Hello Dear Sven and Martin:

Thanks for your advisement

I hope to aviod Excavation of underground pipeline in the smart community or Park .

if Batman-adv can support smart relay ( networking code ) at mesh network really , and it will be very valuable for us .

i think one of core valuable point is relay mode and Client roaming

i prepare to build more ap evironment and test for the part later

As market competition intensifies,

the gap between similar productsis getting smaller and smaller,

likewise the evolution of growing homogenization trends within the industry.

i hope we can find valuable point for Blue Ocean each other .

if you have some different point , and I would be happy to be the first and build win-win mode each other .

Best Regards

Tiger

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

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 1546

Your 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). 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).

...

if i send a packet from host A to hostC via hostB, whether hostB will open relay mode at layer2 .

I completely failed to parse this.

batman-adv will send your data from hostA to hostC via hostB when the TQ value for the link "from hostA to hostC via hostB" is higher than the TQ value for the link "hostA to hostC directly". This has nothing to do with network coding and is a standard feature of batman-adv (this is actually what it is about).

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. This seems to be especially problematic when some nodes are for example 2x2 MIMO devices and others are 3x3. At least this would be a good way to let the 2x2 miss important packets when the 3x3 devices talk between each other.

I would even guess that things like dynamic transmission power would make overhearing packets also more problematic.

...

but i have a question ? How many relay nodes can be supported at NetworkCoding ( mtu 1546 ) .

I am not sure what you are asking here. The implementation in batman-adv can combine two packets into one. And this combining of these two packets is done by exact one relay node. The decoding is done by the two receiving nodes. What you can build with it is been shown in the documentation from Martin. The network coding used here is therefore done by a relay node and its neighbors. But there can be multiple relay nodes in the mesh doing network coding at the same time.

I personally haven't used network coding with batman-adv. But since you've created multiple new threads on the mailing list [1,2,3,4] (beside the private mail *grml*) - here is at least a pseudo-answer.

Kind regards, Sven

[1] https://www.open-mesh.org/projects/batman-adv/wiki/NetworkCoding#Drawbacks [2] https://lists.open-mesh.org/pipermail/b.a.t.m.a.n/2016-November/016586.html [3] https://lists.open-mesh.org/pipermail/b.a.t.m.a.n/2016-November/016587.html [4] https://lists.open-mesh.org/pipermail/b.a.t.m.a.n/2016-November/016588.html [5] https://lists.open-mesh.org/pipermail/b.a.t.m.a.n/2016-November/016592.html