On Thu, Jun 14, 2012 at 04:51:01PM -0300, gto...@inti.gob.ar wrote: > Hi, > > we are interested too in interface alternating, so we made some > tests to understand how it works. As you can see on the attached > sketch.png, we connected two pair of routers using their ethernet > interfaces, E6 with E7, and E8 with E9. All of them have eth0, and > an ad hoc interface, wlan0-1, managed by batman. E6 and E8 are in > channel 11, whereas E7 and E9 are in channel 1. Besides we used two > other routers, E12 and E13, both in channel 11, with their tx power > set to just 0 dbm, to avoid a direct sight between them. > > Then we sent traffic from E12 to E13. We expected that packets > travelled from E12 to E6, and that E6 forwarded them to his eth0 to > use the interface alternating feature, making traffic flow to E7, > then E9, E8 and finally E13. But instead, we observed that the > actual path was E12--E6--E8--E13. The resulting routes for each > router are attached in a text file, and also the graph from the > batctl vd dot command. > > After this result, we read again the thread mentioned by Guido, > specially in this part: > > https://lists.open-mesh.org/pipermail/b.a.t.m.a.n/2012-March/006344.html > > And if we understand correctly, the alternation feature works > after the batman path has been selected. So in our case, E12 looks > at his table to know where to send a packet to E13, and finds E6. > Then E6 receives the packet and looks in his own table, finding that > the best path to reach E13 is E8. At this point, the alternating > should work, but there's only one interface directly connected to > E8, so the packet goes there, and so on. We think that if E6 and E7 > were not two different routers running batman-adv but they were two > radios of the same batman-adv router, and the same for E8 and E9, > the alternating would work, because the unique router would choose > the best path, and then would find two possible interfaces to the > same next-hop, changing the interface.
This is entirely correct - batman-adv has only one link to choose from
(E6 -> E8) to reach its best nexthop E8, so there is no way to
"alternate" the interfaces.
> We'd like to know if this interpretation is correct, and in that
> case, if it were possible to use interface alternating in a case
> like this, with two routers connected to work together. Thanks!
Mhm, with the current implementation - no, unfortunately not. We would
need some kind of multipath routing to select between routes, this is
much more complex.
An alternative might be to use the routers E7/E9 as secondary routers
without batman, but only forwarding traffic between Ethernet and
WiFi. Then the "primary" routers (E6 -> E8) would think they have
an alternative route via Ethernet (because they don't see the
intermediate hops E7/E9). This comes with some caveats however, e.g.
4-addr mode in Ad-Hoc, you need some very simple ethernet forwarder,
and most probably other things I forgot.
Cheers,
Simon
signature.asc
Description: Digital signature
