Networks

CPS120

Introduction to Computer Programming

Lecture 4

What Is a Network

A network is a group of connected computers that allow people to share information and equipment

Types of Networks

LAN (Local Area Network) connects computers within a small geographic area like a building

WAN (Wide Area Network) connects computers across a large geographic area like a city or country (often via satellite)

Internet: World-wide network of networks

Advantages

Road warriors

Eliminate “sneakernet”

Share information

Share equipment

Who Runs It?

A network administrator manages the network and makes sure it runs smoothlyOften called a systems administrator or an

IS manager

Network Applications

Electronic mail

GroupwareCalendaringScheduling

Video-conferencingRequires sound card, speakers, mike &

camera

Physical Networking

Hubs A hub is a device that provides a central location

where all the cables on a network come together

NICs (Network Interface Card) An expansion card that physically connects each

computer to the network

Cables Coaxial, Unshielded Twisted Pair (UTP), Shielded

Twisted Pair, Fiber-optic Wireless

How Information Is Stored

Client-Server: Used for large networks Files are stored on a central computer and

everyone who can access the network can be given access them

Easy to create scheme to backup and protect files Client: a computer that can access information

stored on the server Server: Central computer that stores files NetWare, UNIX, Windows NT/2000

How Information Is Stored

Peer-to-Peer:Used for a small number of computes (e.g.

10)Files stored on own computers; access

given to them to others on the networkLANtastic, Windows-98, Windows-ME

How Information Is Exchanged

Ethernet:Most popular and least expensive solutionEach computer waits for a pause before

sending informationLike polite conversation

Collisions between information often occurComputers wait a moment, then resend

Ethernet – 10 Mbps, Fast Ethernet – 100 Mbps, Gigabit Ethernet 1000 Mbps

How Information Is Exchanged

Token-ring is a type of network where a token that collects and delivers information is passed from compute to computer Speeds of 4 or 16 Mbps

Asynchronous Transfer Mode (ATM) is a type of network that works by sending information in equal-sized pieces called cells 25, 155, 622 or 2488 Mbps Often networks networks

Network Security

Operating System Security Other system software

Firewall – specialized hardware or software package designed to protect a private computer network from unauthorized access Think “Moat”

User name and password Used for authentication Good passwords

Intranet

Small version of the Internet in a companyUses familiar web-browsers and email packagesAllows hyper-linkingVPNs (Virtual Private Network)End-to-end encryptionMore cost efficient than private lines

Internet and WWW

Chapter 10

Internet Fundamentals

Dates from DARPA in the 1960sConsists of thousands of connected networks around the world Each organization on the Internet is responsible

for maintaining its own equipment These organizations allow you to pass-through their nets

Designed to provide multiple routing to bypass disabled computersCalled cyber-space or the information superhighway

Internet Offerings

Electronic mail (Most popular application)

Information

Entertainment

Discussion Groups

Chat

Programs (Shareware)

Online shopping

Connecting

Computer

Software

Modem or high-speed connection

ISP (Internet Service Provider)Access for a fee

World Wide Web

Part of the Internet consisting of a huge collection of documents stored on computers around the world Web server: computer that stores and delivers

web pages Web site: collection of web pages

URL (Uniform Resource Locator) – unique address HTTP, Computer, Directory, Name of Page

Hyperlinks jump to different web pages

Browsers

A program that lets you view and navigate information on the World Wide Web Home Page: Web page that appears each time

you start your web browser Browser:

Internet Explorer Netscape Navigator

Features Bookmark History lists

Multimedia

MP3 – compressed files containing music or video WinAmp

Streaming video – requires player RealPlayer, QuickTime

Enhancements Java JavaScript ActiveX

Web Portal

Central starting point for browsing personalized by the individualYahoo, Excite, Go, Lycos InfoFree services like email, shopping, chat,

games, stock quotes and sports scores

Shopping

Auctions

Secure web sites – i.e. HTTPS

Children on the Web

Inappropriate information Pictures Documents

Protection Adult supervision Browser restrictions Restriction programs

CyberPatrol NetNanny

Create & Publish Web Pages

HyperText Mark-up Language is a computer code used to create Web pages

There are many programs available, called visual editors which can help you create Web pages without having to learn HTML

Publishing your pages – loaded to an addressable server