Re: Our lead over SolNet...?

Karl J. runge (runge@jfku.edu)
Sat, 3 May 1997 02:09:33 -0700


On Fri, 2 May 1997, nelson@media.mit.edu (Nelson Minar) wrote:
> >a.Somebody (don't remember at the moment, not looking through all my mail)
> >determined that if we cooperated, assuming either exponential or linear
> >growth, it really wouldn't make much difference.
>
> I still don't believe this. Could someone explain it in more detail?
> My gut intuition is it makes a 50% speedup if two sites to cooperate.

Hi, I was the poster from last week on the cooperation estimations, sorry
for not getting back earlier but my ISP connection was shut down since
Tuesday, and I'm just now getting caught up on about 200+ deschall emails!

The basic idea is one can compute the *average* time to find the key
by making various assumptions about cooperating and non-cooperating
keyservers. Note that these models may become invalid as the weeks
go on.

First, if there are two keyservers going at equal and constant rates,
the average time to find the key is 33% higher for non-coop versus coop.
(it would be 100% higher, i.e. take twice as long, if they were doing
the same keys in order, but the chances for that are very small)

I then did some modeling of our growth rate, exponential and linear. I
note our growth rate has dropped off in the last week so I should rerun
those calcs...

Anyway, the basic idea is with a rapidly growing search rate, what's
happening now doesn't have much weight compared to what is happening
near the end. Roughly, it "all" just gets done really fast near the
end, and so with non-cooperating keyservers only 33% of, say, the last
two weeks is wasted by not cooperating, not 33% of the total time.

So when you look at the *total* time, cooperating does not seem to help
much, for our rate from last week, cooperating only saved 2-3 days (3%)
if the growth was exponential. If we had linear growth the savings from
cooperation was more, about 12 days (11%).

Of course if the key search rate saturates and does not grow, we
are back at the 33% savings situation and we might want to consider
cooperating to save (on average) a month or two...

Also, if one keyserver has a higher rate than the other then the
cooperating savings is less. I hope we have a great weekend and
get some distance ahead of Solnet!!!