OSI Model(7 Layers)

Answer:
OSI model is a way of describing how different applications and protocols interact on network-aware devices.
Functions of each Layer:
Physical Layer(Layer 1):This layer defines the physical and electrical characteristics of the network. Helps to pass strings(data) of ones and zeros down the wire.
Device:Hub, NIC, Repeater.. etc
Data Link Layer:
It defines the acess strategy for sharing the physical medium. Helps convert the bits into frame.
Devices: Bridge, Switch
Network Layer:
Layer 3 is the Network Layer, providing a means for communicating open systems to establish, maintain and terminate network connections.
Device:Router
Transport Layer:
The main function of Session Layer is to ensure data reliability and integrity.
Session Layer:
It provides two communicating presentation entities to exchange data with eachother.
Presentation Layer:
Application data is either unpacked or packed only in this layer. Protocol conversions, encryption/decryption and graphics expansion all takes place here.
Application Layer:
This is where you find your end-user and end-application protocols, such as telnet, ftp, and mail(pop3 and smtp).

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