[116026] in North American Network Operators' Group
RE: Quick question about inbound route-selection
daemon@ATHENA.MIT.EDU (Deepak Jain)
Thu Jul 16 18:33:04 2009
From: Deepak Jain <deepak@ai.net>
To: Richard A Steenbergen <ras@e-gerbil.net>, Drew Weaver
<drew.weaver@thenap.com>
Date: Thu, 16 Jul 2009 18:32:32 -0400
In-Reply-To: <20090716201802.GQ51443@gerbil.cluepon.net>
Cc: "'nanog@nanog.org'" <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
> As for trying to determine where your inbound traffic is coming from by
> looking at natural bgp, this is absolutely impossible to do correctly.
> First off, your inbound is someone else's outbound, and the person
> sending the traffic outbound is in complete and total control. The vast
> majority of the traffic on the Internet is being picked by local-prefs
> based on policies like "what does this make/cost me monetarily" or
> "which major networks can I grab in a simple as-path regexp to balance
> some traffic". But even if you ignore all of that, the "natural" path
> selection is based on criteria which is specific to the other network
> or
> even to a specific session which you can't possibly know about remotely
> (e.g. their router id).
Another way to say what Richard is getting at (which was full of good infor=
mation) is:
Just because you aren't modifying what your BGP process sees, at this stage=
of the Internet's maturity, it is safe to assume almost everyone else is. =
Therefore, rather than pray for BGP to make a logical selection, even thoug=
h its *probably* being fed prefs based on other people's engineering, you s=
hould take charge of the parts you can.
HTH,
Deepak Jain
AiNET
