The Relay Service

The Relay Service is a MS Windows service, which facilitates distribution of inmation Core and Connector components across different physical networks (e.g. Field, Control, and MES network). It will typically be installed on machines with two or more network adapters in order to be able to reach both components.

There are different scenarios of server component combinations possible:

  • The Relay service bridges the connection between a Core service and a Connector service located in different networks.

  • The Relay service bridges the connection between a Core service and another Relay service located in different networks.

  • The Relay service bridges the connection between another Relay service and a Connector service located in different networks.

Relays can be installed as either passive or active components. Passive Relays listen for incoming connection requests from the Core service whereas active Relay components actively send connection requests to the Core service. Both passive and active Relays are able to handle multiple Connector connections at a time (the Connectors should be of the same type as the relay - active or passive respectively).

The following schematics show two different use cases of the Relay service. In the first example only one network barrier exists between the Core and Connector services.

Relay service (example scenario 1)
Figure 1. Relay service (example scenario 1)

In the second example scenario the Core and Connector services are located in networks with two physical network barriers in between. Both barriers are bridged by separate Relay services installed on machines with two network adapters each.

Relay service (example scenario 2)
Figure 2. Relay service (example scenario 2)

In passive mode, the incoming connection request contains information about where the connection should be forwarded (IP and port). In active mode, forwarding is always made to the configured core (fixed IP and port).

The advantage a Relay component has over standard port forwarding rules, is that a passive Relay can forward TCP connection requests from an inmation Core component to different passive Connector services without additional configuration. With port forwarding alone, a new forwarding rule would be required for each new passive Connector.