[RC5] Cartographie

Ben Ketteridge ben.ketteridge at proact.net
Thu Feb 10 09:19:59 EST 2000


----- Original Message -----
From: "Gunny" <gunny at dma.be>
Subject: Re: [RC5] Cartographie

> > every single one of them would have to download about 300kB *each day*,
> > every day, for 2 years. Assuming the current distribution of contribution,
> > the top contributors would have to download more than 10MB each day. Will
> > people be willing to do that? And those numbers are assuming no inter-block
> > data dependency....
> 300KB is less than 2 minutes on an 28.8 modem. Or a few seconds on my cable
> modem...

Imagine a person running, say, 12 clients on a slow college link? That's 3.6MB.
Not insignificant.

Remember the fuss when Seti at home started. Lots of networks blocked Seti
because of the impact it had upon network traffic. Now, admittedly, their block
size was even larger, but if we want people to make a really significant
contribution
to the problem, then 300KB is going to be a serious underestimate. Furthermore,
if you have a set-it & forget-it client which lurks for a modem connection, how
are
you going to ensure that the modem connection stays up long enough when the
reason
the user initiated the connection was to check their mail - a process that
doesn't
often take as much as 2 minutes. Of course, people with permanent connections
or cable
modems aren't going to worry about that. ;-)

On the other hand, since we are talking about downloading 300KB+ we should be
looking
very seriously at compression technologies. No-one has said what form this data
is in,
but there is every likelihood that the real packet size could be very
significantly
reduced by sensible use of compression, perhaps by a factor of 10 or more
(depending
upon original data format, and the algorithm chosen).

But back to the original problem of serving 150kb/s from d.net. That's only the
mean,
I am sure (admin correct me if I'm wrong?) that clients do not keep up a
consistent
stream of contacts with the server, therefore, the serving rate must peak
several times
per day. This is probably quite predictably, perhaps (I am guessing here)
around 9am,
5pm, 6pm and perhaps 11pm (local times around the world) - this may all even
out of
course, but I doubt it, due to the geographic distribution of clients.
So the serving capacity will have to be much more than 150kb/s. Having said
that, I
used to get 120kb/s as a user on a shared university T1 link, so if d.net can
get this kind
of connection then the bandwidth may be achievable.

Tara,
Ben.

p.s. btw, I'm also a bit of a map freak.... thanks to Martin Harvey for the
link to IMCoS!

| Dr Ben Ketteridge: ben.ketteridge at proact.net, ObjectLab Group |
| ProAct International, PO Box 100, Denbigh. Tel: 01745 817161. |
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