OSI Reference Model
1.4 Describe the purpose and basic operation of the protocols in the OSI and TCP/IP models
---> OSI Reference model is developed by ISO organization around 1980.
----> It is layered architecture which defines and explains how the communication should take place between 2 or more network devices within the organization or Internet.
-------> Each layer defines a set of functions in data communication.....
Application Layer:
------> Providing an interface for the users to interact with the applications or network services.
-------> Identifying communication partners.
-------> Determining Resource Availability.
--------> Synchronizing Communication.
Ex: Web Browser
Presentation Layer:
-----> Providing Proper format for the data ( performs encoding & decoding).
-----> Performs Encryption & Decryption.
-----> Performs Compression & Decompression.
Ex: JPEG,GIF,ASCII.
Session Layer:
-----> Session Layer basically keeps different application data separate from other.
-----> Establishes, manages and terminates connections between local & remote applications.
-----> It provides half duplex, full duplex and simplex communication.
------> Basically implemented in Remote Procedure Calls.
-------> Session ID is used to identify a session or interaction.
Ex: RPC, SQL, NFS
Transport Layer:
-----> End to End transportation of data between the applications.
-----> Identifying a service, Multiplexing,Demultiplexing,segmentation
-----> sequencing&reassembly,error control,flow control.
-----> sequencing&reassembly,error control,flow control.
-----> Services are identified with the help of port numbers.
-----> The major protocols takes care of data transportation at transport layer are TCP,UDP.
Network Layer:
-----> It is responsible for end to end transportation of data across multiple networks.
-----> Logical addressing & Path determination done at this layer.
Ex: IPV4, IPV6.
Data Link:
-----> End to End delivery of data between the devices on a LAN network segment.
-----> Error control & Flow control are the functions.
Ex: PPP
Physical Layer:
-----> It defines electrical & physical specifications of the data connection.
-----> It deals with physical transmission of binary data on the given media.
Ex: Ethernet,Token ring, FDDI.
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