Electronic Commerce

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Electronic Commerce COMP3210

• Dr. Paul Walcott
• 29/10/04

The Department of Computer Science Mathematics
and Physics, University of the West Indies, Cave
Hill Campus, Barbados
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Contents

• Web Server Basics
• Web Server Software
• Web Server Hardware

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Web Servers Back To Basics

• A Web Server computer responds to requests from a
  Web Client
• A Web Server comprises of
• Hardware
• Operating system
• Web server software

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Software/hardware Requirements

• From the company goals you should be able to
  estimate
• The number of visitors that will use your site
• The number of pages viewed by the average visitor
• The average and maximum allowed size of each page
• The maximum allowed number of simultaneous
  visitors
• This allows the software and hardware
  requirements to be determined

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Web Site Types

• There are numerous different types of Web sites
  including
• Development sites are used by companies to
  evaluate web site designs. The initial investment
  in these sites are small since they use existing
  hardware (i.e. no special hardware is purchased)
• Intranets these are corporate networks that
  hold documents such as internal memos, corporate
  handbooks, expense account worksheets, budgets
  and newsletters

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Web Site Types (I)

• Extranets which allow external entities, e.g.
  suppliers and strategic partners to access a
  subset of the information on the Intranet
• Transaction-processing These sites operate 24
  hours a day, seven days a week and require fast,
  reliable hardware and e-commerce software
• Web sites hosting B2B and B2C activities must
  have spare capacity to support an increase in
  customer volume.

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Web Site Types (II)

• Content-delivery sites must be available seven
  days a week, 24 hours a day and require fast and
  precise search engines to help visitors locate
  information quickly
• These sites deliver content such as news,
  histories and other digital information.

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Web Clients and Servers

• When an individual connects to the Internet to
  view a document, they become a client on the Webs
  client/server network
• The client/server architecture is used for LANs,
  WANs and the Web.
• Typical request serviced by servers connected to
  these networks include request to print, to
  retrieve information and to access databases

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Web Clients and Servers (I)

• Web servers typically have
• More memory
• Larger and faster disk drives
• than client computers
• Web browser software e.g. IE, Netscape and
  Firefox is the software that makes computers work
  as Web clients
• The Internet connects several different types of
  computers together, therefore Web software must
  be platform neutral

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Dynamic Content

• A static page is an unchanging page retrieved
  from a disk
• A dynamic page is a page created by a program
  (script) based on user input
• E.g. a Web client inquires about the status of an
  order and the Web page that is returned is
  created from information stored in a database
• This property (being dynamic) can affect the
  performance of the Web Server
• static pages are delivered faster than dynamic
  pages

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Dynamic Content

• The first Web site to provide dynamic pages used
  server side scripting
• Programs running on the Web server that create
  web pages
• These technologies are slow
• Newer technologies used for generating dynamic
  content include
• Microsofts Active Server pages (ASP)
• Suns Java Server Pages (JSP)
• Apaches PHP Hypertext Preprocessor (PHP)

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Dynamic Web Pages The Future

• Some critics say that ASP/JSP/PHP etc. do not
  solve the problem since they simply shift the
  responsibility of Web page creation from people
  to programs
• A project that is currently underway to tackle
  the problem of dynamic Web page creation is the
  Apache Cocoon project

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Dynamic Web Pages The Future

• The Apache Cocoon project
• Is creating a Web development framework that
• Allows programmers to query the system using data
  in XML format
• Receives output in multiple formats including
  HTML
• The content is stored in XML tags which describes
  the semantics (meaning) of each content item
• A Java servlet handles the information request
• A style sheet is applied to the data

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Server

• A Server is any computer used to provide files or
  make applications available to other computers
  connected to it through a network
• Server software refers to the programs that run
  on the server
• Web Servers are connected to the Internet and
  serve Web pages

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Server (I)

• E-mail Servers handle incoming and outgoing email
• Database Servers are server computers on which
  database management software runs

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Web Client/Server Communication

• When a Web Client requests a page from a Web
  server the following occurs
• The request is converted into HTTP by the browser
  and sent to the Web Server
• The Server receives the request and retrieves the
  information requested by the Client
• The Server formats the information using HTTP and
  sends it back to the Client
• The Client displays the information in the
  browser
• Web pages may take long to appear because each
  page element requires a separate request/response

