Did your BGP crash today?

Kevin Oberman oberman at es.net
Mon Aug 30 11:40:10 CDT 2010


> Date: Mon, 30 Aug 2010 10:55:03 -0500
> From: Jack Bates <jbates at brightok.net>
> 
> 
> Florian Weimer wrote:
> > This whole thread is quite schizophrenic because the consensus appears
> > to be that (a) a *researcher is not to blame* for sending out a BGP
> > message which eventually leads to session resets, and (b) an
> > *implementor is to blame* for sending out a BGP messages which
> > eventually leads to session resets.  You really can't have it both
> > ways.
> > 
> 
> As good a place to break in on the thread as any, I guess. Randy and 
> others believe more testing should have been done. I'm not completely 
> sure they didn't test against XR. They very likely could have tested in 
> a 1 on 1 connection and everything looked fine.
> 
> I don't know the full details, but at what point did the corruption 
> appear, and was it visible? We know that it was corrupt on the output 
> which caused peer resets, but was it necessarily visible in the router 
> itself?
> 
> Do we require a researcher to setup a chain of every vender BGP speaker 
> in every possible configuration and order to verify a bug doesn't cause 
> things to break? In this case, one very likely would need an XR 
> receiving and transmitting updates to detect the failure, so no less 
> than 3 routers with the XR in the middle.
> 
> What about individual configurations? Perhaps the update is received and 
> altered by one vendor due to specific configurations, sent to the next 
> vendor, accepted and altered (due to the first alteration, where as it 
> wouldn't be altered if the original update had been received) which 
> causes the next vendor to reset. Then we add to this that it may pass 
> silently through several middle vendor routers without problems and we 
> realize the scope of such problems and why connecting to the Internet is 
> so unpredictable.

This only way they could have caught this one was to have tested to a
CRS which had another router to which it was announcing the attribute in
a mal-formed packet. Worse, the resets should just keep happening as the
CRS would still have the route with the unknown attribute which would
just generate another malformed update to cause the session to reset
again. 

While it may be possible to recover from something like this, it sure
would not be easy.
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634
Key fingerprint:059B 2DDF 031C 9BA3 14A4  EADA 927D EBB3 987B 3751




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