Standard High-availability Seamless Redundancy Research Articles

A Combined Approach Effectively Enhancing Traffic Performance for HSR Protocol in Smart Grids

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.

A Novel Dual Separate Paths (DSP) Algorithm Providing Fault-Tolerant Communication for Wireless Sensor Networks.

Fault tolerance has long been a major concern for sensor communications in fault-tolerant cyber physical systems (CPSs). Network failure problems often occur in wireless sensor networks (WSNs) due to various factors such as the insufficient power of sensor nodes, the dislocation of sensor nodes, the unstable state of wireless links, and unpredictable environmental interference. Fault tolerance is thus one of the key requirements for data communications in WSN applications. This paper proposes a novel path redundancy-based algorithm, called dual separate paths (DSP), that provides fault-tolerant communication with the improvement of the network traffic performance for WSN applications, such as fault-tolerant CPSs. The proposed DSP algorithm establishes two separate paths between a source and a destination in a network based on the network topology information. These paths are node-disjoint paths and have optimal path distances. Unicast frames are delivered from the source to the destination in the network through the dual paths, providing fault-tolerant communication and reducing redundant unicast traffic for the network. The DSP algorithm can be applied to wired and wireless networks, such as WSNs, to provide seamless fault-tolerant communication for mission-critical and life-critical applications such as fault-tolerant CPSs. The analyzed and simulated results show that the DSP-based approach not only provides fault-tolerant communication, but also improves network traffic performance. For the case study in this paper, when the DSP algorithm was applied to high-availability seamless redundancy (HSR) networks, the proposed DSP-based approach reduced the network traffic by 80% to 88% compared with the standard HSR protocol, thus improving network traffic performance.

A Novel Optical High-Availability Seamless Redundancy (OHSR) Design Based on Beam Splitting / Combining Techniques

The standard high-availability seamless redundancy (HSR) protocol utilizes duplicated frame copies of each sent frame for zero fail over time. This means that even in cases of a node or link failure, the destination node will receive at least one copy of the sent frame, resulting in no network downtime. However, the standard HSR is mostly based on the electrical signal connection inside the node, which leads to the production of considerable latency at each node due to frame processing. Therefore, in a large scale HSR ring network, the accumulated latencies become significant and can often restrict the mission-critical real-time application of HSR. In this paper, we present a novel design for optical HSR (OHSR) that uses beam splitting/combining techniques. The proposed OHSR passes the frames directly to adjacent nodes without frame processing at each node, thereby theoretically generating no latency in any node. Various simulations for network samples, made to validate the OHSR design and its performance, show that the OHSR outperforms the standard HSR.

A novel ring-based dual paths approach for reducing redundant traffic in HSR networks

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.

RMT: A novel algorithm for reducing multicast traffic in HSR protocol networks

The high-availability seamless redundancy (HSR) protocol is one of the most important redundancy IEC standards that has garnered a great deal of attention because it offers a redundancy with zero recovery time, which is a feature that is required by most of the modern substation, smart grid, and industrial field applications. However, the HSR protocol consumes a lot of network bandwidth compared to the Ethernet standard. This is due to the duplication process for every sent frame in the HSR networks. In this paper, a novel algorithm known as the reducing multicast traffic (RMT) is presented to reduce the unnecessary redundant multicast traffic in HSR networks by limiting the spreading of the multicast traffic to only the rings that have members associated with that traffic instead of spreading the traffic into all the network parts, as occurs in the standard HSR protocol. The mathematical and the simulation analyses show that the RMT algorithm offers a traffic reduction percentage with a range of about 60–87% compared to the standard HSR protocol. Consequently, the RMT algorithm will increase the network performance by freeing more bandwidth so as to reduce HSR network congestion and also to minimize any intervention from the network administrator that would be required when using traditional traffic filtering techniques.

Developing a New HSR Switching Node (SwitchBox) for Improving Traffic Performance in HSR Networks

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 redundancy protocols for Ethernet networks have been developed and standardized, such as rapid spanning tree protocol (RSTP), media redundancy protocol (MRP), parallel redundancy protocol (PRP), high-availability seamless redundancy (HSR) and others. RSTP and MRP have switchover delay drawbacks. PRP provides zero recovery time, but requires a duplicate network infrastructure. HSR operation is similar to PRP, but HSR uses a single network. However, the standard HSR protocol is mainly applied to ring-based topologies and generates excessively unnecessary redundant traffic in the network. In this paper, we develop a new switching node for the HSR protocol, called SwitchBox, which is used in HSR networks in order to support any network topology and significantly reduce redundant network traffic, including unicast, multicast and broadcast traffic, compared with standard HSR. By using the SwitchBox, HSR not only provides seamless communications with zero switchover time in case of failure, but it is also easily applied to any network topology and significantly reduces unnecessary redundant traffic in HSR networks.

