OPC Tunnelling – Know Your Options
This article will look at how tunnelling solves the issues associated with DCOM, and show you what to look for in an OPC tunnelling product.
Since OPC was introduced over ten years ago, it has seen a steady rise in popularity within the process control industry. Using OPC, automation professionals can now select from a wide range of client applications to connect to their PLCs and hardware devices. The freedom to choose the most suitable OPC client application for the job has created an interest in drawing data from more places in the plant. Industry-wide, we are seeing a growing need to connect OPC clients on one computer to OPC servers on other, networked computers. As OPC has grown, so has the need to network OPC.
At the same time, anyone who has attempted to network OPC knows that it is challenging, at best. The networking protocol for OPC is DCOM, which was not designed for real-time data transfer. DCOM is difficult to configure, responds poorly to network breaks, and has serious security flaws. Using DCOM between different LANs, such as connecting between manufacturing and corporate LANs, is sometimes impossible to configure. Using OPC over DCOM also requires more network traffic than some networks can handle because of bandwidth limitations, or due to the high traffic already on the system. To overcome these limitations, there are various "tunnelling" solutions on the market.
Author: Bob McIlvride, Andrew Thomas, Cogent Real-Time Systems | File Type: PDF