Bristol Babcock Network 3000 Setup Manual page 53

Chapter 4 - Guidelines For Configuring the BSAP Data Link
9,600, then a 'worst case' calculation of the poll period is:
7,650 * (12) / (9600) = 9.56 seconds
If line turnaround time is a factor (due to modems, or radios), this must be taken
into account when calculating the poll period. For example, if a modem/radio
combination requires 0.2 seconds after RTS assertion before CTS is asserted, then
0.8 * (number of nodes on the line) should be added to the poll period calculated by
the formula above. 0.8 was chosen because it represents 4 times the RTS/CTS delay;
this amount of time is needed because there can be up to four messages per data
transaction.
The 'worst case' poll period can be entered
as the initial value for the poll period
signal when creating the ACCOL load. The
value can then be altered, on-line, using
DataView, based on the tuning technique
described below.
Technique For Fine-Tuning the Poll Period
Once the system is 'up and running' with the initial 'worst case' poll period, the poll
period may be able to be shortened based on observed performance of the network.
This must be done carefully, however, because making the poll period too short may
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have a negative impact on performance.
To perform this 'fine tuning', the system must be operating normally. All nodes on
the line must be on-line and communicating, and there must be no non-existent
nodes.
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Making the poll period too short will cause the system to go as fast as it can, but can reduce
throughput by eliminating preferred polling and other aspects of the polling algorithm.
Network 3000 Communications Configuration Guide Page 4-7