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Transcript

  • 1. The World-Wide Web CP3397 Design of Networks & Security
  • 2. Objectives
    • To highlight how technologies fit together within the WWW
    • To look briefly at some of the emerging technologies XML and .NET
  • 3. Features of The Internet
    • Client/Server Architecture
    • Simple, standard Protocols & Language
      • World Wide Web Consortium (W3C)
    • Available to any IP connected network
    • Globally Distributed Hypermedia
  • 4. 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
  • 5. 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
  • 6. Web Site Design Issues
    • Intended Audience
    • Site Objectives
    • Link Templates
    • Navigation Aids
    • Media Types
    • Meaningless links
    • Poor Layout
  • 7. Proxies
    • A Proxy is an intermediary program that is both client and server
    • There can be more than one Proxy on the route
    Request Response User Agent Proxy Server Request Response Server Client
  • 8. 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
  • 9. 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      • Likely to be supplemented/superseded by XML
  • 10. XML
    • Allows new data types to be formulated
    • Allows most types of information to be described.
    • Human and machine readable.
  • 11. HTTP
    • Application level
    • Generic
      • Can be used for many purposes
      • Stateless
    • System Independent Data Representation
    • Versions
      • HTTP/1.0
      • HTTP/1.1
    • URL’s
  • 12. 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’
  • 13. 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
  • 14. 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
  • 15. 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
  • 16. .NET
    • A distributed application solutions framework
    • Quite versatile supports multiple development languages and environments
  • 17. 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
  • 18. 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)
  • 19. 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
  • 20. .NET Components
    • A newer version of ActiveX
    • Offers a better security model than Authenticode the standard on ActiveX.
  • 21. 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
  • 22. 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
  • 23. 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
  • 24. 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
  • 25. 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
  • 26. 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
  • 27. 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)
  • 28. Media Convergence
    • What Will Be Possible?
      • Banking, Shopping, On Line Video
      • Software not loaded on local machine
        • downloaded from the net
        • pay per use?
  • 29. Summary
    • This should have made clear how the various technologies are converging on the WWW
    • The future --- is there for the taking…