Contention ratio and your internet connection

The dial-up connection of the 1990s is something a member of Generation Z knows as little about as a cassette player or a VCR. The characteristic noise that is associated with a dial-up connection is actually the sound of two modems “speaking” to each other to establish a connection to the internet using a telephone line.


Dial-up soon gave way to ADSL (Asymmetric Digital Subscriber Lines), still utilising a telephone line, but with much faster connection speeds. Since being introduced to the South African internet landscape with the Parkhurst fibre project in 2014, fibre is quickly becoming one of the most popular ways to connect to the web.

What is the difference between ADSL and fibre?

While there is still some link between a traditional dial-up connection and an ADSL connection due to both requiring the copper cabling of a telephone line to connect to the internet, fibre has broken away from that mould in a significant way by using glass cables that allow for much faster data transfer speeds. Fibre is also not as susceptible to theft and weather as traditional copper cables, and it is gaining ground thanks to competitive pricing and greater accessibility to more people. One other thing sets fibre apart from ADSL connections: its contention ratio.

What is contention ratio?

If you’ve ever read about internet speeds, you may have come across the term “contention ratio”. Contention ratio refers to the amount of users sharing the same data capacity. In other words, it refers to the number of people who have to contend with each other in terms of bandwidth. When it comes to contention ratio, lower is better.

If you feel like the previous paragraph was just tech jargon that you do not understand, let us explain some more.

Think of your internet connection as a highway. At any given time, you are not the only “driver” on the highway, as you have to share it with other “road users”. When there are more users, traffic gets progressively more congested, leading to an overall slower speed for each individual “driver”. If you leave work during times of peak traffic, it’ll take you longer to get home – as anyone that uses the N1 in Johannesburg to commute will confirm. Leaving when traffic is not at its peak will allow you to travel home at higher speed, simply because the road is open and there are less people that you have to share the limited amount of lanes with.

Contention ratio works on the same principle. A greater amount of users means that the contention ratio for users that are on the same data capacity is higher, leading to slower connection speeds. A smaller amount of users means that the contention ratio is lower and that connection speeds are, consequently, higher. But what does all of this have to do with fibre?

Fibre, ADSL and contention ratio

The copper cables that are used to establish ADSL connections were not intended to transfer data in the way they are doing now. Copper cables were originally designed for voice transmission, and have a limited bandwidth. Although we, thankfully, do not have to contend with the ridiculously low connection speeds that came with a dial-up connection, there is no way to increase the bandwidth capacity of copper cables. Copper allows for a limited amount of “lanes”.

Fibre, on the other hand, is made of either glass, polymers (plastic optical fibres, or POF), or a combination of glass and polymers. These materials lend themselves to much greater bandwidth capacity than traditional copper cables. Greater bandwidth means that more data (or “drivers”) can be carried at higher speed.

Fibre is exponentially faster than ADSL because of its greater bandwidth and lower contention ratio, making fibre the connection of choice for internet users. Although took some time to become available in certain areas, the infrastructure is gradually being upgraded to support fibre connections all over the country. As it becomes easier to access, and more users sign up for a fibre connection, the price of fibre is also gradually coming down.

For more information about fibre from Smartcom, please drop us a line.

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