated traffic performance is similar to the analytical traffic performance. The results of Simulation 3 demonstrate that network traffic performance of SwitchBox-based HSR is much better than that of the standard HSR. Unlike standard HSR, which duplicates and circulates unicast traffic frames in all rings, SwitchBox-based HSR does not forward the unicast traffic frames to DANH rings that do not contain the destination of the frames. In addition, SwitchBox-based HSR prevents traffic unicast/broadcast frames from circulating in rings. Therefore, SwitchBox-based HSR significantly reduces network traffic compared with the standard HSR. Numerically, in our sample networks, SwitchBox-based HSR reduces unicast network traffic by up to 89% for unicast traffic and by 50% for broadcast traffic compared with the standard HSR. Table 6 shows a comparison of SwitchBox-based HSR and existing redundancy protocols including RSTP, MRP, PRP and standard HSR. In this paper, we have developed a new HSR switching node, called SwitchBox. By using SwitchBoxes, HSR can be applied to any network topology, such as ring, mesh or star topologies. SwitchBoxes forward unicast traffic frames based on the MAC table and filter unicast traffic frames for DANH rings that do not contain the destination of the frames. Additionally, SwitchBox-based HSR prevents networks from doubling and circulating unicast and broadcast traffic frames in HSR networks. Therefore, SwitchBox-based HSR significantly reduces network traffic compared with the standard HSR. The simulation results showed that, for our sample networks, SwitchBox-based HSR reduced network traffic by up to 89% for unicast traffic and by 50% for broadcast traffic compared with the standard HSR protocol, thus saving network bandwidth and improving network traffic performance for time-critical and mission-critical systems, such as substation automation systems, automation networks, and other industrial Ethernet networks. Our future work will develop and implement SwitchBox-based HSR in hardware ...
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... In addition to the CAN bus, researchers have also developed other protocols aimed at providing fault-tolerant IVNs. Tien and Rhee [21] proposed a novel HSR switching node (SwitchBox) that is capable of forwarding and filtering unicast traffic, thus preventing unnecessary frames from circulating in HSR networks. This approach allows the use of HSR in any topology (e.g., ring, mesh, star) as well as significantly improving traffic performance in an HSR network. ...
Because there is always a demand for robust fault-tolerant automotive networks, recent works have focused particularly on replacing controller area networks (CANs) with more reliable protocols for time-critical bandwidth-demanding in-vehicle network (IVN) systems. However, as the automobile industry normally relies on proven technologies, an interim solution to fault-tolerance capability for CAN systems is still essential during the transition phase to other protocols. In this paper, we propose a novel fault-tolerant algorithm for the CAN protocol that we refer to as seamless CAN. Its operating concept is based on a high-availability seamless redundancy (HSR) implementation inside the vehicle network’s ring structure, and the fault tolerance is achieved by encapsulating the CAN frame inside the HSR frames and sending them in the ring topology. The simulation results showed that seamless CAN provided better performance regarding no frame loss in the case of link failures and up to ten times lower number of error occurrences.
... The main drawback of the techniques, however, is to generate additional control overhead in the networks because they exchange control messages to discover and establish dual paths. In addition, there are other techniques for reducing redundant traffic in HSR networks, including the HSR SwitchBox technique [18], the integration of HSR and OpenFlow (HSE + OF) [19], the reducing multicast traffic (RMT) [20], the cost-effective topology design for HSR resilient mesh networks [21], and the latency and traffic reduction technique for process-level network [22]. The HSR SwitchBox technique defines a new switching node in HSR networks that forwards HSR frames based on looking up of media access control (MAC) tables instead of flooding the frames. ...
The effective filtering approach (EFA) is one of the most effective approaches for improving the network traffic performance of high-availability seamless redundancy (HSR) networks. However, because EFA uses port locking (PL) for detecting nondestination doubly-attached nodes with HSR protocol (DANH) rings in HSR networks, it forwards the first sent frame to all DANH rings in the network. In addition, it uses a control message for discovering passive QuadBox rings in both unidirectional and bidirectional communications. In this study, we propose an enhanced version of EFA called enhanced-EFA (eEFA) that does not forward unicast frames to nondestination DANH rings. eEFA does not use any control message to discover passive QuadBox rings in bidirectional communications. eEFA thus reduces the network traffic in HSR networks compared with EFA. Analytical and simulation results for a sample network show that the traffic reduction of eEFA was 4–26% and 2–20% for unidirectional and bidirectional communications, respectively, compared to EFA. eEFA, thus, clearly saves network bandwidth and improves the network performance.
