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Running Head: THE SEVEN LAYER MODEL OF OSI Kao 1

THE SEVEN LAYER MODEL OF OSI Kao 2

The Seven Layer Model of OSI

Kao Badi Prudence

CMIT 265

Professor: Ryan Thomas

Date: 06/25/2020

The Seven Layer Model of OSI Comment by Prof Thomas: Paper format changes between sections. Review format

The Open System Interconnect (OSI) is a very important concept in networking when considering the creation of a a networking system for the university. “It was created by the international organization of standards 1978 and its main purpose is to help describe the architecture of a network so as make it possible for computers to send and receive data from other computers”. Although the model is conceptual, appreciating its purpose and function will help the university in understanding how the protocol suits and network architecture work on an application basis. The OSI model is usually built from bottom to top in this order; physical, data link, network, transport, session, presentation and lastly application. Every layer of the OSI model has its own special function. The following sections describe the function of each layer.

The layers of the OSI model

Physical Layer (Layer 1)

The OSI model layer identifies the networks’ physical characteristics and specifications. This is the type of media used on the network for example type of connector, cables, and pinout format cables.

Topology

The topography is defined by the physical layer. This layer shows the type of topology to be applied in the network. Additional characteristics in this layer define voltage used on a given frequency and medium at which the signals that carrying the data operates. They dictate speed and bandwidth of a given medium and the maximum distance over which a specific media type can be applied

Data link Layer (Layer 2)

The layer is a designed protocol that operates in a program involved in data movement into and out of a physical link in a network. Layer 2 of the OSI model is responsible for receiving data for layer 1. It is then sent to layer 3 and the data from layer 3 is sent to layer 1. This layer also detects and corrects errors. The word ‘frame’ is usually used to refer to the logical data grouping at this layer. It has two distinctive sub-layers:

· Access control (MAC) - MAC address is the physical/hardware address burnt into each network interface card (NIC). It accesses specific areas that are found within the interior of buildings. Provides access that is faster to the people authorized and restricts access of people not authorized.

· Link control (LLC) – “this controls the error and flows control mechanism of the data link layer [2].” It plays the role of managing the transmissions of data to ensure that there is integrity. For NLC, it has a role of providing data link layers.

· Network Layer (Layer 3).

The primary faction of layer 3 is to giving access to the ways by which information can disseminate to and from different network systems. It does not specify how the information is passed but rather gives the mechanism of doing so.  Comment by Prof Thomas: function

The responsibility of protocols in this layer is to ensure route selection which is to identify the best path the information should go all through the network. It uses software configured addresses and unique routing protocols to pass on to the network. Packet is a term usually used to explain the logical grouping of information at this layer. Large data transmissions TCP and UDP are used to transport data faster globally as the protocols ensure that there are no data packets lost.

Transport Layer

The most important function of layer 4 is to give the different ways for transporting data between network devises. It does so in the following ways.

· Checking: protocols at this layer ensure information is disseminated appropriately.

· Addressing: TCP/IP protocols support various network services. Layer 4 also ensures that the information is disseminated to the correct service at the upper layers of this model (Aggarwal et al, 2019). Comment by Prof Thomas: Incorrect in text citation

· It lower levels as the segmentation responsibility of layer 4 Comment by Prof Thomas: I am not sure what you are trying to say here

· At the transport layer: protocols operating at the transport layer can be connectionless or connection-oriented such as DCCP and frame relay.

· Control - data flow control is also another responsibility of the transport layer (data flow control refers to how the receiving device can take information transmissions). There are two common ways of flow control used; buffering: while using buffering flow control, information is temporarily stored while waiting for the final device to be made available. A problem can be caused by buffering if the sending device transmits the information rather fast while the receiving device is not ready to manage it; windowing: Data is transferred in groups of segments that need only one acceptance in a windowing environment. The window size can be explained as when the session in between two devices is established (the number of segments that fits into an acknowledgment). “Imagining there is a need of having only one acknowledgment for every segment there would be a great reduction in the overhead [3]”

Session Layer (Layer 5)

Managing and controlling the synchronization of information between applications of two devices is the responsibility of this layer. The function is accomplished by breaking, establishing and maintaining sessions. The transport layer’s responsibility is setting up and maintenance of connections between the two nodes. This layer does the same instead of the application.

Presentation Layer (Layer 6)

The most important function of this layer is transforming the information that is meant to be received from the application layer into another format as the applications don't need to read this conversion. Encryption which is the scrambling of data to make it not possible to be read and decryption which is making a data readable is also an important function of this layer. Most common data formats handled in this layer may include; 

· Files: These are files that need the data to be formatted in a certain way, like GIF, TIFF, and JPEG.

· Data: This layer also translates data into several formats such as EBCDIC and ASCII.

Video: These files also need to be converted in a different format, like MIDI, MPEG, and MP3. Comment by Prof Thomas: Missing bullet

Application Layer (Layer 7)

An easy way of defining the functions of this layer is taking requests and information from the users and passing it over to lower layers of the OSI model. Information coming in is transferred to the application layer which avails it to the users.

People confuse the application layer to be representing the applications being used on a system such as a word processor, spreadsheet and web browser but instead, this layer defines the process that enables applications to use the network services.

Conclusion

The OSI model is used in networking to show what and how the tasks are handled at each level. However, on a practical level, the view gets more complicated. Some of the devices protocol and applications can fit perfectly to form a single layer whereas the others function in many different layers and perform operations affecting each layer. The security of information in the form of encryption can be enclosed to the presentation layer, although the security of the network affects all the layers from the physical layer to the application layer. In the real world, the OSI model is more defined than other models. The OSI model can be used to visualize interactions of networks providing a conceptual framework for both designing better networks and troubleshooting existing networks in the future.

References

[1] Aggarwal N, Gupta R, Saxena P. Comparative Study of OSI & TCP/IP Reference Model. International Journal for Research in Applied Science & Engineering Technology (IJRASET). 2019. Retrieved from http://cloud.politala.ac.id/politala/1.%20Jurusan/Teknik%20Informatika/19.%20e-journal/Jurnal%20Internasional%20TI/International%20Journal%20For%20Research%20in%20Applied%20Science%20and%20Engineering%20Technology%20(IJRASET)/2014/Volume%202,%20Issue%20XI,%20November%202014/fileserve_12.pdf Comment by Prof Thomas: You can remove the hyperlink from the reference

[2] Howser, Gerry. "The OSI Seven Layer Model." In Computer Networks and the Internet, pp. 7-32. Springer, Cham, 2020. [3] E. Chou, Mastering Python networking: Advanced networking with Python, 2017. Retrieved from https://link.springer.com/chapter/10.1007/978-3-030-34496-2_2 Comment by Prof Thomas: Should be its own reference

[4] Singh, Harpreet. Implementing Cisco Networking Solutions: Configure, implement, and manage complex network designs. Packt Publishing Ltd, 2017. Retrieved from https://www.packtpub.com/virtualization-and-cloud/implementing-cisco-networking-solutions