The Open Systems Interconnection (OSI) reference model has significantly influenced the development of internet protocol we use today. Created in the 1980’s by the International Standards Organization (ISO), a multinational body dedicated to worldwide agreement on international standards, this reference model has defined the entire network communication process into seven structured layers. In ascending order these layers are the physical, data link, network, transport, session, presentation, and application layers. The purpose of this model was, and still is, to simplify and set a standard for the design of communication and networking products that can communicate with each other, regardless of system differences.
The Open Systems Interconnection model breaks down host-to-host transmissions into seven different layers where each one performs a specific function. At the same time each layer has the ability to also communicate with adjacent layers in either direction. In essence each layer interacts directly with the layer below it and at the same time also provides support to the layer above it.
1. Physical Layer
The first layer in the OSI model is the physical layer, which deals primarily with all of the hardware aspects of communication, essentially defining the standards for signaling and wiring. The main purpose of this layer is to handle the translation of binary bits in each frame into signals. And then transmit these signals one at a time over some physical medium connecting other network entities. On the receiving end, the physical layer will retrieve these individual signals and restore them to their bit representations before passing them up to the Data Link layer as a complete frame. Methods of signaling depend on the type network media used. Some of the standards of network media or wiring include copper cable, fiber, and even wireless transmissions. For copper cable wiring, the signals are transmitted as patterns of electrical pulses. For fiber, the signals are transmitted as patterns of light. And for wireless media, the signals are broadcasted as patterns of radio transmissions in different frequencies. Other important components and physical-layer devices associated with this layer include Network Interface Cards (NIC), hubs, repeaters, as well as connectors and adapters for physical interfaces.
2. Data Link Layer
The second layer of the OSI model is the data link layer, here the bits from layer one become single units of data otherwise known as frames. This layer is responsible for managing the flow of those frames across a physical medium or “link” between network entities. This layer has two main purposes, one of them is to allow the upper layers access to the medium, and secondly it must controls how the data is placed into and received from that medium. This is achieved by using protocols such as media access control (MAC) and error detection which may sometimes be handled by other software or by the...