What sort of performance can I expect from a Modbus TCP/IP system?
The performance depends on the network and the hardware. If you are running Modbus TCP/IP over the Internet, you won’t get better than typical Internet response times. However, when communicating for debug and maintenance purposes, this may be perfectly adequate and save you from having to catch a plane or go to site on a Sunday morning! For a high-performance intranet with high-speed Ethernet switches guaranteeing performance, the situation is completely different. In theory Modbus TCP/IP carries data at up to 250/(250+70+70) or about 60 percent efficiency when transferring registers in bulk. Since 10BaseT Ethernet carries about 1.25 Mbps raw, the theoretical throughput is 1.25M/2 * 60% = 360000 registers per second and the 100BaseT speed is 10 times greater. This assumes that you are using devices that can service Ethernet as fast as the available bandwidth. Practical tests carried out by Schneider Electric using a MOMENTUM™ Ethernet PLC with Ethernet I/O demonstrated that up to 4000