A Comparison of Techniques for Reducing Unicast Traffic in HSR Networks

This paper investigates several existing techniques for reducing high-availability seamless redundancy (HSR) unicast traffic in HSR networks for substation automation systems (SAS). HSR is a redundancy protocol for Ethernet networks that provides duplicate frames for separate physical paths with zero recovery time. This feature of HSR makes it very suited for real-time and mission-critical applications such as SAS systems. HSR is one of the redundancy protocols selected for SAS systems. However, the standard HSR protocol generates too much unnecessary redundant unicast traffic in connected-ring networks. This drawback degrades network performance and may cause congestion and delay. Several techniques have been proposed to reduce the redundant unicast traffic, resulting in the improvement of network performance in HSR networks. These HSR traffic reduction techniques are broadly classified into two categories based on their traffic reduction manner, including traffic filtering-based techniques and predefined path-based techniques. In this paper, we provide an overview and comparison of these HSR traffic reduction techniques found in the literature. The concepts, operational principles, network performance, advantages, and disadvantages of these techniques are investigated, summarized. We also provide a comparison of the traffic performance of these HSR traffic reduction techniques.

FHT: A Novel Approach for Filtering High-Availability Seamless Redundancy (HSR) Traffic

High-availability seamless redundancy (HSR) is a protocol for Ethernet networks that provides duplicated frames with zero recovery time in the event of any network component’s failure. It is suited for applications that demand high availability and a very short time-outs such as substation automation systems (SAS). However, HSR generates excessive unnecessary unicast frames and spreads them throughout connected-ring networks, whether or not the destination node exists in network’s rings. This unnecessary redundant traffic causes high bandwidth consumption, resulting in degradation of network performance. In this paper, we introduce a novel approach for filtering and reducing HSR unicast traffic in connected-ring networks, called “filtering HSR traffic” (FHT). The purpose of FHT is to filter HSR unicast traffic and remove circulated traffic for all rings in connected-ring networks. Therefore, FHT significantly reduces network unicast traffic in connected-ring networks. The traffic performance of FHT has been analyzed, evaluated, and compared to that of standard HSR protocol and the port locking (PL) approach. Various simulations were conducted to validate the traffic performance analysis. Analytical and simulation results showed that, for our sample network, FHT reduced network unicast traffic by about 82% compared with standard HSR and by about 56% compared with the PL approach, thus freeing up network bandwidth and improving network traffic performance.

DVP: A Novel High-Availability Seamless Redundancy (HSR) Protocol Traffic-Reduction Algorithm for a Substation Automation System Network

The high-availability seamless redundancy (HSR) protocol, a potential candidate for substation automation system (SAS) networks, provides duplicated frame copies of each sent frame, with zero fault-recovery time. This means that even in the case of node or link failure, the destination node will receive at least one copy of the sent frame. Consequently, there is no network operation down time. However, the forwarding process of the QuadBox node in HSR is not smart and relies solely on duplication and random forwarding of all received frames. Thus, if a unicast frame is sent in any closed-loop network, the frame copies will be spread through most of all the links in both directions until they reach the destination node, which inevitably results in significant, unnecessary network traffic. In this paper, we present an algorithm called the dual virtual paths (DVP) algorithm to solve such an HSR excessive traffic issue. The idea behind our DVP algorithm is to establish automatic DVP between each HSR node and all the other nodes in the network, except for the QuadBox node. These virtual paths will be used for DVP unicast traffic transmission, rather than using the standard HSR transmission process. Therefore, the DVP algorithm results in less traffic, because there is no duplication or random forwarding, contrary to standard HSR. For the sample networks selected in this paper, the DVP algorithm shows more than a 70% reduction in network traffic and about an 80% reduction in the discarded traffic compared to the standard HSR protocol.

Improvement of high-availability seamless redundancy (HSR) traffic performance for smart grid communications

High-availability seamless redundancy (HSR) is a redundancy protocol for Ethernet networks that provides two frame copies for each frame sent. Each copy will pass through separate physical paths, pursuing zero fault recovery time. This means that even in the case of a node or a link failure, there is no stoppage of network operations whatsoever. HSR is a potential candidate for the communications of a smart grid, but its main drawback is the unnecessary traffic created due to the duplicated copies of each sent frame, which are generated and circulated inside the network. This downside will degrade network performance and might cause network congestion or even stoppage. In this paper, wepresent two approaches to solve the above-mentioned problem. The first approach is called quick removing (QR), and is suited to ring or connected ring topologies. The idea is to remove the duplicated frame copies from the network when all the nodes have received one copy of the sent frame and begin to receive the second copy. Therefore, the forwarding of those frame copies until they reach the source node, as occurs in standard HSR, is not needed in QR. Our example shows a traffic reduction of 37.5% compared to the standard HSR protocol. The second approach is called the virtual ring (VRing), which divides any closed-loop HSR network into several VRings. Each VRing will circulate the traffic of a corresponding group of nodes within it. Therefore, the traffic in that group will not affect any of the other network links or nodes, which results in an enhancement of traffic performance. For our sample network, the VRing approach shows a network traffic reduction in the range of 67.7 to 48.4% in a healthy network case and 89.7 to 44.8% in a faulty network case, compared to standard HSR.