Who has AS 1712?

Randy Bush randy at psg.com
Wed Nov 25 04:58:28 UTC 2009

> Right. You can't advertise an ASN
> you can only advertise a route and include an AS_PATH attribute on it
> which makes mention of a particular AS number.

that bit of biff-like pedantry quickly leads to you can't advertise a
prefix.  a bgp announcement has, in the case of ip unicast, an nlri and,
among other things, an as-path.  see rfc 1771 4.3 on Path Attributes.
as to what is being announced and what is merely loitering waiting for a
hot pick-up, you can work that out with your mullah, priest, rabbi,
spouse, ...

for unusual utility of intentionally announcing a particular asn, see
as-path poisoning, e.g. lorenzo's thesis [0], the talk which was banned
at nanog [1], or the full paper [2].

> My point is that in the absence of any mechanism for announcing an
> ASN, a plan to gate assignment of numbers based on an announcement
> doesn't make any sense.

seeing if an asn is in a currently-announced as-path is useful, as has
been pointed out in this discussion.  and it very well might have caught
the problem at hand.  the problem is that it is far from definitive as
bgp presents a highly biased view (see [1] and [2]), and an asn may be
held but not announced.  but, as chris morrow said, every little bit



[0] - http://www.colitti.com/lorenzo/publications/phdthesis/thesis.pdf

[1] - http:archive.psg.com/091006.nag-default.pdf

[2] - http://portal.acm.org/citation.cfm?id=1644893.1644923&coll=portal&dl=ACM&type=series&idx=SERIES10693&part=series&WantType=Proceedings&title=IMC
      acm member portal, sorry.  those really interested, email me for a copy

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