On Mon, Nov 12, 2018 at 8:18 AM Juliusz Chroboczek <[email protected]> wrote: > > >> do loop-free routing. > > > Hah. :) > > > I note that babel doesn't actually do that, any more. > > Pick a pair (p, id), where p is a prefix and id is a router id. Consider > the graph defined by all route table entries indexed by (p, id). Then > Babel guarantees that at any time this graph is acyclic. > > Since the union of multiple acyclic graphs is not in general acyclic, > Babel does not guarantee that the forwarding graph for a prefix p is > acyclic in the case where p is originated at different routers, although > it does guarantee that any loops disappear in linear time (with a constant > that depends on the amount of packet loss). And of course Babel does not > guarantee loop-freedom in the presence of redistribution between protocols > (as in your case with DHCP).
I DO get it. :) The practical thing, is that you won't see unreachables (while a gateway reboots, for example, or the routing table is optimized) while duking it out with other metrics from other protocols. If we really really care about loop freedom for those short intervals, keeping the babel metric the same when going unreachable is the way to go. 'course if that route is GC'd we end up with the same problem a few minutes later. It would be really good to get all the distro designers and all the routing protocol daemon writers and all the address assignment daemon developers in one room, to hammer out one, consistent way to do this stuff right. But I'm pretty sure we'd run out of pizza and the ranks decimated by the ensuing cannibalism long before that universal solution was achieved, and we'd be back to using sneakernet universally. (see also the addrlabel discussion for ipv6) > > -- Juliusz > > _______________________________________________ > Babel-users mailing list > [email protected] > https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/babel-users -- Dave Täht CTO, TekLibre, LLC http://www.teklibre.com Tel: 1-831-205-9740 _______________________________________________ Babel-users mailing list [email protected] https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/babel-users
