Communication models and protocols

Communications models and protocols

In this blog post I will be explaining the different communications models and the protocols. For the models I will be explaining the OSI (Open System Interconnect) model and the TCP/IP model. The protocols I will be covering are Wi-Fi, Bluetooth, 3G and 4G and the Wireless Security Protocols (WEP, WPA).

OSI model

The OSI model stands for (Open System Interconnect). The OSI model is made up with seven different layers that I will be explaining. The model is for how applications can communicate over a network. Down below is a simple description of all of the seven layers.  

Layer one: Physical

The first layer is where the hardware for the system is. This allows the devices to send and receive data on cables. This layer transfers the bit stream via the cables that I mentioned.

Layer two: Data link

The second layer is where the packets of data are encoded and decoded into bits of data. The data is split into sub layers. These are the MAC (Media Access Control) and Logical Link Control (LLC). The MAC sub layer controls how a computer gets access to the data and gets permission to send it.

Layer three: Network

The third layer is where routing and switching happens. This allows data to be sent from node to node.

Layer four: Transport

The fourth layer provides the transfer of data between the different systems. It also ensures that the data transfer was complete without any errors.

Layer five: Session

The fifth layer is where connections are created, managed and terminated between applications.

Layer six: Presentation

The sixth layer is for organising data into a format that can be used. Some examples of formats that can be used would be JPG (Joint Photographic Engineers Group), MP3 (Multimedia Players Engineers Group) or doc (word documents).

Layer seven: Application

The final layer is used by applications. An example of some of these applications would be email or web browsers. This layer has many protocols linked to all of the different applications.

TCP/IP model

The TCP / IP model stands for Transmission Control Protocol / Internet Protocol. It is like the OSI model as they both use layers for tasks. The development of the Internet was based on this model so it is quite well known. The TCP/IP model is made up of four layers that I will explain below.

Layer four: Application layer

This layer is like the application layer for the OSI model. It includes the processes that involve user interaction. This layer also determines the presentation of the data.  

Layer three: Transport layer

There are two different transport layers for this layer. They are TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). TCP guarantees that information is received after it had been sent. UDP does not do any checks if the information has been sent.

Layer two: Internet layer

The internet layer is the TCP/IP network layer. All of the upper and lower layers go through the IP as they are passed through the model.

Layer one: Data flow / Network access layer

This layer is the data link layer and the physical layer. In TCP/IP these are normally grouped together. TCP/IP uses existing data links and physical layers because it allows it to be adaptable and so it can work across many systems.

Protocols

Wi-Fi

Wi-Fi is a popular wireless technology that allows you to connect devices to the internet at high speeds. Wi-Fi uses radio waves to allow devices to connect to the internet. It also uses IEEE 802.11 (Institute of Electrical and Electronics). IEEE 802.11 has four different types. They are 802.11n, 802.11a, 802.11b and 802.11g and they all operate at a different frequency and speed.

Bluetooth

Bluetooth is a short range radio technology and it is aimed at making communications between internet devices simpler. It is available in many devices and it uses a range of frequencies and techniques.

3G & 4G

 3G stands for third generation. It is used in mobile technologies and it uses high frequency radio waves. It allows you to connect to the internet wirelessly without wireless. 4G is the same as 3G however it is a lot faster than 3G. 4G is not around a lot at the moment as it is quite a new technology.

Wireless Security Protocols (WEP)

WEP stands for Wired Equivalent Privacy. One of the issues with wireless networks is that security can be pretty poor. WEP keeps the wireless secure by encrypting every packet of data that has been sent.

References

Anderson, K. Atkinson-Beaumont, D.Kaye, A. Lawson, J. McGill, R. Phillips, J and Richardson, D., 2011. Information Technology Level 3 Book 2 BTEC National. Harlow: Pearson Education Limited.

Webopedia (2015) OSI Layers [Online] Available at: http://www.webopedia.com/quick_ref/OSI_Layers.asp [Accessed on: 26/01/15]

Webopedia (2015) Bluetooth definition [Online] Available at: http://www.webopedia.com/TERM/B/bluetooth.html [Accessed on: 26/01/15]