value of co-location

Hans-Werner Braun hwb at
Sun Jan 21 23:28:43 UTC 1996

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.  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.

>> 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.

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