Agent Mode for Large Scale Modbus Network Deployment

Barriers Of Traditional Modbus Gateway Communication Mechanism – Transparent Mode

Transparent mode communication, using the traditional round-robin polling mechanism, is usually standard in the Modbus gateway market. Gateways performing transparent mode conversions are usually set up easily and quickly. If only a few power meters are connected to a gateway, scan times might not be so much of an issue. However, it’s a very different story when it comes to large-scale networks like DCIMs (for data center power management).

 

Mgate Transparent Mode
Mgate Transparent Mode

 

The major concern is the resultant latency in the transparent mode communication, especially during peak traffic periods. It also wastes precious SCADA resources and network bandwidth which can cause delay for the critical command accuracy and sequence.

 

Intelligent Modbus Gateway Communication Mechanism – Agent Mode

To handle a big amount of collected serial data in the above example, we recommend using high-port density Modbus Gateway such as Moxa MGate MB3660, which gives you an intelligent way to handle multiple devices on a large scale network. It works as the data concentrator to collect all information as an agent. With the agent mode function, you don’t need to waste time to configure hundreds of Modbus commands in a gateway setting. It can reply to the SCADA request immediately with pre-read data without waiting for any slow serial device responses. Using agent mode, this type of intelligent Modbus Gateway can deliver a performance that is more than ten times faster than a traditional round-robin polling mechanism offered in another Modbus Gateway.

 

Mgate Agent Mode
Mgate Agent Mode

Using the agent mode, on one side, this type of intelligent Modbus Gateway acts as an RTU master actively polling the power meters; on the other side, the gateway functions as a Modbus TCP server polled  by the SCADA system. An all-important feature of gateways that support agent mode is a fast internal memory that facilitates seamless data retrievals.

From a SCADA system’s vantage point, its scan time is much faster than transparent mode communication. Because only the duration of the Modbus TCP request and Modbus TCP response make up the scan time as there is no need for the SCADA system to wait on the RTU leg of the protocol conversion process.

More information about Intelligent Modbus TCP Gateway