Principles and technologies of local area networks - Intelligent Buildings and Building Automation - page 49

Node 1

Node m

. . .

Interface Interface

Communications link

Figure 4.6 Communication architecture concept.

Node m

Node 1

AP 1 AP m

Interface Interface

CP 1 CP m

Interface Interface

Communications link

Figure 4.7 Three-layer architecture.

transfers from a source AP to a destination AP. The interface between the AP
and CP can be regarded as a mailbox (namely, the application-communica-
tion [A/C] interface). The AP deposits messages to be transmitted and collects
messages received. Messages deposited by the AP in a source node should be
picked up by its CP and transferred, through the interface between the CP
and communication link, and communication link to the CP in a destination
node, and then be placed in its A/C interface and finally consumed by the AP.
The same process applies in the opposite direction.
Such a partition of network operations into three parts, i.e. AP, CP and a
communication link, brings very important benefits. Each of the parts can
be defined and implemented separately, simplifying the development task.