BACnet Transport Options
With the exception of PTP, which is unique to dialed and point-to-point communications, BACnet
generally provides the ability to choose the most appropriate trade-off between cost and performance
in the transport mechanism.
As the diagram shows, there is a fairly clear division of increasing cost for increasing performance
between the various BACnet transport options. There are certainly areas of overlap, where in some
circumstances it may be possible to use several different transports to accomplish the same job,
and where the cost/performance ratio may not always be the same. There are, for example, some
circumstances where ARCNET can be less costly to implement for the same performance than LonTalk.
The implication of this may be important to specifiers in some circumstances. You may, for example,
be able to include more bidders in a competitive situation, due to the increased flexibility in
specifying. The flip side of this flexibility is that generally the different LAN types are highly
incompatible without the addition of extra devices, such as routers. So one side effect of allowing
mixed networks that include more than two LAN types is the requirement for providing router devices
to couple the networks together.
You can reduce the impact of this by specifying particular LANs to be used. However, this may have the
unintended side effect of eliminating some vendors from competing, since not all vendors support all of
the LAN types.