LinuxSA Mailing list archives

  From: Alan Kennington <akenning@topology.org>
  To  : LinuxSA <linuxsa@linuxsa.org.au>
  Date: Tue, 5 Jun 2001 16:49:14 +0930

Re: BPA & 100mb / Day Limit

On Tue, Jun 05, 2001 at 05:28:02PM +0930, Adam Dixon wrote:
> Email to Cable / Adsl Telstra users was sent today at about 2:30pm.
> How funny is that :)
> 
> If anyone want to flame telstra go to just about any forum thats
> broadband/australia related.
> 
> Can anyone tell me though, intellegantly why as of late dialups have lost
> there 'unlimitability' and broad band as it will be next month has also lost
> it. Did data traffic and maintainance costs boom or something that in the
> last 6months - year they have had to resort to almost killing internet
> usage?


Adam,

The way I always think of this is that even if your
upstream costs (i.e. ISP to core internet) are fixed
for a fixed bit-rate, your number of customers that
you can support - the monetary capacity of the link -
is determined by the amount that each uses.

It's like running a pizza business or something.
If some customers take the single pizza that they can eat,
and other customers fill up the back of their
ute with pizzas (and sell them to your own customer
base maybe), then you're not going to make much money.

So usage-proportional (or usage-monotonic-non-decreasing)
charging must be used, as in all other areas of the
economy.

The problem at the moment is the fact that there is
no technology to enforce "reasonable usage" - apart from
a human watching the meter. Many ISPs have thought over
the last few years that there does exist a "reasonable usage",
as in how much pizza you can eat at one sitting.
But internet usage is not like that. There are lots of
really greedy users out there.
ISPs are faced with usually two options:
1.	per-MB charges or limits
2.	per-month unlimited
The first is bad for users, the second is bad for ISPs.
So you can use instead a third philosophy, which occurred
to me in march last year while working with a big
European ISP, and that is:
3.	per-QoS charging.

The idea is that you specify something like the following
SLA:
1.	you get peak 1 Mbit/sec anytime, subject to 2 and 3.
2.	You must not exceed 100 kbit/sec average over
	any hour. But the 100 kbits/sec over each hour will
	always be available subject to 3.
3.	You must not use more than 50 kbits/sec average
	over any 8 hours.

The user can customise the numbers, and pay accordingly.
The above is a specification of "reasonable usage".

Now how does linux come in?
1.	The trend seems to be away from ISPs now and
	towards IAPs - internet access providers which
	deliver no services but an IP pipe.
	And linux is typically used on sites which
	want just an IP pipe.
2.	Linux can very easily implement the above SLA.
	All you do is activate the diffserv software
	which I mentioned in the iptables talk,
	and you run a user process to measure the
	traffic of all users every 5 seconds, and
	you compare it to their 3-clause SLA.
	If they are within the SLA, they get high
	priority. If they exceed the SLA, they get a
	low priority. And you can then use various
	"tc" commands to implement all of this.
	This is an SLA-comparator concept.

This then solves all of the problems of broadband
IAP traffic control worldwide.
http://www.topology.org/comms/statshaper.html

Cheers,
Alan Kennington.

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