Broken Internet?

Greg A. Woods woods at weird.com
Tue Mar 13 22:48:46 UTC 2001


[ On Tuesday, March 13, 2001 at 12:52:41 (-0800), Roeland Meyer wrote: ]
> Subject: Broken Internet?
>
>  Even co-lo boils down to single-home dependency.

It doesn't have to.

> Yes, there are a bunch of hacks to work around this problem. But, that is
> exactly what they are ... hacks. They are not something I could build a
> sustainable business around.

For _small_ businesses it is extremely trivial to multi-home (i.e. to
truly multi-home all their network-visible servers).  Well there's one
small trick that requires each host have decent support for something
like IP Filter that's capapble of re-directing packets based on source
address.  (I'll post a technical description the trick I use with IP
Filter if enough people don't think it's obvious how it works.  There
have also been hacks by others to the BSD networking stack to allow
multiple default routes and to do source-routing kinds of tricks.)

With a small amount of planning and skill it's possible to make this
kind of real multi-homing fully functional through the DNS (and even to
enjoy some load-balancing as a result).

For most any _small_ business this works very well (been there, done
that, would even do it with my machines here at home if Rogers at Home
didn't charge as much as they do for IP addresses).  Conveniently about
the time your network gets big enough that this scheme gets too hard to
manage, you're up to the size where network multi-homing via BGP,
etc. is possible.

> Any business needs:
> 1. to be able to change upstream providers without having to renumber.

Why?  If you're _small_ then renumbering is relatively easy!  It's the
big guys (who didn't use DHCP from the start) who have a hard time
renumbering.

> 2. to be able to change access providers without having to suffer
> multi-month down-times.

If you're multi-homed then all your providers have to go down before
you'll suffer any down-time that's not your own doing.

The real issue is with lead times on ordering local loops, etc.  If
you've already got them in place because you are already connected to
multiple providers and are doing host-based multi-homing then you don't
have to worry.

> 3. to be able to have its net-block(s) visible regardless of which ISPs they
> are currently using.

By properly multi-homing all your servers (and not networks via routing)
there's no issue about net-block visibility, BGP peering, or the like.
You simply use as many/few IP addresses from each provider as you need
to multi-home all your servers, and they aggregate them into their own
routes as necessary.

Same thing goes for co-locating multiple identical servers in multiple
locations.

> Currently the only ones that can do that are those that;
> 1. Are large enough to justify a /20 (begging the question of how they got
> that large).
> 2. Can afford their own datacenter.

Yes, exactly.  They're the only ones who really need network
multi-homing (which is such a poor phrase to describe what it is).

Everyone else can afford to multi-home their servers one way or
another.

> It looks like our technical solutions are raising unreasonable barriers to
> entry for small businesses.

I think not.

I fully agree that Internet-based businesses critically require multiple
network access points.  However since this can be done trivially with
either multiple co-located servers, or properly multi-homed servers,
there's no reason to consider /20 netblocks, etc., to be barriers of any
sort.

-- 
							Greg A. Woods

+1 416 218-0098      VE3TCP      <gwoods at acm.org>      <robohack!woods>
Planix, Inc. <woods at planix.com>; Secrets of the Weird <woods at weird.com>




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