OSI 7 LAYER

Introduction to Model Open Systems Interconnection (OSI)
Model Open Systems Interconnection (OSI) was created by the International Organization for Standardization (ISO) that provides a structured framework logic how processes interact via a data communication network. Standards were created for the computer industry to communicate on different networks efficiently.
OSI Layer Model
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There are seven layers in the OSI model. Each layer is responsible for a particular aspect of data communications. For example, one layer may be responsible for establishing connections between devices, while another layer may be responsible for correcting the "errors" during the process of data transfer.OSI Layer Model is divided into two groups: the upper layer and lower layer. "Upper Layer" focus on user applications and how files are represented on the computer. For Network Engineer, the main part of the attention is on the "lower layer. Lower layer is the essence of the actual data communication over a network."Open" in the OSI
open.gifâ œOpenâ € €? in the OSI model is to express the interconnection of networks that perform regardless of hardware / hardware to use, all in accordance with standard communications software. This indirectly led to "modularity" (can be dismantled pairs).Modularity
"Modularity" refers to the exchange of protocol at a certain level without affecting or damaging relationships or functions of other levels.In a layer, protocols are interchangeable, and allows communication continues. These exchanges take place based on the hardware "hardware" from different vendors and a variety of different reasons or desires.Modularitymodularity_1.gifAs examples of the Inter Services / Courier. "Modularity" at the level of transport that is not important, how to package up to the plane.modularity_2.gifPackage to reach the plane, can be sent by truck or ship. Each of these ways, the sender still sends and hope the package arrived in Toronto. The plane flew to Toronto to bring the package regardless of how the package is delivered to the plane.
7 Layer OSI
OSI model consists of 7 layers:

    * Application
    * Presentation
    * Session
    * Transport
    * Network
    * Data Link
    * Physical
What does the seven layer OSI?
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When data is transferred over the network, before the data must pass through all seven layers of a single terminal, from the application layer to physical layer, then at the receiver side, the data is through the physical layer to application. At the time of data through one layer of the sender, it will add a "header" while on the receiving end "header" was removed in accordance with layernya.
OSI Model
The main purpose of the use of the OSI model is to help network designers to understand the function of each layer are associated with the flow of data communications. Including the types of protoklol network and method of transmission.
The model is divided into 7 layers, with the characteristics and functions of each. Each layer must be able to communicate with the layer above it and below it directly through a series of protocols and standards.OSI Model
Informationosilayers_1.gifApplication Layer: Provides services for user applications. This layer is responsible for the exchange of information between computer programs, such as e-mail programs, and other service roads in the network, such as a printer server or other computer applications.osilayers_2.gifPresentation Layer: Concerned with how data is converted and formatted for data transfer. Example conversion of ASCII text format for documents,. Gif and JPG for pictures. This layer performs code conversion, data translation, encryption and conversion.osilayers_3.gifSession Layer: Determines how two devices establish, maintain and manage the connection - how they relate to each other. Connections in this layer is called "session".osilayers_4.gifTransport Layer: Responsible for breaking data into segments, logical connection "end-to-end" between the terminals, and provide error handling (error handling).osilayers_5.gifNetwork Layer: Responsible for determining the network address, specify the route to be taken during the trip, and keep the network traffic congestion. The data in this layer-shaped package.osilayers_6.gifData Link Layer: Provides links to data, packaged into frames associated with the "hardware" and then transported through the media. It communicates with a network card, set the physical layer communications between connecting systems and error handling.osilayers_7.gif
Physical Layer: Responsible for the process data into bits and transfers them via the media, like cable, and maintain the physical connection between systems.

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