A Layperson’s guide to the NBN in Regional Towns and Cities
Why this post?
Now that the implementation of the NBN is well underway in Albury-Wodonga, I have been asked about the NBN and what it means by so many friends, that I thought I might take the time to layout some of the realities of its implementation in the local area.
What I say below is a gross simplification and uses terminologies like node, backhaul and exchange, the use of which would horrify most modern network practitioners. It is sure to be picked to pieces on specific details and terminology but I am confident that the explanation that follows reasonably models the situation.
What you gets depends on where you live!
The reality is that the implementation of the NBN in regional towns and cities varies depending on your specific geographic location. For the purposes of this explanation of the NBN they can be thought of as:
- · Residences in established residential areas within a city or town,
- · Residences in relatively new residential estates;
- · Residences and businesses in areas surrounding significate cities and towns; and
- · Remote residences and businesses
While the implementation of the NBN differs in all of these different areas they do share a large number of similar characteristics. Even though this is an attempt to address the questions raised by friends in established residential areas in Albury-Wodonga, I will make some comments on the connections for people leaving in other residential situations at the end of this post.
The NBN in established areas of Regional Towns
What is the NBN?
As far as regional towns and cities are concerned, the NBN can be thought of as a reworking of the connections between our houses/premises and the local central exchange – the NBN is not the internet - it is simply a way of getting from our house to a point from which an internet provider can provide us with internet access.
The provision of the Internet and telephone services for the last 15 years or so!
In the past, pieces of copper wire ran from our house all the way to the local exchange albeit through many twisted wire connections of variable quality. We were able to get BOTH telephone and internet access over this copper wire.
While the telephone was provided in the same way it had been for 80 years, the internet was provided by a technology called ADSL. This superseded the old dial up modems which we will all remember effectively took over our telephone lines as they squeaked and squawked and chattered away to a modem at our service provider’s premises. The advantages of ADSL over the old dial up modems were that firstly we could use the internet and the telephone at the same time and secondly that they were capable of much higher speeds.
The Internet through an ADSL Connection
An ADSL connection involved placing one modem in the home and one in the exchange – there was one modem in the exchange for every modem in a house and the connection between them was dedicated to that house. The modem in the exchange was owned by which ever ADSL service provider we had selected and that service provider ensued the modem at the exchange was connected to the service provider’s own network and eventually to the internet.
There were at least three problems with the ADSL service. Firstly it normally shared the same piece of copper with the telephone service, secondly its speed deteriorated very rapidly as the length of copper wire increased – in other words the further you were away from the exchange and the older your copper wire the worse your service would be. Thirdly the capacity of ADSL over copper wires was starting to limit the internet services that could be provided to the home.
So what was the NBN going to do for us?
The original and grand scheme for the NBN (for which I was a passionate advocate) would have seen all of the copper replaced with fibre so that the problems of aging copper wires, distance from the exchange and capacity would have be largely eliminated. Costly? - Certainly! – Essential national infrastructure refurbishment? – Certainly!
The plan was for the NBN was to provide a local central point for connectivity in an area (much like the old Telstra exchanges). These central points would house connection points for all of the service providers that wanted to sell internet connectivity to people in that general area. It would be where the NBN would hand-over any traffic on their network to the respective service providers. This central point would be the boundary of the NBN network in the local area.
The NBN then planned to run fibre from this central point to multiple points in the town with one in each neighbourhood – these points I have called nodes – my guess (and it is only a guess) is that there might be 10 to 20 of these in central Albury.
Importantly, the original proposal would have seen fibre running from each of these neighbourhood nodes to each house where the fibre would be connected to a fibre-optic modem. This would mean that there would be no use of copper and the traffic from the premises to the internet would occur entirely as pulses of light rather than as electrical currents. The presence of fibre from the node to the premises is described as a “Fibre to the Premises”
What do we now have in the existing residential parts of Albury?
What has been delivered to established areas in Albury is that rather than installing fibre from the neighbourhood node to each premises a decision has been made to use a different technology capable of utilising the existing copper wires. In other words there is no fibre from the premises to the node.
This technology, called VDSL, has been substituted for the old ADSL – the old ADSL modems in the home have been changed to VDSL modems – the old ADSL modems in the exchange have been changed to ADSL modems located in so called nodes (green boxes in the street) (one outside the old university site in Olive Street), the copper wire running from the home to the exchange has been rerouted to go to one of these nodes and new fibre has been installed from each node to the central exchange. It is at this exchange point that NBN ends and any traffic becomes the responsibility of the service provider. This approach is known as “Fibre to the Node”.
So what is really new?
- Rather than speeds over the existing copper being limited because the voice and data was kept separate everything is now carried as data. I.e. the voice traffic is turned into conventional internet traffic – this allows the use of VDSL modems and allows the achievement of higher speeds. It does not take away the existing telephone service – it simply requires the old telephone handset to be plugged into the new VDSL modem.
- Rather than Telstra owing the copper to our homes it is now owned by the NBN – we therefore don’t have to pay Telstra a telephone line rental just to get an internet service.
- The NBN makes its network from the home to the exchange available to all providers at standard prices. Exactly what that cost is depends on what the service provider orders from the NBN.
- All providers pay the same amount for their connections over the NBN from your house to a NBN node point in Albury. The NBN charges them a different amount depending on whether you have ordered a 25, 50 or 100 Mbps service over the NBN. In addition the NBN charges the service provider for a circuit to carry their traffic from the street node to the exchange.
What is not new?
