Understanding Networked Applications A First Course 1 CONTENTS INTRODUCTION. WHAT IS CLIENT SERVER...

Understanding Networked Applications A First Course1

CONTENTS

INTRODUCTION.WHAT IS CLIENT SERVER ARCHITECTURE ?WHY WE NEED CLIENT SERVER ARCHITECTURE ?APPLICATION OF CLIENT SERVER ARCHITECTURE ?HOW COMPONENTS INTERACT ?WHAT IS NETWORK PROTOCOL ?WHAT IT DOES ? WHAT IT PROTECTS YOU FROM ?LIMITATION CONCLUSION


CLIENT / SERVER SYSTEM

What Is a Client/Server system?

A system that links a client and server through networks.

It describes a computing model for the development of computerized systems.

This model is based on the distribution of functions between two types of independent and autonomous processes; servers and clients.


Client / Server System

Server process Client process

Network

Clients request services from different server processes.

Services: File, print, fax, multimedia, communicationsClients can request services from several servers and servers can provide services for more than one clients.


Clienthost

Serverhost

Clienthost


Part of the rationale

• Specialization:– Clients specialize in user interface– Servers specialize in managing data and

application logic

• Sharing:– Many clients can be supported by few servers– Often data and logic are shared among

applications and users

Understanding Networked Applications A First Course6Client/server

Peer-to-peerServer

“I want to access some information”

“I want to collaborate

with my colleague”

Client


Distinctions

• Client-server– Asymmetric relationship– Client predominately makes requests, server

makes replies

• Peer-to-peer– Symmetric relationship


ClientServer

Client

Email client sends message to server

Message is stored on POP server

Later, recipient’s email client retrieves message from server

Email application


Client

Server

Client

Chat clients send user’s typing to server

Chat server aggregates typing from all users and sends to all clients

Other user’s clients display aggregated typing from chat server

Chat application


Client/Server Architecture

The client/Server architecture is based upon hardware and software components that interact to form a system.

• Front-end application(Client): Any computer process that requests services from the server.

• Back-end application(Server): Any computer processing providing services to the clients.

• Communications middleware(Middleware): Any computer process through which clients and servers communicate.


How components interact?

Clientprocess

Communicationsmiddleware

network

Databaseserver

SQL

Data Data

SQL

Clients process sends SQL request through

communications middleware.

Middleware routes SQL request to

database server process.

Database server process receives request, validates it, and

executes it.


Client

Webbrowser

Webserver

Application logic

Databases and DBMS

Commongatewayinterchange

Host architecture

Application partition


Network protocols

Network protocol is a set of rules that determines how messages between computers are sent, interpreted, and processed.

As a result of the client/server computing boom, many mainframes and midrange computers are now implementing support for more open, nonproprietary network standards such as TCP/IP, to allow direct access from client/server PC-based front-end applications.

The selection of network topology and protocols is one of the most critical decisions in a client/server system’s development. For the commercial software developers, this may be market-driven. Because this will decide the number of people they can reach.


Network Protocols

• Transmission Control Protocol/ Internet Protocol (TCP/IP)

The official communications protocol of the Internet. TCP/IP is the main communications protocol used by Unix systems, is supported by most operating systems at the midrange and personal computer levels.

• Internet Packet Exchange/Sequenced Packet Exchange (IPX/SPX)

Communications protocol developed by Novell. IPX/SPX is supported by the majority of client/server network applications and by all PC operating systems.


Departments

Enterprise

CommerceEnterprise-to-enterprise

Consumer


Customers

Consumer Enterprise

Customer-servicedepartment Technical-support

department

software4u.com


Web server

Customer logic

Customeraudit

Softwaredocumentation

Webbrowser

Problemknowledge

base

Databases

Agent logic

Consumerapplication

Enterpriseapplication

Technician logic

Web server

Webbrowser

Web server

Webbrowser

Cus

tom

er c

are


Accounts Products Orders

Customer logic

Databases

Agent logic

Customers Agents Technicians

Technician logic


Book distributioncenters

books4u.comCustomers

Financial institution

Consumer Enterprise Inter-enterprise


Clients

Customers Merchandise

Acquirerbank

BookdistributorsOrders

Customer logic

Databases

Fullfillment logic


Stock marketstocks4u.com

Customers

Information providers



Clients

Accounts Products

Informationproviders

FinancialmarketsOrders

Customer logic

Databases

Trading logic


Local floristsflowers4u.com

Customers

Financial institution


Understanding Networked Applications A First Course 1 CONTENTS INTRODUCTION. WHAT IS CLIENT SERVER...

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