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Re: NAT for an ISP
From: "David G. Andersen" <dga () lcs mit edu>
Date: Wed, 4 Jun 2003 21:56:10 -0400

On Wed, Jun 04, 2003 at 07:07:28PM -0400, Andy Dills quacked:

  I've got a friend who puts all of his internal servers,
routers, and _customers_ on RFC1918 space and pipes them out
thrugh a PNAT.  Fairly small ISP - maybe 15 megabits of bandwidth -
operating at the state local level.

Why on earth would they do this? What you've said implies DS3 level
connectivity, so to skimp on ARIN fees seems a little ridiculous.

Historical accident in many ways.  I implied DS3-level
connectivity, but what it really means is multiple bonded
T1s from multiple providers.  It started out as a T1 from
here, a T1 from there, and no local BGP knowledge (and
discouragement from the upstreams).  In fact, using a bunch
of NATs is a great way to resell cheap upstream connections.

Yeah, I read you loud and clear. "My friend is a half-baked cluebie using
techniques I'll term fun and later encourage my competitors to employ". :)

Actually, I do mean the fun part.  You can do some cool tricks with
it.  Renumbering to different providers is mostly seamless,
particularly since he runs the DNS for his customers.  Easy to
experiment with throwing transparent caches and things like that
in front of the customers since they're already going through a
firewall.  Now that he's about large enough to get ARIN space, the game
is changing, and they're moving in the directions one would expect
them to.

It's not an approach that I would ever encourage a large ISP
to take.  In fact, I don't necessarily think of him as providing
standard "Internet" services - he provides primarily web, mail, 
and VPN services, and then some customized stuff on a per-customer
basis.  But he's had a decent customer base for a small ISP, and
he seems to be filling a niche, and hasn't gone out of business
doing it.


work: dga () lcs mit edu                          me:  dga () pobox com
      MIT Laboratory for Computer Science           http://www.angio.net/
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