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.
|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.|
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.
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