Introduction
A New Paradigm
The ongoing modernization of rail transport is driving fast-growing demand for onboard connectivity and connected services. Today’s trains need robust, reliable networks to run services like passenger information systems, automated ticketing, security systems, and train control systems efficiently.
Multifunctional devices such as routers and rail servers play a key role in these networks. They manage data flows efficiently and virtualize applications essential to train operations. This whitepaper examines the architecture of such deployments, typical use cases, possible failure modes, and strategies for improving reliability. It also looks at how these setups adapt to train-coupling scenarios, where multiple train units join into a single operational system.
Routers and Rail Servers
Typical Network Architecture of Modern Trains
At the center of a modern train’s network architecture are routers and rail servers, used either separately or as one integrated device to keep effort and costs down. These components connect onboard technologies reliably with each other and with external networks.
Router Functions
A train router handles essential tasks: data transmission, network operations management, and secure remote access. It typically runs Unwired Edge Cloud OS, a Linux variant of OpenWRT, and offers these core functions:
- LAN and WAN management: The router coordinates communication between local onboard networks and external networks for uninterrupted operation.
- Uplink aggregation: By combining multiple LTE/5G modems, trackside Wi-Fi, and satellite links, the router delivers a more robust, higher-performance internet connection.
- L2 and L3 network services: The router manages Layer 2 (data link) and Layer 3 (network) services so data is forwarded and processed efficiently inside and outside the train.
- Remote access and VPN services: Secure virtual private networks (VPNs) let you access, monitor, and manage onboard systems remotely.
- Software-defined networking (SDN): Tools like Tailscale and ZeroTier extend network capabilities with peer-to-peer communication and global control.
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The whitepaper also covers:
- Three deployment scenarios compared: From the cost-effective combined device to a high-end setup with two routers and two rail servers — each with benefits, failure modes, and suitability per train type.
- Rail servers and train network topology in full: Container virtualization, persistent storage access, resource management, and how it all works with access points, switches, and onboard devices.
- Failover strategies: Redundancy and failover mechanisms, spare-hardware concepts, plus monitoring and observability with Prometheus integration.
- Train coupling scenarios: Dynamic network coupling, single-device failover, and cluster operation with load balancing across four devices.
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Get the Whitepaper by EmailFAQ
How much bandwidth does my train need?
Here’s how to calculate the bandwidth requirements for your router infrastructure:
- 0.5–0.7 Mbps per passenger for commuter trains
- 1–2 Mbps per passenger for long-distance services
- Multiply by the number of seats and factor in a concurrent usage rate (usually below 50%)
This gives you accurate sizing for cellular uplinks and Wi-Fi capacity.
How do I choose the right railway router for my train type?
Router configuration requirements vary by train type:
- Trams (light rail): Compact routers with 1–2 LTE/5G modems
- Regional trains: Modular routers with multiple uplinks and edge computing capabilities
- High-speed trains: High-performance rack routers with satellite connectivity and 4–6 cellular modems
Tip: Before choosing, always assess the specific use case, passenger numbers, and operational requirements.
Is Wi-Fi 7 necessary for railway routers?
No — Wi-Fi 7 is currently not required in most rail scenarios.
- Wi-Fi 6: Best balance of performance, device compatibility, and future-proofing
- Wi-Fi 5: Can become a bottleneck under heavy load
- Wi-Fi 7: Still expensive, with limited added value in rail today
How many railway routers does my train need?
Rule of thumb:
- 1 router supports up to 4 single-deck cars
- 2+ routers for double-deck trains or long trainsets, for better bandwidth aggregation
Recommendations:
- For basic requirements: LTE CAT12+
- For demanding requirements: 5G with 2–3 modems
- Avoid more than 3 modems — antenna cabling becomes too complex
- LEO satellite uplinks (e.g. Starlink) can further improve performance — where available
Which certifications and cybersecurity standards should a railway router meet?
Certification requirements differ by operator, region, and use case.
Essential in procurement:
- EN 50155 (operational safety)
- EN 45545 (fire protection)
Depending on timing and deployment:
- RED (EU 2022/30) — mandatory from 2025
- EU Cyber Resilience Act (CRA)
- IEC 62443 / DIN EN 50701 (IT/OT security in rail)
- NIS 2 Directive and GDPR
Recommendation: Choose platforms with proven certifiability through documentation, test evidence, and OTA updates. That avoids costly upfront certification and keeps you flexible as requirements evolve.
