Specifications

This means there is a huge market for applications to allow consumers to access

and manipulate their home or office appliances and HVAC systems while away

from the building. This also ensures optimum settings to save energy and money

when the user is away from the building. Below is a discussion on how such a

system would be implemented in order to provide remote access.

2.7.2 TCP/IP

The Internet Protocol Suite, or TCP/IP, is a set of communication protocols used

for the Internet. A TCP/IP will be required to connect our system to the internet.

This abstraction allows encapsulation of the data as it travels from one layer to

the next. Each layer uses a set of protocols to send its data down the layers,

being further encapsulated at each level. This suite is constructed as a set of

layers as seen in Figure 14 below.

Figure 14 Layers of the TCP/IP reference model

2.7.3 Host-to-Network Layer

This layer interfaces the higher layer protocols to the local network. This layer is

primarily representative of the physical connection between two devices and

often does not run any TCP/IP protocols as they are simply not needed. Its

primary functions are to provide logical link control (LLC) and Media Access

Control (MAC). LLC refers to the functions required to establish and control

logical links between local devices on the network. Most LAN devices use the

IEEE 802.2 LLC protocol. MAC refers to the methods used by devices to control

access to the network medium. Since most networks use devices that share a

medium, it is necessary to have a rule set in place to manage the connection to

avoid collisions. One example is that Ethernet uses CSMA/CD while Token

Rings uses token passing. In addition to the two different control methods used,

this layer is also responsible for the final encapsulation of higher-level messages

into frames that are sent over the network; with the frames in place, the Host-to-

Network layer must also manage the address of the receiving device. Finally the

Host-to-network Layer is also responsible for error detection and handling.