OSI MODEL
Joseph Lucero
College America

Abstract
In this paper it is going to explain the OSI model and all the layers. There are 7 layers in total: the layers are Application, Presentation, Session, Transport, Network, Data Link and Physical. It is going to explain what all the layers are and how they work in the OSI Model, it is also going to explain what every layer is. It is also going to explain why it was created and what the use for the OSI model is for today. You are going to know why we need the OSI model and how it evolved from the first time. You are also going to find out about the past history about the model and the other name is what called before.

OSI Model
The OSI model has been used for a long time. Why do we use it? OSI, formally known as the ISO OSI model, is the most standard model for networking communication. The ISO formed the OSI or Open System Interconnection, so that you can communicate and connect with another system over the network without having system specific configuration. The OSI model consists of 7 different layers: Physical, Data Link, Network, Transport, Sessions, Presentation, and Application. One reason why the OSI model was created, is so that the process of communication that were between two end points in a telecommunication network can be split into layers. The main reason why the OSI Model was created was to standardize the networking rules so that all the systems can communicate over the OSI reference model, which was a set of seven layers that data had to travel through from one device to another one over the network. The defined standards for: the way in which you can communicate between devices, when to inform a device to send data and when not to transmit data, to ensure that the device has the correct data flow rate, to make sure that the data is passed to and received by the intended recipient and the way physical media is arranged and connected. The main reason why the OSI model is layered is it helps to solve different issues and problems, by having a better chance on figuring out what is wrong. It also helps to divided and differentiating different protocols so that it is able to be developed by specialized group.
The First layer that is going to be explained is the Application Layer. This is the layer that serves as the user’s window and application process to access network services. In this layer are some of the functions that are commonly needed they are: Remote file access, Network management, Electronic messaging (such as mail) and Network virtual terminals. In this layer it receives the data and then performs a variety of maintenance checks before it is passed down to the layers that are beneath it. The second layer that is going to be explained is the Presentation layer. “This layer works by converting information into a wide variety of file formats and forms of encryption. The way this is done is by using built-in algorithms and it is able to standardize information whether it is handled by XML, C++, or TLV.” (spencer, 2013). This layer can also pass information from the Session layer back to the Application layer. The Session layer establishes, manages and terminates connections between applications. This layer sets up, coordinates, and terminates conversations, exchanges, and dialogues between the applications at each end. It deals with session and connection coordination.
The next layer is going to be the transport layer. This layer is what provides the transferring of the data between the end systems, or hosts, also it is responsible for the flow control and the end-to-end error recovery. (Street, 2013). It also ensures that all the complete data has been transferred correctly. The last three layers are the: Network, Data Link and Physical. The Network layer provides switching and routing technologies, creating logical paths, known as virtual circuits, for node to node data transmission. There are other functions of this layer and they are: internetworking, addressing and congestion control. Data Link is the next layer, “at this layer, data packets are encoded and decoded into bits, flow control and frame synchronization. The data link layer is divided into two sub layers: The Media Access Control (MAC) layer and the Logical Link Control (LLC) layer. The MAC sub layer controls how a computer on the network gains access to the data and permission to transmit it. The LLC layer controls frame synchronization, flow control and error checking.” (Street, 2013). The last layer is the Physical, “This layer conveys the bit stream - electrical impulse, light or radio signal -- through the network at the electrical and mechanical level. It provides the hardware means of sending and receiving data on a carrier, including defining cables, cards and physical aspects. Fast Ethernet, RS232, and ATM are protocols with physical layer components.” (Street, 2013)
In conclusion, you have now been told about the OSI model, the reason why the OSI model was created, and the use for it today. All the layers of the model are used for a specific reason from Application all the way to Physical. It is the most standard model for networking communication, it was originally called the ISO model then later on it became the OSI model. So now with understanding why the OSI model was created will help people to understand how powerful it is it the networking life.

References: spencer, w. (2013). tech-faq.com. Retrieved from www.tech-faq.com/osi-model.html
Street, Q. (2013). webopedia.com. Retrieved from http://www.webopedia.com/quick ref/ OSI layers.asp