Cisco For All

Presentation Layer

Manages the presentation of the information in an ordered and meaningful manner. This layer’s primary function is the syntax and semantics of the data transmission. It converts local host computer data representations into a standard network format for transmission on the network. On the receiving side, it changes the network format into the appropriate host computer’s format so that data can be utilized independent of the host computer. ASCII and EBCDIC conversions, cryptography, and the like are handled here.

The presentation layer provides a variety of coding and conversion functions that are applied to application layer data. These functions ensure that information sent from the application layer of one system would be readable by the application layer of another system. Some examples of presentation layer coding and conversion schemes include common data representation formats, conversion of character representation formats, common data compression schemes, and common data encryption schemes.

Common data representation formats, or the use of standard image, sound, and video formats, enable the interchange of application data between different types of computer systems. Using different text and data representations, such as EBCDIC and ASCII, uses conversion schemes to exchange information with systems. Standard data compression schemes enable data that is compressed.

Presentation layer implementations are not typically associated with a particular protocol stack. Some well-known standards for video include QuickTime and Motion Picture Experts Group (MPEG). QuickTime is an Apple Computer specification for video and audio, and MPEG is a standard for video compression and coding.

Among the well-known graphic image formats are Graphics Interchange Format (GIF), Joint Photographic Experts Group (JPEG), and Tagged Image File Format (TIFF). GIF is a standard for compressing and coding graphic images. JPEG is another compression and coding standard for graphic images, and TIFF is a standard coding format for graphic images.

• Presents data to the application layer.
• Acts as a data format translator.
• Handles the structuring of data and negotiating data transfer syntax to Layer 7.
• Processes involved include data encryption, decryption, compression, and
• decompression.

Points:

• Provide format and Present data in appropriate format.
• extension : gif,jpg,doc,xcls
• gif will not open in notepad
• notepad will not open in gif

Add comment February 15th, 2012

Application Layer

Application Layer enable the user, whether human or software, to access the network. It provides user interfaces and support for services such as electronic mail,file access and transfer, access to system resource, surfing the world wide web, and network management.

Application layer is Responsible for Providing Services to the user.

• Application Layer is a term used in categorizing protocols and methods in architectural models of computer networking. Both the OSI model and the Internet Protocol Suite (TCP/IP) define application layers.
• In TCP/IP, the Application Layer contains all protocols and methods that fall into the realm of process-to-process communications via an Internet Protocol (IP) network using the Transport Layer protocols to establish underlying host-to-host connections.
• Provides a means for the user to access information on the network through an application. This layer is the main interface for the user to interact with the application and therefore the network.
• The application layer is the OSI layer closest to the end user, which means that both the OSI application layer and the user interact directly with the software application. This layer interacts with software applications that implement a communicating component. Such application programs fall outside the scope of the OSI model. Application layer functions typically include identifying communication partners, determining resource availability, and synchronizing communication. When identifying communication partners, the application layer determines the identity and availability of communication partners for an application with data to transmit. When determining resource availability, the application layer must decide whether sufficient network resources for the requested communication exist. In synchronizing communication, all communication between applications requires cooperation that is managed by the application layer.

Examples

Some examples of application layer implementations include Telnet, File Transfer Protocol (FTP), and Simple Mail Transfer Protocol (SMTP).

                                                                                                OSI  Model

Points:

• Application Layer do Interaction (Providing Services to the user)
• 80% Application on internet do interact
• i.e  google.com —–> will auto —–>  www.google.com ——> Here www intract  on port 80
• i.e  for buy house property dealer do interact

Application Layer Protocols

Add comment January 8th, 2012