OSI Reference Model Layers
OSI model is a conceptual model that characterizes and standardizes how different software and hardware components involved in a network
communication should divide labor and interact with one another. It has
seven layers.The application layer of OSI model interacts directly with
software applications to provide communication functions as required,
and it is the closest to end users. Functions of application layer
typically include verifying the availability of communication partners
and resources to support any data transfer. This layer also defines
protocols for end applications, such as domain name system (DNS), file
transfer protocol (FTP), hypertext transfer protocol (HTTP), Internet
massage access protocol (IMAP), post office protocol (POP), simple mail
transfer protocol (SMTP), Simple Network Management Protocol (SNMP), and
Telnet (a terminal emulation).
The presentation layer checks the data to ensure it is compatible with the communications resources. It translates the data into the form
that the application level and lower levels accept. Any needed data
formatting or code conversion is also handled by the sixth layer, such
as converting an Extended Binary Coded Decimal Interchange Code (EBCDIC)
coded text file to an American Standard Code for Information
Interchange (ASCII) coded text file. It functions for data compression
and encryption as well. For example, video calls will be compressed
during the transmission so that it can be transmitted faster, and the
data will be recovered at the receiving side. For the data that has high
security requirements, such as a text message containing your password,
it will be encrypted at this layer.
