Ethernet Switch

An Ethernet Switch is a network device that connects multiple devices on a local area network (LAN), forwarding data packets between them based on MAC addresses. In AGL applications, industrial-grade Ethernet switches are used to build the communication backbone that links the Airfield Lighting Control and Monitoring System (ALCMS) server, programmable logic controllers (PLCs), Remote I/O units, fiber converters, and other intelligent devices. Unlike standard commercial switches, industrial Ethernet switches are designed for harsh environments: they support extended temperature ranges (-40°C to +75°C), provide redundant power inputs, offer ruggedized enclosures, and implement advanced networking features such as redundant ring topologies (e.g., ERPS, RSTP), VLAN segmentation, quality of service (QoS), and cybersecurity features (port security, ACLs). These switches ensure reliable, deterministic, and secure communication critical for airfield lighting control.

The industrial Ethernet switch exists to give the ALCMS server, PLCs, and Remote I/O units a communication backbone that's actually reliable in the same environment the lighting equipment itself has to survive — extreme temperatures, electrical noise from high-voltage AGL circuits, and continuous operation with no acceptable downtime. A standard commercial-grade switch simply isn't built to survive those conditions without becoming a point of failure for the entire control network.

Features like redundant ring topologies and redundant power inputs exist specifically because a single point of network failure in an airfield lighting control system could mean losing visibility or control over multiple circuits at once. By designing resilience into the network layer itself, the switch ensures that a single cable break or power supply fault doesn't cascade into a broader control system outage.

Ethernet switches are deployed in all areas of the AGL network infrastructure, including:

• ALCMS Control Room: Core switches connecting servers, workstations, and network management consoles to the airfield network.
• CCR Substations: Managed switches connecting PLCs, Remote I/O, and fiber converters to the main network backbone.
• Runway Edge Cabinets: Switches providing local connectivity for lighting control modules, sensor nodes, and cameras.
• Approach Lighting Control Shelters: Switches for sequencer modules, strobe controllers, and fiber media converters.
• RWSL (Runway Status Light) Systems: Dedicated switches for the RWSL processing units, field controllers, and sensors.
• Airfield Sensor Networks: Connecting weather stations, visibility sensors, wind measurement systems, and RVR equipment.
• Gate & Apron Control Systems: Switches for docking guidance, gate management, and apron surveillance.
• Security & Surveillance: Switches supporting IP cameras, access control, and perimeter monitoring systems.

Switches are DIN-rail or rack-mounted inside the control room, substation, or field cabinet they serve, with industrial-rated (wide-temperature, vibration-resistant) units specified for outdoor runway-edge cabinets and approach lighting shelters, and standard rack-mount units for the air-conditioned ALCMS control room. Power is fed from the same DC supply as the other equipment in that cabinet, often with a redundant supply input on critical switches; uplink connections to the network backbone run on fibre between cabinets/shelters (for distance and electrical isolation) and on copper for short local runs within a single cabinet, with cable routing kept separate from lighting series-circuit power cable throughout.

The Ethernet switch operates at Layer 2 of the OSI model, forwarding data frames based on MAC address tables. Key functional aspects in AGL networks include:

• MAC Address Learning: The switch builds a table of MAC addresses associated with each port, learning which devices are on which segments to forward frames only to the necessary port (reducing unnecessary traffic).
• Store-and-Forward Switching: Receives the entire frame, checks for errors using CRC, and forwards it to the destination port, ensuring error-free transmission.
• Redundant Ring Topology: Supports protocols like RSTP (Rapid Spanning Tree Protocol) or ERPS (Ethernet Ring Protection Switching) to provide automatic failover in case of a cable break or switch failure, with recovery times as fast as 50 ms (ERPS).
• VLAN Segmentation: Virtual LANs allow logical separation of traffic (e.g., control data, video surveillance, management traffic) for improved security and performance.
• Quality of Service (QoS): Prioritizes critical AGL control traffic (e.g., PLC-to-CCR commands) over less time-sensitive data (e.g., video streams) to ensure deterministic communication.
• Network Management: Supports SNMP (Simple Network Management Protocol) for remote monitoring, diagnostics, and configuration, allowing administrators to view port status, traffic statistics, and alarms.
• Cybersecurity: Implements features like port security (MAC locking), Access Control Lists (ACLs), and DHCP snooping to protect the network from unauthorized access and cyber threats.

Industrial switches are typically powered by 24 VDC (airfield standard) or 48 VDC, with dual redundant power inputs for high availability. They are often DIN-rail mounted in control cabinets.

The Ethernet switch is the shared backbone that every IP-capable node in the AGL system connects through — PLCs, Remote I/O, Communication Gateways, the SCADA Interface, Touchscreen HMIs, weather stations, and surface movement radar all terminate on switch ports rather than wiring directly to the ALCMS server. It does not participate in control logic itself; it forwards frames at Layer 2 based on MAC address tables and, where configured, segments traffic into VLANs so lighting-control data, radar/A-SMGCS data, and general IT traffic stay logically separated on the same physical fibre or copper backbone. Airfield deployments typically run switches in a redundant ring or dual-homed topology with RSTP or similar, so that a single fibre cut or switch failure reroutes traffic within milliseconds rather than dropping the affected branch off the network entirely.

The switch is housed in a rugged extruded-aluminium or steel enclosure with a wide operating-temperature rating, built for DIN-rail mounting inside a control cabinet or field enclosure rather than a server-room rack. Copper ports use shielded RJ-45 connectors with integrated magnetics, while SFP cages for fibre uplinks are soldered directly to the backplane and accessed through dedicated front-panel cutouts, keeping the fibre optics separate from the copper ports for EMI isolation. Internal electronics are conformally coated to resist dust, humidity, and airborne contaminants, and the dual redundant power inputs terminate at screw-clamp terminals rated for the nominal 24 VDC supply. Where deployed outside a conditioned cabinet, the switch is fitted into a sealed IP65 enclosure with cable glands for each cable entry, and a chassis earth stud is provided for bonding to the cabinet ground bus.