CHAPTER 8

Learning Objective

1.  Explain connectivity, the wireless revolution, and communication systems.

2.  Describe physical and wireless communications channels.

3.  Differentiate between connection devices and services, including dial-up, DSL, cable, satellite, and cellular.

4.  Describe data transmission factors, including bandwidth and protocols.

5.  Define networks and key network terminology including network interface cards and network operating systems.

6.  Describe different types of networks, including local, home, wireless, personal, metropolitan, and wide area networks.

7.  Describe network architectures, including topologies and strategies.

8.  Explain the organization issues related to Internet technologies and network security.

Introduction

We live in a truly connected society.

Increased connectivity potentially means increased productivity, especially in business.

You will learn more about the concept of connectivity and the impact of the wireless revolution in this chapter.

Communication

Computer communications is the process of sharing data, programs, and information between two or more computers

Numerous applications depend on communication systems, including

E-mail

Texting

Video Conferencing

Electronic commerce

Connectivity

Connectivity uses computer networks to link people and resources

Connects your personal computer to other computers and resources on a network and the Internet

The Wireless Revolution

Single most dramatic change in connectivity in the past decade

Allows connectivity with anyone from almost anywhere at any time

Communication System

Electronic systems that transmit data from one location to another

Basic Element of communication

Four basic elements of communication systems

Sending and receiving devices

ü  Computer or a specialized communication device

Connection devices

ü  Interface between sending and receiving device

Data transmission specifications

ü  Rules and procedures that coordinate the devices

Communication channel

ü  Carries the message

Communication Channels 

Communication channels carry the data from one computer to another; essential element of every communication system

Two categories of communication channels

1.        Physical Connections using wire or cable

2.      Wireless Connections

Physical Connections

Physical connection between sending and receiving device include :

Twisted pair cable: two pairs of copper wire twisted together

·         Telephone lines

·         Ethernet cables

Coaxial cable: single solid copper core

·         Cable TV

Fiber-optic cable: tiny glass tubes

·         Faster and more reliable than coax

·         Rapidly twisted pair

Wireless Connections

Wireless connections do not use a solid substance to connect; uses the air itself. Most use radio waves to communicate

     

Primary Wireless Technology

 Bluetooth (short-range)

·         Radio communication standard

 Wi-Fi (wireless fidelity)

·         Uses high frequency radio 

 Microwave

·         Uses high frequency radio wave signals

 WiMax (extends Wi-Fi)

·         New standard that uses microwave to extend WiFi range

 Cellular

·         Use multiple antennae to communication

  Satellite

·         Uses satellites as microwave relay stations

 Infrared

·         Use infrared light wants to communication over short distances

 GPS

·         Determine geographic location of the devices

Connection Devices

Devices need to convert digital signal to analog

Modem – modulator-demodulator

·         Modulation is the process of converting from digital to analog

·          Demodulation is the process of converting from analog to digital

Transfer rate

·         Speed in which modems transfer data

·          Usually measured in megabits per second (Mbps)

Types of Modems

 Digital subscriber line (DSL)

·         High speed telephone lines

 Cable

·         Uses coaxial cable

 Wireless

·         Also known as WWAN                

Connection Device Signals

Types of signals:

 Analog

 Digital

Transfer rates

 Mbps – million bits per second

 Gbps – billion bits per second

 Tbps – trillion bits per second

Connection Services - Corporations

Leased lines

•          T1 combined to form T3 and DS3
•            Have been replaced by OC lines

o   Faster optical carrier lines

 Higher capacity

·         Not affordable for individuals

Connection Services - Individuals

 Digital subscriber line (DSL)

• Uses phone lines 
• ADSL is most widely used type of DSL 

 Cable

•      Uses existing TV cable 
•       Faster than DSL

 Satellite connection services 

•        Use almost anywhere
•      Slower than DSL and cable modem

 Cellular Services

•      3G and 4G cellular network connectivity

 Fiber Optic Service (FiOS)

•         New technology

Ø  Google and Verizon 

Data Transmission

Factors that affect data transmission

Bandwidth is how much information can move across the communication channel in a given amount of time

Ø  Measurement of the width or capacity of the communication channel

Ø  Categories of bandwidth

§  Voiceband (or low bandwidth) – standard telephone

§  Medium band – leased lines for high-speed

o   Mid-range computer and mainframes

Ø  Broadband for DSL, cable, satellite connections to the Internet

Ø  Baseband for individual connections for computers in close range

Making IT Work for You ~ Mobile Internet

Have an “always-on” connection to access e-mail, websites, cloud services, and apps.  Devices that can keep you always connected.

Protocols

Communication rules for exchanging data between computers

 HTTPS – Hypertext Transfer Protocol Secure

•   Widely used to protect the transfer of sensitive data.

TCP/IP

TCP/IP (Transmission control protocol/Internet protocol)

 Most widely used protocol

 Each computer is identified with unique IP (Internet Protocol) address

 DNS – Domain name service resolves IP addresses to names

 Packetization – information broken down into small parts (packets) and then reassembled.

Networks

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

Specialized Terms in a Network

 Nodes

• Any device connected to a network

 Client

•  A node that requests and uses resources from other nodes

 Server

• A node that shares resources with other nodes

 Directory Server

•  Specialized server that managers resources

 Host

• Computer system that can be accessed over a network

 Router

•  Node that forwards or routes data packets

Switch

•  Central node that coordinates the flow of data

 Network Interface Cards (NIC)

• Expansion card that connects a computer to a network

 Network Operating System

• Control activities of all computers on the network

 Network Administrator

• Computer specialists responsible for network operations

Network Types

Network Architecture

How the network is arranged and resources are shared:

Network Topology 

• Physical arrangement of the network

Network Strategy

• How the information and resources are shared

Ring Network

 Topology where each device connected directly to a central network switch

Star Network

Topology where each device connected directly to a central network switch

                                                                                                                         

Tree Network

 Topology where each device connected to a central node either directly or through subordinate nodes. Also called hierarchical.

Topology that does not use a specific physical layout, but requires that each node have more than one connection to other nodes.  Wireless technologies are frequently used.

Mesh Network

Network Strategies

Client/Server Network

·         Central computers coordinate and supply services to other nodes on the network

·         Server provides access

Peer-to-Peer (P2P) Network
All nodes have equal authority
 Can act as both client and server

Organizational Networks

Internet technologies support effective communication within and between organizations Intranet

• Private network within an organization
• Works like the Internet

Extranet

•   Private network that connects more than one organization
•  Works like the Internet, but provides suppliers and other trusted partners with limited access to the organization’s networks 

Network Security

Commonly used technologies to ensure network security

 Firewall

•   Hardware and software that controls access to network
•  Proxy server provides pass-through access
•  Protects against external threats

 Intrusion detection system (IDS)

•  Works with firewall to protect organization's network
•  Analyzes all incoming and outgoing network traffic

 Virtual private network (VPN)

•   Creates a secure private network connection between your computer and the organization

Intranet, Extranet, Firewall, Proxy Server