Networking

The Seven Layers of the OSI Model (How Computers Communicate)

 

The OSI-Model (Open System Interconnection) is a reference model for how applications can communicate over a network and was developed by the International Standard Organization (ISO) is 1984. A reference model is a conceptual framework for understanding relationships. The TCP/IP protocols, which defines the internet, do not map cleanly to the OSI-Model.

This model breaks down data transmission over a series of seven layers. The layers 1-4 are considered the lower layers and mostly concern themselves with moving data around while layers 5-7 the upper layer, contain application-level data.


The Seven Layer OSI-Model with their functions and Protocol Examples.

LAYER NAME FUNCTION PROTOCOL EXAMPLE.
7 Application It is a service that is used with end user applications. SMTP, HTTP, FTP, DNS, TELNET, SNMP.
6 Presentation It formats the data so that it can viewed by the user. It also encrypt and decrypt data. HTTPS, GIF, JPG, SSL, TLS, MPEG.
5 Session It establishes ends connection between two hosts. Apple Talk, WinSock, NetBIOS, PPTP.
4 Transport It is responsible for the transport protocol and error handling. TCP,UDP, SPX.
3 Network It reads the IP address from the packet. Routers, Layer of the Switch, IP, ICMP, IPX. IPSec, ARP.
2 Data link It reads the MAC address from the data packet. Switches, Ethernet, ATM, Bridge, PPP.
1 Physical Its sends data on to the physical wire to get access to media. Hubs, NICs, Cable, Ethernet, Token Ring, repeater, USB, Bluetooth, IEEE802.11.

 

Also read: 40 Network Protocols with Port numbers and examples

NOTE: The fact is that the OSI-Model isn’t much difficult to know and memories, so here are some enthusiastic tips of sayings to easily remind you of the seven layers of the OSI-Model.

SOME ADDITIONAL SAYINGS OF THE OSI-MODEL.

 

Top to bottom Bottom to Top Top to bottom Bottom to Top Bottom to Top
7 Application All Away All Advice Around
6 Presentation People Pizza People People’s People
5 Session Seem Sausage Should Sales Stupid
4 Transport To Throw Try Take Tease
3 Network Need Not New Not Not
2 Data Link Data Do Diet Do Do
1 Physical Processing Please Pepsi Please Please

 

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