What is the simplest explanation of the OSI model involving real examples?
Well!OSI!! Open System Interconnecting reference model released in 1984.it has 7 layers and two running processes.If the data is moving from layer 7 to layer 1 the process is Encapsulation If the data is moving from layer 1 to layer 7 the process is DecapsulationTalking about layers :Layer 1 : Physical layer : Where data travel in the form of Bits (0’s and 1’s) Binary.On this layer Actual data transmission happens. Devices like, Hubs, Repeaters, Wires work here.Layer 2 : Data Link Layer : Where data got converted into frames and Source MAC + Destination MAC header is added/removed. Switch works on this layer. And get the details of Destination MAC by broadcasting the ARP (Addressing Resolution Protocol) packet. It perform Error Detection & not correction.Layer 3 : Network Layer : where data got converted into Packets and Source + Destination IP header added/removed. Router work on this layer, and select Best available path for the packet to travel. It use Logical Addressing(IP Addressing).Layer 4 : Transport Layer : Data converted into segments and TCP OR UDP header added here. It provides error correction before transmitting thus insure reliable data transport .a) UDP Protocol - unreliable & connectionless, used in LIVE SCENARIOS.b) TCP Protocol - reliable because of 3-way handshake, flow control.Layer 5 : Session Layer : This layer establishes, manages, and terminates sessions between Peer to Peer. It keep different application’s data separate from other applications.Layer 6 : Presentation Layer : It ensures that data transferred from application layer of one system can be read by application layer of other system. It’s responsible for converting data into standard format which may include:JPEG, MPEG, BMP, MIDI, WAV, MP3Tasks which can be performed:a) Encryption >< Decryptionb) Encoding >< DecodingLayer 7 : Application Layer : Can be described into two words : User Interface.This layer is concerned with user interaction with the computer and the network. It acts as an interface between the actual application program. Contains many protocols and utilities, such as telnet, FTP, HTTP,SMTP.A port number is a way to identify a specific process to which an Internet or other network message is to be forwarded when it arrives at a server.Layer 7 to Layer 5 considered as Upper Layers (for software professionals)Layer 4 to Layer 1 considered as Lower Layers (for network Professionals)RegardsAdithya SrivastavaYouTube Channel : https://goo.gl/ENnjX1