Intro to Web Architecture Chapter 1

8/8/2019 Intro to Web Architecture Chapter 1

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Introduction To Web Architecture


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ER/CORP/CRS/OS30/003

Version no: 2.02Copyright 2004,

Infosys Technologies Ltd

Course Objectives

Understand the Request - Response Cycle

Understand the various options available in terms of servers

To be able to understand the various types of components of a web application

Understand interaction between the components

Understand the tier-ed architecture of Internet Applications

This course covers

Http Request and its contents

Http Response and its contents

Introduction to various Web servers

Introduction to various types of components

N Tier architecture


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Course Objectives (Contd)

To be aware of the issues involved in security, performance at the client and serverend

Understand the need of Confidentiality, Authentication, Authorization, PerformanceManagement for web applications

To appreciate architecture documents

Overview of basic Sun Architecture

Overview of basic Microsoft Architecture

Awareness of the security, performance issues in web applications.

The second chapter covers architecture documents, Sun Architectures, Microsoft

Architectures etc.


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Session Plan

1 lecture session

Basics of Web Architecture

Overview of Sun and Microsoft Architectures

The first chapter covers overview of World Wide Web, the meaning of basic terms popularly

used in architecture documents of web applications.

It also covers awareness about security and performance related issues.

Few sample Architecture documents using Microsoft and Sun Technologies are covered inthe second chapter.


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References

Current Web Architecture found online athttp://www.objs.com/survey/WebArch.htm

Introduction to Web Architecture found online athttp://www.w3.org/2001/tag/2002/11ac-tag-tb/

Architecture of the World Wide Web found online athttp://www.w3.org/TR/webarch/

Andres, Great web architecture book, IDG books,1999

Derek & Atkins, Internet Security - Professional Reference, Publisher Techmedia,2001

Comer Douglas E, Computer Networks and Internets 2nd edition, Publisher PrenticeHall, 2000


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Basics of Web Architecture

30 minIssues involved in security, performance ofWeb applications

30 minComponents of a Web Application

20 minWeb Servers

20 minBasic Terms in Web Architecture

Estimated DurationTopic

This chapter covers the meaning of basic terms like Web Server, App Server etc.

It also covers the working of Web Servers , various components hosted by the servers

The chapters aims at introducing security, performance issues of Web applications


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Differences in Internet and World Wide Web

Internet : The Internet is a network of networks

Information travels over the Internet, via a protocols (TCP/IP)

The World Wide Web, (popularly known as web) is the way of accessing information over the medium of the Internet.

the model of sharing information and that's why is sits on the of the Internet


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Web Architecture

Why architect the Web Applications?

What is N "Tier architecture?

Usually developers would like to attack the programming as soon as they encounter aproblem.We must realize there is lot more to programming than simple coding.

Coding web-application without architecting it can result in critical problems at the later stagebecause Web applications run under environments like browser, web servers , applicationservers and they communicate using specific protocols like HTTP

One can compare this to building a huge complex without involving a good architect or by by-passing the Architecture stage.

The architecture is the winning factor of the web-application ( which might become the losingfactor if not handled properly).

In this course we will talk about architecting the Web applications and the importance of thesame.

What is usual N Tier architecture of Web applications?

In an web application, usually the terms tier and layer are used interchangeably.

N "Tier architecture can be defined as two or more levels arranged one above anotherwhere each level serving distinct and separate tasks like presentation, business logic, dataaccess etc.

Any number of such levels (or tiers) can be arranged above another.Web Applications usually use N-tier architecture because it provides a model for flexible/reusable/ maintainable application.

By breaking up a system into tiers, developers only have to modify or add a specific tier,rather than rewriting the whole application

, if a particular tier (say database) needs change or if the application needs to scale up.

An example for the same in real life is that a CAR is more scalable than 3 wheeler which ismore scalable than a Bi-Cycle.


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N "Tier architecture

Data Tier also known as back end tier

The Presentation Tier also known as front end tier

The Business Logic Tier also known as brain of the application

Data Tier: Is always a part of Web-application.

Though System can exist without data tiers, all real-life examples explicitly need a data tierto handle the complex requirements of data storage.

This layer is the Database Management System (usually RDBMS).

