OSI Model and Functions

OSI - Open System Interconnection

Layer 7 Application

Layer 6 Presentation

Layer 5 Session

Layer 4 Transport

Layer 3 Network

Layer 2 Data link

Layer 1 Physical

TCP/IP - Transmission Control Protocol/User Datagram Protocol

Layer 4 Application

Layer 3 Transport

Layer 2 Internet

Layer 1 Network Access

Functions of OSI

Layer 7 Software Application, User Login Access Also Done Here

Layer 6 Data Format and Encryption Happens Here. Jpeg, HTML, .doc etc

Layer 5 Starts and Ends Session and Maintain The Session

Layer 4 Maintains Error Recovery,Flow Control, Port Facility

Layer 3 Provides Logical Address, Determines The Best Route For The Packet to Travel

Layer 2 Provides Physical Address, Provides Headers &Tailers for Error Free Delivery (FCS), Encapsulation etc.

Layer 1 Provides Physical Connection like emulation, cable, devices, repeaters etc.

OSI Device

Layer 7 - 5Firewall, Intuition Detect Devices

Layer 4

Layer 3 Router

Layer 2 NIC, Lan Switch, Wireless Access Point, Cable Modem, DSL Modem

Layer 1 Hub, Repeaters

OSI Concept

Instead of A Network Model, It is a Big Concept Breaked into Multiple Layers So That Experts In Each Layer Can able to concentrate on inventing technology without considering about other Layers.

OSI PDU (Protocol Data Unit)

Each Layer Data Encapsulation Denotes By Layer Number,Example L2PDU, L3PDU

TCP/IP Packet, Frame and Segments are Called TCP/IP PDU