OSI layer

                                      Open System Interconnection (OSI) 

The OSI Model is a logical & conceptual model that defines network communication used by systems open to interconnection and communication with other systems.

Layer-1 (Physical Layer) – 

Its consist of hardware which is require Ethernet & Serial technology.

RJ45, BNC, 10B2, 10BT, HUB, CAT4/5/6 this are use in Ethernet technology.

RS323, RS422, V.35 this are use in Serial technology.

Layer-2(DATA Link)- 

Its use to understand communication between two devices.

In Ethernet technology 802.2, 802.3, ARPA,CSMA/CD this protocol is use.

Serial technology PPP, HDLC, Frame-Relay, ATM, X.25 this protocol is use.

Layer-3 (Network Layer)- 

Network layer is for updating routing protocol.

Router exchange information router to router to reach the destination.

Protocol is use- RIP, EIGRP,ISIS, OSPF, BGP, IGRP.

Layer-4 (Transport Layer)- 

The role of transport layer is transmit & receive the data.

The data flow from Application to Presentation, presentation to session & session to transport layer.

Transport layer transmit the data with the help of TCP & UDP.

Sliding window is perform in Transport layer.

Layer-5 (Session layer)- 

Session layer is use to establish, maintain and disconnect between two devices.

This layer allows a process to add checkpoints which are considered as synchronization points into the data.

These synchronization point help to identify the error so that the data is re-synchronized properly, and ends of the messages are not cut prematurely and data loss is avoided.

The session layer allows two systems to start communication with each other in half-duplex or full-duplex.

Layer-6 (Presentation layer)- 

Presentation layer is known as Translation layer.

This layer is for Compression, decompression, encryption, decryption of the data if only tool is allow.

Layer-7(Application layer)-

Application layer is use by User to perform the task like Telnet, HTTP, WWW, FTP etc.

If the user want to file transfer it can use FTP

If user want remote access its use Telnet.