-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 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 <ww@styx.org> http://www.irl.styx.org/ +49 30 8894 9942 CD70 0498 8AE4 36EA 1CD7 281C 427A 3F36 2130 E9F5 -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (Darwin) iEYEARECAAYFAki+TKQACgkQQno/NiEw6fUsqQCeO4DN2glRopnWZwfgrhw1MdpZ 4kcAniuNr+O5KNl8GJKGM2C5RgHsd3ID =5AsJ -----END PGP SIGNATURE-----