Re: [B.A.T.M.A.N.] i have a question ? How many relay nodes can be supported at NetworkCoding ( mtu 1546 ) .

[Simon Wunderlich <sw@simonwunderlich.de>]

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On Tuesday, November 8, 2016 11:55:14 AM CET johnzeng via B.A.T.M.A.N wrote:
> 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 .

Hi Johnzeng,

why are you insisting on using network coding? Batman-adv can do relay without 
network coding enabled, this is part of the basic mesh technology. Network 
Coding (or CATWOMAN) was research project/proof of concept implementation 
which isn't actively maintained right now. But from what I understood, your 
setups can be supported with "standard" batman-adv mesh.

Thanks,
    Simon 

> 
>                                               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-technica
> > l *
> > https://downloads.open-mesh.org/batman/papers/batman-adv_network_coding.p
> > df *
> > https://vbn.aau.dk/da/publications/catwoman(214ee21a-e786-495d-85c9-3efac
> > 4718ead).html *
> > 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#Drawback
> > s [2]
> > https://lists.open-mesh.org/pipermail/b.a.t.m.a.n/2016-November/016586.ht
> > ml [3]
> > https://lists.open-mesh.org/pipermail/b.a.t.m.a.n/2016-November/016587.ht
> > ml [4]
> > https://lists.open-mesh.org/pipermail/b.a.t.m.a.n/2016-November/016588.ht
> > ml [5]
> > https://lists.open-mesh.org/pipermail/b.a.t.m.a.n/2016-November/016592.ht
> > ml
> End of encapsulated message


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