- The new VDSL technology is essentially the next generation of ADSL and is not something startling
- Capacity of a connection still depends on the length of the copper wire – most homes will be connected by shorter lengths of copper but not ALL.
- The service provider is still entirely responsible for getting your traffic from the exchange into its network and on to the internet.
Reliability?
What I find distressing about this VDSL implementation known as “Fibre to the node” is that it has moved the rather fragile modem technology out of the controlled environment of a central exchange into street cabinets subject to all sorts of potential damage – I am certainly no expert in this particular area but it seems to me that the number of potential points of failure have been dramatically increased – I do worry about overall reliability of the system compared to what could have been achieved through a fibre to the premises approach
Service Quality?
The simple assumption is that if you order a 100Mbps NBN service then you will get download speeds of 100 Mbps. This is not the case for three reasons:
- Firstly it is possible that your copper connections from your house to the street node will not deliver that speed,
In addition to basic service charges based on capacity, the NBN charges the service provider for a circuit to carry their traffic from the street node to the exchange. The cost of this circuit varies with its capacity so it is possible (perhaps even probable) that a service provider will not buy sufficient capacity on this circuit to ensure a full service to each of its customers. In other words even though you have ordered a 100Mbps service it may have already been degraded even before it leaves the NBN network.
- And thirdly, your provider may not have brought enough capacity between the exchange and their internet connection point
Even if you have ordered a 100 Mbps service and it emerges unscathed from the vagaries of the copper within the NBN and circuit restrictions between the street node and exchange, then it is then necessary for the provider to take your data to internet access points which at the moment are probably in Sydney or Melbourne – this is called “backhaul” and is the responsibility of the service provider and not the NBN itself ... ie. Telstra, Optus, TPG, Dodo, iiNet etc.
A reasonable but false assumption would be that when you have ordered a 100 Mbps service then the provider will ensure that they are able to provide 100 Mbps of capacity dedicated to your specific traffic on that backhaul circuit. This is rarely if ever true because:
· The backhaul is carried over circuits on fibre optic cables that make their way across the country – the reality is that there are very few of these cables even though the absolute capacity of each is enormous – essentially it is primarily Telstra, Optus and a company called NextGen that own physical cables capable of carrying the backhaul. This leaves Telstra and Optus in a very strong position since they already own these cables but it does require other providers like TPG, iiNet etc. to buy capacity on these cables in order to provide you with an internet connection.
· The costs of individual circuits on these backhaul cable is very high and is dependent on the capacity (or bandwidth) of the circuit that the provider buys from the backhaul company. Backhaul circuit providers usually only provide circuits with specific capacities. E.g. 100 Mbps, 1 Gbps, 10 Gbps, 100 Gbps etc. – i.e circuits capacities come in lumps of 10.
· Because it is the cost of backhaul that is the primary cost variable available to the provider, of course they look for every conceivable way of reducing the amount of backhaul capacity (bandwidth) they need to buy off the backhaul provider. The simplest way they can do this is to implement what is known as contention ratios.
What is a contention ratio?
In essence providers argue that not everyone of their customers will be using the NBN at any one time so that if they have 100 customers each with a 100 Mbps service then they don’t need a full 10 Gbps circuit – they can get away with very, very much less. ALL providers (Optus and Telstra included) implement contention ratios particularly on their back haul circuits. Their decision on an acceptable contention ratio is primarily dependent on the service quality their customers are prepared to accept – planned contention ratios of 100 to 200 are probably not unusual – in other words a provider with 100 customers each ordering 100Mbps NBN service will only purchase between a 50 and a 100 Mbps service rather than a full 1 Gbps.
When an NBN area opens up the various service providers buy sufficient backhaul service capacity to provide their initial services – I suspect the reality is that very few of them would buy less than 1Gps of initial capacity. So they could have at least 10 full 100 Mbps customers connected before any one of them saw any contention at all so their first 10 customers would report fantastic service – after that the quality would deteriorate with every new customer until such time as the complaints became too much for the service provider to tolerate at which time they buy more backhaul capacity.
What is the effect of contention ratios?
The effect of the contention ratio issue in Albury is that as more and more of the town becomes connected and the service providers get more and more customers their contention ratios will increase and the average service quality will deteriorate until a critical contention ratio for each provider is reached. They will suddenly buy more capacity on the backhaul and temporarily at least the performance of their service with improve.
Particularly for the smaller lower priced NBN providers like Dodo and others of that ilk, this can mean that while their customer numbers are low their service quality is exceptional and their reputation skyrockets - this reputation will rapidly fall away as the number of customers increases since their business model is primarily based on running higher contention ratios.
Choosing an ISP in an established residential area.
In making a decision on a service provider for the NBN, I think you can probably think along the following lines:
- The higher the speed of the service you order the more likely you are to get an acceptable service;
- The higher the price charged by the particular provider the higher the average performance will be.
- Performance of any connection you get will deteriorate overtime until service quality complaints force the provider into action
This means that something like a 50Mbps service from a tier one provider like Telstra or Optus is likely to cause less grief than 100Mbps service from a low cost tier 3 provider like Dodo.
Comments on other residential areas
The services to all types of residential areas varies only in way in which services are provided from the node to the premises and to some extent how the nodes themselves are distributed. Essentially the service from the node to the internet is the same for all areas and involves all the same issues of contention ratio adopted by the various ISP’s.
In the case of new residential areas I understand that the original vision for the NBN remains with fibre running to the premises. For rural areas adjacent to towns and cities the connection between the premises and the node is achieved using wireless technologies while remote residences can utilise the NBN satellite link to connect between their premises and the satellite node.
Mike Rebbechi
January 2017
