Osi Model

The OSI Model

The Open Systems Interconnection Reference Model or OSI Reference Model for short is a seven layer description for communications and computer network protocol design. It is commonly known as the OSI seven layer model. Its primary feature is to define the interface between layers and to dictate how each layer would interact or communicate to the layer below it and above it. By adhering to these standards, a layer manufactured by one vendor should be able to operate with a layer from a different vendor.

The layers of the OSI model can be divided into Media Layers and Host Layers.

Description of the OSI Layers

Layer 1 - Physical Layer. The OSI Physical Layer "define all the electrical and physical specifications for devices" (Wikipedia, n.d.). The major functions addressed by the physical layer are: establishment and termination of a connection to a communications medium, Ethernet standards and conversions or modulations over a communications medium.

Layer 2 - Data Link Layer. "The data link provides reliable transit of data across a physical network link" (Teare, 1999). This layer physical addressing, network topology, error notification, sequencing of frames and flow control.

Layer 3 - Network Layer. The network layer addresses data transfer from a source to a destination via one or more networks. This layer involves network routing, flow control, segmentation/desegmentation and error control functions.

Layer 4 - Transport Layer. The transport layer addresses the movement of data across the network. This layer is responsible for ensuring that the data from the session layer is delivered error-free and in the correct sequence to its destination.

Layer 5 - Session Layer. The session addresses the establishment, management and termination of communication sessions are requested by applications in different network devices.

Layer 6 - Presentation Layer. The presentation layer ensures that the data from the application layer are readable by an application layer of another system.

Layer 7 - Application Layer. This layer is the closest to the end user. The application layer addresses the communication component of a software application.

TCP / IP Architecture

TCP / IP stand for Transmission Control Protocol / Internet Protocol and are sometimes called the internet protocol suite. TCP / IP are used on the internet and has become the standard for network communications. Internet Protocol or IP is responsible for identifying networks or paths to networks and hosts. IP addresses are the numeral counterpart of computer addresses over the network. IP is also responsible for breaking up data into chunks or IP packets and transmitting it over the network. Transmission Control Protocol (TCP) assures that the data transmitted is received in the correct sequence.

The Four Layers of the Internet Reference Model

Network Interface Layer. This layer includes the datalink and the physical layer. This layer addresses how the data would interact with the physical devices so that it can