We get frequent questions about how to use OPC Unified Architecture in conjunction with traditional OPC servers. Regardless of the new technical details of OPC UA, we cannot get around the fact that majority of the communication systems worldwide are still running traditional OPC servers.

OPC UA is not directly backward compatible with traditional OPC. Therefore if one must use traditional OPC and OPC UA together, interfaces for both would have to be implemented. Still, it is not necessary to avoid using OPC UA because of this. Prosys is a retailer for the products of Unified Automation who have created a tool called UaGateway to solve this issue.

Basic Usage

UaGateway can be connected to servers using multiple protocols: OPC UA TCP, OPC DA, OPC AE and OPC XML-DA. All these connections are published to other clients as OPC UA TCP, OPC DA and OPC AE servers. UaGateway comes with a graphical user interface and with it connections to servers and server endpoints can be configured. Next, I will present two common use cases with UaGateway.

Use case #1

In the first use case, an OPC UA client is connected to traditional OPC DA or AE servers and to an OPC UA server through a firewall. This is a common use case when trend data and process event messages need to be transferred from the process to higher level information systems, such as Manufacturing Execution Systems (MES). Traditional OPC uses DCOM for communication between computer nodes. Firewall configuration is complex for DCOM communication, because DCOM dynamically assigns port numbers for connections. Therefore it is best to use OPC UA to communicate through firewall, because OPC UA uses only one TCP port for communication. In this use case, only one UaGateway is needed to aggregate data from three servers. UaGateway eliminates the need for other products that would combine data from multiple OPC servers.

Use case #2

In the second use case, an OPC DA client is connected to an OPC DA server over Internet. OPC DA uses DCOM to communicate and communication with DCOM over Internet cannot be done efficiently. Fortunately, OPC UA uses single port TCP communication which can be used over Internet with ease. OPC DA nodes can be connected to separate UaGateways which communicate with OPC UA to each other. In the OPC UA Security Model, asymmetric encryption and authentication methods are introduced, which assure safe and confidential communication over Internet.

Summary

UaGateway is a simple solution to start upgrading your systems to using OPC Unified Architecture. With it, the pitfalls of traditional OPC can be avoided. It allows you to use your old systems in harmony with newer ones. There is no question of either/or, with UaGateway, both OPC UA and traditional OPC can co-exist in an industrial communication system.