The Seven Levels of The OSI Model (APA Paper)

Introduction

OSI model, an abbreviation for Open System Interconnection model, is a conceptual network architecture made up of protocols that govern how different systems communicate over a network irrespective of their underlying architecture (Forouzan & Fegan, 2007). This model is made up of seven related layers that play a part in transmitting information over a network. Below are the functions, purposes and hardware requirements of the seven layers of the OSI model.

The seven levels of the OSI Model are as follows:

Layer 7: Application Layer

According to White (2016), is the top most layer that houses application programs using the network. When two applications are communicating over the network, this layer identifies and ensures that the opposite party can be reached, certifies the recovery processes, and data integrity agreed upon by both ends. It also confirms the availability of such communication resources as modems and authenticates the communicating parties (Rouse, 2006).

Layer 6: Presentation Layer

This layer is concerned with ensuring that data being sent is formatted to a syntax that the receiving system can understand (Forouzan & Fegan, 2007). This layer translates data from machine independent encoding format to bit stream formats like ASCII and binary before sending them. On the receiving end, the presentation layer translates the bit streams to a data format independent to the receiving system. The layer also encrypts and compresses data to increase security while transmitting and reduce the size of data respectively.

Layer 5: Session Layer

The session layer, as the name suggests, is a dialog or session controller. White (2016) argues that this layer starts and maintains communication between network systems. It uses token management to harmonize the interaction between the communicating systems. Token management uses software tokens that are sent back and forth to help the session layer decide who should send and who should receive data first. Lastly, this layer creates error and failure recovery points known as synchronization points. This points allow communicating systems to resume the transmission of data by moving back to an older synchronization point during a transmission failure.

Layer 4: Transport Layer

The Transport Layer is accountable for consistent data transmission. This layer ensures that data segments reaching the receiver are identical to the packets that left the sender. Transport layer of the sender splits data into small packets or segments while the transport layer of the receiver recombines the segments to data that is identical to what was sent (Butler et al., 2007). Application Switches, Proxy Servers, Content Filtering Firewalls, Gateways and Hardware Firewalls are some of the hardware devices that reside in this layer.

Layer 3: Network Layer

This layer handles the transfer of data from the sender to the receiver across different network links. It offers paths through which data follows to reach the destination. The network layer generates the essential network addressing that determines the route to the target receiver (Anttalainen, 2003). It handles communication among devices within and outside a network. This layer requires the following hardware devices: Switches, Firewalls, Routers and Gateways.

Layer 2: Data Link Layer

The Data Link Layer converts the physical layer’s bits into error-free frames. Its main functions are: segmentation and reassembly of packets from the upper layers, physical addressing, bit ordering, and flow control, error control and access control (InetDaemon, 2014). Some of the hardware devices needed for by this layer include: Bridges, Network Interface Controllers (NICs), Wireless Application Protocols (WAPs), Switches and Modems.

Layer 1: The Physical Layer

This Layer’s main concern is the transmission of a bit streams across a physical channel. White (2016) maintains that this layer handles the electrical and mechanical configurations such as voltage levels and pin, plugs, and connector structures and sizes. Since data is converted to either digital or analog form before transmission, the physical layer defines the conversion method used. According to Dean (2010), the physical layer, on the receiving end senses and receives signals which are then directed to the data link layer while on the sending end it sets the sending speed and measures the rate of data errors. The physical layer uses the following hardware: Hubs, Modems, WAPs, NICs, Repeaters and interfaces for Local Area Network (LAN) and Wide Area Network (WAN).

Conclusion

The OSI model expresses a networking outline that implements communication protocols in seven layers. Below is a summary of functions, purposes and hardware requirements of the seven layers. The application layer houses application programs and permits them to use the network resources. The presentation layer’s main functions are translation of data from machine independent formats to bit streams formats like ASCII, encryption, and decryption and data compression. The session layer starts, manages and maintain or terminate communication between network systems. The transport layer ensures message identical to what was sent reaches the receiving end and recovers from data transmission errors using synchronization points. The network layer transports data packets from the sender to the receiver across different network links. The data link layer converts the physical layer’s bits into error-free frames and offer point-to-point delivery. Finally, the physical layer defines the electrical and mechanical configurations and also conveys bit streams across a physical channel.

References

Anttalainen, T. (2003). Introduction to telecommunications network engineering. 2nd ed. Norwood, MA: Artech House, p. 252-260.

Butler, C., Rogers, R., Ferratt, M., Miles, G., Fuller, E., Hurley, C., Cameron, R. and Kirouac, B. (2007). IT Security Interviews Exposed: Secrets to Landing Your Next Information Security Job. Indianapolis, IN: John Wiley & Sons, p. 24-25.

Dean, T. (2010). Network+ Guide to Networks. 4th ed. Boston, MA: Cengage Course Technology, p.54.

Forouzan, B. A., & Fegan, S. C. (2007). Data communications and networking. 4^th ed. New York: McGraw-Hill Higher Education, p. 29-45.

Inetdaemon. (2014). The OSI Model – Data Link Layer. Retrieved from http://www.inetdaemon.com/tutorials/basic_concepts/network_models/osi_model/data_link.shtml

Rouse, M. (2006, August). Application layer. Retrieved from http://searchnetworking.techtarget.com/definition/Application-layer.

White, C. M. (2016). Data communications & computer networks: a business users approach. 8^th ed. Boston, MA: Cengage Learning., p.18-20.

Further Reading

The OSI Model Explained

Cryptography: Quantum Key Distribution (QKD)