Allen-Bradley Ethernet Driver
Optimizing Communications
The Allen-Bradley Ethernet Driver is designed to provide the best performance with the least amount of impact
on the system's overall performance. While the driver is fast, there are a couple of guidelines that can be used
to control and optimize the application and gain maximum performance.
The server refers to a communications protocol like Allen-Bradley Ethernet as a channel. Each channel defined
in the application represents a separate path of execution in the server. Once a channel has been defined, a
series of devices can be defined under that channel. Each of these devices represents a single Allen-Bradley
PLC from which data is collected. While this approach to defining the application provides a high level of per-
formance, it doesn't take full advantage of the Allen-Bradley Ethernet Driver or the network. An example of how
the application may appear when configured using a single channel is shown below.
Each device appears under a single Allen-Bradley Ethernet channel. In this con-
figuration, the driver must move from one device to the next as quickly as possible to
gather information at an effective rate. As more devices are added or more inform-
ation is requested from a single device, the overall update rate begins to suffer.
If the Allen-Bradley Ethernet Driver could only define one single channel, the example above would be the only
option available; however, the driver can define up to 256 channels. Using multiple channels distributes the
data collection workload by simultaneously issuing multiple requests to the network. An example of how the
same application may appear when configured using multiple channels to improve performance is shown
below.
Each device has is defined under its own channel. In this new configuration, a single
path of execution is dedicated to the task of gathering data from each device. If the
application has 256 or fewer devices, it can be optimized exactly as shown here.
The performance can improve even if the application has more than 256 devices.
While 256 or fewer devices may be ideal, the application still benefits from additional
channels. Although spreading the device load across all channels causes the server
to move from device to device again, it can do so with far fewer devices to process on
a single channel.
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