1. Understanding Networked Applications A First Course 1 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

2. Understanding Networked Applications A First Course 2 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.

3. Understanding Networked Applications A First Course 3 Client / Server System Server process Client process Network Clients request services from different server processes. Services: File, print, fax, multimedia, communications Clients can request services from several servers and servers can provide services for more than one clients.

4. Understanding Networked Applications A First Course 4 Client host Server host Client host

5. Understanding Networked Applications A First Course 5 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

6. Understanding Networked Applications A First Course 6 Client/server Peer-to-peer Server “I want to access some information” “I want to collaborate with my colleague” Client

7. Understanding Networked Applications A First Course 7 Distinctions Client-server –Asymmetric relationship –Client predominately makes requests, server makes replies Peer-to-peer –Symmetric relationship

8. Understanding Networked Applications A First Course 8 Client Server Client Email client sends message to server Message is stored on POP server Later, recipient’s email client retrieves message from server Email application

9. Understanding Networked Applications A First Course 9 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

10. Understanding Networked Applications A First Course 10 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.

11. Understanding Networked Applications A First Course 11 How components interact? Client process Communications middleware network Database server SQL 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.

12. Understanding Networked Applications A First Course 12 Client Web browser Web server Application logic Databases and DBMS Common gateway interchange Host architecture Application partition

13. Understanding Networked Applications A First Course 13 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.

14. Understanding Networked Applications A First Course 14 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.

15. Understanding Networked Applications A First Course 15 Departments Enterprise Commerce Enterprise-to-enterprise Consumer

16. Understanding Networked Applications A First Course 16 Customers Consumer Enterprise Customer-service department Technical-support department software4u.com

17. Understanding Networked Applications A First Course 17 Web server Customer logic Customer audit Software documentation Web browser Problem knowledge base Databases Agent logic Consumer application Enterprise application Technician logic Web server Web browser Web server Web browser Customer care

18. Understanding Networked Applications A First Course 18 AccountsProductsOrders Customer logic Databases Agent logic CustomersAgentsTechnicians Technician logic

19. Understanding Networked Applications A First Course 19 Book distribution centers books4u.com Customers Financial institution Consumer EnterpriseInter-enterprise

20. Understanding Networked Applications A First Course 20 Clients Customers Merchandise Acquirer bank Book distributors Orders Customer logic Databases Fullfillment logic

21. Understanding Networked Applications A First Course 21 Stock market stocks4u.com Customers Information providers Consumer EnterpriseInter-enterprise

22. Understanding Networked Applications A First Course 22 Clients AccountsProducts Information providers Financial markets Orders Customer logic Databases Trading logic

23. Understanding Networked Applications A First Course 23 Local florists flowers4u.com Customers Financial institution Consumer EnterpriseInter-enterprise