Parallel Redundancy Protocol Research Articles

PRP and HSR for High Availability Networks in Power Utility Automation: A Method for Redundant Frames Discarding

Critical systems require zero recovery time when a failure occurs in a communications network. The soon to be implemented standard IEC 62439-3 defines the only two protocols, parallel redundancy protocol and high-availability seamless redundancy, which fulfill this requirement and ensure no frame loss in the presence of an error. These protocols also provide a hot-plugging capability, which allows elements to be added to or removed from the network without interrupting communications and the operation of the plant. The electricity sector has adopted these for power utility automation in the recently published IEC 61850-90-4. The challenge is to obtain an efficient approach for use in electronic devices, capable of managing the characteristic duplicates, and circulating frames of these protocols, coupled with agile architectures capable of dealing with real-time processing requirements, fast switching times, high throughput, and deterministic behavior. The main contribution of this paper is the in-depth analysis it makes of network parameters imposed by the application of the protocols to power utility automation, and the proposition of a frame management system based on a segmented memory system that improves frame detecting time and uses the smallest memory required in order to resolve all the issues dealt with.

Applying High Availability Design and Parallel Redundancy Protocol (PRP) in Safety Critical Wide Area Networks

Networks which protect the safety of human lives place special emphasis on network availability and survivability. The nation’s Air Traffic Control (ATC) and First Responder public safety networks used by police departments, fire and rescue, and emergency medical teams are examples of networks that require high availability and survivability. The term mission critical network is often used to describe the characteristics of networks which protect the safety of human lives. There is not a universally accepted standard definition of the term, but much literature on the subject typically identifies three salient characteristics: • Highly Secure • Highly Available • Highly Survivable Highly secure is an important characteristic and needed to design a safety critical network, but the focus of this paper is availability and survivability. It should be noted that mission critical safety networks are private networks and should not be confused with the public Internet simply because they use IP. A private network in itself does not constitute a mission critical network, but it is a significant characteristic of a mission critical network due to the security and performance benefits it supports. The security benefit is risk mitigation from external threats because only authorized internal users can access the network. The performance benefit is similar in that only authorized users have access to the network and their network usage does not have to compete for bandwidth with other external users. Availability and Survivability are related, but they are not the same thing. Availability is simply a measure of the time the network is operating compared to the total time it should be operating. Availability is defined as Uptime divided by Uptime plus Downtime. This same reference defines Survivability as the capability of a system (or network in this case) to perform its mission recognizing that failures are going to occur. As will be explained later in this paper, survivability considers catastrophic events that cannot be easily predicted in an inherent availability model. Specifically, this paper focuses on the availability and survivability of the Wide Area Network (WAN) terrestrial core backbone component of safety critical networks. Much literature on public safety networks for First Responders is devoted to the wireless radio networks including Land Mobile Radio (LMR), P.25 packet radio, cellular telephony and evolution towards broadband 4G Long Term Evolution (LTE) wireless networks. Air Traffic Control networks rely on other wireless forms of communication including narrow-band Air-to- Ground (aircraft to ground based controller) voice and data links in the Very High Frequency (VHF) spectrum. All of these wireless forms of communication rely on a terrestrial core backbone for backhauling and distributing information to the right place. The terrestrial core backbone is a foundational building block for other safety critical network components. This paper also describes some of the differences between legacy Time Division Multiplexing (TDM) technology and modern Internet Protocol (IP) packet switched technology. Historically, networks such as the nation’s Air Traffic Control (ATC) network have relied on point-to-point TDM technology.

Availability improvement of layer 2 seamless networks using OpenFlow.

The network robustness and reliability are strongly influenced by the implementation of redundancy and its ability of reacting to changes. In situations where packet loss or maximum latency requirements are critical, replication of resources and information may become the optimal technique. To this end, the IEC 62439-3 Parallel Redundancy Protocol (PRP) provides seamless recovery in layer 2 networks by delegating the redundancy management to the end-nodes. In this paper, we present a combination of the Software-Defined Networking (SDN) approach and PRP topologies to establish a higher level of redundancy and thereby, through several active paths provisioned via the OpenFlow protocol, the global reliability is increased, as well as data flows are managed efficiently. Hence, the experiments with multiple failure scenarios, which have been run over the Mininet network emulator, show the improvement in the availability and responsiveness over other traditional technologies based on a single active path.

Arquitecturas de red LAN para la automatización de subestaciones, basadas en la norma IEC 61850 (RSTP, PRP y HSR)

La norma IEC 61850 es la base en la implementación de subestaciones eléctrica automatizadas, permite que los equipos de protección, control y medición de diferentes fabricantes puedan trabajar en una misma red Ethernet. Dependiendo de la disponibilidad requerida para cada subestación, se adoptan esquemas y protocolos de protección en las redes Ethernet, los cuales incrementan la disponibilidad del sistema.
 Actualmente para esta protección se utiliza el protocolo RSTP (Rapid Spanning Tree Procotol), sin embargo, para subestaciones principales, es necesario el empleo de nuevos esquemas de protección, que disminuyan e incluso eliminen el tiempo de indisponibilidad, en el caso de una falla en algún segmento de la red, esto se consigue a través de los protocolos PRP (Parallel Redundancy Protocol) y HSR (High-availability Seamless Redundancy.
 El presente documento incluye una introducción a la norma IEC 61850, el análisis de los protocolos de protección de las redes LAN empleados para la conexión de los IEDs y switches: RSTP, PRP y HSR, y su comparación, concluyendo finalmente con criterios de selección de uno u otro dependiendo del diseño de la subestación a ser construida.