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Networked Applications

Networked Applications

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Networked Applications

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  1. Networked Applications Chapter 11Updated January 2009 Raymond Panko’sBusiness Data Networks and Telecommunications, 7th edition May only be used by adopters of the book

  2. Client Program Server Program Client/Server Computing • The client does at least some of the work Client PC Server

  3. Client Program Server Program Client PC 11-2: Client/Server Computing 3 Client/Server Processing with Request-Response Cycle Request Message Response Message Does Light I/O and Post-Download Processing Does Heavy Database and Other Heavy Processing File Server Use larger server as number of clients increases

  4. Client is Browser Server Program 11-3: Web-Enabled Application 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. Client PC E-Mail Server

  5. E-Mail

  6. The E-Mail Delivery Process Receiver’s Mail Server Sender’s Mail Server Each e-mail user has a mail server. The sender transmits a message to its mail server. The sender’s mail server delivers the message to the receiver’s mail server. The receiver’s mail server delivers the message to the receiver. Sending E-Mail Client Receiving E-Mail Client

  7. 11-5: E-Mail Standards: Sending 2. SMTP To Send 1. SMTP To Send Receiver’s Mail Server Sender’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 Sending E-Mail Client (Outlook, etc.) Receiving E-Mail Client (Outlook, etc.) Note that SMTP provides immediate delivery—usually in a few seconds.

  8. 11-5: E-Mail Standards: Receiving 3. POP or IMAP to Receive Receiver’s Mail Server Sender’s Mail Server POP or IMAP to download mail to receiver when the receiver next downloads mail Receiver-initiated Receiving E-Mail Client (Outlook, etc.) Sending E-Mail Client (Outlook, etc.)

  9. 11-5: E-Mail Standards: Web-Based E-Mail SMTP HTTP SMTP POP or IMAP On the left, we have just seen that traditional e-mail clients send with SMTP and receive with POP or IMAP. On the right, Web-based e-mail clients only need a browser and use HTTP both to send and to receive. Server-server communication always uses SMTP. Web-Based E-Mail Client Browser Traditional E-Mail Client (Outlook, etc.)

  10. HTML and HTTP

  11. 11-7: HTML and HTTP The Hypertext Transfer Protocol (HTTP) is the standard for transferring messages between the client (browser) and the server (webserver). The Hypertext Markup Language (HTML) is a standard for text documents that have tags to indicate formatting and other files to be downloaded

  12. Peer-to-Peer Computing

  13. Client PC Client PC Client PC Client PC Client PC 11-15: Traditional Client/Server Application Disadvantages: Network Overload at Server Underused Client Power Central Control Advantage: Central Control Server Does Heavy Processing Work

  14. P2P Applications • Direct service, although most P2P systems use facilitating servers for some of the work Peer Peer Peer Peer Peer Peer

  15. Client PC Client PC Figure 11-16: Simple Peer-to-Peer (P2P) Application Request Response Benefits: End User Freedom No Network Bottleneck at Server Uses Client Capacity Better Problems: Transient Presence of Clients Transient Client IP Addresses Security (No Central Control)