It can be very complex like a high-end product (Oracle/SQL Server), which do include

features like backups/recovery/query optimization etc.Or it can be the simplistic plain text files.

Famous formats of structured, plain text files are CSV files, XML files, etc.

This tier is to deal with the storage and retrieval of the information.

It is not about manipulating or styling the data. It is also known as back end tier

The Presentation Tier : This layer provides an interface for the end user into your

application.

It takes the results of the Business Tier (mentioned below) and renders the data into formatslike HTML (for browser users) or WML (for Mobile users) or the other formats readable by

the end user of the system. It is also known as front end tier.

The Business Tier :This is called as brain of the application. It contains business rules usedfor data manipulation etc. For example, if you're creating a application to calculate the tariff

of a courier then you might want to consider the details like weight, delicacy , mode ofsending for a courier. Also the discount depends on who is sending the courier etc. This

logic is called as business Logic.


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Web server E.g. Tomcat, IIS

Application Server E.g. Weblogic, WebSphere

Basic Terms in Web Architecture

We will go through meaning of some basic terms before we understand the complete structure ofthese tiers.

Web server

Is a computer that serves Web pages to specific clients like Web Browser.

When you type www.infosys.com in the browser, then it searches for a Web Server corresponding tothis URL on the web.

Every web server has an IP address and host name.

For example, the URL http://www.infosys.com sends a request to the server which maps to thedomain name infosys.com.

The Web server then fetches the page named index.html and sends it to your browser.

Any computer which has web server software (for ex: Apache/Tomcat) installed on the same is calledas Web server.

This machine is usually it is connected to the Internet so that it can be accessed from anywhere.

But for the servers which are used over intranet, the access is limited and thats why they do not needto have connection to Internet.

Application Servers

A machine having a software called Application Server( for example WebSphere/ Inprise ApplicationServer) installed on the same and which provides various services to many types applications is called

application server.For Examples, An application might need to store its data in Database.

The ready made product called application server can help in this by creating the required connectionsto the database. This reduces the burden on the application developer and helps in increasingproductivity.

Example: There are various companies who have developed application Server Products.

Example Weblogic by Bea, Oracle 11i AS Portal Server


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Basic Terms in Web Architecture (Contd)

Directory service

Search engines

Persistence

Directory service

Directory service is repository for information about objects located on networks, such as applications,files etc. Directory services provides a consistent way to name (or register) these objects when theyare created, describe their functionality, locate them from client machines, access their methods, andprovide secure way to connect to them.

With web applications, there are various network resources that need to be contacted from variouslocations.

Such resources register themselves with Directory Service. While registering a unique name has to beprovided to these objects. Directory service acts as database to store this unique name and thecorresponding object.

The clients contact directory service to find the relevant objects by providing the corresponding name.( Just like you use the telephone directory by providing the appropriate employee ID)

Directory Service then identifies these resources and makes them accessible to users according to theaccess rules specified for the resource. Ideally, the directory service should be developed in such waythat the client need not depend on the network topology or protocols to access any resource.

For example Java Naming and Directory interface, Lightweight Directory Access Protocol

Search engines

A program that searches documents for specified keywords and returns a list of the documents thatmatch the specified keyword is called as Search engine.

For ex: Google.com

Although search engine is generic word, the term is often used to specifically describe systems like

Google, Alta Vista and Excite that enable users to search for documents on the World Wide Web

Persistence service

Persistence Service is offered by various application servers to persist the volatile data into thedatabase. The volatile data is usually in the form of Objects or sometimes in form of a new Markuplanguage named XML.

Persistence is the service which can automate the storage of this volatile data into the database


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Basic Terms in Web Architecture (Contd)

Load balancing

Transaction management

Authentication / authorization service

Load balancing

Load balancing is distributing processing and communications activity evenly across acomputer network so that no single device is overwhelmed. Load balancing is especiallyimportant for networks where it's difficult to predict the number of requests that will be issuedto a server. Busy Web sites typically employ two or more Web servers in a load balancingscheme. If one server starts to get swamped, requests are forwarded to another server with

more capacity. Load balancing can also refer to the communications channels themselves.

