Hi Henning, On Tue, Aug 25, 2015 at 1:50 PM, Henning Rogge <[email protected]> wrote:
> On Tue, Aug 25, 2015 at 7:38 PM, Alia Atlas <[email protected]> wrote: > >> There is also the point that multipath choices tend not to be > >> isometric... just because the two paths from your local point of view > >> seem to be good they are not necessarily good from the point of view > >> of the next hop. > > > > > > In a way that can't be captured by link metrics? I haven't really > looked at > > the unique characteristics for wireless. I'm happy to do a bit of > > self-education. > > Imagine a network with three wireless routers (A,B,C)... A is the > uplink, you are C, but both A and C can only see B. > > All routers are dualband routers (all have both a 2.4 GHz and a 5 GHz > radio). > > From your (C) point of view the multipath-solution is "easy", one path > use 2.4 GHz (C to B to A), the other one uses 5 GHz (C to B to A). > > But when your IP packet arrives at B, B doesn't know it is part of a > multipath stream... so forcing both streams to stay on their frequency > is not trivial if you don't want to do source routing. > Ok - I was assuming that each router would hash and pick a next-hop for the traffic. So traffic that came in on a 2.4 GHz could go out the 5 GHz. With consistent hashing, maybe one could force traffic to specific paths, but that isn't usual for ECMP. > There is a solution for this easy example (as Juliusz will certainly > be able to tell you), but there are more complicated setups which are > even more difficult. > > Multipath on wireless links is easy to mess up, so I would suggest NOT > including it into the feature-set required by Homenet. > Ok. Let me poke a bit more. Is it safe to use parallel wireless links between two routers A and B? Consider that there's a square topology, as below, where E<->F and D<->E are both wireless, and links have the same metric. Can C safely send traffic to reach F via both D and E? Can F safely send traffic to reach C via both D and E? How is this case different than if C were split into a C1 and a C2 so that F-E-C1 and F-D-C2? [ C ]---------[ D ] | | w | | [ E ] ---w--- [ F ] Basically, I'm trying to understand the restrictions. Thanks for your explanations! Alia
_______________________________________________ homenet mailing list [email protected] https://www.ietf.org/mailman/listinfo/homenet
