[131996] in North American Network Operators' Group
Re: AS path question.
daemon@ATHENA.MIT.EDU (Stefan Fouant)
Wed Nov 10 16:36:54 2010
From: Stefan Fouant <sfouant@shortestpathfirst.net>
To: Joe Maimon <jmaimon@ttec.com>
In-Reply-To: <4CDB0ABE.4030207@ttec.com>
Date: Wed, 10 Nov 2010 16:35:41 -0500
Cc: Greg Whynott <Greg.Whynott@oicr.on.ca>, "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
BGP community attributes are optional transitive attributes, so in =
theory they could be used by secondary or tertiary providers for policy =
processing. However, that is under the assumption that those providers =
have the proper policies in place and understand those communities. =
Alsi, in some cases a given provider will strip the communities out =
before advertisement to upstreams or upon receipt from a downstream, so =
there is no guarantee that the communities will remain intact.
Typically however, the community tagging is used to influence the direct =
upstream providers, and the AS Path prepending is used to influence the =
secondary providers.
Stefan Fouant =20
My apologies for the top post. Sent from my iPad
On Nov 10, 2010, at 4:12 PM, Joe Maimon <jmaimon@ttec.com> wrote:
>=20
>=20
> Stefan Fouant wrote:
>>> -----Original Message-----
>=20
>>=20
>> IMO, a combination of both community tagging to influence localpref =
coupled
>> with AS Path prepending on the secondary link is the best approach, =
and
>> seems to accommodate both steady state as well as failure scenarios
>> properly.
>>=20
>> Stefan Fouant
>=20
>=20
> So how far from you can you propagate community tags to influence the =
route decision process to your second transit upstream peer?
>=20
>=20
> Joe
