[83863] in North American Network Operators' Group
Re: Order of ASes in the BGP Path
daemon@ATHENA.MIT.EDU (Paul Jakma)
Mon Aug 29 14:51:09 2005
Date: Mon, 29 Aug 2005 19:50:18 +0100 (IST)
From: Paul Jakma <paul@clubi.ie>
To: Abhishek Verma <abhishekv.verma@gmail.com>
Cc: nanog@nanog.org
In-Reply-To: <ce8d9033050829094562f3dc2e@mail.gmail.com>
Mail-Copies-To: paul@hibernia.jakma.org
Mail-Followup-To: paul@hibernia.jakma.org
Errors-To: owner-nanog@merit.edu
On Mon, 29 Aug 2005, Abhishek Verma wrote:
> Legend: {} denotes the sequence, while [] denotes the set
>
> Path {1 2} [3 4] {5}
>
> Would somebody mind if this was represented as {1 2 5} [3 4] ?
Yes, they are different paths. You are allowed to merge adjacent
sequences, eg:
{1 2} {5} [3 4]
the two sequences can be merged, to give:
{1 2 5} [3 4]
You can *not* merge AS_SET's, as the current BGP specs imply an
AS_SET has a fixed path-length, hence you should NOT merge the sets
in:
{1 2} [3 4] [5 6]
into:
{1 2} [3 4 5 6]
as the former path has a length of 3, the latter a length of just 2 -
merging sets could change their meaning. Note though that you're not
at all likely to see such paths with BGP speakers implementing the
RFC / draft-ietf-idr-bgp-26.txt draft.
regards,
--
Paul Jakma paul@clubi.ie paul@jakma.org Key ID: 64A2FF6A
Fortune:
The best way to make a fire with two sticks is to make sure one of them
is a match.
-- Will Rogers
