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  From: Alan Kennington <akenning@topology.org>
  To  : LinuxSA <linuxsa@linuxsa.org.au>
  Date: Mon, 11 Jun 2001 14:09:54 +0930

Re: [OT] Telstra ADSL 'Unlimited' Introduces Download Limit

On Mon, Jun 11, 2001 at 07:59:06AM +0930, Dan Shearer wrote:
> 
> I've got an ADSL account, but not with Telstra (Internode, in fact - you
> may have heard of them.) Internode have a 500Mb/month limit. I do not
> download music or movies, but I do run a large number of free operating
> systems, and I do operating systems simulations which involve large
> filesystems in strange formats. On the other hand I do know how to run
> rsync and web proxies.
> 
> So far, admittedly not tested over many months, my only problems with this
> limit are:
> 
>   - it isn't intelligently managed. So if I am to get maximum benefit
>     out of the limit I have to write download scripts which know about
>     the date of the next traffic billing period. I'm hopeful that this
>     can be changed over time. The trick is finding an equitable way of
>     doing this. Simon has already mooted a kind of credit arrangement,
>     whereby what you didn't use this month you can use next month. I
>     am experimenting with formulae and will ask Internode about them
>     when I know a bit more.


Dan,

My opinion on this is that the most rational way to organise
limits without artifical month-edges is to use a leaky bucket
approach.

E.g. You start with a credit of 500 MBytes, and every day
you get credit for a further 500/30 MBytes, with max crecit = 500 MBytes.

Thus every day you run the algorithm:

$credit -= $todays_usage;
if ($credit < 0) {
    pay_for(-$credit);
    $credit = 0;
    }

$credit += 500/30;
if ($credit > $max_credit) {
    $credit = $max_credit;
    }

Probably the initial value of $credit should be more like 100 MBytes.

If I were an ISP, that's how I would do it.
Then every day is the same.

As I have suggested to people like Simon from time to time,
an ISP service which I call a "budget shaper" would be quite popular.
The user would specify their hourly, dail, weekly and monthly
budget limits, and the ISP-collocated shaper would enforce these
requirements by reducing the bandwidth gradually to a low value as the
limits are approached. This would be quite easy to implement
in linux with the "tc" command and the qdisc approach.

The "budget shaper" protects the subscriber from an excessive bill,
and can be made very flexible indeed. For instance, it could include
scheduled pricing, i.e. pricing that varies according to time of
day and week etc., just like cheap overnight STD calls.

But most of the ISPs I've discussed this with are too preoocupied with
day-to-day money-making and network-building to be able to
consider this sort of avant-garde approach.
The first ISP to start using intelligent network-side per-subscriber
shaping is going to make a mint.
But they have to do a bit of forward thinking first!!

Cheers,
Alan Kennington.

-- 
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