Peter Honeder
CTO | Unwired Networks
A new paradigm
As rail transportation modernizes, the demand for onboard connectivity and networked services has grown substantially. Trains today require robust and reliable networking solutions to ensure the efficient operation of services such as passenger information systems, automated ticketing, security monitoring, and train control systems.
Central to these networks are multifunction devices, such as routers and rail servers, which enable both the management of data flows and the virtualization of applications critical to train operations. This whitepaper explores the architecture of these deployments, their typical scenarios, associated failure modes, and strategies for improving reliability. We also examine how these deployments adapt to train coupling scenarios, where multiple train units are joined to form a single operational system.
Typical Train Network Architecture
The network architecture of a modern train is centered around routers and rail servers, which may be deployed separately or combined into a single device to reduce complexity and cost. These devices, in turn, connect to various onboard systems, ensuring reliable communication both within the train and with external networks.
Core Functions of Routers
The router in a train network is responsible for the essential functions of data transmission, network management, and remote access. A typical train router runs on Unwired Edge Cloud OS, a Linux distribution based on OpenWRT, and includes a range of functionalities:
WAN and LAN Networking
The router manages both local area networks (LAN) and wide area networks (WAN), ensuring seamless communication between onboard devices and external networks.
Uplink Aggregation
By aggregating multiple LTE/5G cellular modems, trackside Wi-Fi, and satellite links, the router ensures a more resilient, higher-capacity internet connection. This technique improves network performance and redundancy by leveraging multiple connections.
L2 and L3 Networking
Layer 2 (data link) and Layer 3 (network) services are managed by the router to provide efficient routing and switching of data across the train’s internal and external networks.
Remote Access and VPN Services
The router supports secure remote access through virtual private networks (VPNs), allowing external monitoring and management of onboard systems.
Software-Defined Networking (SDN)
The router can integrate with SDN solutions like Tailscale or ZeroTier, which provide peer-to-peer mesh networking capabilities and global access control.
Rail Server Functions
The rail server provides virtualization services onboard the train. By isolating applications in containers, the rail server allows multiple software applications to run concurrently without interfering with each other. Key functions of the rail server include:
