[101385] in North American Network Operators' Group
Re: v6 subnet size for DSL & leased line customers
daemon@ATHENA.MIT.EDU (Brian Dickson)
Wed Jan 2 19:32:35 2008
Date: Wed, 02 Jan 2008 19:29:35 -0500
From: Brian Dickson <briand@ca.afilias.info>
To: NANOG list <nanog@nanog.org>
X-SA-Exim-Mail-From: briand@ca.afilias.info
Errors-To: owner-nanog@merit.edu
>> As to "there must be better knobs" I think it may be a little late
for that; by design (or as a consequence of it) the set of IPv6 knobs is
the same as the set of IPv4 knobs.
> The trouble is that BGP doesn't have a meaningful inter-AS metric.
(Although there is something that is called that.) If I want to increase
my path length by 10% through a certain neighboring AS, I don't get to
do that. I only get to double or triple it. (Unless I was doing very
heavy prepending to begin with.)
Actually, while it isn't a true metric as such, there *is* just such a knob.
The "origin" attribute, can act as a fractional AS-path-length. It's
mandatory and transitive.
It gets evaluated after as path length, but before other attributes.
It has three possible values (internal, external, unknown), and as such,
gives the limited ability to influence path choice at third-party
locations quite distant.
The only caveat is, that some parties may mess with it on prefixes they
receive.
I've used it in the past, with considerable success.
Brian Dickson
