Osi Model

OSI model

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OSI Model

7 Application layer

6 Presentation layer

5 Session layer

4 Transport layer

3 Network layer

2 Data link layer

LLC sublayer

MAC sublayer

1 Physical layer

The Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model for short) is a layered, abstract description for communications and computer network protocol design, developed as part of the Open Systems Interconnection initiative. It is also called the OSI seven layer model.

Contents [hide]

1 History

2 Description of OSI layers

2.1 Layer 7: Application layer

2.2 Layer 6: Presentation layer

2.3 Layer 5: Session layer

2.4 Layer 4: Transport layer

2.5 Layer 3: Network layer

2.6 Layer 2: Data Link layer

2.7 Layer 1: Physical layer

3 Interfaces

4 Examples

5 Humour

6 See also

7 External links

[edit] History

In 1977, the International Standards Organization (ISO), began to develop its Open Systems Interconnection (OSI) networking suite. OSI has two major components: an abstract model of networking (the Basic Reference Model, or seven-layer model), and a set of concrete protocols. The standard documents that describe OSI are for sale and not currently available online.

Parts of OSI have influenced Internet protocol development, but none more than the abstract model itself, documented in OSI 7498 and its various addenda. In this model, a networking system is divided into layers. Within each layer, one or more entities implement its functionality. Each entity interacts directly only with the layer immediately beneath it, and provides facilities for use by the layer above it. Protocols enable an entity in one host to interact with a corresponding entity at the same layer in a remote host.

[edit] Description of OSI layers

OSI Model

Data unit Layer Function

Host

layers Data Application Network process to application

Presentation Data representation and encryption

Session Interhost communication

Segments Transport End-to-end connections and reliability (TCP)

Media

layers Packets Network Path determination and logical addressing (IP)

Frames Data link Physical addressing (MAC & LLC)

Bits Physical Media, signal and binary transmission

[edit] Layer 7: Application layer

The application layer is the seventh level of the seven-layer OSI model. It interfaces directly to and performs common application services for the application processes; it also issues requests to the presentation layer.

The common application layer services provide semantic conversion between associated application processes. Note: Examples of common application