ISO – OSI model

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This is a simple Post in OSI model, Hope it will help you to understand the concept of OSI model. Apart from all other Post I tried to make it simple, so everyone can understand.

International Standards Organization’s OPEN SYSTEM INTERCONNECT (ISO/OSI) model is the standard model for networking protocols and applications. It defines the seven network layer. This is a conceptual model that explains and depicts while standardizing the function of a communication system by dividing it into abstract layers.

                LAYER 1: Physical layer

                Layer2: Data link

                Layer 3: Network

                Layer 4: Transport

                Layer 5: Session

                Layer 6: Presentation

                Layer 7: Application

# Every layer adds a header except physical layer, header contains the control bits for the identification of that particular layer by the cross ponding layer of the specific machine. Data format in every layer is called as PDU, PDU= protocol Data Unit

# Tailor is added in the data-link layer for the error checking which is called CRC, CRC stands for Cyclic Redenrendency Check.  

PDU

Application	Software Layer	Top most layer	Data or Messages	Address	Devices
Presentation
Session
transport	Core layer	Middle layer	Segment	Port address=16 bit	n/a
Network	Hardware Layer	Lower Layer	Packet	IP address	Router, L3 switch, Brouter
Data link			Frame	MAC address	Bridge, Switch L2
Physical			Signal	n/a	Repeater, HUB

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