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Why filtering? (was Re: Verio Peering Question)

  • From: Sean M. Doran
  • Date: Fri Sep 28 22:45:03 2001

Historical notes, rather than disagreement follows:

Jeff McAdams writes:
| Filtering on prefix length?  There's just no solidly backed up reasoning
| to support it that I've heard.

1. it was easy to do (although the EACL was a little hairy)
2. there wasn't a flap-damping choice at the time

Note that the network I'm associated with now does RIPE-210
and applies it uniformly.   And we figured that out ourselves, 
some years ago.   I think it may have something to do with the fact
that even less-experienced people understand that rapidly flapping
announcements are (a sign of something) bad. :-)

We've also learned that table size just makes a problem more likely
to occur in the steady state, and have mitigated against "great
big change" events with things like soft resets and checkpointing.
Constraining size is now known to be an indirect treatment of the 
illness best expressed as "too dynamic a network".