On 5/28/2012 9:42 PM, David Conrad wrote: > On May 28, 2012, at 1:59 PM, Paul Vixie wrote:
>> third, rsync's dependencies on routing (as in the RPKI+ROA case) are not
>> circular (which i think was david conrad's point but i'll drag it to here.)
> Nope. My point was that anything that uses the Internet to fetch the data (including rsync) has a circular dependency on routing. It's just a question of timing.
when you say it's a question of timing, i agree, but then i think you
won't agree again. in batch mode i can express a policy that's true from
that moment forward until removed. in real time mode i have to be able
to express a policy which is both valid and reachable at the moment of
validation. that's a question of timing but the word "just" as in "just
a question of timing" trivializes a galaxy-sized problem space. >
>> ROVER expects that we will query for policy at the instant of need.
> Might want to review https://ripe64.ripe.net/presentations/57-ROVER_RIPE_Apr_2012.pdf, particularly the slide entitled "Avoid a Cyclic Dependency".
i read it. this is also what draft-gersch-grow-revdns-bpg says. this
makes for a "fail open" design -- the only thing the system can reliably
tell you is "reject". this precludes islands of, or a mode of, "fail
closed". while i don't consider a mode of "fail closed" to be
practically likely, i'd like to preserve the fig leaf of theoretical
possibility. (and the more likely possibility that islands of "fail
closed" could be sewn in.) > As far as I can tell, ROVER is simply Yet Another RPKI Access Method like rsync and bittorrent with its own positives and negatives.
i can tell more than that. rover is a system that only works at all when
everything everywhere is working well, and when changes always come in
perfect time-order, where that order is nowhere defined, and is in any
rsync's punt of the ordering problem is batch mode with policy start
times rather than policy valid instants. to my mind anyone who doesn't
punt the ordering problem has to instead solve it. rover does neither.