value of co-location


Religious arguments aside, the obstacle for TCP/IP performance over ATM has
been due to two factors, small buffers and no explicit flow control.

I think you forgot one. The requirement to do VC-based reassembly also
makes router interfaces hideously complex (relative to interfaces to
frame-based networks, certainly), and hence prone to all the difficulties,
limitations and unhappy corner cases that complexity breeds. And an
additional requirement that the interfaces do something with flow control
indications is not going to make them simpler.

You know it is very hard not to wax poetic about ATM, despite one's
best efforts to be objective. I am quite sure that ATM will support
IP just fine in the end, just throw a few more bizillion dollars of
R&D at it and fix everything. With all that fancy silicon laying
around being sold at bargain-basement prices it'll be impossible to
ignore. And all the while the segments of the industry which might
be building routers are instead sitting on their hands waiting for
the ever-delayed release of the next latest-and-greatest, all-seeing
all-knowing SAR chipsets with fantasy visions of big honking ATM switches
surrounded by teeny tiny routers dancing in their heads. And so I'm
sure we'll get the big honking ATM switches surrounded by teeny tiny
routers, and all will be happy and working well, just five years too
late and five times too complex as the ATM industry figures out what
many people already knew and funds yet more research, and produces yet
more Forum standards, to work around the conceived-in defects with the
technology when supporting this type of service. So you are indeed
right, ATM will work very well for IP in the end and we'll never need
to think about how irrelevant it might have been if we'd spent just a
tenth of the effort advancing router technology.

So, in any case, I agree with you, if you pick your equipment right
and shake out the bugs ATM will carry IP just fine. And if the
phone company prices the service so that it looks attractive compared
to that provided by (cheaper and more reliable) TDMs, it'll sell like
hotcakes. But I don't think it is being "religious" to be unwilling
to let the phone company use one's own data to get its primary-school
education about high-end data networking, and to shake the bugs out of
a buggy technology, nor is it being "religious" to have regrets about
what might have been. ATM can be its own self-fulfilling prophesy all
by itself, just phone (not using ATM, no doubt, even the phone company
is smart enough to avoid this for its bread and butter) when you get it

Dennis Ferguson
Speaking only for myself.