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Le 08-09-03 à 02:23, Paul Wall a écrit :
That's correct. A network purchasing transit will advertise its
internally-originated prefixes, as well as those it's learning from
downstream customers, to its provider.
I'm not sure what "valley-free" means in this context. You might want
to try the Rosetta Stone patches and make sure your copy is up to
date.
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]
(slightly abusing the notation for clarity)
The idea is that a small, customer AS should not provide transit between
its upstreams, though this does, apparently happen sometimes.
Barring misconfigurations, I believe that AS paths are normally valley-
free.
See, for example,
"Toward Valley-Free Inter-domain Routing"
http://nsrc.cse.psu.edu/tech_report/NAS-TR-0054-2006.pdf
"AS Relationships: Inference and Validation"
http://www.caida.org/publications/papers/2006/as_relationships_inference/
Cheers,
- -w
- --
William Waites <[EMAIL PROTECTED]>
http://www.irl.styx.org/ +49 30 8894 9942
CD70 0498 8AE4 36EA 1CD7 281C 427A 3F36 2130 E9F5
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