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The World-Wide Web

CP3397 Design of Networks

& Security

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Objectives

To highlight how technologies fit together within the WWW

To look briefly at some of the emerging technologies XML and .NET

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Features of The Internet

Client/Server ArchitectureSimple, standard Protocols & Language

World Wide Web Consortium (W3C)Available to any IP connected networkGlobally Distributed Hypermedia

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Issues

The drive from E-Commerce Static Nature of the Web

Speed Most of the Internet isn’t fast enough for more than simple

graphics (yet) Standards

HTML is already “broken” (Netscape, Microsoft extensions) and abused / misused

Security/Authentication how to restrict access - HTTP has primitive authentication

protocol Data Integrity

consistency of documents could be a major problem

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Client / Server Architecture

Clients Run on local machine Any client can be used can pass files to other programs

Server Runs on remote machine Any server can be used

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Web Site Design Issues

Intended Audience Site Objectives Link Templates Navigation Aids Media Types Meaningless links Poor Layout

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Proxies A Proxy is an intermediary program that is both client and

server

There can be more than one Proxy on the route

RequestRequest

ResponseResponse

UserUserAgentAgent

ProxyProxy

ServerServer

RequestRequest

ResponseResponse

ServerServer ClientClient

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Caching

Bandwidth is a major problem As bandwidth increases, so does usage (cf. Road building)

Caching minimises bandwidth

decreases object retrieval time

reduces bottlenecks

Caching can be implemented hierarchically departmentally, institutionally, nationally, internationally

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The Language of The Web - HTML

Hypertext Mark-up Language

HTML is device independent

Developing standards Fairly simple set of elements in HTML 2.0

Increasingly complicated in HTML 3.2 and 4.0

Further Complicated by proprietary “extensions” and

“enhancements”

Likely to be supplemented/superseded by XML

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XML

Allows new data types to be formulated

Allows most types of information to be described.

Human and machine readable.

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HTTP

Application level

Generic Can be used for many purposes Stateless

System Independent Data Representation

Versions

HTTP/1.0

HTTP/1.1

URL’s

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MIME Information

Multipurpose Internet Mail Extensions Originally Text Only 1991 other file types added Servers Insert MIME header Clients use the header to select an appropriate

‘player’

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Distributed Objects

Are software components A Component should be free of

Languages, OS, Vendors, Networks, Applications Components can be reused by many applications Off the Shelf black boxes Emerging standards

CORBA / Java Beans COM / ActiveX & .NET

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Java

Developed by Sun Microsystems 1995 Extra Client-side functionality Look & feel of C++ Browsers download Java “Applets”

makes it possible to interact with the page

Compiles into Java bytecode can run on any server or client with a Java Virtual Machine

Javascript

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CORBA

Common Object Broker Request Architecture Middleware for managing distributed objects An interface specification

uses IDL, Interface Definition Language Allows programs at different locations or from

different vendors to communicate Microsoft has it’s own solution - DCOM

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.NET

A distributed application solutions framework

Quite versatile supports multiple development languages and environments

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Metadata

Metadata is Data about data In WWW terms it means data about web Resources

Needed for: Management of the Web Effective searching Authentication

No Current Standard Lots of Proposals

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XML

Removes dependence on a single document type

Overcomes some of the limitations of HTML

Enables user groups to define custom markup Chemical Markup Language (CML) Channel Definition Format (CDF) Open Financial Exchange (OFX) Handheld Device Markup Language (HDML)

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ActiveX

Set of OO technologies developed by Microsoft You develop components in ActiveX called controls An ActiveX control is equivalent to a Java Applet Can be created using

C++ Visual Basic VB Script

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.NET Components

A newer version of ActiveX

Offers a better security model than Authenticode the standard on ActiveX.

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Portals

A starting site for users when they connect to the web Feature text intensive fast loading pages Typical services

web directory search facility email news reports / share prices facility to tailor

Yahoo, AOL, Microsoft Network, Netscape, Lycos

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Push Technology

The Web is currently passive and static You have to actively seek information

Pushes information to users rather than them having to request it

Is active and dynamic Several competing technologies

IE6 Channels, Pointcast I-Server, Castanet, BackWeb, Headliner ChannelManager, Incisca, Communicator

Bandwidth

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VRML

Virtual Reality Mark-up Language An extension of HTML to handle 3D objects Objects defined by Mark-up Objects can be linked Users can manipulate those objects (viewing, moving, etc) Enables

virtual environments telepresence visualisation

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Packaged Software

MS Office 2000 All the tools need for Web Site creation and maintenance Front Page includes pre-designed web page templates Publisher Photodraw 2000, a new drawing and image editing package Convert to Web Page wizard

WordPerfect Office 2000 will provide similar functionality

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Accessibility

Web Accessibility Initiative (WAI) purpose is to make the Web formats and protocols (HTML,

XML. CSS, HTTP, etc) more accessible to people with a disability

Disability increases with age appeal to self interest (i.e., we all get old)

Accessibility not just limited to permanent disability - e.g., when driving a car, everyone’s “ability” is temporarily modified

Will require strict conformance with any standard Requires institutional/individual will

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IP Telephony

1997 Company in Finland introduces voice-over-the-internet on corporate data networks

Uses the Internet instead of PSTN Cheaper - No per minute charges for usage of the internet unlike

PSTN Many companies have achieved significant discounts with

existing providers Internet bandwidth is not guaranteed

Quality of Service (QAS) capabilities need to be established so that bandwidth is set aside for voice communication. Quality of voice transmission over the internet is not as good as PSTN

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Video Technology

Vmail User records short video clips using low cost video camera S/W Compresses the file and makes it self executing Sent via the internet as an email message

Video Conferencing Will become widespread in use as cost of technology reduces

an usage of PC’s continues to increase Will remain a specialist application (video phone)

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Media Convergence

What Will Be Possible? Banking, Shopping, On Line Video Software not loaded on local machine

downloaded from the netpay per use?

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Summary

This should have made clear how the various technologies are converging on the WWW

The future --- is there for the taking…