Use of Default in the DFZ: banned in philly, see it now on the net!

Randy Bush randy at psg.com
Tue Jun 23 14:51:01 CDT 2009


due to nanog pc silliness, my lightning talk on $subject was not given
in philly.  i had promised to report to nanog the results of our winter
experiment which used as path poisoning.  here is the lightning talk i
would have given.

   http://archive.psg.com/090615.nanog-default.pdf

this is really meant to be a talk, so the slides can be a bit hard.

on slide 6
  /20 is the as path length of a /20, i.e. a 'normal' distribution,
      as seen from bgp monitors at RV, RIS, and a jillion others
  /25 is the as path length distribution we saw pinging from the /25
  BGP is the as path length distribution we saw from RV/RIS
i.e. BGP views are significantly skewed.  but most of us knew that.

on slides 10 and 11, the categories stub, small isp, large isp are from
a ucla study.  imiho, you should take them with a grain of salt.

on 12, the reason for the funniness around 30 test points is because, we
really wanted >= 30 test points in an AS.  so if we got close, we
scanned harder to find them.

please do check your as at <http://psg.com/default/> and then actually
look at your router config.  i found one of my routers still had a
default from when i was bringing it up.

randy




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