This Model define by International Organization for Standardization (ISO) in 1970.
- This is not a Physical model
- This model divides the network communication process in smaller and simpler component.
- This is very useful tools for network Troubleshooting
- There are seven layers in OSI Model
- layer 7 – Application Layer
- layer 6 – Presentation layer
- layer 5 – Session layer
- layer 4 – Transport layer
- layer 3 – Network layer
- layer 2 – Data Link layer
- layer 1 – Physical layer
- Layers 7, 6 and 5 (Upper layers) main focus on services to application
- Layers 4,3,2, and 1 (Lower layers) main focus on end to end data delivery
- Data Unit in L4 is called Segment
- Data Unit in L3 is called Packet
- Data Unit in L2 is called Frame
- Data Unit in L1 is called Bits
- Encapsulation – Data moves down (7>6>5>4>3>2>1)
- Decapsulation – Data moves up (1>2>3>4>5>6>7)
amirkhalak 