1 / 32

Chap 15 Application Layer

Chap 15 Application Layer. Andres, Wen-Yuan Liao Department of Computer Science and Engineering De Lin Institute of Technology andres@dlit.edu.tw http://www.cse.dlit.edu.tw/~andres. Overview. Client-Server Redirectors Domain Name System E-mail/Telnet/FTP/HTTP.

signa
Download Presentation

Chap 15 Application Layer

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chap 15 Application Layer Andres, Wen-Yuan Liao Department of Computer Science and Engineering De Lin Institute of Technology andres@dlit.edu.tw http://www.cse.dlit.edu.tw/~andres

  2. Overview • Client-Server • Redirectors • Domain Name System • E-mail/Telnet/FTP/HTTP

  3. Basics of the Application Layer • Application processes • Direct network applications • Indirect network support • Making and breaking a connection

  4. Application processes • Supports the communicating component of an application • The OSI layer closest to the end system • Does not provide services to any other OSI layer

  5. Application processes • Direct interface • Browser, e-mail, FTP, Telnet • Indirect interface • Word processors, spreadsheets, presentation managers with a network redirector

  6. Direct network applications • Client-server applications (most) • FTP, web browsers, and e-mail • The client side • On the local computer • The requestor of the services • The server side • On a remote computer • Provides services

  7. WWW • Browsers (NN and IE) are probably the most commonly used network applications • An easy way to understand a Web browser is to compare it to a television remote control

  8. Indirect network support • If a client wants to save a file from a word processor to a network server, the redirector enables the word processing application to become a network client

  9. Redirector • A protocol that works with computer operating systems and network clients instead of specific application programs

  10. Redirectors • Apple File Protocol • NetBIOS Extended User Interface (NetBEUI) • Novell IPX/SPX protocols • Network File System (NFS) of the TCP/IP protocol suite

  11. Redirector • Allows a network administrator to assign remote resources to logical names on the local client (F:, G:, … )

  12. Advantages • The applications on the client never have to recognize the network • Expand the capabilities of non-network software

  13. Making/breaking a connection • Web • The connection was maintained just long enough to download the current Web page • Printer • The connection was maintained just long enough to send the document to the print server

  14. Domain Name System • Problems with using IP addresses • The domain name server

  15. Problems with using IP addresses • A domain is a group of computers that are associated by their geographical location or their business type • A domain name is a string of characters and/or numbers • More than 200 top-level domains

  16. Generic names • .edu - educational sites • .com - commercial sites • .gov - government sites • .org - non-profit sites • .net - network service

  17. The domain name server • Domain name -> IP address • The DNS system is set up in a hierarchy that creates different levels of DNS servers

  18. Network Applications • Internet applications • E-mail message • DNS function

  19. Internet applications • The WWW uses the HTTP protocol • Remote access programs : Telnet protocol • E-mail programs : POP3 application layer protocol for electronic mail • File utility programs : FTP protocol

  20. E-mail message • The first is to send the e-mail to the user’s post office • The second is to deliver the e-mail from that post office to the user’s e-mail client

  21. Application Layer Examples • Telnet • File transfer protocol • Hypertext transfer protocol

  22. Telnet • All processing and storage take place on the remote computer • Works mainly at the top three layers of the OSI model • Application, presentation , session layers

  23. FTP • Be designed to download files (e.g. receive from the Internet) or upload files (e.g. send to the Internet)

  24. Hypertext transfer protocol • The fastest growing and most used part of the Internet • A Web browser is a client-server application • Requires both a client and a server component in order to function

  25. Hyperlink • A hyperlink is an object (word, phrase, or picture) on a Web page that, when clicked, transfers you to a new Web page

  26. Summary • Direct and indirect network applications • The domain name system • Telnet, FTP and HTTP

More Related