Saad Allawi Nsaif

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.

RURT: A novel approach for removing the unnecessary redundant traffic in any HSR closed-loop network type

The high-availability seamless redundancy (HSR) protocol is one of the most potential redundancy protocols that provides two frame copies for each sent frame; one copy from each direction or path. The HSR protocol is a seamless redundancy protocol because if one of the sent copies is lost due to an error or a component failure, the destination node will stay ready to receive the other frame copy without any interruption; therefore, it is a zero recovery time protocol. However, in a closed-loop network, HSR traffic performance suffers from unnecessary redundant frame copies generated and spread through the network due to the consecutive duplication of every sent frame copy at each QuadBox node. These duplicated frame copies will consume the available network bandwidth and may cause network congestion or delay. In this paper, we introduce a novel approach called removing the unnecessary redundant traffic (RURT). The idea of the RURT approach is to remove the unnecessary redundant traffic from the network at an early stage instead of keeping it circulating in the network. For the network sample selected in this paper, the RURT approach shows a 38.4-50% reduction in network traffic under failure-free and failure cases compared to the standard HSR protocol. Consequently, the RURT approach will increase network performance by freeing more bandwidth to avoid any network congestion or delay. As a result, more applications can be run on the network without any network problem.

Quick removing (QR) approach using cut-through switching mode

We previously introduced a quick removing (QR) approach to improve the high-availability seamless redundancy (HSR) protocols traffic performance. The idea of the QR approach 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. In our earlier paper, we adopted the store and forward switching mode, whereas in this paper, we present the HSR nodes behavior and the QR approach performance using a cut-through switching mode. The performance analysis shows a reduction percentage in frame latency that reaches about 49% compared to the store and forward switching mode. Consequently, this will improve network performance, free more bandwidth, and deliver sent frames quickly to their required destinations, which is a firm condition in many industrial and automation applications.

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.

LPLB: A Novel Approach for Loop Prevention and Load Balancing in Ethernet Ring Networks

Ethernet networks using rapid spanning tree protocol (RSTP) to ensure a loop-free topology and provide redundant links as backup paths in case an active link has failed. However, when a failure occurs, RSTP requires a significant amount of reconfiguration time in order to find an alternative path. RSTP is also limited by the number of nodes in a ring network, and its performance degrades when the number of nodes increases. In this paper, we introduce a new approach, called loop prevention and load balancing (LPLB), which can be applied to Ethernet ring networks. If failure occurs, LPLB only requires a very short amount of time to switch to an alternative path and in most cases; LPLB needs zero recovery time for that switching. In addition, under most situations, no data frames are lost when a node switches to an alternative path. Unlike RSTP and the media redundancy protocol (MRP), LPLB also provides load balancing among network links that in turn improves the network performance and reduces the probability of bottleneck occurrence.

A comparison study of the quick removing (QR) approach (HSR mode X) under cut-through and store and forward switching modes

We previously introduced a quick removing (QR) approach (currently part of the IEC 62439-3 standard under the terminology of “HSR Mode X”) to improve the high-availability seamless redundancy (HSR) protocols traffic performance. The idea of the QR approach is to remove the duplicated frame copies from the network when all nodes have received one copy of the sent frame and begin to receive the second copy. Therefore, forwarding the frame copies until they reach the source node, as occurs in a standard HSR, is not needed in a QR. In our previous paper, we applied the store and forward switching mode, whereas in this paper, we present the performance of the QR approach using a cut-through switching mode. The performance analysis showed a reduction percentage in frame latency that reaches about 49% compared to the store and forward switching mode. Consequently, this will improve network performance, free more bandwidth, and quickly deliver sent frames to their required destinations, which is a firm condition in many industrial and automation applications.

Seamless ethernet approach

In this paper, we introduce a novel approach called seamless Ethernet to allow Ethernet switches to provide seamless redundancy with zero recovery time and without the need to modify the standard Ethernet frame layout or even use RSTP protocol. The idea is to flood the frame whose destination is unknown until it reaches the destination switch. The destination switch will consume the first fast frame copy that reaches it, forwarding it to the destination node and then deleting all the remaining flooded frame copies that will be delivered later through other trunk ports. As a result, all terminal off-shelf Ethernet devices will be suitable to be connected to seamless Ethernet switches to produce seamless redundancy, and at the same time, they are still able to connect to standard Ethernet switches without any modifications. Besides this feature, our seamless Ethernet approach shows a traffic reduction percentage of 50% compared to the standard HSR protocol that also provides zero recovery time service, which is another advantage for our seamless Ethernet approach, because it will free more bandwidth than the HSR protocol.

A Novel Method for Eliminating Duplicated Frames in Ethernet Standard (IEEE 802.3) Networks

If assumed that each Ethernet standard (IEEE 802.3) node has more than one port connected to the network and the node duplicates each sent frame, then an active or a seamless redundancy will be established because the destination node will receive at least two frame copies with zero recovery time. In this paper, we present a novel method for eliminating the duplicated frames in any Ethernet network type. This will ensure that the destination node will only consume one frame copy from each sent frame and eliminate the other copies. The proposed method will set a counter on each receiving port in the destination node. The destination node will consume the copy that arrives through the fastest path, or in other words, through the port that has the fastest counter value. The proposed method does not need to disable ports as required by rapid spanning tree protocol (RSTP) or the media redundancy protocol (MRP), to avoid looping issues; instead, it activates all ports to provide a type of better traffic distribution among the network links.

Traffic-Reduction for High-Availability Seamless Redundancy (HSR) Protocol Using Dual Virtual Paths Algorithm

The high-availability seamless redundancy (HSR) protocol provides duplicated frame copies of each sent frame, with zero recovery time. This means that even in cases of node or link failure, the destination node will receive at least one copy from the sent frame. Consequently, there is never any network-operation down time. However, the forwarding process with the QuadBox node type is not smart and relies solely only on duplication and random forwarding. Thus, if a unicast frame is sent in any closed-loop network except a ring topology, the frame copies will be spread through all the links until they reach the destination node. In this paper, we present an algorithm called the dual virtual paths (DVP) algorithm. The idea behind our DVP algorithm is to establish dual virtual paths between each HSR node and all the other nodes in the network, except for the QuadBox node type. These virtual paths will be used for unicast traffic type, rather than using the standard HSR transmission process. The DVP algorithm results in less network traffic because there is no duplication or random forwarding, as in the standard HSR protocol. For the sample network selected in this paper, the DVP algorithm shows a 72-73.7% reduction in network traffic and an 85.7-88.9% reduction in the discarded traffic compared to the standard HSR protocol.