Ensuring robust networks in demanding industrial applications: choosing the right Ethernet switch for rugged embedded computers

Author : Mark Jeffrey | Technical Director | Recab UK

01 November 2020

Drone embedded technology

Whether used for on-board entertainment on trains or video feed transmission from military drones, connectivity is becoming a crucial factor in industrial applications. As more embedded systems adopt networked architectures, Ethernet switches are playing an increasingly important role.

This article was originally featured in the November 2020 issue of EPDT magazine [read the digital issue]. Sign up to receive your own copy each month.

Here, Mark Jeffrey, Technical Director at networked embedded systems expert, Recab UK explains how to select Ethernet switches for demanding operating environments.

In today’s interconnected world, the number of devices connected to the internet climbs every day. According to research firm, McKinsey, 127 new devices are connected to the internet every second, with billions of devices connected globally. These numbers increase when we consider local area networks (LANs) consisting of connected, mission critical embedded systems in sectors such as rail, military and defence, industrial and offshore.

Switches are central to the performance of networked architectures, allowing data to be relayed between connected computers and devices, and trafficked out to a larger network via protocols such as Ethernet. Protecting these switches is especially important for critical applications used in harsh environments, such as on-vehicle networks, both discrete and process manufacturing applications, and more.

Ensuring the protection of Ethernet switches in demanding environments requires the switch to be ruggedised. However, before an Ethernet switch can be considered as part of a ruggedised solution, it is worth looking at the role of switches and network requirements. Recab UK’s experience developing rugged embedded systems with Ethernet capabilities has shown us that designing the network first, and then subsequently ruggedising it and the components, ensures the best solution.

Network technology features

In its white paper on the subject, our trusted partner, Diamond Systems outlines several key requirements for network-based applications. These include the ability to establish and manage multiple networks using a single physical device, mirror ports to monitor traffic, daisy chain switches for local network expansion, secure network traffic and ruggedise the network components.

To manage several networks in a single device, it’s possible to create a virtual LAN (VLAN) that groups networked devices under a logically separate internet protocol (IP), based on needs and requirements. Different types of VLANs can be set up to meet application requirements, such as a port-based VLAN to allow several IP networks and subnets to exist on the same switched network, or MAC-based, where specific MAC addresses are associated with one VLAN.

Mirroring allows traffic from one port to be duplicated onto another, by copying sent and received data packets to another port or VLAN for local or remote monitoring purposes respectively. This is vital for any application that analyses network traffic, such as for intrusion detection, event validation or traffic monitoring.

Daisy chaining Ethernet switches is a physical connection scheme in which multiple switches are wired together in a sequence or ring. This is a simple way to expand a network when more nodes are needed at different points along the physical network, but is not well suited to a network where nodes are scattered over a large geographic region.

Security is a far more complex area, but a vital one for critical applications. There are two types of network security: virtual security, primarily via software systems and data encryption; and physical security, where components play a role in maintaining data integrity.

An example of network virtual security would be the intruder detection system, which detects potential security breaches, logs information about the possible breach and signals an alert on the console or through the serial port. This is complemented by a network’s encryption standards. An encryption standard like SNMPv3, for example, means that simple network management protocol (SNMP) services can be used with authentication and authorisation to monitor and manage the networked equipment.

Physical security comes from the ports of specific switches, which is why working with an embedded specialist is invaluable in critical embedded network projects. Small form-factor pluggable (SFP) ports can convert a network’s copper medium into a fibre optic channel. Because fibre optic technology is dielectric, the medium is protected against electromagnetic (EM) snooping and other malicious attacks. Fibre optic channels also boast the benefit of being able to transmit data longer distances, with less signal loss.

A common mixed media application uses copper wire networks for local communication and interfaces with fibre optic networks for higher-speed applications, network-to-network connectivity and long-distance communication. As such, several manufacturers of small form factor Ethernet switches include a combination of ports on their products. At Recab UK, our partnerships with leading Ethernet switch manufacturers means we can develop a solution that provides flexibility and increased network security.