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2/3-Tier Client/Server Architecture

• The typical Web Client/Server model is two tier
  because it has one client and one Server
• In the three-tier Client/Server model the third
  tier includes Server applications that supply
  information to the Web Server
• E.g. a catalog style Web site with search, update
  and display functions the catalog database and
  database management software would make up the
  third tier

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Web Server Software

• The most popular public Web server programs today
  are (April 2004 survey)
• Apache HTTP Server (69.01)
• Microsoft Internet Information Server (IIS)
  (23.26)
• Sun Java System Web Server (JSWS) (former names
  are Sun One, iPlanet Enterprise Server and
  Netscape Enterprise Server) (0.86)
• http//news.netcraft.com/archives/2004/04/01/april
  _2004_web_server_survey.html

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Apache (A Patchy Server)

• Developed in 1994 by Rob McCool
• The original core system has many patches applied
  to it, and thus its name
• Apache has dominated the Web since 1996
• Available free
• Runs on operating systems including FreeBSD-UNIX,
  HP-UX, Linux, Microsoft Windows, SCO-UNIX and
  Solaris

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Microsoft Internet Information Server (IIS)

• Comes bundled with Microsoft Windows Server
  operating system
• IIS used on many corporate intranets (Microsoft
  standard product)
• Originally written to run on Windows NT and
  Windows 2000 runs on Windows 2003 Server and
  Windows XP
• Supports ASP, ActiveX Data objects and SQL
  queries

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Sun Java System Web Server

• This is a descendant of the original NCSA server
• Cost US1500-per-CPU licensing fee
• Runs on HP-UX, Solaris and Windows
• Is ODBC compatible (i.e. full access to ODBC
  databases)

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Web Server Hardware

• Web Servers have more memory, faster hard drives
  and faster processors (or multiple processors)
  than desktop machines

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Cost

• A high-end desktop PC with 512MB RAM, 3GHz
  processor, a 200GB IDE drive, a good monitor and
  DVD/CD-RW drive cost between US2000 - 4000
• A low end Web server might cost the same amount
• Companies spend between US6,000 and 400,000 for
  a Web server
• Suppliers of these servers include Dell, Gateway
  and Hewlett Packard

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Web Server Architectures

• Server farms refer to large (hundreds, or
  thousands) of Web servers used to handle daily
  traffic on large Web sites
• A Centralised architecture uses a few very large
  and very fast computers
• A Distributed/decentralised architecture uses a
  larger number of less powerful computers

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Web Server Architectures (I)

• The Centralised architecture requires
• Expensive computers
• Is more susceptible to technical problems
• If one or a few of the servers are available then
  a large proportion of the site is unavailable
• As a result a backup/recovery plan is essential

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Web Server Architectures (II)

• The Distributed/decentralised architecture
• Spreads the risk over a large number of servers
• The smaller servers are less expense that larger
  ones (the cost of 100 smaller servers is usually
  less that the cost of one large one)
• Additional hubs and switches are required to link
  the servers together and to the Internet
• These sites might also use load-balancing systems
  which are an additional cost

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Load Balancing Systems

• A load-balancing switch
• A piece of network hardware that monitors the
  workload of servers attached to it
• assigns incoming web traffic to the server with
  the most available capacity at the given time

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Why Load-balance?

• Allows Highly-Trafficked Sites To Maintain Fast
  Response Times
• Server Redundancy - If An Application Server Goes
  Down, Your Site Stays Up
• Better Site Performance Better User Experience
  Better Sales Results
• Readies Your Hosting Configuration For Traffic
  Growth Intense Traffic Spikes
• Source www.inetu.net/services/
  loadbalancing.php

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Simple Load-Balancing

• Traffic enters the site from the Internet through
  a router (not shown in diagram)
• This traffic is then directed to the appropriate
  Web server by the load-balancing switch

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Load Balancing Systems Cost

• Load-balancing switches and software cost between
  US10,000 and 50,000

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References

• Sch2004 Schneider, Gary, P., Electronic
  Commerce The second wave, Thomson Course
  Technology, Fifth Annual Edition, 2004