On Tue, 8 Aug 2000, John Wiltshire wrote:
> > Sure - 2 meg - SHARED_ access - and if you have, say, 20
> > people on each
> > cable segment - that 2 meg disappears pretty quickly.
>
> This is based on the somewhat false assumption that all people are using
> their full bandwidth all of the time. Given that the average ISP has at
I've got news for you - as more and more people get onto HFC systems,
they'll _all_ expect to be able to run streaming video all day, and
download gigabytes of music and files all day etc. It's already happening
now. Ask Optus. There's a guy at work here - he PC anywhere's his PC, from
work, to home, and STILL runs stuff all day.
> least 10 users per modem and at least 10 times the number of modems that
> their external bandwidth can handle I think 20 people sharing a cable
> segment (which can handle 33Mb) is a pretty fair amount. If it got up to
> about 100 I'd start to get a little worried.
33 mb is a bit of an exaggeration. Some of that bandwidth is reserved for
voice signalling. Some is reserved for TV signallnig. Only 2 meg _per
segment_ is reserved for data.
> > The difference between ADSL and HFC systems is that HFC system uses a
> > _shared_ carrier - it's more of a broadcast system - and ADSL is a
> > _direct_ connection - you get your 1.5 meg ALL the time - not
> > just when none of your neighbours are using the net as well as you.
>
> Except for the fact that all ADSL lines still come into an exchange and you
> get a shared medium there. If you are lucky then they have the bandwidth
And you think HFC systems are any different? Hell, even an E1 connection
to the net will bottleneck _somewhere_ - it's simply the lay of the land -
there is a balance between effectiveness and cost - with cost winning more
often than not.
> from the exchange to support the number of ADSL users they plug in. You
> have to assume they are running better than 100Mbps equipment in the
> exchange before they can exceed the capacity of HFC systems. The idea that
> ADSL gives you the bandwidth to yourself and cable doesn't is such a mind
> boggling oversimplification it's almost a delusion.
{laughter} Just how much trunking bandwidth do you think the average
telephone exchange has? Hint - 100 Mb/s is, except in the case of a tinpot
shed out the back of beyond {waves to Jon Biddel} is the very _bottom_ end
of the spectrum. Remember, once it hits the exchange in a digital network,
dedicated bandwidth for data is _not_ required, because it's all a packet
switched network anyway.
> Having been connected to BPA (cable) for a while now, I can say that the
> real bandwidth problems have been with the Big Pond Direct connection from
> Perth to the USA and never with the saturation of the local loop.
So you're lucky - you don't have many users in your local cable segment -
the same as I am with Optus. But I know people who are on _busy_ bigpuddle
cable segments - and the service is terrible. ADSL will make them much
happier.
> Occasionally there are problems with the local servers or with routing but
> I've never gotten less than my capped speed between my machine and the local
> router.
I repeat - you're lucky. Not everyone is so well off.
DaZZa - who'll still be going ADSL if Telstra makes it available in his
area.
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