[107419] in North American Network Operators' Group
Re: Is the export policy selective under valley-free?
daemon@ATHENA.MIT.EDU (Valdis.Kletnieks@vt.edu)
Wed Sep 3 13:29:07 2008
To: William Waites <ww@styx.org>
In-Reply-To: Your message of "Wed, 03 Sep 2008 10:36:52 +0200."
<E3803895-7731-4EAF-85B9-CC54A25B8320@styx.org>
From: Valdis.Kletnieks@vt.edu
Date: Wed, 03 Sep 2008 13:26:54 -0400
Cc: NANOG list <nanog@merit.edu>
Errors-To: nanog-bounces@nanog.org
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On Wed, 03 Sep 2008 10:36:52 +0200, William Waites said:
> Valley-free is a property of AS mesh models that says that, where edges
> are classified as peering (p2p) or transit (c2p) that a valid path
> contains zero or one peering link and that the peering link occurs
> adjacent to the top of the path. That is that valid paths look like,
>
> [c2p c2p ... c2p p2p p2c ... p2c p2c]
OK, I'm looking at this, and having a *little* trouble buying that there's
exactly zero or one p2p links - consider the case where the last 'c2p' link
is to provider A, who peers with B but not C, and B peers with both A and C,
and the first p2c link lands at C. Don't you end up with "cp2 p2p p2p p2c" in
that case? Or is there a convention saying we compress the A-B and B-C
links into a notational A-C link? Or are we defining A-B or B-C links as
being a c2p type instead, even though they're peering and not transit?
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