A look into broadband, the internet of things and the rise of the “DSL heads.”
To define contention literally, it means “To compete in order to win something” – this being highly applicable to the data havoc we experience on a digital subscriber line (DSL). It is “DSL thinking” that has led us astray with understanding next generation broadband and the way networks are designed.
We also, before we define next generation broadband, need to define what broadband is. As part of its 2015 Broadband Progress Report, the Federal Communications Commission has voted to change the definition of broadband by raising the minimum download speeds needed from 4 Mbps to 25 Mbps, and the minimum upload speed from 1 Mbps to 3 Mbps, which effectively leaves the vast majority in South Africa without broadband. The fact that previously the ruling upload was set at 1 Mbps makes us understand that we never really had broadband at all. So based on this, next generation broadband is now just “broadband”.
So moving on let’s look at the perceived issues around contention with relation to high speed broadband. The “DSL heads” amongst us will tell you 1:1 is perfect, 1:10 is low and 1:50 is high. We are all screaming for uncontended services that we cannot afford and condemning any quality reasonably priced service with comments like “Well at that price they must be contending the crap out of it”. All the fellow DSL heads will nod in agreement like a suede dog on the rear shelf of a Ford Cortina.
We also love doing speed tests but in reality they do not show you much. The speed test is a snapshot of speeds at a particular point in time. Not only can a single speed test be unrepresentative of a connection’s average capacity, it cannot show some aspects of traffic management which mean that the end user will experience certain activities more slowly than others.
Let’s look at our DSL heads favourite order from the menu, the 4 Mbps line! At best it gets close to 4 Mbps down and 400 Kbps up, hardly impressive but the ISP’s are contending it at 50:1 (forgive me for the possible poetic licence there) so at any one time you could theoretically be sharing the line with 49 other people. If this was to happen the link would just flat-line. The ISP’s argue that the contention is justified as all users will not be using at the same time and it is an effective way to offer low cost packages. The contention is also amplified by the number of users within your home. Here is the maths;
We turn the 4 Mbps into Kbps
4 Mbps = 4 x 1024 Kbps = 4096 Kbps
So in a perfect world of 4096 Kbps download being given a good simultaneous pounding by eight people could only deliver 512 Kbps to each user!
The devil could have assistants
If the devil is contention I believe he taking the blame for the work of his accomplices as there are many other contributing factors that can affect line speed and we have to blame someone. These include physical distance from the exchange, attenuation, lack of twisted pair, corroded copper joints and electromagnetic interference. Adding to this the ISP’s are friends with the devil too by introducing shaping which will slow certain things down, P2P torrents being the favourite and throttling where everything is slowed down.
As the contention only comes into play when other users are online the speed of the line becomes its own worst enemy with regards to contention. On a 4Mbps line working well it can take in excess of 2 hours to download a HD movie as opposed to a few minutes on high speed fibre, so the chances of simultaneous movie downloads on a DSL is extremely high. The speed of fibre means the chances are considerably reduced due to the rapid download so translates into contention being a much smaller issue.
FTTX is our saviour
Fibre to the home and business has gained momentum and contention plays a much lesser part in network design than it did in the past due to the falling cost of international bandwidth capacity, high speed gigabit passive optical network (GPON ) design and a lack of “DSL heads” in the mix. So let’s look at how GPON actually works.
The diagram below shows how the optical line terminator (OLT) headend feeds into the optical network terminator (ONT)- the router as it were- within the client premises via fibre splitters.
It can be seen that the network download speed is 2,5 Gbps and upload 1,25 Gbps, this is monster capacity and allows us to offer symmetrical broadband packages to clients. Also note that the distance between the OLT and ONT can be 20km without affecting throughput so no distance issues plus all the other DSL copper issues mentioned earlier disappear. At the OLT headend a high speed “backbone” is installed that will deliver Layer3 broadband capacity to the GPON network via the ISP’s core network. This backbone can be anything from 100 Mbps to many Gbps and can be managed in a way that as demand increases the backbone capacity can be increased. So in simple terms it’s like having a large high pressure water pipe (the backbone) feeding much smaller pipes (your service) and you can all switch on the water without losing pressure (line speed). You are still on a contended service but not noticing any detrimental effect.
Fig. 1: GPON network.
Beware of the devil reincarnated
So having now a better understanding of why contention played a big part in the degradation of DSL due to its slow speed, high cost of capacity and the greed of the ISP’s over contending, beware! Greed is addictive behaviour that can run seamlessly through all technologies and organisations. Just because we can build networks that that can deliver a great end user experience does not mean that we will. I have seen many new FTTx offerings of recent that are nothing more than DSL thinking on fibre. The services are capped, what use is a 50 Gig cap on a 50 Mbps line? It reminds me of what we used to call in the old days a “one day internet pass”, with bundles being offered at around R8 per Gig so a 100 Gig top up is going to add R800 on your bill. Throttling and shaping is still prolific on some of the new fibre services and many do not offer symmetrical services, all in the name of bandwidth management but it is really just greed!
It is very important when comparing fibre services from different providers to compare apples with apples. What you are looking for is a truly uncapped service, with the growth of IPTV and 4 K streaming you are going to need it. As well as being uncapped it must be unshaped and not throttled. With the advent of cloud based services very much on the increase upload speed is becoming more important so we need symmetrical services. Don’t worry about contention it is not an indicator of service,what you are interested in is deliverable symmetricspeed. Another factor to be considered is that you don’t want to be tied into long term contracts. Who knows what the price of fibre will be in a year’s time never mind two, only one certainty it will be cheaper than today.
So next when a “DSL head” asks you what the contention ratio on your service is, tell them “Don’t worry, I’ve gone to fibre and have truly seen the light” and check to see if he nods like the dog.
Contact Paul Colmer, Greencom, Tel 087 160-0106, paul@greencom.co.za
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