Echelon LNS User Manual

Page 174

LNS Programmer's Guide

160

Start

Unicast?

Use acknowledged service with the transport
properties set to their default values. Set the
AliasOptions and BroadcastOptions
properties as follows:

AliasOptions = lcaAliasForSelectorConflicts,
BroadcastOptions = lcaBroadcastNever

Yes

All targets

on the same

subnet?

Yes

Use the unacknowledged/repeat service with the
default transport property values. Set the
AliasOptions and BroadcastOptions
properties as follows:

AliasOptions = lcaAliasForSelectorConflicts,
BroadcastOptions = lcaBroadcastAlways

Small number

of targets (Z)?

Yes

Use acknowledged service with the transport
properties set to their default values. Set the
AliasOptions and BroadcastOptions
properties as follows:

AliasOptions = AliasForUnicast
BroadcastOptions = BroadcastNever

Use the unacknowledged/repeat service with the
default transport property values. Set the
AliasOptions and BroadcastOptions

properties as follows:

AliasOptions = lcaAliasForSelectorConflicts
BroadcastOptions = lcaBroadcastGroup

Figure 7.4 Automated Predictive Connection Strategy

The decision-aid presented in this flowchart is deliberately vague in the last decision. If a

multicast connection targets a small number of devices on multiple subnets, it might be

best to break up the group-addressed multicast connection into multiple unicast
connections using aliases, thereby preserving groups. No guidance is given for the cut-off

figure Z. So, exactly how many aliases should be used by a single connection?

The answer to this question requires knowledge of the available aliases on the source

device (this defines the maximum for Z), and the number of similar connections sourced

from the same device. Generally speaking, it is advisable to keep Z fairly low, perhaps
less than 5, to limit the impact on the total transaction time introduced with the use of

aliases.

You application can read the AppDevice object’s AliasCapacity and AliasUseCount

properties to determine the used and available alias table entries on a given device.