North American Network Operators Group

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Re: Routescience?

  • From: E.B. Dreger
  • Date: Wed Aug 22 12:36:04 2001

> The details of the measurement method were written up in Network World
> yesterday; see

[ snip ]

> PathControl then offers advice in the form of BGP updates to the edge
> routers.  The prefixes, the rate of change and the factors to optimize
> can be constrained, between CLI commands on PathControl and the
> conventional filtering offered within BGP on the edge routers.  (FWIW,

[ snip ]

Let me go out on a limb:

Not sure that the NW article was "detailed", but I ass-u-me that one
measures the time from packet sent out until ACK, then uses packet
size and timing to determine the effective bandwidth.

Perturb the routing decision by inserting a longer subnet prefix.
Measure.  Repeat until all paths have been timed.  Repeat again to
lower standard deviation until the paths are statistically separated,
or bail if it's a losing battle.  Now inject the "winning" route "for

Setup procedure includes making sure that the border router doesn't
damp(en) paths learned from the route server.  Measurement statistics
are keyed to the subnet learned from the border router, perhaps
aggregated with adjacent CIDR blocks if the results overlap.

Because it's futile to try tuning that occasional packet to Albania,
there's a low-water mark that a subnet (learned from the border) must
hit before any tuning occurs.  Maintaining state is expensive, and
traffic follows the 80/20 rule... don't bother tuning unless many
packets go to that destination.

Observe-netflow-statistics-time-paths-and-reprogram-router done via
an automated black box.  It's a route server whose adverts are
derived from empirical measurements.  No?


I hope that the patent-pending part isn't any of the above, as the
above is hardly unique, innovative, or something that hasn't been done
before.  If the above is "secret", and these boxen sell for ~$200k,
then I should turn this company into an R&D shop and implement some of
the ideas that we have on a much larger scale...

Shrouding something in secrecy tends to leave this crowd (NANOG-l) to
believe that there really is nothing to it... if it's that hard to do,
and has valuable substance, then why the hush?


I feel that I'm probably not the only one on NANOG-l who would like to
see some technical information ("technical" to routing geeks, not
"technical" to an end user or a Webbie) as opposed to "it's really

Back to my lurking corner,

Brotsman & Dreger, Inc. - EverQuick Internet Division
Phone: +1 (316) 794-8922 Wichita/(Inter)national
Phone: +1 (785) 865-5885 Lawrence

Date: Mon, 21 May 2001 11:23:58 +0000 (GMT)
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