Access methods

Access methods

In this blog I will be explaining the different access methods. The ones I will be explaining is CSMA/CD, CSMA/CA and token passing. I will use diagrams to make it easier to understand what I am saying.

CSMA/CD

CSMA/CD stands for Carrier Sense Multiple Access / Collision Detection. This is a set of rules that control how network devices respond when two devices try to use the same line at the same. This creates a collision with the data. An example that uses CSMA/CD would be an Ethernet network. This checks the line if it is clear and then it will send the data. Figure one is a simple diagram on how it detects activity before it sends off. As you can see it also checks if there was a collision as well as if there is activity

An example of how CSMA/CD works

CSMA/CA

CSMA/CA stands for Carrier Sense Multiple Access / Collision Avoidance. This is like CSMA/CD but it works differently. CSMA/CA normally works before CSMA/CD to avoid the most data collisions.

Token passing

Token passing is a way of granting permission to a device to send data over a network. Token passing uses a token to allow access to the network. Only one device at a time can send data. Once the device is finished with the network, it passes onto the next device. This goes around till all of the devices have used it.

References

Webopedia (2015) CSMA/CD definition [Online] Accessed at: http://www.webopedia.com/TERM/C/CSMA_CD.html [Accessed on: 25/01/15]

Webopedia (2015) CSMA/CA definition [Online] Accessed at: http://www.webopedia.com/TERM/C/CSMA_CA.html [Accessed on: 25/01/15]

Webopedia (2015) CSMA/CD definition [Online] Accessed at: http://www.webopedia.com/TERM/T/token_passing.html[Accessed on: 25/01/15]

Images

Figure one: BlogSpot (2015) CSMA/CD diagram [Online] Accessed at:  https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCg-npPmuAI9Rvna0RZraABQvxo7h0cm9T0iTuePHPoDUc7VFoqH6IYkTl4rJsb6q36FfZk5U0y1yWiFRu47BEJQK054eTwnhllqmIEb4aXwE9fuPW67j1-TODTGj865iJusBTvZkohBc/s1600/CSMA-CD+Process.docx.png [Accessed on: 25/01/15]