lead black slide

Lead Black Slide

Powered by DeSiaMore 2

Chapter 6

Information System Networksand

the Internet


Our Agenda Communications Concepts Communications Hardware Communications Software


Our Agenda (cont’d.) Network Concepts Local Area Networks Wide Area Networks Internetworks The Internet Electronic Commerce


Learning Objectives Summarize the communications

hardware and software needed for computers to communicate with other computers.

Describe the main characteristics of communications channels.


Learning Objectives (cont’d.) Describe the main types of

communications processors and give several examples.

Describe the main functions of communications software.

Explain how local area networks are organized and list the special hardware and software used in them.


Learning Objectives (cont’d.) Describe the structure of wide area

networks. Explain how and why networks are

interconnected. Explain what the Internet,

intranets, and extranets are. Describe the special hardware and

software needed for E-Commerce.


Communications Concepts


the Internet


Communications Concepts Two main types of communications

hardware Communications channel – the link

over which data is sent Communications processors – provide

processing capabilities between the computer and the communications channel

A modem is a communication processor


Communications Hardware


the Internet


Communications Hardware Communications channel

characteristics Data is transmitted over the channel

as bits. Each bit is sent one after the other. Bits are grouped to form bytes that

represent characters using ASCII, EBCDIC, Unicode or some other code.


Communications Hardware (cont’d.) The way in which bits are sent

determines two main characteristics of the channel Signal type Data rate


Signal Type Bits can be sent either as

An Analog signal – data is transmitted by a wave pattern that varies continuously

A Digital signal – data is transmitted as a series of high and low pulses

The human voice is analog Telephones are analog Computers are digital


Data Rate Data rate is measured as bits per

second (bps). Each type of channel has a

maximum data rate. Baud rate is used to express data

rate 9,600 baud = 9,600 bps. Bandwidth describes how much

data can be transmitted over a channel.


Communications Channel Media Wire cables – sometimes called

“copper” have been used since the 1800s. Two main forms

Twisted-pair wiring Coaxial cable


Communications Channel Media (cont’d.) Twisted-pair wiring

Two wires twisted together Most telephone lines are twisted-pair Can also be used for data Data transmission rate is slow

compared to other media


Communications Channel Media (cont’d.) Coaxial cable

Copper wire insulated with rubber and plastic.

Used with cable television systems. Data transmission rate is faster than

twisted-pair, and more expensive, but slower than other media.


Communications Channel Media (cont’d.) Fiber-optic cables

Bundles of glass or plastic fibers. Each fiber is 1/2000 inch thick – about

the size of a human hair. Data is transmitted by a laser that

pulses light through the fiber. Data transmission rate is very fast.


Communications Channel Media (cont’d.) Microwave

Special types of radio signals sent from one microwave antenna to another.

Transmission is line-of-sight, i.e, one antenna must be able to “see” the other.

Two types Land based – antenna approximately 30

miles apart. Satellite – positioned 22,300 miles in

space – geosynchronous orbit.


Communications Channel Media (cont’d.) Other media

Infrared spectrum Very short distances Relatively slow

Wireless systems Used for mobile computing Usually in small areas or hard to wire

areas


Communications Processors Channel interface devices Communications control units Communications protocols Communications security


Channel Interface Devices Modems – convert digital signals to

analog signals at the origin and reverse the process at the destination of the signal. Digital to analog is modulation. Analog to digital is demodulation.

Modems may be either internal or external to the computer.


Channel Interface Devices (cont’d.) Modem data rates are typically 33

Kbps to 56 Kbps. Cable modems – are devices to

provide the interface between a computer and a cable system’s data transmission capability.

For ISDN or DSL a terminal adapter is required.


Communication Control Units Multiplexer – combines signals

from several slow-speed devices to transmit over a faster device.

Controller – stores and forwards signals to improve the throughput of the channel.

Front-End Processor – operates between the channel and the main computer.


Communications Protocols Protocols are the rules computers

must follow when they communicate with one another.

Computers that wish to communicate and have different protocols must use a protocol converter to standardize their communication.


Communications Security A problem with data communications

is the lack of security over a communications channel. One way of solving this problem is to use data encryption to convert the data to an unintelligible form for transmission and to return it to an intelligible form at the destination.

Encryption requires a key.


Communications Software


the Internet


Communications Software Communications software is

required to control communications between computers. It receives data from communications processors connected to the channel and passes the data to other software in the computer for processing.


Communications Software (cont’d.) Types of communications software

Terminal emulators Client software – as used in

client/server computing File transfer protocol (FTP) – software Network Operating System software

(NOS)


Network Concepts


the Internet


Network Topologies Star network – each node is

connected to each other node. Hierarchical network – organized

like a family tree. Bus network – each node is

connected to a single, common communications channel.

Ring network – each node is connected to a common channel forming a loop.


Types of Networks Local Area Network (LAN) Wide Area Network (WAN) Metropolitan Area Network (MAN) Internetwork – connected networks


Local Area Networks


the Internet


Local Area Networks Local Area Network Structure

Connection Topology. Media for communications channel. Usually either Ethernet or Token Ring. Require Network Interface Cards (NIC)

in each device on the network. Permits sharing of resources.


Wide Area Networks


the Internet


Wide Area Networks Connection Topology. Media for communications channel. Permits sharing of resources. Can include a Virtual Private Network. Often a combination or resources.


Internetworks


the Internet


Internetworks Connecting two or more networks

using Bridges Gateways Routers


The Internet


the Internet


Internet Origins in ARPANET in 1969. Grew slowly at first and “exploded” in

1993 with the adoption of the HTML standards for the World Wide Web.

Two protocols Transmission Control Protocol (TCP) Internet Protocol (IP)

Most users require a relationship with an Internet Service Provider (ISP).


Internet Services Electronic Mail – E-Mail World Wide Web (WWW) Telnet File Transfer Protocol (FTP) Gopher Usenet or NetNews Chat


Intranets and Extranets An Intranet is an Internet like

network but access is restricted to within a business or organization.

Firewalls are used to control access to an Intranet.

An Extranet permits controlled outside access to an Intranet like network.


Electronic Commerce


the Internet


Hardware and Software Requires the business have a web

site. The web software runs on a web

server which has special e-commerce software.


Information System Networks and the Internet

Key Terms


Key Terms Analog Signal Bandwidth Baud Rate Bus Network Cable Modem Channel Interface Device Client Software

Communications Channel Communications Control Unit Communications Processor Database Server Data Encryption Digital Signal


Key Terms (cont’d.) Downloading DSL Electronic Commerce (E-commerce) Electronic Mail (E-mail) Extranet File Server File Transfer Firewall

Hierarchical Network Hybrid Network Information Superhighway Internet Internet Service Provider (ISP) Internetwork Intranet


Key Terms (cont’d.) ISDN Local Area Network (LAN) Modem Network Computer Network Interface Card (NIC) Print Server Protocol

Protocol Converter Ring Network Star Network Terminal Adapter Terminal Emulation Software Uniform Resource Locator (URL) Uploading


Key Terms (cont’d.) Value Added Network (VAN) Virtual Private Network (VPN) Web Server Web Site Wide Area Network (WAN) Wireless LAN

World Wide Web (WWW)


Summary Communications Concepts Communications Hardware Communications Software


Summary Network Concepts Local Area Networks Wide Area Networks Internetworks The Internet Electronic Commerce

Final Black Slide

lead black slide

Documents