Redundant networks can be used with OPC UA in either transparent or non-transparent Redundancy.

Network Redundancy can be combined with Server and Client Redundancy.

In the transparent network use-case a single Server Endpoint can be reached through different network paths. This case is completely handled by the network infrastructure. The selected network path and Failover are transparent to the Client and the Server. Transparent network Redundancy is illustrated in Figure 34.

Figure 34 – Transparent network Redundancy

Examples:

• A physical appliance/device such as a router or gateway which automatically changes the network routing to maintain communications.
• A virtual adapter which automatically changes the network adapter to maintain communications.

In the non-transparent network use-case the Server provides different Endpoints for the different network paths. This requires both the Server and the Client to support multiple network connections. In this case the Client is responsible for selecting the Endpoint and for Failover. For Failover the normal reconnect scenario described in 6.7 can be used. Only the SecureChannel is created with another Endpoint. Sessions and Subscriptions can be reused. Non-transparent network Redundancy is illustrated in Figure 35.

Figure 35 – Non-transparent network Redundancy

The information about the different network paths is specified in NonTransparentRedundancyType ObjectType defined in OPC 10000-5.