North American Network Operators Group
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Re: an effect of ignoring BCP38

  • From: Jo Rhett
  • Date: Thu Sep 11 13:25:13 2008
On Sep 11, 2008, at 10:10 AM, [email protected] wrote:
Part of the problem is that if you're talking about the 5 biggest providers,
and the 5 biggest transit, you're talking about places with routing swamps
big enough, and with sufficient dragons in residence, that you really *can't*
do BCP38 in any sane manner. AS1312 (us) is able to do very strict BCP38
on a per-port level on every router port, because we *know* what's supposed to
be on every subnet. By the time you walk our list of upstreams to any of
the '5 biggest anything', you've gotten to places where our multihomed status
means you can't filter our source address very easily (or more properly, where
you can't filter multihomed sources in general).

I don't agree with this statement. I hear this a lot, and it's not really true. Being multihomed doesn't mean that your source addresses are likely to be random. (or would be valid if they were)

A significant portion of our customers, and *all* of the biggest paying ones, are multihomed. And they might have a lot of different ranges, but we know what the ranges are and filter on those.

The MIT Spoofer project seems to indicate that closer to 50% *of the edge* is
doing sane filtering. And that's where you need to do it - *edge* not *core*.


I've said much the same myself. With the caveot that if you aren't doing it at the edge, you need to be doing it at the closest edge you can find.

--
Jo Rhett
Net Consonance : consonant endings by net philanthropy, open source and other randomness