[64198] in North American Network Operators' Group
RE: Pitfalls of _accepting_ /24s
daemon@ATHENA.MIT.EDU (Howard C. Berkowitz)
Thu Oct 16 21:03:38 2003
In-Reply-To: <000001c39442$0791bd90$0200000a@netsec.net>
Date: Thu, 16 Oct 2003 21:01:11 -0400
To: nanog@merit.org
From: "Howard C. Berkowitz" <hcb@gettcomm.com>
Errors-To: owner-nanog-outgoing@merit.edu
A proposal was made some years ago, which I thought was by Tony Li,
but, IIRC, he says it wasn't original with him. It does require
cooperation from competitors, but can reduce the number of
announcements. Under some circumstances, it may cause blackholing,
but so can /24 filtering.
The idea is to establish bilateral blocks of provider space. Let us
say Provider A and Provider B recognize that they have a significant
number of common multihomed customers. Arbitrarily, one of the
providers (assume A) starts off with a block -- let's say a /19 or
/20 to which both providers will assign their multihomed customers. A
and B peer and send more-specifics to each other.
To the outside world, however, A advertises its largest aggregate
plus the multihomed block. B advertises this block of Provider A
space as well as its own aggregates.
If A and B do not peer, the likelihood of blackholes become much
higher since they may not see the more-specifics in the multihomed
block.
Has anyone reexamined this proposal lately?