... The main drawback of the techniques, however, is to generate additional control overhead in the networks because they exchange control messages to discover and establish dual paths. In addition, there are other techniques for reducing redundant unicast traffic in HSR networks, including the HSR SwitchBox technique [19] and the integration of HSR and OpenFlow (HSE + OF) [20]. The HSR SwitchBox technique defines a new switching node in HSR networks that forwards HSR frames based on looking up of media access control (MAC) tables instead of flooding Energies 2017, 10, 1356 3 of 18 the frames. ...
In this paper, we propose a very effectively filtering approach (EFA) to enhance network traffic performance for high-availability seamless redundancy (HSR) protocol in smart grids. The EFA combines a novel filtering technique for QuadBox rings (FQR) with two existing filtering techniques, including quick removing (QR) and port locking (PL), to effectively reduce redundant unicast traffic within HSR networks. The EFA filters unicast traffic for both unused terminal rings by using the PL technique and unused QuadBox rings based on the newly-proposed FQR technique. In addition, by using the QR technique, the EFA prevents the unicast frames from being duplicated and circulated in rings; the EFA thus significantly reduces redundant unicast traffic in HSR networks compared with the standard HSR protocol and existing traffic filtering techniques. The EFA also reduces control overhead compared with the filtering HSR traffic (FHT) technique. In this study, the performance of EFA was analyzed, evaluated, and compared to that of the standard HSR protocol and existing techniques, and various simulations were conducted to validate the performance analysis. The analytical and simulation results showed that for the sample networks, the proposed EFA reduced network unicast traffic by 80% compared with the standard HSR protocol and by 26–62% compared with existing techniques. The proposed EFA also reduced control overhead by up to 90% compared with the FHT, thus decreasing control overhead, freeing up network bandwidth, and improving network traffic performance.
Because more and more on-board electronics devices are being used inside such complicated systems as cars or spacecraft, Ethernet-based protocol with high bandwidth capability might be an alternative to legacy low-speed protocols. Many efforts have been made to improve the reliability of Ethernet for safety-critical networks, including the IEC 62439–3 (High-availability Seamless Redundancy) and IEEE 802.1CB (Frame Replication and Elimination for Reliability) standards. This paper is a comparative study of the two aforementioned protocols. Although both achieve seamless redundancy by replicating and sending multiple copies of the same frame over disjointed paths, their characteristics might be suited for different network configurations
Relay protection devices based on sampling and tripping over shared networks, including the switch tree network and High-availability Seamless Redundancy (HSR) ring network, have been widely used in smart substations. These networks all have uncertainties in the relay operation system, such as data congestion, delays, errors and storms, etc., leading errors to sampled value (SV) in digital protection. Therefore, the effective delay measurement and evaluation method over shared networks are important for the reliable relay operation. Based on the principle and implementation of SV propagation delay measurement in shared network, a novel evaluation method of propagation delay measurement is proposed in this paper. With this method, the credibility of the delay measurement could be evaluated and the threshold of delay could be adjusted flexibly in engineering. The credibility indicator and engineering threshold method could mitigate spurious tripping and improve the reliable operation in the protection system.
In this paper, we propose a novel dual paths-based approach, called ring-based dual paths (RDP), to significantly reduce redundant unicast traffic in high-availability seamless redundancy (HSR) networks. RDP establishes dual paths for forwarding unicast frames between nodes in HSR networks. Unlike existing dual paths-based approaches, such as dual virtual paths (DVP) that establish dual paths for each connection pair of HSR terminal nodes, RDP sets up dual paths for each connection pair of HSR rings. Therefore, RDP significantly reduces the number of established dual paths, which, in turn, reduces the overhead in discovering and establishing dual paths, as well as the memory space required to store these paths compared with the existing dual paths-based approaches. The performance of RDP has been analyzed, evaluated, and compared to that of the standard HSR protocol and the DVP approach. Various simulations were conducted to validate the traffic performance analysis. Analytical and simulation results showed that for the sample networks RDP reduced network unicast traffic by 80–88% compared with the standard HSR protocol, thus freeing up network bandwidth and improving network traffic performance.
