OSI Reference Model



OSI (Open system inter connection) Reference Model:



The following are OSI reference model

  1. Application layer
  2. Presentation layer
  3. Session layer
  4. Transport layer
  5. Network layer
  6. Data Link layer
  7. Physical Layer
 

Application Layer: the top layer of OSI reference model. the HTTP, FTP,SMTP, DHCP, SNMP protocols are work in this layer.

Presentation layer: this is 2nd  layer of OSI reference model.this layer's  responsibility is translating the Syntaxes used by different types of application in different computer in the network. in this layer a computer translate the data accumulated  by its own applications from its own abstract syntax to a common syntax which is suitable to transmit  through the network.

Session layer: the most important task of this layer are dialog control and dialog separation. dialog control is exchange information between two systems on the network. This layer Establishe, manages as well as  terminates sessions between applications


Transport Layer: The TCP & UDP protocol works in this layer. This layer provides   end-to-end connection between processes.

Network layer: in this layer the is responsible for packaging transport layer data in diagrams, addressing them to its final destination, routing them across the internet-work and fragmenting the diagrams as needed. the internet protocol (IP) work in this layer. This layer translate between different network types

Data link layer: This layer is responsible for network layer packaging network layer data ,addressing to its next destination. the PPP, SLIP works in this layer.

Physical Layer: The bottom layer of OSI reference model. This layer define what kinds of medium will be in the network

Types of Networking


There are three basic types of networks include:
  1. LAN: Local area network
  2. MAN: Metropolitan  Area Network
  3. WAN: Wide Area Network

Local Area Network

A Local Area Network (LAN) is a network where computer are connected with each other relatively small area. It is usually limited to a geographic area such as a  lab, school, or building. LAN computers can be not more than a mile apart.
LAN consists of the following components:
  •  Computers
  •  Network interface cards
  •  Peripheral devices
  •  Networking media
  •  Network devices
LANs are designed to:                      
  Operate within limited Geographic Area.                                                                                                                                                                                    
  • Allow multi access to high band with media.
  • Control the network privately under the local  administration
  • Provide full time connectivity to local services
  • Connect physically adjacent devices.

Some common LAN technology include the following:

  Ethernet: In  LAN configuration, one computer is for the file server. In the file server all software is stores that controls the network and  the software which can be shared by the all computers which is attached to the network. All Computers which are connected to the file server are named workstation. The workstations may be less configuration than the file server. LANs, can be setup by all kinds Topology.
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