|Exterminate the orc?|
The crux of his point is that the very definition of a broadband service is that it is rate adaptive and so it is a service that will try and get the best performance on the voice grade copper pair to which it is attached. It is possible for the characteristics of a voice grade copper pair to be so bad (very long line) that it cannot even do broadband, and that would be tough. That basically the performance of the broadband line is kind of whatever it is. Indeed, a comment on my previous post about TalkTalk was raising this very point.
He has a very good point, and it has allowed me to hone the arguments I can use against such points with the likes of BT and TalkTalk.
Yes, the broadband is what it is, "as well as it can do" on the voice grade copper pair to which it is attached. We do accept that to some extent. There are caveats - in that the copper pair will have a forecast speed, and if the line is way out of that, then that probably means something is wrong. But in general, you get what you get. However, this relates to the rate of the broadband, as it is rate adaptive.
I would argue that there is a huge difference between a line that is a low rate on a line because it is all the line can do, even if that means the rate has reduced a bit over time due to increases in cross talk from other lines and so on, and an actual fault.
The issue comes down to how you define a fault in the broadband. This is different to how you define a fault in the voice grade copper pair.
One of the key aspects in defining a fault - perhaps the key aspect - is that a fault can be fixed. It is a condition that is the result of some aspect of the copper pair which is not as good as it could be giving the length and routing of the pair. Faults could be down to poor joints, corrosion, water ingress, poor insulation, electrical contacts, degraded materials. It could be fixed by using a different pair, or repairing joints or equipment.
So how do you spot a fault? Well, BT plc t/a BT Wholesale actually defined one way of doing this. They monitor the line in the first 10 days and find the maximum stable rate for the line, and set a fault threshold rate (FTR) for the line based on that (with a percentage taken off). This defines a sync speed below which the line is considered to have a broadband fault. That is excellent as it gives a crystal clear metric which we can all agree defines a fault. TalkTalk don't do this, but it would not be hard for us to do the same based on sync speed history and agree a metric with them.
Another way to measure a fault would be to consider that the line loses sync lots of times. To be honest, once a day is too often. Normal lines stay in sync indefinitely and would only lose sync do to some external interference, or a power blip or some such. So frequent loss of sync should be a fault. Bear in mind, even a long and highly lossy line should stay in sync, albeit at a slower speed.
We also have metrics in terms of packet loss. Whilst we measure latency, that is not normally a clue to any sort of line/sync issue and more likely to be backhaul congestion (or a router moving enough traffic to build up a queue). I think packet loss (when no traffic) is a really good indicator of a fault. Also, if the line has any internal metrics (OAM frames, Header errors, FEC errors) that is an indication of a fault.
Indeed, the DSLAM can almost certainly report if there are lots of bit swaps, problem frequency bins, FEC errors, HEC or other error stats that indicate a fault, as opposed to simply being a poor/long line.
Unfortunately, neither BT nor TalkTalk define metrics for packet loss, or line errors or re-syncs as a fault metric. I think they should.
Fortunately, when there is a fault, the levels are pretty clear cut. It is rare for a line to have a "tiny bit of loss", though not impossible.
In practice, the fact that the broadband has a fault of some sort, based on our monitoring, or the DSLAM stats, is not itself usually the issue. Usually we can agree that there is an issue with the broadband. We can also usually agree that the copper pair meets the voice spec, when it does.
One of the key things that tells us we have a fault is when a line that used to just work fine (at whatever speed it had) now has problems which it did not have before by any of those metrics. That suggests it can be fixed and made to be back the way it used to be by some means. We know what is possible at that point.
I think we just need to pin down ground rules with providers for what is and is not a broadband fault, and pin down that they are responsible for broadband faults, not us.
So let's start the discussions with them, and try to make things better. Well done TalkTalk for being the ones wanting to talk at this stage. Well, either that or we send round the exterminator!
|Did not fit through the door|