Chapter 9 Communications and Networks

Chapter 9 Communications and Networks

Communication Systems

Four basic elements

1.         Sending and receiving devices

2.         Communication channel

3.         Connection devices

4.         Data transmission specifications

Physical Connections

•          Ethernet cable - consists of twisted pair cable; slowest; being phased out by more advanced and reliable media

•    Coaxial cable – single solid copper core; 80 times transmission of twisted pair; television and computer networks

•          Fiber optic – 26,000 times capacity of twisted pair cable; more secure and reliable; best over limited distances; lighter, more reliable, and less expensive than coaxial cable

Types of wireless connections are:

•    Infrared

•    Light waves used over short distances

•    Sometimes called line of sight communications

•    Sending and receiving devices must be in clear view of one another

•    Broadcast radio

•    Uses towers called transceivers (key term)

•    Web-enabled devices follow a standard known as Wi-Fi (wireless fidelity)

•    Microwave

•    Uses high-frequency radio waves

•    Also line of sight

•    Used for short distances

•    Satellite uses satellites orbiting about 22,000 miles above the earth as microwave relay stations; many of these offered by Intelsat, the International Telecommunications Satellite Consortium which is owned by 114 governments and forms a worldwide communications system

•    Satellites can be used to send and receive data; Uplink is sending data to satellite and Downlink refers to receiving data from a Satellite

•    GPS (Global Positioning system)  use a network of 24 satellites owned and managed by the Defense Department which continuously sends location information to earth

Networks

A computer network is a communication system that connects two or more computers so that they can exchange information and share resources.

The types of computer networks:

•    Node – any device connected to a network

•    Client – a node that requests and uses resources available from other nodes

•    Server – a node that shares resources with other nodes; dedicated servers  specialize in performing specific tasks—could be an application server, communication server, database server, file server, printer server, or Web server

•    Directory server – a specialized server that manages resources such as user accounts for an entire network

•    Host – large centralized computer

•    Switch – the center or central node for other nodes; previously done by something called a hub

•    Network interface cards (NIC) – connects the computer to a network

•    Network operating system (NOS) – software to control and coordinate activities between computers on a network

•    Network administrator – a computer specialist; network administrator