复旦大学：《计算机网络 Computer Networking》课程教学资源（PPT课件讲稿）Networked Applications

Networked Applications Chapter 11 Revised January 2007 Panko’s Business data Networks and Telecommunications 6th edition HonBaoDoouoaoooo Copyright 2007 Prentice-Hall May only be used by adopters of the book

Networked Applications Chapter 11 Revised January 2007 Panko’s Business Data Networks and Telecommunications, 6th edition Copyright 2007 Prentice-Hall May only be used by adopters of the book

Application Architectures An application architecture is the design decision about which network host or hosts to use to do the processing work in an application

Application Architectures An application architecture is the design decision about which network host or hosts to use to do the processing work in an application

Figure 11-1: Simple Terminal-Host System All Processing is done on the host Host gets overloaded: slow response EXtensive network traffic: expensive Dumb Direct wire connection erminal Telephone Network Modem Modem Host Dumb Terminal 3

3 Figure 11-1: Simple Terminal-Host System Telephone Network Modem Modem Host Dumb Terminal Dumb Terminal All Processing is done on the host. Host gets overloaded: slow response. Extensive network traffic: expensive

Client/Server Computing The client does at least some of the work Made possible by growing PC processing power Two versions File server program access Request/response processing Server Client Pc

4 Client/Server Computing • The client does at least some of the work • Made possible by growing PC processing power • Two versions – File server program access – Request/response processing Server Client PC

Figure 11-2: Client/Server Computing weg File server Program Access rogram Program Stored on Program Eⅹ ecuted on Downloaded to File server C lient Pc Client Pc Client Pc File server When called Only useful for small programs(e-mail, word processing, etc. Because clients do not get very large

5 Figure 11-2: Client/Server Computing 1. Program Stored on File Server File Server Client PC 2. Program Downloaded to Client PC When Called 3. Program Executed on Client PC! Only useful for small programs (e-mail, word processing, etc.) Because clients do not get very large File Server Program Access

Figure 11-2: Client/Server Computing Client/Server Processing with Request-Response Cycle Request Message Client Program Response Message Server Program Does Light I/O and Post-Download Does Heavy Processing Database and other Heavy Client PC Processing File server Highly scalable: Use larger server as number of clients increases 6

6 Figure 11-2: Client/Server Computing File Server Client PC Highly scalable: Use larger server as number of clients increases Client/Server Processing with Request-Response Cycle Client Program Server Program Request Message Response Message Does Light I/O and Post-Download Processing Does Heavy Database and Other Heavy Processing

Figure 11-3: Web-Enabled Application(E-Mail) Http reQuest Message Client is Browser Http Response mEssage Server program Web-enabled applications Form of client server processing that uses browsers as clients Almost all client Pcs now have browsers Client pc No need to install new software E-Mail server 7

7 Figure 11-3: Web-Enabled Application (E-Mail) E-Mail Server Client PC Client is Browser Server Program HTTP Request Message HTTP Response Message Web-enabled applications: Form of client server processing that uses browsers as clients Almost all client PCs now have browsers. No need to install new software

E-Mail

E-Mail

Figure 11-5: E-Mail Standards SMTP o Send SMTP To Send Sender's mail Receiver's mail Server Server Simple mail Transfer Protocol Sending Receiving E-Mail (SMTP)is used to transmit mail E-Mail Client in real time to a user's mail Client server or between mail servers Sender-initiated

9 Figure 11-5: E-Mail Standards 2. SMTP To Send 1. SMTP To Send Sending E-Mail Client Receiving E-Mail Client Sender’s Mail Server Receiver’s Mail Server Simple Mail Transfer Protocol (SMTP) is used to transmit mail in real time to a user’s mail server or between mail servers Sender-initiated

Figure 11-5: E-Mail Standards POP OI IMAP To Receive Sender's mail Receiver's mail Server Server Sending E-Mail POP or IMAP to download mail to ReceIving Client receiver when the receiver next E-Mail downloads mail Client Receiver-initiated 10

10 Figure 11-5: E-Mail Standards Sending E-Mail Client Receiving E-Mail Client Sender’s Mail Server Receiver’s Mail Server POP or IMAP To Receive POP or IMAP to download mail to receiver when the receiver next downloads mail. Receiver-initiated