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Paper title: OSI model
Written by: Chroniccommand
For: CodeShock
Credits: Chroniccommand + wiki
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OSI model. What is it?
Understanding the OSI model is pretty critical. OSI stands for Open System Interconnection Reference Model. It can be called OSI, Open System Interconnection Reference Model, OSI reference model or OSI model. It is a description for layered communications and computer network protocol design. The OSI model was developed as a part of the OSI initiative. It splits network architecture into 7 different layers. These layers are:
#Application
#Presentation
#Session
#Transport
#Network
#Data Link
#Physical Layers
It is therefore often referred to as the OSI Seven Layer Model.
http://home.earthlink.net/~tt4titans/sitebuildercontent/sitebuilderpictures/osi-model.jpg
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History of the OSI model
To understand the OSI model more thoroughly you must learn its history. In 1970, work on a layered model of network architecture was started and the International Organization for Standardization (ISO) began to develop its OSI framework architecture. The OSI model has two core components. an abstract model of networking, called the Basic Reference Model or seven-layer model, and a set of specific protocols.
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Layer 1: Physical layer
The physical layer defines physical specifications for devices. It defines the relationship between a device. The major functions and services performed by the Physical Layer are:
#To establish and terminate connections
#Conversion between digital data in user equipment and the corresponding signals transmitted over a communications channel.
#Participation in the process of communication
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Layer 2: Data Link Layer
The Data Link Layer is the layer in the OSI model that provides functional and procedural means to transfer data between network entities and to detect and possibly correct errors. This layer was intended for point-to-point and point-to-multipoint media. Both WAN and LAN services arrange bits, from the Physical Layer, into logical sequences called frames. Not all Physical Layer bits necessarily go into frames, as some of these bits are purely intended for Physical Layer functions.
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Layer 3: Network Layer
The Network Layer defines network addresses in a way that route selection can be determined systematically by comparing the source network address with the destination network address, and thus applying the subnet mask. The TCP/IP Model has a layer called the Internet Layer. This is located above the Link Layer. Most of the time people will consider the Internet Layer (TCP/IP Model) as an equal or equivalent of the network layer (OSI Model). The Internet Layer is only a subset of functionality of the network layer.
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Layer 4: Transport Layer
The Tranport Layer, Is the layer in the OSI model that transfer's data between end users. Although not developed under the OSI Reference Model and not strictly conforming to the OSI definition of the Transport Layer, typical examples of Layer 4 are the Transmission Control Protocol (TCP) and User Datagram Protocol (UDP).(Study TCP/UDP more, It will increase your knowledge).
UDP: User Datagram Protocol.
TCP: Transmission Protocol data.
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Layer 5: Session Layer
Simply put it, the Session Layer controls the connections between computers. It can establish and end connections between a local and remote connection.
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Layer 6: Presentation Layer
Layer 6 establishes a context between layer entities. This layer provides independence from differences in data representation (e.g., encryption) by translating from application to network format, and vice versa.
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Layer 7: Application layer
Finally, we are near the end. The last layer is the Application Layer. This layer interacts with software applications. Such application programs fall outside the scope of the OSI model. Application layer functions typically include identifying communication partners, determining resource availability, and synchronizing communication.
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This was just an insight on the OSI model. If you wish to learn more use your google-fu skills and see what you can learn :) I hope this helped many people understand what OSI means, and what it does etc.