[Babel-users] a new way to mesh in openwrt

[Juliusz Chroboczek]

Hi Donald!

>> It never worked well beyond a few nodes, since it requires global
>> synchronisation (of beacons?  I forget) across the whole mesh.  I could be
>> wrong, but I believe tha 802.11s doesn't have that flaw.

> I think the main problem with ad-hoc mode is that all the stations
> need to be able to see each other's transmissions. 802.11s is
> multi-hop and does not have that problem. Ad-hoc mode was just for
> something like a modest number of people with laptops sitting around a
> table or the like.

I think Benjamin was assuming that there is a routing protocol running
over the ad-hoc mesh.  In MANET terms, 802.11 in ad-hoc mode is the
underlay, and a proper layer 3 routing protocol (such as OLSR-ETX, Babel
or BMX6) is the overlay.

However, it turns out that doesn't work very well in practice, the
underlay tends to get partitioned due to synchronisation issues.  So
people have been running their underlays in infra mode, which causes a lot
of extra complexity, since you need to manually choose the gender of every
router.

802.11s routing doesn't scale, but people have been experimenting with
using a degenerate form of 802.11s as the underlay with Babel as the
overlay.  I haven't tried it myself, but I've heard that it doesn't work
very well due to buggy firmware in off-the-shelf routers.

If I understand the blog posting correctly, with APuP, the Freifunk guys
are trying to use infra mode, which is well supported by off-the-shelf
routers, but simplify the administration by allowing APs to mesh with each
other using the 4-address (WDS) frame format.  Which is pretty cool if it
turns out to work at scale.

-- Juliusz