[88774] in North American Network Operators' Group
RE: metric 0 vs 'no metric at all'
daemon@ATHENA.MIT.EDU (Doug Marschke)
Fri Feb 17 06:08:24 2006
From: "Doug Marschke" <doug@ipath.net>
To: "'Danny McPherson'" <danny@tcb.net>, <nanog@nanog.org>
Date: Fri, 17 Feb 2006 12:07:45 +0100
In-Reply-To: <8EB32C2D-AE44-4EE3-880D-5773A40F1C60@tcb.net>
Errors-To: owner-nanog@merit.edu
And just to update, those drafts have made it into RFC 4271
http://www.ietf.org/rfc/rfc4271.txt
-----Original Message-----
From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of
Danny McPherson
Sent: Tuesday, January 03, 2006 3:49 PM
To: nanog@nanog.org
Subject: Re: metric 0 vs 'no metric at all'
On Jan 3, 2006, at 1:03 AM, Daniel Roesen wrote:
>
> So the spec is fuzzy about how "no MED vs. MED=0" should be
> treated, but
> vendors seem to largely agree to "no MED == MED 0". I know of no
> deviation, except the old ERX bug which got fixed (ERX treated "no
> MED"
> as best, even better than MED=0 - contrary to documentation).
I recall some earlier implementations from "well known" vendors that
had varying behavior for MED processing as well.
Fortunately, the update to RFC 1771:
http://www.ietf.org/internet-drafts/draft-ietf-idr-bgp4-26.txt
is considerably more explicit about this behavior, as well as a slew
of other previously-left-to-the-implementation items ironed out
through a great deal of implementation and deployment experience.
The "BGP Experience" and "BGP MED Considerations" Internet-
drafts provide a good bit of additional insight into some of these
behaviors.
-danny