Transaction management

In the scenario of a web application, Transaction Management becomes even more crucialbecause various clients would be contacting the same resource simultaneously. The codeincluded in the web application needs to clearly indicate the begin and the end oftransactions and the various isolation levels associated with a transaction. This can either bedone with code or can be done with the help of Application Server. Application Serverprovides a facility to declare the isolation levels of transaction and auto generates code forthe same. This is called as Declarative Transaction management. It is one of the mostpopular service provided by different application severs.

Authentication / authorization service

Authentication service helps is identifying a user and authorization service helps to find outwhether the user has access rights to the required resource. Example: JASS (JavaAuthentication / authorization service) helps in fulfilling authentication / authorizationrequirement


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Web Servers

Web Browsers

HTTP

Web Server

WebSite Web Content

(HTML Pages)

Web Browser here acts as a Client providing us a means to send the request to the server.

Various browsers like Internet explorer and Netscape Navigator are famous products in thebrowser market.

Web Server provides services to the clients which are sending request over HTTP protocol.


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HTTP Protocol

HTTP/1.0 was the originalversion

HTTP 1.1

HTTP1.1. providesPersistent Connection

Web Browser

Web Server

File System

Document

Request

Web server

searches for

the document

on file system

Server retrieves

the document

Server sends the

document to Browser

This last step of hanging up after each interaction was accurate with HTTP1.0. HTTP1.1 provides Persistent Connection that can be used by the browser

for the next request/response. While using HTTP1.1 the connection would notbe closed. Instead the same connection is used in the next interaction by thebrowser.

Hangs upHangs up

Reads the contents of the filesand displays it

Copies the contents of the file into thesocket

Writes HTTP/1.0 200 OK \n\n.

Reads a local file named /index.html

And that HTTP 1.0 is a valid protocolversion

Sees that the GET is the knowncommand

Reads up until the second end of the line(\n)

Writes GET/index.html HTTP/1.0 \n\nAccepts the Connection

Connects to Port 80Listens to Port 80

ServerClient


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HTTP Protocol ( Contd )

HTTP defines a simple request -response protocol

Client sends the Request to server - HTTP Request

Server sends the Response to the client - HTTP Response

Application Layer protocol on TCP/IP Suite

Stateless Protocol

HTTP Request is sent to the server and the Server sends a response in the format that is

understood by the client.

Though this cycle sits on HTTP, the underlying still remains the TCP-IP.

What is Stateless:

Stateless means having no information about what occurred when the user previouslyaccessed this application.

Current applications maintain state, which means that they remember what you were doinglast time you used the application.

It means you can change the application according to a users previous interaction/ personal

likings in terms of fonts/colors.

The HTTP protocol is stateless because each request for a new Web page is processed

without any knowledge of previous pages requested.

This is one of the main drawbacks to the HTTP protocol.

So the programmer find it difficult to code the web sites that intelligently react to the userinput.

Because maintaining state is extremely useful, people have developed techniques to addtrack the state.

These include server APIs, cookies etc. You will learn about cookies and these APIs in

further course.


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Http Request : GET Vs POST method

With POST, the data is not cached either in thehistory or in the bookmark so it is more secure.If the user bookmarks a GET page, the

querystring info will also be saved withit. A querystring also shows up in the

history list .Get isnt very secure.

The form data is available on STDIN,which is ahandle for the standard input . It defines theinput stream for the program.

In the server script that handles thesubmitted information, the form data isretrieved from the QUERY_STRINGenvironment variable .Environmentvariables are the variables that areautomatically created by the server foreach process.

PostGet

In GET, since the form data is part of the URL, ends up in the server logs while as in POST

data does not make it into the server logs

GET has a limit on the length of the querystring which depends on the browser (usually 255)

and there is almost no size limits on a HTTP header.

The data sent in the querystring is visible in the address bar and thats why not very safe.The data sent using the POST method is not visible in the address bar and thats why it is

more safe.


