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Re: Global BGP - 2001-06-23 - Vendor X's statement...

  • From: Robert E. Seastrom
  • Date: Tue Jun 26 14:56:05 2001


Sean Donelan <sean@donelan.com> writes:

> Sigh, the motto "be liberal in what you accept and conservative in what
> you send" applies to BOTH parties.

Making guesses as to what is meant when one gets malformed routing
updates is well beyond the scope of being "liberal in what you
accept".  It is only noteworthy that the bad update didn't crash the
Brand "C" router because it used to be notoriously easy to kick
one over by that method.

> The failure of one party not to
> liberally accept what is received does not excuse the sending party from
> being conservative in what they send.  And vice-versa.

Being "conservative in what you send" refers to interpretations of the
specification, backwards compatability with older specifications,
requiring weird extensions to the protocol, etc.  These all fall along
the axis of "what might be expected in a properly functioning
implementation".  Output that is clearly wrong, as is the case here,
is not just breaking conservatism in what one sends, it's a sign that
Something is Screwed Up (tm).

A convincing argument can be made for a "max-malformed-update-resets"
knob such that if the peer sends bogons and gets reset more than N
times in T minutes, the session is admin-downed the same way it is
when it exceeds max-prefixes.

Of course, if more router manufacturers were to enable clairvoyant
route update divination (CRUD), Sean would get more interesting
outages to write about, so at least _someone_ is ahead.  :)

                                        ---Rob





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