protecting against failure

Protecting Against Failure

• Backups – multiple generations

• Surge Protector – power surges

• UPS – uninterrupted power supply

• Mirroring data / RAID

People are Risky

• don’t see themselves as a risk.

• work around security.

Reliability

• when we rely on computers, and something goes wrong, the impact can be significant :

• Therac 25 • Y2K – $100 billion

• cannot find all of the bugs• they harder bugs are to find, the worse

they are may be.• increased complexity compounds the

problem.

Security vs. Privacy

• balancing.

• examples :– e-mail at work– cell phone with GPS – active badge

Internet & Web

• the World Wide Web and the Internet are not the same thing.

• WWW – an application of the Internet.

• Popularity :– easy to use.– easy to add– easy to search.

Internet Applications

• email & mailing lists

• FTP & file sharing

• Usenet & boards & forums

• World Wide Web

• Instant Messaging & Chat

• Remote Login & Telnet

• VOIP

Web

• distributed information system.

• hypertext & hypermedia.

• browser : software for accessing www.

• Plug-in : extend the capabilities of your web browser.

• documents linked in non-linear ways• web is only one example (help

files, DVDs, multimedia applications)

Hypertext & Hypermedia

• may not have the links you want• dead links – maintenance• not like hardcopy – notes and

highlighting• hard to read long passages of text on

the computer screen• disorienting

Hypertext & Hypermedia

Web

• url : uniform resource locator

• http : hypertext transfer protocol

• html : hypertext markup language

• web authoring tools

• Domain name registry

<html>

<head>

<title>Web Example</title>

</head>

<body>

<h1>CSCI 1200</h1>

<p>

CSCI 1200 is a computer science

class offered for non-majors.

</p>

</body>

</html>

Tags

• anchor tag

<a href="url">Text to be displayed</a>

• image tag <img src = “happy.gif“>

protecting against failure

Documents