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HTTP Request

An HTTP Request can have an initial line (method , URL, Protocol Ver. )

Zero or More header lines (its configuration and acceptable doc formats)

a blank line

an optional message body (additional data)

Demo : Eg. http://www.infy.com/index.html GET /index.html HTTP/1.0

User_Agent: Mozilla/3.0Gold

Accept: text/plain

Accept: text/html


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HTTP Response

An HTTP Response can have Initial line or Status line ( Server HTTP Ver, Status-code, Reason)

Headers - Description of the header info in the response Message body - Actual information requested


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Example of HTTP Response

Eg. Response for /index.html HTTP/1.0 Status 200 OK

Server : NCSA/2.0 Date: Mon, 10 Mar 2003 12:04:04 GMT

Content-type: text/html

Content-length: 5800

Last-modified:

XYZ Home Page

... other content of /index.html ...


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Various components of Web Application

Web Servers host Various components of Web Applications E.g. Active Server Pages ( ASP) /ASP.NET

Technology is developed by Microsoft.

ASP uses scripting language as VB Script

ASP .NET uses any compliant language like VB. NET or CSharp as scripting language

Active Server Pages

Abbreviated as ASP, a specification for a dynamically creating Web page with a .ASPextension that uses scripting languages usually VB Script or Jscript code for creating thedynamic web page. When a browser requests an ASP, the Web server generates a pagewith HTML code and sends it back to the browser.


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Various components of Web Application (Contd..)

Java Servlets Technology is developed by Sun.

Defined as Java Program best suited to handle and route Web requests

Java Servlets

Servlets are the units of Java programs that handle Web requests and routes the request tothe appropriate element for processing. It can also generate dynamic HTML but is not well

suited for the same being a Java Program. This is a technology by Sun Microsystems.


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Java Server Pages Technology is developed by Sun.

Uses Java as a scripting language

Java Server Pages

Abbreviated as JSP, a specification for a dynamically creating Web page with a .JSPextension that uses scripting language as Java for creating the dynamic web page. When a

browser requests an JSP, the Web server generates a page with HTML code and sends itback to the browser.

This is a technology by Sun Microsystems.


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Web Services Is a standard that can be implemented in many technologies

Provide data and services to other applications

Web Services:

Are units of logic providing data and services to other applications (usually to the remote andheterogeneous clients).

Applications access Web services via standard Web protocols.

For example, if CNN provides the temperature of various cities in world through web service

then various sites can call this web service and receive the data in the standard format.


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Few Popular Web Servers

Microsofts Personal Web Server

+ Freeware+ Easy to setup and use

+ ASP support

- Vulnerability : On Win95/98 allows files on the server to be read by an unauthorized user

Best suited for testing and serving small web sites

Mainly used for personal web pages.

Can host web applications like Active Server Pages ( ASP)


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Few Popular Web Servers.

Microsofts Internet Information Server

+ performance and security enhancements.

+ Well-integrated server administration tools

+ Easy to configure & Better Clustering.

- Only runs on Windows OS like WinNT Server /2000/XP

Best suited for MS Platforms

Mid Range Web server

It can be used for developing commercial web sites as well as for the intranet web sites for acompany.

Many sites used for the internal purpose in Infosys are working on IIS.

Mainly used to host web applications like Active Server Pages ( ASP)


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Apache - A PATCHy Server Origin: NCSA

+ Multi-platform support, protocol support HTTP/1.1+ Overall performance and robustness

- More extensive technical support requires the purchase of a third-party support contract

High-end enterprise server for Unix and Win32

Most preferred Web server


Apache is one of the oldest web severs which is still taking lots of market share even today.

Now a days lots of plug in software are available for Apache which makes it possible to host

various types of web applications like

Active Server Pages ( ASP)

Java Servlets

Java Server Pages

Java Servlets.


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WebSphere: Web Server by IBM+ Support for various web applications like Servlets/JSP

+ Unique services provided to communicate with the Legacy systems running onMainframe Ex: CICS Transaction Gateway

Best suited for large scale sites involving communication with legacy systems

It works on various platforms including IBM Mainframes


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Performance of Web Application

Performance of a web application is directly depending on the actual end-userresponse time.

Performance of many Web sites depends on the load on the site at peak time

Performance in a Web application is very important because the Web applications are

accessed remotely.

When there is single user, web applications might provide good response but what about the

loads of users?

Imagine Testing a Web applications performance for 1 lakh simultaneous requests.We cannot do this by manual testing. So performance testing is normally conducted in asimulated environment with the help of performance testing tools.

