Ethernet Based IEC61375 for Train Communication Networks

Industrial Ethernet Solutions

Ethernet based IEC61375 for Train Communication Networks

Ethernet technology has been widely deployed for train communication networks (TCN) and also onboard EDs (End Devices). The international IEC standard has structured the Ethernet based TCN into a hierarchical way with ETB (Ethernet Train Backbone, referred to IEC61375-2-5) and ECN (Ethernet Consist Network, referred to IEC61375-3-4). The ETB solution takes care of the interconnection and interoperability between train consists, while the ECN solution looks after the communications of end devices within each consist.

Since the train borne network is different from the typical communication network with fixed locations, especially in the train set coupling and decoupling scenarios, ETB has to be adaptive to the topology change and also react for layer 3 routing. TTDP, R-NAT, and also other features are defined in IEC61375 to build an Ethernet based TCN for TCMS (Train Control and Management System)

TTDP, Train Topology Discovery Protocol All ETBNs (ETB Nodes) has to support TTDP for train network inauguration and topology resilience. In the following diagram, when Consist #2 is coupled with Consist #1, TTDP helps ETBNs renew the topology along with new IP assignment, so that there will not be any IP conflicts or mismatching.

10.128.0.1/18 10.128.0.2/18 10.128.0.1/18 10.128.0.2/18

A B C D Consist #1 Consist #2

10.128.0.1/18 10.128.0.2/18 10.128.0.3/18 10.128.0.4/18 ETB

A B C D Consist #1 Consist #2

R-NAT, Railway-Network Address Translation In order to keep identical configuration as well as network scheme of each ECN but still allows the communications between EDs across different consists, R-NAT is introduced for IP address mapping and translation between different subnets. As shown in the diagram, the EDs are assigned with the same IP in different consists. When EDs have to communicate with each other, the upper level ETBN will help translate and forward the packets towards the destination.

DA 10.128.128.7 DA 10.129.0.7 SA 10.129.0.7 SA 10.128.128.7 1 2 3 4

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A B C D Consist #1 Consist #2

DA 10.129.0.7 DA 10.0.0.7

SA 10.0.07 SA 10.128.128.7 DA 10.0.0.7 DA 10.128.128.7 SA 10.129.0.7 ED SA 10.0.0.7 ED 10.0.0.7 10.0.0.7

144 www.kyland.com Version: V1.11 7 DHCP Industrial Ethernet Solutions To simplify the IP assignment and to reduce the configuration time & efforts of EDs, the ETBN has to support DHCP sever, so that the EDs can obtain proper IP addresses through DHCP client automatically.

Bypass Since the communications of TCMS is crucial for train operation, high Availability of train network is critical. In case one single consist failure, the network should remain uninterrupted regardless of one ETBN malfunction. In the following diagram, the bypass function of ETBN_B ensures the communications between ED on ETBN_A and ED on ETBN_D even when ETBN_B is down. 1 2 3 4 10.128.0.1/18 10.128.0.2/18 10.128.0.3/18 10.128.0.4/18

A B C D

Consist #1 Consist #2

ED ED 10.0.0.6 10.0.0.7