The phrase “contention ratio” gets thrown around quite a bit in the context of internet connectivity, but what does it actually mean?
This is similar to our roads where there isn’t a dedicated lane on the highway for each and every person that needs to commute to and from work every day! Your own driveway is probably the only point where you can claim that it’s only you that’s allowed to drive there.
Once you’re on the road, at least your neighbors share your street with you, but as you drive you move towards roads that carry more and more vehicles, many more, and yet the number of lanes does not increase in proportion to the increase in number of vehicles!
Single lane in your street, maybe two lanes in a main connecting road, and three or four lanes in city centers where we now also have to content with one-way streets! At this stage we still typically drive 60km/h and have to stop and go quite a bit (especially when the dreaded load shredder strikes). When we move onto high ways we get to drive at 120km/h (assuming that there is no congestion).
As you may have guessed by now, the Internet works in a similar manner, with networks of links of varying capacity (speed). Close to your home you have a dedicated cable or fibre coming into your house. This link in many cases (GPON being the norm) is shared between multiple users (neighbors in the street).
In a similar way to streets, the closer you get to certain areas or links the higher the capacity gets, but the more people use that capacity. A highway often sees more congestion than a suburban road, even though plenty cars travel over it every day in comparison. A highway in South Africa varies in the number of lanes, similar to the Internet, where higher capacity links are installed in areas of more demand.
In spite of all of this, the capacity on the Internet is not infinite, and both the Fibre Network Operator (FNO) and Internet Service Provider (ISP) have to balance costs of expensive links to usability for customers. This is a large factor in pricing that FNOs charge towards ISPs, as well as a factor into the pricing of ISPs towards customers. Cheaper is not always better.
In the same manner as roads have a fixed capacity irrespective of the current usage, Internet links also have a fixed capacity. It doesn’t make financial sense for ISPs to build a dedicated lane on the highway for each and every user that it has since users tend to use capacity at different times. We do still have peak consumption times, at this stage typically between 18:00 and 23:00.
It is during this time that Interexcel World Connection aims to maintain a usage capacity of no more than 80% of all links, meaning that as soon as a road inside our network reaches 80% peak usage we start the process of upgrading the road to a bigger one in order to maintain the best possible service to our customers.
As a rule we express contention ratio as a mathematical fraction of the absolute maximum possible demand divided by the available capacity on the network. Assuming that an ISP has sold total capacity of 100Gbps to all customers and has a total available capacity of 10Gbps, this equates to a contention ratio of 10:1 (100 divided by 10 gives us 10 which is the figure in front of the colon).
As networks grow more and more complicated, it becomes harder and harder to calculate an overall contention ratio. The potential contention on each and every link could be very different (imagine all the highway users in Gauteng deciding to exit the highway towards Mall of Africa at the same time – the highway might be capable, but the roads leading to Mall of Africa will not!). For this reason most ISPs don’t publish contention ratios. Whilst easier to calculate for FNOs they don’t publish this information, or even provide it to ISPs.
We hope that the above information has helped you to understand contention and the internet a bit better!