1

Network Technology

2

Computer Networks

A network exists whenever two or more computers are linked together through some type of medium. Computer networks have many uses:• Sharing information and resources• Handling the present by enabling transactions and

capturing/storing transaction data• Remembering the past by providing access to

shared data storage• Prepare for the future by providing communications

to aid decision making

3

Computer Networks: Network Type

Networks may be classified by size:

• Local Area Networks (LANs)• Wide Area Networks (WANs)• The Internet

Connections to the Internet are through:• LANS• Internet Service Providers (ISP)

4

Computer Networks: Network Backbone

Internet

Customer service LAN

Distribution LAN

HumanResources LAN

Com

pany B

ackbone

5

ISP

Customer’sPC

Regional Network Regional Network

Internet Backbone

Company Lan

Employee PC

ISP Connection to Internet

6

Wide Area Networks (WAN)

ApplicationSoftware

NetworkingSoftware

Physical

ApplicationSoftware

NetworkingSoftware

Physical

Sender Receiver

7

WAN: Application Software Layer

The software that the user sees and uses to send and receive messages. (E-mail, Web browser, etc)

• Formats the messages to fit a protocol– Simple mail transfer protocol (SMTP)– Hypertext transfer protocol (HTTP)– Electronic Data Interchange (EDI)

• May also process message in other ways (encryption for example)

8

WAN: Networking Software Layer

Works behind the scenes to format the message so that it may be sent over network.

• Popular transmission protocols include:– Transmission control protocol/internet protocol

(TCP/IP)– Ansi X 12 or Edifact– Wi-Fi

9

WAN: TCP/IP

The transmission protocol for the Internet:• Converts address of destination computer to

IP address– President@whitehouse.gov 198.137.241.30

• Divides message into packets

11001101011100110011… 11001101010 128.192.93.53

11100110011 128.192.93.53

10

WAN: Physical Layer

Once the message is ready, it is sent out over the physical layer.

The physical layer includes connection devices and various transmission media.

• Twisted pair (standard telephone)• Coaxial Cable (cable television)• Fiber optic cable• Microwaves

11

Media Cost Error Rates Speed

Twisted Pair Low Low Low-high

Coaxial cable

Moderate Low Low-high

Fiber optics High Very low High –very high

Radio Low Moderate Low

Infrared Low Moderate Low

Microwave Moderate Low-moderate

Moderate

Satellite Moderate Low-moderate

Moderate

WAN: Physical Layer

12

WAN: Transmission Speeds

Media Speeds Comments

Standard telephone

56 Kbps Available everywhere

ISDN 128 Kbps Available in most urban areas but requires special adapters

DSL 1.544 M in;

128 K out

Becoming more available; doesn’t require special equipment. Doesn’t slow down as more people sign up.

TV Cable As high as 30M but 2.5M to 500K on average

Cable must support 2-way communication; available in many locations but slows down as more people use it.

T-1 to T-4 1.544M-275M Used for commercial purposes. A single T-1 line costs over $1000 per month.

13

WAN: Physical Layer Routing

• Packet switching – technology used to route the individual packets through the network to their final destination

• Router – specialized computers on the network with the sole purpose of determining the best way to send packets to destination

14

ServerComputer

ISP

Router

Router

RouterPackets

Packets

Packets

Packets

Packets

User’s PC

Router

Router

Router

Sending Data over the Internet

15

WAN: Electronic Data Interchange (EDI)

EDI is a set of protocols for submitting common business documents between business partners.

• Uses traditional communication channels (mostly phone)

• Reduces human involvement and paperwork

• Often sent over Value Added Networks (VANs)

16

Local Area Networks (LAN)

Two main types in use today:• Dedicated server networks

• Servers – computers dedicated to managing all or part of the network

• Clients – computers that individuals may use to connect to the network

• Peer-to-peer networks• Designed for smaller networks where emphasis is on

sharing files between computers• Each computer functions as both a client and a

server

17

LAN Components

• Network cabling – physically connects each component to the network

• Hub – a device that allows cables to be connected together

• Network interface card – allows network cabling to be connected to a computer

• Network Operating System – software that controls the network

• Bus – a main cable to which all clients and servers are connected

• Ethernet - protocol for transmitting packets over a bus

18

Wireless Networks

The fastest growing trend in networks – no wires are necessary to make connections

• Wireless Application Protocol (WAP) – a special protocol that allows mobile telephones to connect to the Internet

• Short Message Service (SMS) – a service for sending text messages up to 160 characters long to mobile phones

• Global System for Mobile (GSM) communication protocol – the most widely used mobile telephone protocol worldwide

19

Wireless Networks: Wireless LANs

LAN cabling is replaced with wireless transmissions between computers

• Uses radio frequencies to transmit information between individual computers

• Hubs and routers are used as connection devices between the computers and as bridges to traditional wired networks

• Wi-Fi (wireless fidelity) which uses the IEEE 802.11b standard is currently the most popular approach to wireless LANs

20

Can be thought of as a “Network of Networks”

• Server address – part of Internet address that identifies the computer what you want to connect to

• Domain name – a server address that identifies the computer using several parts ranging from specific to general (top-level)

• E-mail address – combination of username and server address

sales @ fareastfoods.com

Username

Server address

The Internet

21

Internet: Internet Operations

E-Mail Asynchronously exchange electronic messages with other Internet users

FTP Download files (software, documents, or data) from or upload to a server located on the Internet

Newsgroups Participate in a wide variety of online discussion groups

Telnet Work on a computer elsewhere on the Internet

IRC Synchronously exchange electronic messages with other Internet users

World Wide Web Transfer text, images, video, and sound to your computer; search for information on the Internet

22

The World Wide Web

The Web – software, protocols and conventions based on hypertext and multimedia that make the Internet easy to use and browse

• Hypertext – a method of linking related information in which there is no hierarchy or menu system

• Multimedia – an interactive combination of text, graphics, animation, images, audio, and video displayed by and under the control of a personal computer

23

The World Wide Web: BrowserBrowser - application software that allows your computer to act as a client when contacting servers of the Internet (client-server network)

• Hypertext Markup Language (HTML) – computer language used to create Web pages that consist of text, links, and multimedia elements

• Web Page – a special type of document (file) that contains HTML and hypertext links to other documents or elements

• Web Site – an Internet server that stores a collection of related Web Pages

• Uniform Resource Locator (URL) – a standard means of locating Web pages or other resources over the web

24

The World Wide Web

Characteristics Web Page Physical Page

Form Electronic Ink on paper

Amount of information Can extend beyond a single screen

Restricted to single piece of paper

Types of information Can include text, images, audio, and video information

Restricted to text and images

Links to other pages Can be linked to other pages through hypertext

Can be linked only through a separate index

Creation Can be created with HTML and saved to a server

Can be created using word processor and printer