If the performance is not satisfactory, then various measures need to be taken to tackle theissues.

In further chapter, we will look at various inherent problems in web applications likeperformance and security.


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Heterogeneity involved in Web Apps

Traditional apps generally have 1, 2 or 3 software pieces talking to each other

e.g. VB ODBC (Open Database Connectivity) - SQL Server, or PowerBuilder - Nativedrivers - Sybase, or IBM 3270 - CICS - DB2

Generally, the entire solution is from one or two collaborating vendors

The wire protocol for communication between collaborating parts is proprietary;implying that it is difficult or impossible to extend the solution: i.e. replace the VBclient with a different kind of client

It is essential to understand history of applications before we begin with the basic terms of webarchitecture.

A Traditional application consists of the User Interface as the front tier and the Database at the backend. The connectivity is done with the help of standards like Open Data Base Connectivity, JavaData Base Connectivity etc.

Usually all the tiers are coded with the help of products developed by a single company.

Also the protocols used were proprietary because of that.

The users of applications were known in advance.

With the evolution of WWW (World Wide Web) we also need to concentrate on

a) Searching the correct application before calling it. This is done with the help of UniversalResource Locators

b) Represent the data in the standard data formats

c) Use the required protocols for communication between different tiers

d) Prepare for the large base of unknown users :

Elaboration:

Demography of users in a traditional applications are generally known in advance. Their login pattern,

usage pattern, general behavior, etc are known in advance. Generally, users on an intranet are

reasonably predictable.

While as profile of users in an application exposed to the Internet is not known.

They could be genuine buyers, hackers, frivolous people, frauds, or people all out to have

some fun.

Transaction rate is not known upfront; could vary by time of the day (or night!); there could be

sudden peaks and troughs


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Issues involved in performance of Web applications

Following are the main reasons because which performance issues occur in WebApplications

Web application inherently needs lots of layers as compared to traditional application. Manyof these layers are remote.

The load of an application (in general and at any given time) cannot be estimatedaccurately.

And there is no seamless integration between multivendor products used in all these layers,so the performance of an application is not always predictable.

Performance might go down because of the extra mechanism added like security

The issues can be further categorized as

a) Component level issues

b) Issues at the server level

For some issues related to security and performance, the server level solution works well.

For example, if the performance is decreasing because of the increase in load at peakhours, then the load balancing feature of a web server can be used. (The feature isdiscussed in detail in the sub-sequent slides). With this feature the load is spread outamong various server machines.

At the same time some care need to be taken at component level too.

The programmer needs to make sure that components are capable of spreading out acrossvarious servers and still provide the required functionality.

To take care of this the component has to be built according to the rules of certain standard.


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Issues involved in security of Web applications

Following are the main reasons because which security issues occur in Web Applications

Users not known in advance Because of various types of users are connecting to a web application, the set of resources

that they can access has to be limited depending on the user profile

Information send out to particular user has to be protected

In the subsequent slides we will study about the various issues, their impacts on server side

and at the component level


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Load balancing

Server 1Server 2

Server 3

Browser

Load Balancing Software decides which server to direct traffic to

The solution to catering to the issue of heavy load on Servers is Load balancing.

Assume that a courier industry is running across various geography locations and need to maintainthe centralized repository of the data. In this case a single web server used by such application, maynot be able to take the load from various requests coming in from different locations.

For many such reasons, Popular web sites need ways to spread their load out - usually across

multiple machines, and sometimes across multiple sites.

Examining the access patterns for the site is crucial to the performance tuning and load balancingprocess.

Scalability of the servers is enhanced by a technique known as load balancing.

Quite a few times load balancing in database servers can be done with the concepts of disk arrayswhere there is single DB server software and an array of multiple disks ( few of which can be fall backdisks) to store the data.

But with web server or application server disk arrays dont help always because its not just thequestion of storing the data but it also about various interlinked components running simultaneouslywhich are contacted by load of users at a time.

In this case a clustering of multiple servers (not just multiple disks) sharing the incoming load helpsbetter.

Round robin between these server is the most popular mechanism of spreading the load.

The figure in the slide illustrates the concept of a load-balanced Web server mechanism.


