Hi,
On 2016-11-05 15:28, Sven Eckelmann wrote:
Hi,
When i compile the part , whether i need make CONFIG_BATMAN_ADV_BATMAN_V=y at batman-adv-2016.2
2016.2 is "old". And BATMAN_V has nothing to do with network coding.
i read some detail about NetworkCoding , my understanding :
every relay node will detects neighbors packet at promisc mode and combine these packet into a single transmission ,
I think Martin can help here. He also provided some documentation:
- https://www.open-mesh.org/projects/batman-adv/wiki/NetworkCoding
- https://www.open-mesh.org/projects/batman-adv/wiki/NetworkCoding-technical
- https://downloads.open-mesh.org/batman/papers/batman-adv_network_coding.pdf
- https://vbn.aau.dk/da/publications/catwoman(214ee21a-e786-495d-85c9-3efac471...
- https://downloads.open-mesh.org/batman/misc/wbmv4-network_coding.avi
If you are looking into network coding as a research project, batman-adv is a fine starting point. But as Sven hinted in his answer, it isn't really useful in a real setup.
And it will not try to forward each packet is overheard. Instead it will try to find coding opportunities which it then uses to forward its own packets in less transmissions (by using packets which the other nodes should already know).
batctl nc 1 echo 1 > /sys/class/net/bat0/mesh/network_coding ip link set dev wlan0 promisc on ip link set dev wlan0 mtu 1546Your cards/drivers will most likely not even support promiscuous mode. Some of them require to have an monitor mode interface at the same time and some of them will simply not work.
You can test it by simply checking what tcpdump is showing you on the underlying interface (wlan0). If it doesn't show you the packets between two other nodes then promiscuous mode is not working for you.
The feature itself is not used very often (Martin, please correct me here).
I don't use it myself, and don't know of anyone else using it.
It is not enabled by default because it is not making things "better" all the time [1]. So it is also not tested as much as other components in batman-adv and you should think first if it is really useful for your scenario/HW. I knew at least from some Freifunk communities played around when it was enabled by default but had to revert when they experienced "non functional mesh links" (nothing more about it is known to me - sorry Martin).
No problem.
[snip...]
network coding can only (when lucky) try to combine some packets - but this will only work when promiscuous mode is actually working and the nodes can overhear packets. Otherwise it will (in theory - Martin please correct me if I overlooked a safety mechanism) just create a lot of coded packets which cannot be decoded anymore.
Yeah, packets are lost if the nodes are not promiscuous.
Good luck with the project :)
// Martin