RFC 1771, further thoughts

Wed Jun 27 04:27:51 UTC 2001

>
>In an attempt to return to an argument, rather than simple contradiction
>(ok, ok, it's far more polite and reasonable so far than that would imply,

>but I couldn't miss the cheap shot; apologies hereby tendered), perhaps we

>should consider *what* the RFC should say, if it should be changed? Going
>to the WG with a proposal in hand and a rationale to support it would seem

>to be the best path.
>
>So, a summary of my view on it at the moment:
>
>Assumption #1) Resetting a BGP session is 'costly'. Both in terms of the
>time it takes, the stability it removes, and the fact that it flaps all
>of your *outgoing* announcements as well as incoming ones.
>
>Assumption #2) A router that sends a malformed route is clearly doing
>something which it Should Not Be Doing (tm) (ok, this might be axiomatic,
>but should still be laid out)
>
>Assumption #3) The current practice has been shown to demonstrably
>increase the brittleness of the Internet, by causing severe flapping when
>someone only partially follows the RFC (in particular, propagating bad
>route data, whether or not the origional source session is reset).
>
>Assumption #4) Routing errors which are bad data, but *not* malformed
>routes, will not generally be caught by normal means in normal operation,
>until a case of human intervention to cross-check the data.
>
>Assumption #5) Any router which breaks so badly as to start spewing large
>amounts of validly formed but errorneous data, and is *also* spewing badly

>formed data, will spew noticeable amounts of said badly formed data. (This

>one is key, and is only a conjecture; field evidence would be of great use

>in validating it).
>
Hello;

Can "badly formed data" be reasonably clearly defined ? 
What tests are there for "validly formed but errorneous data" ?

There are  several monitoring efforts (including the one done here) which compare
sets of (m)bgp routing tables over time.
It seems to me that such (m)bgp pollution
should be detectable with a monitoring project.

BTW, what seems to be the clearest sign here of the
recent flap was the dropping of
43 Autonomous Systems by UU.net for the
Sat Jun 23 16:37:41 2001 status run. This is not a good 
enough metric to relieably detect such problems. There do seem to be a lot of
weird changes in the routing table in that
dump, but a simple test for this is not apparent to me at present.

Regards
Marshall Eubanks

   Multicast Technologies, Inc.
   10301 Democracy Lane, Suite 410
   Fairfax, Virginia 22030
   Phone : 703-293-9624          Fax     : 703-293-9609     
   e-mail : tme at on-the-i.com     http://www.on-the-i.com         

>Conclusion: changing the RFC from saying you MUST do a NOTIFY and ditch the

>session could be adjusted to stating that you MUST handle the error in one

>of two ways: do a NOTIFY and ditch the session (traditional), or send an
>ALERT and discard the badly formed route. Additionally, this alternative
>handling MUST NOT be enabled by default, and SHOULD have a threshhold
>parameter at which the session will undergo a NOTIFY/reset, under the
>assumption that the host sending an appreciable amount of badly formed
>routes is, in fact, in danger of sending correctly formed but erroneous
>data as well.
>
>Suitable threshold values are left as an excercise to local admins and BCP

>documents; I would think this could be negotiated as a capability extension

>to BGP4, with the fallback, of course, being to follow the traditional RFC

>practice.
>
>Thoughts?
>-- 
>***************************************************************************

>Joel Baker                           System Administrator - lightbearer.com

>lucifer at lightbearer.com              http://www.lightbearer.com/~lucifer
>

Marshall Eubanks

tme at 21rst-century.com