Presentation Layer of OSI Model - MetaTutorials


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Presentation Layer of OSI Model

In this networking article, you will learn about the Presentation Layer of the OSI reference model in detail with its diagram and functions. We will also discuss the protocols used by the presentation layer. 
presentation layer_cover

What is the Presentation Layer of OSI model?

The presentation layer of the OSI Model receives the data from the higher layer and manipulates it according to the required format, and then transmits it over the network. 
This layer is also referred to as the translation layer because it acts as a translator between the two communicating devices. 
presentation layer

This OSI layer mainly deals with the syntax and semantics of the message which it transmits over the network. It maintains the data format and defines the encryption/decryption methods for the sensitive data. 
It is also responsible for reducing the size/bandwidth of the data which is to be transmitted over the network.

Functions of Presentation Layer

The functions of the presentation layer are described below:

1. Translation: The main function of the presentation layer is to translate the message into an acceptable and compatible format for communication between two different devices. 
At the sender node, it translates the data of sender-understandable format into a common format and at the receiver node, it again translates the common format into receiver-understandable format.

2. Encryption/Decryption: Encryption and Decryption techniques are used to maintain data privacy and data integrity. The encryption mechanism is used at the sender device to encrypt the data which is to be transmitted, and the decryption mechanism is used at the receiver device to decrypt the received data.

3. Compression: Data Compression is also another main function performed by the presentation layer. It helps in reducing the size of the data which is to be transferred over the network. Due to this, the speed and efficiency of communication become increase.

4. Character Code Translation: Another aim of the presentation layer is that it also translates the ASCII code/characters to EBCDIC code/characters. 

Protocols of Presentation Layer

Following are the various networking protocols used in the presentation layer for performing its functions:
1. AFP
2. LPA
3. NDR
4. SSL
5. NCP
6. XDR

AFP (Apple Filling Protocol)

Apple Filling Protocol is a type of communication protocol which is basically designed for providing file services to Mac-based platforms across the network. 

LPP (Lightweight Presentation Protocol)

The Lightweight Presentation Protocol is defined in RFC 1085, which offers the ISO presentation services running on the TCP/IP-based protocol stacks.

NDR (Network Data Representation)

The Network Data Representation is also a presentation protocol which offers various primitive and constructed data types. This protocol represents the data (images, videos, audio, numbers, etc) over the network.

SSL (Secure Socket Layer)

The Secure Socket Layer protocol gives a high level of security to encrypt the data which is being passed between the web browser and web server.  

NCP (Netware Core Protocol)

The Netware Core Protocol is a network protocol which allows users to access files, directories, messages, prints, and other services of the network. Users can run this protocol on Mac OS X, Linux, Microsoft Windows, Windows NT, and Classic Mac OS.

XDR (External Data Representation)

External Data Representation is also another presentation protocol which was introduced in 1987. It is used for communication between different kinds of computer architectures. The process of converting the data from Local to XDR is called encoding. And the process of converting the data from XDR to Local is called decoding.