Verio Decides what parts of the internet to drop

George Herbert gherbert at
Mon Dec 6 21:10:30 UTC 1999

James Smith <jsmith at> wrote:
>Based on past experiences, I would say that the big backbone providers
>shouldn't do any filtering at all.  Then, the lower tiers can do all the
>filtering they want, and still rely on default routing to send the packets
>to the backbone.  It may not be the prettiest way to route traffic, but
>this would allow smaller ISPs to filter if they cannot afford buying
>bigger equipment to hold all the routes.  Since the tier-1 guys are the
>glue of the Internet, they should be required to take everyone routes.

There are numerous instances where that sort of policy would
have blown up large chunks of the net.  It's already happened.

Part of the problem is that the Tier-1 guys can't buy bigger
equipment to hold all the routes, either.  When Sprint started
this sort of filtering in 206.* I yelled and screamed, thinking
it was foolish.  History has proven us wrong.  Without it,
we'd be at route announcement levels which would blow up
the available backbone hardware.  Plus, without that sort
of selective filtering, accidents can kill things right and left.

I am not sure whether the danger in opening up the B space for
/17 blocks is particularly bad, but lacking a single consistent
policy body with sufficient clue about both the Tier-1 backbone
issues and the address allocation issues, it's hard to fault
any given ISP for insisting on /16s in B space.

-george william herbert
gherbert at
Disclaimer: I am a CRL end user, not employee, and speak for myself only.

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