[IP] Re: Engineers fixing networks & IntServ

[David Farber <dave@farber.net>]

________________________________________
From: craig@aland.bbn.com [craig@aland.bbn.com]
Sent: Tuesday, July 29, 2008 11:35 AM
To: David Farber
Cc: mo@ccr.org
Subject: Engineers fixing networks & IntServ

Mike O'Dell observed:

> that would have been "IntServe" the failed Integrated Services model
> promulgated in the IETF half a decade later which was never viable at
> at the scale of the Global "Big-I" Internet.

As the former co-chair of the IETF IntServ Working Group I think the
failure had more important lessons than Mike suggests.  I may be wrong,
but my sense was that IntServ failed less due to scalability issues
(which existed, but I think were solvable) than to the interesting
paradox that we designed precisely what the majority of ISPs, user groups
and vendors said they wanted -- namely the ability to reserve guaranteed
bandwidth with sturdy delay bounds -- and discovered no one wanted the
service badly enough that they'd pay what it cost to offer it.  It was
more cost-effective to buy more bandwidth.

Even more important, from my perspective, was that the IntServ work was firmly
grounded in some excellent theoretical work which strongly suggests that
something like the IntServ solution is about as good as you can get.
Lots of fascinating papers ground down into three sentences: Most (all?) of
the packet handling schemes that give delay & bandwidth guarantees have
been shown to be variants of what could be called a
Demers-Keshav-Shenker-Parekh-Guerin system (as a field, we lack a name
for it).  And we can map between bitwise and packetwise schemes.
So bits/packets, doesn't matter, you want guarantees, you're stuck
in a result space people don't like.  And, last I checked, all
proposals for performance guarantees in the past 15 years
(ATM, IntServ, etc...) have been, at their core, the same ideas.

Which is why, when you read things about improving Internet service, you
see lots of discussions of "priorities" and "improving" service without
discussions of guarantees.  We've been down the guarantees road and don't
like the result.

Craig

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Chief Scientist, BBN Technologies
Outreach Director, GENI Project Office

E-mail: craig@aland.bbn.com or craig@bbn.com
Phone: +1 517 324 3425



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