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Five Key Requirements of Railway Trackside Backbone Networks

Today’s railway infrastructure must shoulder greater demands for inter-city and inter-state transportation. Ideally, a railway system should meet growing capacity requirements while still using existing infrastructure and not compromising on safety and security. Thanks to advances in automated signaling and train control systems, this is now possible.

Whereas conventional train control systems use manual, solid-state-based route management and interlocking mechanisms, modern electronic, computer-based approaches that harness Information and Communications Technology (ICT) dramatically improve railway safety and capacity. However, computer-based train control relies on a robust and reliable communications network—as do other railway devices, LEUs, axle counters, interlocking controllers, balises, and intercoms.

The most popular off-the-shelf ICT solutions are all based on TCP/IP communications, while at the same time, more and more Ethernet-enabled devices are available for mainline signaling and train control applications. To build a robust trackside backbone communication network using TCP/IP and Ethernet technologies, operators must achieve five key requirements:

  • Vital and Non-Vital Network Segregation
  • User-Friendly Network Management
  • Reliable and Self-Healing Fiber Links
  • Flexible Network Expansion
  • Connectivity with Legacy Devices

Vital and Non-Vital Network Segregation

TCP/IP is very widely used, so most railway mainline communication systems now share the same network with other, often non-vital applications. This network convergence is very convenient for system builders and operators, but poses a potential risk: auxiliary data (such as diagnostics data) may interfere with the transmission of core data (such as signal and interlocking data).

Unless the core network and the auxiliary network are physically separated, railway communication networks need a solution that will not hinder the transmission of critical data. Railway operations would grind to a halt if a virus infection and/or broadcast storm were to shut down all of the communications on the network.

VLANs (Virtual LANs) are a solution that can segregate core from auxiliary data and protect vulnerable network devices from attack. However, even when the network is segregated by a VLAN—indeed, even if the network is physically separated—communications between the core network and the auxiliary network is still inevitable. Therefore, layer 3 switches, or even a gateway or router, must be used with the network.

Moxa’s Featured Solution: IKS-G6824A and IKS-6726A/6728A series industrial Ethernet switches

Moxa’s industrial rackmount switches, including the IKS-G6824A and IKS-6726A/6728A series switches, are specially designed for wayside applications. All switches in the series are EN 50121-4 compliant and support wide temperature features. The IKS-G6824A Layer 3 switch provides up to 24 Gigabit ports with advanced Layer 3 networking and multiple fiber optic connections, making it especially useful for segregating larger networks.

User-Friendly Network Management

An NMS (Network Management System) is important for managing and monitoring network devices, like the Ethernet switches, terminal servers, and interlocking controllers that make up a train communication network.

It’s important to remember that an NMS used with a railway mainline network has very different requirements than one used in an office network. Railway operators expect the following features:

  • A more visualized user interface that displays physical or pseudo links and PoE
  • Automatic topology discovery via LLDP
  • Real-time link status and network traffic statistics
  • Real-time alarms via SNMP Trap or SNMP Inform
  • Network reporting functions
  • Support for large networks (2000 nodes)
  • Displays a diverse range of devices used in railway networks (through a MIB compiler)
  • Visualized Virtual LAN

Moxa’s Featured Solution: MXstudio is an industrial network management suite for installation, operation, maintenance, and diagnostics.

Moxa’s MXstudio industrial network management suite combines all the tools you need throughout the network lifecycle into one toolbox, including the MXconfig network configuration tool, MXview industrial network management software, and the N-Snap industrial network snapshot tool. The all-in-one MXstudio software suite has a tool for every task, including configuration, monitoring, maintenance, and troubleshooting. In addition, MXstudio’s three key benefits—easy configuration, smart visualization, and quick troubleshooting—are designed to meet the demands of industrial automation networks.

Reliable and Self-Healing Fiber Links

Optical fiber, which is widely used with today’s networks, is particularly well suited for long-distance communications, including mainline signaling and control networks. The depots and stations of a mainline transportation grid typically cover a wide physical area, with the distance between two depots anything from a hundred meters to several kilometers. Consequently, it is very important to have a variety of multi-mode, single-mode, and long-haul fiber available for long distance data transmission.

