Issue
What are the effects of a connection object on the I/NET controller lan?
Product Line
Satchwell MicroNet, TAC INET, TAC Vista
Environment
Xenta 527/913/731
I/NET
Cause
The I/NET communication protocol has a maximum baud rate of 19,200 bps and this allows for a maximum of 10 messages a second to occur on the I/NET controller lan. This limit applies to the entire controller lan not just a single controller.
Optimal performance will be at 5 or 6 messages a second on the controller lan.
Resolution
Any connection objects involving I/NET points need to be aware of the limits imposed by the controller lan protocol and adjust the periods of connection objects to avoid exceeding these limits.
Every connection object that the source is from I/NET requires the value to be read from the I/NET controller before it can determine if the value has changed to send to the target of the connection object. If the default period of 10 seconds is used for all connection objects then only 100 points will consume 100% of the bandwidth on the I/NET controller lan to meet the demand and negatively impact the performance of the I/NET network.
Instead count the number of connection objects with source values from I/NET. Divide this number of 4 to allow room for values being written to the I/NET network to determine the minimum recommended period for your connection objects to avoid overloading your I/NET controller lan.
Ex: 250 points being sent from I/NET to a 3rd party system / 4 writes a second = 63 second period.
This could result in some larger then expected periods and some points might be more critical then others which will require some prioritization. If of the 250 points only 15 require faster response time then they can use a lower period, but this will affect the period used for the lower priority points. It is recommended to avoid periods below 10 seconds if at all possible.
Ex: 235 points at lower priority / 4 messages a second = 59 second period
59 second period for low priority points / 10 second period of high priority points = 6 polls per point * 15 points at high priority = 90 reads for high priority points.
235 points + 90 polls = 325 values read from I/NET / 4 messages a second = 82 second period for lower priority points to accommodate 15 high priority points.
