Smart Buildings Systems for Architects, Owners and Builders

the data packet is initially sent each layer takes the data of the preceding layers
and adds its own information or header to the data. Basically, each layer puts
its own “envelope” around the preceding “envelope.” On the receiving
end each layer removes its information or “envelope” from the data packet.
The layers or groups of layers are described in the following sections.

Physical Layer

This layer defines the electrical (or in the case of fiber optic cables, light) com-
munications across a network link or channel. This layer guarantees that bits
of data transmitted by a device on the network are accurately received by
another device on the network. The physical layer initiates, maintains, and ter-
minates the physical connection between network devices. It defines the

Applications

Layer

OSI Model

Layers

Smart

Building

Protocol

Suite

Applications

TCP

IP

Ethernet

Presentation

Layer

Session Layer

Transport Layer

Sending Data Receivin

g Data

Network Layer

Data Link Layer

Physical Layer

Figure 2.1 Network model layers.

The Foundations of a Smart Building 9