IEEE 802.1D/w STP/RSTP was originally designed to eliminate network loops, but it is also used for network recovery and self-healing if a link or node fails. However, the STP/RSTP recovery time has the potential to be much slower than what’s required for critical networks. As more nodes (Ethernet switches or hubs) are added to the network, the recovery time of an STP/RSTP network becomes longer. This is not a big problem for office networks, which have comparatively few nodes with each node handling many network devices. But a railway mainline communications network is just the opposite in that it has many network nodes, with each node only handling a few devices. In addition, network recovery time is much more important for signaling and control communications than it is for an office network. Railway mainline communications networks are expected to recover from node or link failures quickly so that the transmission of critical signaling and control data will not be interrupted.

Moxa Turbo Ring™ is a proprietary enhanced ring network technology that is well suited for mainline signaling and control communications, specifically because it ensures an excellent recovery time on large-scale networks. Even for a large network of up to 250 nodes, network recovery with Moxa Turbo Ring is under 50 ms.

Moxa’s Featured Solutions: Turbo Ring, Turbo Chain, IKS-G6824A, IKS-6726A/6728A, EDS-500E, EDS-600 series Ethernet switches, IMC-101, and PTC-101 series media converters

Moxa’s wide portfolio of Ethernet switches includes the rackmount IKS-G6000/6000 series, and the DIN-rail-mounted EDS-500E and EDS-600 series. These switches support Turbo Ring and Turbo Chain redundancy technology, and are designed to operate reliably in the harsh, industrial environments found at remote railway sites. Important industrial features include a wide operating temperature range of -40 to 75°C and high EMC/EMI resistance.

Moxa also offers the IMC-101 and PTC-101 series fiber-to-Ethernet converters, which are an excellent choice for extending the reach of Moxa’s Ethernet switches.

Flexible Network Expansion

Designing a network that meets all of the stringent requirements of railway operations is only part of what’s required. You must also ensure that the network will be easy to expand, perhaps several years in the future, without causing a severe disruption of service. This is particularly true because railway networks often need to support network redundancy, even for large-scale deployments. In these circumstances, fiber cabling is always a major cost, as is the complexity of the network topology.

Moxa Turbo Chain, which evolved from Moxa Turbo Ring, is a redundancy solution that makes it easy to integrate additional switches into an existing network, without compromising redundancy. Turbo Chain works with any network architecture, including the SONET/SDH telecom networks or STP/RSTP networks that are common in OCC and larger yards.

The beauty of Turbo Chain is that it allows you to attach (or hook) a new network segment to an existing network, while still maintaining the same fast recovery time when a network node or link fails.

Even if it’s not possible to install fiber, you can still extend the range of an Ethernet network with DSL technology and existing copper wiring, which removes the need to deploy a costly fiber infrastructure while still allowing the Ethernet network to communicate over long distances.

Connectivity with Legacy Devices

Even as railway networks embrace new, more reliable, and more convenient communications technologies, operators still need to connect with legacy devices such as interlocking controllers, axle counters, and switchable balises. These devices typically use an RS-232 or RS-422/485 communications interface, either for configuration, diagnosis, or data transmission.

Terminal servers are invaluable for connecting these legacy serial devices to TCP/IP networks. For networks that do not use TCP/IP, traditional serial-to-serial equipment-to-equipment communication and conversion is still very useful in signaling and control applications. In fact, by using serial-to-fiber converters, it’s easy to extend serial communications over long distances.

Moxa’s Featured Solution: NPort IA5000AI series and NPort S8000 series

The Moxa NPort IA5000AI series includes models with 1, 2, and 4 isolated serial ports, with wide temperature (-40 to 75°C) models available for severe operating environments. The NPort 5650I-8-DT is an 8-port option, with a wide temperature model also available.

The NPort S8000 series is a specially designed terminal server with 4 isolated serial ports and 2 fiber ports. As a terminal server, it has all of the managed features of Moxa Ethernet switches, including Turbo Ring, Turbo Chain, LLDP, and VLAN.

Moxa: Unique Expertise for Unique Trackside Requirements

Moxa’s 25 years of networking expertise and industry domain knowledge has resulted in a broad railway product portfolio that includes a solution for every key requirement of trackside backbone networks. Visit the Moxa website for product details, or subscribe to our rail newsletter to stay up-to-date on the latest railway trends and to learn about Moxa’s latest IP-based solutions for railway applications.

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