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 smoothly Often called a systems administrator or an IS manager

Network Applications Electronic mail Groupware Calendaring Scheduling Video-conferencing Requires 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 network LANtastic, Windows-98, Windows-ME

How Information Is Exchanged Ethernet: Most popular and least expensive solution Each computer waits for a pause before sending information Like polite conversation Collisions between information often occur Computers 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 company Uses familiar web-browsers and packages Allows hyper-linking VPNs (Virtual Private Network) End-to-end encryption More cost efficient than private lines

Internet and WWW Chapter 10

Internet Fundamentals Dates from DARPA in the 1960s Consists 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 computers Called 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 individual Yahoo, Excite, Go, Lycos Info Free services like , 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