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PowerSCADA Expert - Maximum number of IODevices of MODNET type

Published date: 19 February 2020

Customer request:
Customer wanted to integrate 400 sets of Ethernet devices which support Modbus TCP protocol in a PowerSCADA Expert (PSE) project.
The question was if all the devices can be integrated to one PSE Server and the Server has to be redundant.
In the legacy software version, one IOServer could only have one TCP/IP Board and 255 Ports can be created on that type of Board.
Can we integrate all the devices into one PSE Server? If yes, then how to configure the communication including IOServer, Board, Port and IODevice?

The maximum number of IODevices per project is 16383 IODevices while having maximum 4095 simultaneous multiple protocols.
An IOServer cannot have duplicate BOARD types.
You may find reference of the word "Channel" in various Driver documentation resources.
To be clear, PORT = Channel, both terms are referring to a communication channel.
PORT number limits are hardcoded into each communication driver.
The TCPIP driver (TCPIP.DLL) supports 512 PORTS per board since DLL version, thus MODNET driver (MODNET.DLL) supports 512 PORTS (channels) since driver version

These limits are theoretical limits, in reality there are Kernel Queues that introduce another limitation.
[Kernel]Queue has a max of 5000 (which is also default value), but some drivers like Modnet consume more queues per channel than others.
Modnet consumes 13 Kernel Queues per PORT.
As a result, a 512 hardcoded limit for Modnet PORTs will be downgraded to 300-350 because of these queues.
So, consider the limit at 350 MODNET PORTS per BOARD (per IOServer).
If you use ModbusTCP/RTU Gateways, then you can have thousands of IODevices on the same IOServer, just because for each of the 350 PORTS you could have several different IODevices, with different Addresses (UnitID).
For example: 1 Gateway to collect 5 SEPAMs means: 5 IODevices (5 different IODevice Addresses), 1 PORT (the same PORT that uses Special Options for Gateway's IP address), 1 BOARD (TCPIP).

To overcome the 350 PORTS limit, more IOServers are needed.

Further, another reduction should be made, imposed by the recommended number of IODevices per IOServer.
In the same project, the same Cluster, the same Network Address, the PowerSCADA team recommendation (rule) is: either 50000 tags or 250 IODevices per IOServer. Whichever comes first.
To create another IOServer in the same Cluster and the same Network Address, simply add another IOServer but specify a different Port (this is the Port from the IO Server dialog window).
Doing so, you will need to define different Ports for the extra IOServers: default is 2082, so you may add any unused TCP port: 3082 for second IOServer, 4082 for third IOServer and so on.

Here are some configuration screenshots (using Excel and DBF Add-in) to illustrate the IODevices distribution per IOServers:





Created on 8th JUL 2015 by
Adrian Dicea
Global Expert Technical Support Engineer - Support Prime PSE / EGX

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