For example, in custom embedded systems where space is a premium, Diamond Systems’ EPSM-10GX4 Ethernet switch module is an ideal option. The EPSM-10GX4 is based on the computer on module (COM) Express Mini standard form factor (84x55 mm), with an ultra-compact footprint and almost fully encapsulated switching technology. It provides 24 1 Gbps copper ports and four 10 Gbps SFI ports. There is also the EPS-24G4X full-feature carrier board, which brings out the 1 Gbps ports to latching connectors and the 10 Gbps ports to SFP+ sockets.

Train driver view

Alternatively, for high power applications with more available space that are using a VPX platform, an option might be to use the new VX6940 6U VPX Ethernet switch from Kontron. This features two front QSFP28 transceivers, which support high speed (up to 100G) optical or passive copper connections, and each allowing for four 10GB or SFP+ ports. These switches are best suited to data intensive applications that require many data paths, such as high definition sensors or radar systems.

Recab UK has a lot of experience in developing systems that include switch designs, either through our own development or using switches from our partners, Aitech, Kontron, duagon or Diamond Systems. The solution depends on the needs of the project and where the application will be used.

For example, a rail application might call for the use of a switch from duagon that is specially designed for harsh rolling stock operating environments. The D510, as one example, is a configurable six-port Ethernet switch that is compliant to EN50155, IEC61375 and IEEE802.3. The switch is housed in a rugged, compact enclosure and features integrated DC/DC conversion to eliminate the need for an external power supply.

Ruggedisation

In many networked applications, ruggedisation is a critical consideration. This is true for outdoor applications, on-vehicle networks, factory floor applications in both discrete and process manufacturing, and more.

For these types of applications, we must consider the environmental conditions. In particular, system designers should note factors such as the operating temperature range, levels of shock and vibration during operation, and the quality of the power source. For many critical applications, the size, weight, power and cost (SWaP-C) of networking devices will also be a key consideration.

Selecting off-the-shelf Ethernet switch products for demanding applications requires a clear understanding of the environmental needs and evaluation of each product’s specifications. To thrive in harsh environments, networks must be designed with these needs in mind. For extended temperature operation, that includes everything from PCB layout and part specification to stringent environmental testing to verify performance.

Rugged switches are rated for an operating temperature spanning -40 to +85 degrees Celsius and have been tested across this temperature range. Conduction cooling solutions play an important role here to efficiently remove heat from the electronics, reducing the local operating temperature and improving overall reliability.

For shock and vibration, there are several steps that embedded computing system designers can take to meet performance requirements. Thicker PCBs, for example, can provide improved shock and vibration resistance, as can the usage of lower profile parts and latching connectors for I/O interfaces.

Tackling power supply problems, such as an unreliable supply or unclean power source, is a relatively simple fix. Ethernet switches with onboard DC/DC power supplies eliminate power source problems by providing clean, steady power to the electronics.

The final general consideration for ruggedising network switches is to use enclosures. Ethernet switches can be built into a sealed enclosure that mitigate much of the temperature, contaminant, shock and vibration concerns. These boxes can be mounted in more protected locations with Ethernet, power and serial cables connecting to the box with rugged or even military grade connectors.

The exact requirements will vary from application to application, so there is no one-size-fits-all approach to switch selection or ruggedisation. Unfortunately for most system designers, it is much more complex than specifying the number of ports or the data speeds required. This is where partnering with an embedded system design specialist like Recab UK is beneficial.

As Diamond Systems summarises in its whitepaper: “For a successful overall network design, it takes forethought on establishing and managing a network, determining the network load and taking into account traffic and security considerations as part of the network design. Additionally, environmental and power considerations are equally important in selecting the best products for any application.”

With connectivity playing an ever-more central role in industrial applications, it’s important that these considerations are made to ensure effective, lasting embedded system performance. Choosing the wrong switch, or failing to fully plan for the operational and environmental requirements, is a costly mistake – but it’s one that can be avoided with planning and forethought.


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