Presentation Layer of OSI Model (Layer-6)

Presentation Layer is responsible for representation & formatting of data for session Layer in encapsulation process. It is the 6th Layer in the seven layer OSI Model after Session Layer. Presentation layer serves like a translator & takes care that the data is sent in such a way that the receiver will understand the information or data and will be able to use the data.
OSI Model divides the network communication processes into seven layers in order to simplify it. Each layer performs specific functions to support the layers above it. This seven Layer model starts from Physical till Application Layer & Presentation Layer is on 2nd place in this model as in below figure:

Functions/Duties of Presentation Layer

Each Layer in OSI Model Performs some important duties. Important functions performed by Presentation Layer are listed here:

The first & most important is, of course Data Formatting & Representation. When the presentation layer receives data from the application layer, to be sent over the network, it makes sure that the data is in the proper format. If it is not, the presentation layer converts the data to the proper format. On the other side of communication, when the presentation layer receives network data from the Presentation layer, it makes sure that the data is in the proper format and once again converts it if it is not.
It is also responsible for Data Encryption/Decryption: Presentation Layer carries out encryption at the transmitter end and decryption at the receiver end to keep data secure during transmission.
Data Compression/De-compression also falls under the responsibility matrix of Presentation Layer. Presentation Layer compresses data to a small size to reduce resource usage such as data storage space or transmission capacity.

*Encryption is typically done at this layer as well, although it can be done on the application, session, transport, or network layers, each having its own advantages and disadvantages

Presentation Layer Protocols

The OSI Model provides a conceptual framework for communication between computers, but the model itself is not a method of communication. Actual communication is made possible by using communication protocols. Each layer on the OSI Model has some protocols associated with it. Some important protocols on Presentation layer are listed in below:

ASCII
EBCDIC
SSL
TLS
JPEG/GIF/PNG/TIFF
MPEG

Network Equipment/Components at Presentation Layer

Firewalls
Gateways
Load Balancers
End Devices e.g. Computers, Smart Phones, Servers, …

Summary

Presentation Layer is the 6th Layer in seven Layer OSI Model. It performs important functions like Data Formatting, Data Representation, Data Encryption/Decryption, Data Compression and De-compression. Important Protocols at Presentation Layer include ASCII, EBCDIC, JPEG, MPEG, GIF, PNG, TIFF, SSL & TLS. Equipment operating at Presentation Layer include Firewalls, Gateways, Load Balancers & Computers.

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