OSI Model Paper

Introduction

The open Systems interconnected Model (OSI) is a reference tool helpful in understanding the data communications between two networked systems.  The model divides the process of communication into seven layers with each layer having specific functions aimed at supporting the layers above it and provides services for the layers below (Yemini, 1993).  The three bottom layers are focused on passing traffic via the network to end systems, and the top four layers then come into play in the end system to ensure a complete communication process between the two systems.  This paper will offer the reader with the understanding of the seven layers, their functions and relationships to one another.

Description of the Layers

Layer 1: The Physical Layer

At number one in the OSI model comes the physical layer whose purpose is to define the connect as well as the interface specifications and the medium requirements for the communication process. It provides the mechanical, functional, and procedural specifications for sending bit stream on the computer network (Day & Zimmermann, 1983).  In other words, it defines the correlation between the device and the physical transmission medium.  That also incorporates the layout of pins, cable specifications, signal timing, line impedance, and similar characteristics for the interconnected devices and frequency for the wireless devices.  The physical layer also defines the transmission mode as being simplex, half-duplex or full-duplex.  The network topologies are also defined in this layer including the network, bus, mesh, and ring topologies. It is the layer of the low-level networking equipment like the cabling, hubs, and repeaters.

Layer 2: The Data Link Layer

The second layer of the OSI model is the data link layer that offers node-to-node transfer of data -a communication link between the two directly connected devices or nodes. It can detect and even correct the errors that may accompany the bit streams coming from the physical layer. It is also the layer that defines the protocols required to create and terminate a connection between the physically connected devices. The protocols for flow control are also defined in the data link layer.  IEEE 802 has subdivided the data link layer into two, the media access control and the logical link control. The former sublayer is responsible for controlling the way devices should gain access to the medium on the network for permission to transmit data. The later sublayer is concerned with the identification of the network layer protocols as well as encapsulating them besides controlling the error checks and synchronization of frames.

Layer 3: Network Layer

Layer three of the OSI model, the network layer, offers an end-to-end logical addressing to allow packets of data to be routed to a number of layer two networks (such as Ethernet, Token Ring, and Frame Relay). To make the management of the network easier, and control the flow of packets, many companies separate their network layer logical addresses into smaller parts referred to as subnets (Simoneau, 2006). Routers to route traffic between various networks use the network or the subnet portions of the IP addressing of this layer.  The network layer is also responsible for diagnosing and reporting the logical variations that may be noted in the normal network operation. As the diagnosis is taking place, the system also communicates with the original sender of the packet that variations from the normal network operation have been noted.

Layer 4: The Transport Layer

The purpose of the fourth layer of the OSI model, the transport layer is to offer the functional as well as the procedural means of transferring data sequences from the sender to the receiver machine through one or more networks, as it also maintains the quality of services (Simoneau, 2006). This layer controls the reliability of links via flow control, segmentation or desegmentation, and error control. The transport layer can monitor the segments and retransmit the damaged or lost ones. This layer also offers the acknowledgment to signify that the data transmission was successful and sends the next data only when there are no errors identified. The transport layer creates packets from the message it receives from the application layer. The creation of packets is known as packetizing, which is the process of dividing the long messages to produce smaller and manageable messages.

Layer 5: The Session Layer

Layer five, the session layer, offers different services, such as tracking the number of bytes received by one end of the session from another. This layer allows applications on devices to establish, control, and terminate dialogs via a network. “The functions of the session layer also include creating virtual connections between entities, synchronizing the data, and creating dialog units. The others include connecting parameter negotiations, acknowledging the data received during a given session, partitioning services to functional groups, and retransmitting any data that has not been received by the device” (Goldman & Rawles, 2004).

Layer 6: The Presentation Layer

The function of the presentation layer is to establish the context between the application layer entities. This layer offers independence from the data representation by translating between the network and application formats. The layer changes the received data into the form that can be accepted by the application. It also formats and encrypts data before sending it across a network. The layer allows the applications to read and understand the message. Some other functions for this layer include the graphics formatting, system-specific translation, encrypting and decrypting the data for security purposes; and compressing and expanding the messages to enable it to travel efficiently (Day & Zimmermann, 1983).

Layer 7: The Application Layer

Layer seven of the OSI model, the application layer, provides the interface that allows the end user is operating a device to interact with the system. This is the layer that the user sees while loading an application (like a Web browser or e-mail); in other words, it is the data the user sees when using those applications (Wetteroth, 2001). The specific applications for the application layer include the identification of communication partners, the determination of resources’ availability, as well as the synchronization of communication.  When it is identifying communication partners, this layer has to determine the identity and availability of the partners for the application with the required data to be transmitted.

Conclusion

The seven OSI model’s layer has been examined in detail in this paper regarding their specific functions and how they work to accomplish the communication process between nodes on a network.  This model is useful in helping us to understand the way communication between devices on a network takes place. The most identified advantage of this model is that it organizes the thinking about corporate networks and gives novices and masters a computer networking language.

References

Day, J. D., & Zimmermann, H. (1983). The OSI reference model. Proceedings of the IEEE, 71(12), 1334-1340.

Goldman, J. E., & Rawles, P. T. (2004). Applied data communications: a business-oriented approach. Wiley.

Simoneau, P. (2006). The OSI Model: understanding the seven layers of computer networks. Expert Reference Series of White Papers, Global Knowledge.

Wetteroth, D. (2001). OSI reference model for telecommunications. McGraw-Hill Professional.

Yemini, Y. (1993). The OSI network management model. IEEE Communications Magazine, 31(5), 20-29.

Sherry Roberts is the author of this paper. A senior editor at MeldaResearch.Com in best custom research papers if you need a similar paper you can place your order from nursing paper writing service.