[ NNSquad ] Re: BT [UK] calls for action on net speeds

[Richard Clayton <richard@highwayman.com>]

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In message <47D95D36.7090107@acb.net>, Andrew Burnette <acb@acb.net>
writes

>Interesting article, as I know BT peers at linx with numerous folks. I 
>would like to hear more about the test criteria.

This is about the "ADSL Max" system in the UK, which runs at 8Mb/s if
you are within 100m of the exchange and a lot slower if you are further
away!  However, the ISPs put "up to 8Mb/s" into the adverts and a lot of
people end up disappointed.

This is compounded by the adaptive nature of the system -- which
regularly tries to change to faster speeds then falls back as errors
occur; which means that the speed tends to be different at different
times of day.

It also means that houses with poorly installed phone systems and lots
of extensions get worse speeds than their neighbours. Changing where the
micro-filters were in my house got me a 25% speed hike!

There are further issues as to what IP throughput you actually get,
which is a lot to do with congestion between the DSLAM and the BT Home
Gateway (this is an ATM cloud). This means that speeds at busy times of
day differ -- or (as Brett might want me to mention) it can be impacted
if lots of your neighbours are keen on downloading feature films from
BitTorrent networks...

Finally there's issues relating to whether the ISP bought enough
bandwidth between BT's system and their own, and then there's the
quality of their peering and transit arrangements with the rest of the
Internet.

Add in tuning of the end user systems, as Andrew explained in great
detail in his message, then you have a very complex system where it is
hard to understand what is slowing down your particular connection and
it is hard to tell whether buying your service from a different ISP
(with some other advertising slogan) will make any difference.

Note especially that there MAY be a choice between a cable TV provider
and copper to the telephone exchange. There MAY be a choice at the
exchange between providers. However, it is often the case that the only
place competition occurs is in choosing who BT hands off the IP traffic
to, and if you go to a new ISP you get the same miles of copper (low
speed) and the same ATM cloud (congestion) and so there's not much scope
for differences to occur.

>> The firm said regulators needed to agree rules about how broadband
>> speeds could be sold to the public."

This is all about truth in advertising, not a lot about net neutrality

- -- 
Dr Richard Clayton                       <richard.clayton @ cl.cam.ac.uk>
                    Computer Laboratory, University of Cambridge, CB3 0FD

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