North American Network Operators Group

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Re: Routescience?

  • From: Mike Lloyd
  • Date: Thu Aug 23 02:19:41 2001

Vadim, others,

Vadim Antonov wrote:
> My guess is that most network operations folks would be quite interested
> in learning what kind of operational impact to expect from the deployment
> of your boxes (and, frankly, what kind of defensive measures they have to
> take to minimise the impact).

As David Schwartz noted on the basis of earlier posts, and I would like
to confirm, the incarnation of PathControl we are discussing optimizes
outbound routing.  I've received off-list mail on this question too, so
I'd like to be clear about it.  The consequence is that ISP folks should
not be worried about new floods of strange-looking BGP data emerging
about their customers which they might be obliged to accept.  The
customer outbound feeds will become no stranger than they are already

Applied in a stub AS, we do not create any prefixes which are not
already present.  So as an ISP serving such a stub, you would be exposed
to what amounts to an (automated) change in internal policy for the
client AS - the same thing that would happen if they shifted local
prefs, or other controls, by hand.  Either they now select you as the
winning advertisement where before they did not, or vice versa.

Once more, we do not cause the stub AS's own advertisement of themselves
to change.  We specifically avoid touching locally originated prefixes. 
If the ISP is currently accepting any of the routes PathControl is
designed to change, then the AS is not stub, it's transit.  Hopefully
this clarifies an important issue.

(Referring back to Paul Vixie's point, we have found that careful
optimization of a single outbound step has very substantial payoffs in
terms of the end to end, bidirectional performance.  The figures quoted
on our web page and in the press release refer to this: end to end
application speedup caused solely by outbound route selection!)