Re: [Idr] [Fwd: I-D Action:draft-chen-rfc4893bis-00.txt]

[David Freedman <david.freedman at uk.clara.net>]

> 
> All the prefixes could have the malformed AS4_PATH attribute (from a
> remote router).  In that case, rejecting the routes has the same effect
> as tearing down the session.

You are correct that, in the tradeoff scenario we sever connectivity to
the prefix, but the implications of this "in the wild" are not as
worrying since a malicious network attempting to cause a user's
disconnection to his upstream through mass prefix advertisement is made
significantly more difficult due to the nature of both the network and
BGP's bestpath selection algorithm.

>One may still debate whether it's preferable to "fix" the broken route
>by dropping the AS4_PATH or treat the broken route as a withdraw (which
>as you point out is effectively what your options a+b are), but if the
>latter is chosen it should be for some reason other than "may cause
>loops".

I'd like to see the "withdraw if you have something to withdraw or
simply don't accept" such that everybody converges to a consistent view
and we don't end up with having a patchwork of attributes recorded for a
prefix, some with and some without an AS4_PATH (depending on who is
doing what).



Dave.



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