Essay on 7 Layers of the Osi Model

774 Words Oct 22nd, 2012 4 Pages
The Seven Layers of the OSI Model
Kevin Ludwig
Bryant and Stratton College
TECH 140
Khaled Sabha
12.08.2009

There are seven layers in the OSI model. Each layer has a function or purpose that is used to set up a network. The International Organization for Standardization began to develop the OSI framework in 1984. The purpose was to have each layer interact with the layer directly beneath it. The layers are starting from the top: Application, Presentation, Session, Transport, Network, Data Link and Physical. The Application layer has the function of providing interface between software applications and network for interpreting the requests and requirements for applications. “This top layer defines the language and syntax
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It is responsible for sending bits across the network media. Hardware and Protocols/Standards are divided under the appropriate layers in the OSI model. Gateways, Proxy servers, Application switches and Content Filtering Firewalls fall under four different layers. They are Application, Presentation, Session and Transport. Routers, Layer 3 switches and Firewalls fall under the Network layer. Bridges, Switches and Wireless access points fall under the Data Link layer. Hubs and Repeaters fall under the Physical layer. NICs, Modems, Cable modems and DSL modems fall under the Data Link and Physical layer. Some common applications in the Application layer possess Internet Message Access Protocol, File Transfer Protocol and Simple Network Management Protocol. Common gateways in the Presentation layer include; Systems Network Architecture: Gateways enable PCs to communicate with mainframe computers and E-mail gateways enable data to be transmitted between different e-mail applications. The Session layer has name lookup and security functions. It also establishes a point where a message starts and a message ends. The Transport layer is where the TCP and UDP protocols are initiated. They are the common transport protocols for this layer. The Network layer possesses flow control, error detection and error recovery. The Data link layer is responsible for the managing error messaging

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