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Consequences

The programmer needs to make sure that components are capable of

spreading out across various servers

still provide the required functionality.

If proper care is not taken while coding these components then when components are

spread across multiple servers , the clients of these components get affected.

For example,

In the past, a component named tariffCalculation was used by another component (Calledas client) which was also present on the same machine where tariffCalculation component

was deployed.Now with the recent load balancing requirement, this component is spread across variousservers and so are the clients. This reflects certain change in the details of the

tariffCalculation component that are be known to the client.

If the component has built-in facilities to accommodate these changes, then using loadbalancing is done smoothly.

To take care of various such issues the component has to be built according to the rules of

certain standard.


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Standards available for building Components - CORBA

CORBA

CustomerCustomer

ItemItem

ShipmentShipmentOrderOrder

AccountAccount

BookBookTV

TV

PCPC

has

places

contains

creates

can be

Java onWin95C++ on Unix

COBOL on MVS

CORBA: Short for Common Object Request Broker Architecture, an architecture that

enables pieces of programs, called objects, to communicate with one another regardless ofwhat programming language they were written in or what operating system they're runningon.

For example, a program coded in Java can call a function in COBOL with help of thistechnology

The diagram shows three modules of an enterprise application namely

Customer: Coded in Java

Account : Coded in C++

Order Processing: Coded in COBOL

These are interrelated modules and the interaction is made possible with CORBA

technology.


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COM+

ObjectObject

ServerServer

ClientClient

COM+ : Component Object Model +, an extension of the Component Object Model (COM)

to receive the standard services from the servers like MTS (Microsoft Transaction Server)

COM+ was developed by Microsoft

The diagram shows the server, the object and the client.

The object contains the required logic which is needed by the client.

The server takes care of various objects by providing them services like persistence,

transaction management etc

The client contacts the required object and receives the results.


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.NET

VisualStudio.NET

C# VB.NET JScript Any .Net Compliant Language

Common Language Specification (Basis of Common Language Runtime)

ASP.NET Windows Forms

ADO .Net and XML

Base Class Library / . Net Framework

Common Language Runtime ( CLR)

Windows OS COM+ Services

.NET : Is suite of products for operating, managing and creating the workflow of Web

Applications and web services

.NET is a different subject in itself. The brief introduction of each part is stated below.

The order is from Bottom to Top

Windows is the OS and .Net currently runs only on windows platform

COM+ Services are services like Life Cycle Management/ Transaction Management/Persistence.

The CLR Common Language Runtime makes sure that the objects written in differentlanguages can communicate with each other.

Base Class Library is the ready made set of classes for faster code development

ADO.NET and XML ADO .NET is the Microsoft way for the application to talk to thedatabase. The base class library also gives extensive support for reading and manipulatingXML files. ADO .Net is the XML based technology.

ASP. NET is the is server side code which would be hosted on the IIS Server and it can bedeveloped in any .NET compliant language like VB .NET, C Sharp etc

Windows Forms are required for console based application. They are used to create the

graphical user interface.

Common language Specification Is published by Microsoft . It describes the rules of a.Net compliant language. Any language which follows these rules can be used in .NET Sothis in turn is an invitation for the vendor companies to write more and more .NET compliant

languages

Visual Studio .NET is the powerful Integrated Development Environment for developing thecode using .Net technology


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J2EE

AppletContainer

Application

ClientContainer

WebContainer

JSP/Servlet

EJB Container

EJBsDatabase

Web Component Enterprise Component

The diagram shows the typical Four tier architecture.

In this architecture, the request is initiated from browser/java application.

The request is received by the web server and is routed to the

appropriate Servlet component.

Enterprise JavaBeans (EJB) is a Java API developed by Sun

Microsystems that defines a component architecture for multi-tierclient/server systems.

Servlet analyzes the request and passes it on to the EJB for processingthat needs the business logic and data access.

EJBs in turn produces the results and the JSP formats the results andsends it back the browser.


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Catering to the problem of Confidentiality

Following are the two main techniques used to cater the problem of Unknown UserProfiles in the web applications.

Authentication

Authorization

Various ready APIs are available for the same JAAS (Java Authentication and Authorization Service

Various techniques like Single signon are also widely used by sites Microsoft Passport etc

Authentication:

Let us consider the example of Campus connect link on the Infosys Web-site.

