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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