value of co-location

Hans-Werner,

This all is probably true if the objective is to provide the best
possible IP service. If you apply other requirements, like integration
of the current telephony system, or, more accurately, evolve the
telephony system, in the telephony company mindset, to something that
also supports data, video, and things like that, things look
different.

I can't disagree with this but I think it misses the point, which
is an issue which should be orthogonal to ATM. I think it may very
well be the case that it is not possible to build a really large,
reliable Internet without really large IP routers. I.e. it is not
ATM that is the problem, it is this picture of a stinking big ATM
switch milking hoards of teeny little routers the may not provide
a scalable Internet. If you want to build a big Internet you may
very well need big routers, it matters little whether they're
plugged into an ATM switch or directly into a TDM (with the proviso
that the router interfaces to plug into the former are going to
be a technology generation or two more complex than the latter, no
matter what you do).

We know we want to build a big Internet. Yet somehow the big routers
one may absolutely require to do this became (a) uninteresting as
topics of research and development, (b) not well-understood as a necessity
because of the big-switch-little-router picture, even though this may
have no relationship to working reality, and (c) even if none of the
above, the big-router development may still be constrained by the view
that a big router is useless unless it is equipped with big ATM interfaces,
even though the latter may turn out to be harder to build than the
former and we're really getting the cart before the horse. So the end
result is, no big routers, even though there is apparently little about
ATM which eliminates the need for big routers if you want a big Internet.
And all ATM has really managed to deliver so far is obfuscation of the
issues, putting us in a holding pattern where we're just waiting to see
what breaks but not doing that much about it.

So I can't deny that the integration thing is attactive (I personally
don't dislike ATM either, to tell the truth), but I really do think
that somehow the priorities got all mixed up somewhere along the way.
Instead of primarily worrying about advancing the state of the art
for each of the services people actually want to buy, using whatever
delivery technology was mature enough to accomodate this reliably,
we've somehow instead made the integration the holy grail and have
just forgotten to even care about whether there's anything left worth
integrating by the time we find it.

            Then again, so far I see little activity in the context of
service integration. More ATM as a level-2 replacement for data
networking. Which brings us back to your comments, as in such an
environment the benefit is more marginal (e.g., ATM may still have
multiple service qualities before it is being implemented in an IP(+)
substrate). Oh well. If there were just concerted goals.

I would suggest that the reason you don't see a lot of activity in
the context of service integration is that (at least at the phone
company I know a little about) the guys that run the voice network are
about the most pragmatic people in the place, which means they make
sure their vendors deliver the big iron switches when they need them,
and that they've got enough fiber in the ground to connect them together,
so that even if it turns out that ATM isn't as great a thing as it was
thought it might be, you still won't get a lot of fast busy signals. I
wish one could say the same about the Internet.

Dennis Ferguson