application layer functionality and protocols

© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicITE I Chapter 6 1

Application Layer Functionality and Protocols

Network Fundamentals – Chapter 3

© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicITE 1 Chapter 6 2

Objectives Identify the Application layer as the source

and destination of data for communication across networks.

Role of protocols in supporting communication between server and client processes.

Features, operation, and use of well-known TCP/IP application layer services (HTTP, DNS, SMTP).


Applications – generate data at the top of the OSI model Applications provide the means for generating and

receiving data that can be transported on the network


Applications – The Interface Between Human and Data Networks Application layer provides an interface between the

user and the network via network applications


OSI layers and TCP/IP Application layer OSI top layers map to TCP/IP Application layer


Presentation and Session layers

The Presentation layer has three primary functions: Coding and conversion of Application layer data to ensure that data from the source

device can be interpreted by the appropriate application on the destination device. Compression of the data in a manner that can be decompressed by the destination

device. Encryption of the data for transmission and the decryption of data upon receipt by

the destination.

The Session Layer Creates and maintain dialogs between source and destination applications. Handles the exchange of information to initiate dialogs, keeps them active. Restarts sessions that are disrupted or idle for a long period of time.


Networking Applications •DNS is used to resolve Internet names to IP addresses.•HTTP is used to transfer files that make up the Web pages of the World Wide Web•SMTP is used for the transfer of mail messages and attachments.•Telnet, a terminal emulation protocol, is used to provide remote access to servers and networking devices.

•FTP is used for interactive file transfer between systems.


The Role of Protocols in Supporting Communication Client - Server The client and server processes support data retrieval


Peer 2 Peer network model Peer-to-peer networking and peer-to-peer applications

Act as both a client and a server within the same communication


DNS Application Layer Service Domain Name Services DNS protocol and its Support of Name

resolution

DNS provides a conversion of domain names to IP addresses.


HTTP in the delivery of web pages Client requests a page.

In response to the request, the HTTP returns the code for a web page.

The browser interprets the HTML code and displays a web page.


E-mail, one of the most popular network services Features of the Post Office Protocol (POP) and Simple Mail

Transfer Protocol (SMTP) protocols; Support e-mail services


Telnet supports Communication and management Telnet Common Client – Server Application Layer

services and protocols


Telnet Application Layer Service Telnet protocol used in examining and managing networks


Features, Operation, and Use of TCP/IP Application Layer Services Server Message Block (SMB) protocol used in supporting file,

printer and directories sharing in Microsoft-based networks

SAMBA does the same for UNIX, LINUS OS’s


P2P Application Layer Service Gnutella protocol supports P2P services files sharing over the

internet. Clients include: BearShare, LimeWire, XoloX


Labs

4.5.2 TCP/IP Transport layer protocols TCP,UDP

3.4.3 Email services and protocols (SMTP,MUA,MDA,MTA, POP and Internet Message Access Protocol; IMAP & Telnet)

application layer functionality and protocols

Technology

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