Electronic Commerce

Contents Web Server Basics Web Server Software Web Server Hardware

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

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

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

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.

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.

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

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

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

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: Microsoft’s Active Server pages (ASP) Sun’s Java Server Pages (JSP) Apache’s PHP Hypertext Preprocessor (PHP)

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

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

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

Server (I) E-mail Servers handle incoming and

outgoing email Database Servers are server computers on

which database management software runs

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

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

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

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

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

Sun Java System Web Server This is a descendant of the original NCSA

server Cost US$1500-per-CPU licensing fee Runs on HP-UX, Solaris and Windows Is ODBC compatible (i.e. full access to

ODBC databases)

Web Server Hardware Web Servers have

more memory, faster hard drives and faster processors (or multiple processors) than desktop machines

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 US$2000 - $4000 A low end Web server might cost the same amount

Companies spend between US$6,000 and $400,000 for a Web server

Suppliers of these servers include Dell, Gateway and Hewlett Packard

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

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

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

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

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 SpikesSource: www.inetu.net/services/ loadbalancing.php

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

Load Balancing Systems Cost Load-balancing switches and software cost

between US$10,000 and $50,000

References [Sch2004] Schneider, Gary, P.,

“Electronic Commerce: The second wave”, Thomson Course Technology, Fifth Annual Edition, 2004