On Fri, Feb 19, 1999 at 02:44:19PM -0800, Greg Skinner wrote:
> >> In the absence of hard data, people will argue their opinion based on
> >> their experience.
>
> > So, tell us about your experience.
>
> Having worked on and studied some applications that require millions
> of bidirectional name-to-address resolutions on a daily basis, I have
> formed the same opinions that Keith Moore and some of the others have
> who feel hundreds of thousands of TLDs pose a serious threat to the
> performance of DNS.
The issue of how many new TLDs could be supported has come up many
times. There is no definitive answer. The IAB was asked to make a
formal study; they did; they said there was no problem with a few
hundred to perhaps a few thousand TLDs; anything past that was
unknowable at the present time.
The problem is extremely complex. The performance of DNS depends
heavily on caching behavior, and caching behavior depends on user
usage patterns, tree structure, leaf node dnsserver performance
characteristics, and so on. The appearance of a new technology (for
example, the smart directory services people talk about) could have a
drastic negative effect. If the number of TLDs approaches the size
of the average resolver cache, and the tree structure changes, then a
much higher percentage of requests will need to go through the root.
It's obvious that, *with current usage patterns*, current technology
will handle a zone with a couple million entries, because .com has
that many. But the current usage pattern is such that the
percentage of cache hits on the local resolver is very high.
Another big issue is operations -- lots of TLDs means lots of
updates. To get to 100,000 TLDs in 10 years you would be adding
like 25 new TLDs a day, constantly.
> >> No one knows for sure what will happen when the safe TLD limit is
> >> exceeded.
>
> > What safe limit would that be?
>
> 100,000 seems to be a popular figure.
Not in my experience. People who really know about this stuff say
few thousand, usually, to maybe a few tens of thousands.
--
Kent Crispin, PAB Chair "Do good, and you'll be
[EMAIL PROTECTED] lonesome." -- Mark Twain
