Tuesday, April 22, 2008

OSI Model Standard

Basically all the networks todays are based on the OSI ( Open Systems Interconnection ) seven-layers Model which was developed by the International Organization for Standardization (ISO).

OSI Reference Model is a set of seven (7) layers that defines the staged that data must go through from one device to another over a network.


Layer 7 : Application Layer

This  layer is actually interacting with the Operating Systems. It is totally all applications and all related network protocols.

Protocols : DNS, FTP, HTTP, SNMP, SMTP, TELNET, SMB etc.

Layer 6 : Presentation Layer

This layer only responsible to translate/convert the data from Layer 7 to Layer 5 or vice versa into a standard format where the other layer can understand.

Layer 5 : Session Layer

This layer manages the data flow from higher layer to the lower by managing the data transmission timing. It also actually establishes the connections with another nodes.

Protocols : NETBios etc.

Layer 4 : Transport Layer

This layer would control the data flows control and provide error checking and recovery of data between devices.

Protocols : NETBios, TCP, UDP, RSVP etc.

Layer 3 : Network Layer

This layer determine the way that the data will be sent to the recipient device. Logical protocols, routing and addressing are handled here.

Protocols : IP, OSPF, BGP, IPSec, IS-IS, RIP, ICMP etc.

Layer 2 : Data Layer

In this layer, the appropriate physical protocols is assigned to the data. The type of network and the packet sequencing is defined here.

Protocols : WiMAX, Ethernet, PPP, L2TP, 802.11, FDDI etc.

Layer 1 : Physical Layer

This layer is actually the actual hardware with physical characteristics of the network such as connections, voltage etc.

Protocols : Modems, Optical Fiber, Twisted Pair etc.

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