At the previous meeting for OLPC enthusiasts at SF State [1], we ran a test where we took three XO laptops and walked to locations on campus where the three were aligned as follows:
- A can talk to B
- B can talk to C
A cannot talk to C directly, because the distance between the two is too much for XO's Wi-Fi radios - they cannot "see" each other directly. At this point, we set up pings to see if data sent from A would get to C and it did! In spite of the fact that A cannot see C on the radio, it can see B, so the packets hop off the XO in the middle and reach out to C. Well, this is no surprise because this is how the XO mesh is supposed to work.
[2] I recreated the experiment at home by borrowing an XO unit from Bonnie Homan [3] (thanks, Bonnie!)
- I set up one link between an XO in my car (A) and another one at home (B). The XOs barely managed to ping each other.
- Then I added a third XO to the mix (C) and started pinging A while I was standing next to B.
- At this point, I fired up another Terminal activity and used tracepath to capture hop info. A to C was one hop.
- Next, I walked away from B so as to get further away from A and B.
- Sure enough, at one point, the pings stopped...and picked up again. This time tracepath showed two hops!
In the following screenshots, you can see the hops change back from 2 to 1 as I come back inside the house. The moment C is able to see A directly, it stops hopping via B. It self-configures. Self-heals. The word "organic" comes to mind (hey, I live in California).
For the following screenshots, A is 169.254.6.215 B is 169.254.9.4 and C is 169.254.4.206
[4]
[5]