Whenever anybody accesses the Campus connect web application from Infosys Web-site, the username andpassword is checked to make sure that only authentic users get to entry in the application. This process ofidentifying an individual, based on a username and password is called as authentication.Most of the web-sites ask you to explicitly register to get this username and password.

Most of the Intranet application uses your Windows (OS) login-id and password to authenticate you.

Authentication is distinct from authorization , which is the process of giving access to certain objects of system tocertain individuals based on their identity. For example delete department can be accessed only by certain groupof people.

Authentication just ensures that the user name and password is valid but does not deal with the access rights ofthe individual.

Authorization

The process of granting or denying access to a resource is called as Authorization. Most of the web-applicationfirst complete authentication and then go for authorization, which allows the user access to resources based onthe user's identity.

For example, in campus connect application only few users would have access to modify the course material keptat the site while as the students would be able to view the contents. This checking is done through authorization.

Single signon

It is a process of authentication where the user, or client, can enter one name and password and have access to

more than one application or access to a number of resources within an enterprise. Single signon takes away theneed for the user to enter further authentications when switching from one application to another.

Single signon is abbreviated as SSO.

Microsoft .NET Passport gives users a single, convenient way to sign in to multiple Internet sites and servicesusing one sign-in name and password.

It also allows to store personal information in the .NET Passport profile and, if you choose, automatically sharethat information when signed in so that personalized services can be provided.


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Techniques for Authentication

Following are few techniques Applying Operating System level authentication, by impersonating login credentials of the

client.

Authenticating the client programmatically.

Token wise authentication.

Examples: Digital certificate

A) Applying Operating System level authentication, by impersonating login credentials of the

client.

This involves a setting with the server software which instructs the server to request the OS

level credentials (for example Windows Login Id and Password) and authenticate the usersby their OS dependant credentials

Usually the Intranet Systems prefer this authentication so that the existing set of Logids andaccess permission can be utilized

B) Authenticating the client programmatically involves creating a set up of Users Ids and

access control Lists of these users and their roles. Many software products like LDAPAuthentication Techniques can be used in this case.

C) Token wise authentication is covered in next slides.


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Catering to the problem of Information Protection

Secure communication is ensured by using an industry standard protocol called SSL(Secure Socket Layer)

Cryptography Symmetric and A-Symmetric key Encryption for confidentiality

Certificates for authentication and non-repudiation

SSL

SSL is short form of Secure Socket Layer is a protocol designed by Netscape Communications toenable encrypted, authenticated communications across the Internet. URLs starting with https:// areknown to use this layer

Cryptography

Is the process of protecting information by transforming it into an unreadable format, called cipher text.Only those who possess a secret key can decipher (or decrypt) the message into plain text.

With the electronic security is becoming increasingly important, Cryptography is widely used to protectthe data. One of the most popular cryptography systems used on the Internet is Pretty Good Privacy

because it's effective and free.

Cryptography systems can be broadly classified into symmetric-key systems that use a single key thatboth the sender and recipient have, and asymmetric-key systems that use two keys, a public keyknown to everyone and a private key that only the recipient of messages uses.

Digital certificate

Is an attachment to an electronic message used for security purposes. The common use of a digitalcertificate is to verify that a user sending a message is the one who he or she claims to be, and toencode the reply and send it to receiver.

A person who wishes to send an encrypted message applies for a digital certificate from a CertificateAuthority (CA)

The CA issues an encrypted digital certificate containing the applicant's public key and a variety ofother identification information. The CA makes its own public key readily available through printpublicity or perhaps on the Internet.

The recipient of an encrypted message uses the CA's public key to decode the digital certificateattached to the message, verifies it as issued by the CA and then obtains the sender's public key andidentification information held within the certificate. With this information, the recipient can send anencrypted reply.

The most widely used standard for digital certificates is X.509.


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Summary

We Covered What is WWW

The Basic Terms of Web Architecture

The tier-ed architecture of Web Applications

Various options available in terms of servers

Various types of components of a web application

Awareness about the issues involved in security, performance at the client and server end


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Intro to Web Architecture Chapter 1

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