[B.A.T.M.A.N.] link alternation when radios are not on batman-adv router?

Guido Iribarren guidoiribarren at buenosaireslibre.org
Fri Mar 30 18:33:14 CEST 2012


If i got your setup right, you plan to flash openwrt on all the
nanostations that belong to the supernode, but install batman-adv only
on the 'central' router, with a single eth nic.
In that case, batman-adv has no (manual or automatic) way of
alternating the different paths (or even knowing which packet came
trough which radio).
You should use vlans for that (i'm not sure about the performance), or
run batman-adv on each individual radio, including both the wlan and
eth0 in bat0.
This last choice will allow packets being relayed along the backbone
to skip passing through every central router on hops. They would
instead get switched directly between nanostations belonging to the
same supernode (unless, of course, the packet's destination is indeed
that 'central' router)

On 3/30/12, dan <dandenson at gmail.com> wrote:
> I have an interesting hardware setup I'd like to explore.
>
> Basically, I would like to take commodity ubiquiti and/or openmesh
> hardware and build a mesh with two different node types, some having
> just 1 radio and others having multiple radios, a standard node and a
> super node.
>
> the standard node is:
> a picostation flashed to openwrt running batman-adv and running the
> radio in Ad-Hoc mode.  Alternately an OM2P flashed to openwrt.  This
> is the basic client radio
>
> the super node is:
> a group of picostations or nanostations, flashed openwrt in adhoc
> mode, but acting only as the L2 transport with a router at the center
> running batman-adv.
>
> The idea is that the super nodes have multiple radios in multiple
> channels and can take advantage of link alternation allowing super
> nodes to keep much higher bandwidth between them while the standard
> nodes are cheap.  The 'router' MIGHT also have a radio for client
> access (unifi station flashed to openwrt maybe, or an ALIX board)
>
> The supernode will have more CPU and also be the target of
> backhaul/shorthaul links to cut down on hop count.  The main router
> would also be a batman-adv device, probably an x86 server, and would
> be the border router for the mesh.
>
> some questions,
> I know that the supernodes will have higher throughput capabilities
> due to dual mesh radios, but how will batman-adv know this or how
> would I tell it?  Is the internal mechanism for determining the best
> path going to take this into account?  Is there a way to identify a
> supernode as being a better path above and beyond the automatic
> batman-adv mechanisms?
>
> Is having separate radios connected to a batman-adv router going to
> behave how I presume?  That multiple node2node connections will be
> identified and the links be alternated when appropriate?
>
> If the supernodes have 2 mesh radios, 1 in 5Ghz and 1 in 2.4Ghz, then
> the standard nodes will only be able to connect to the 2.4Ghz channel
> which might make it inappropriate to do link alternating on these two
> links because of the shared traffic.  Should batman-adv automatically
> stop alternating the tx/rx on these links when one of the channels
> starts to get saturated?
>
> some other info:
> the supernodes may have a link directly to the main distribution
> point, but may also be linked just to another supernode and not to the
> main distribution point, or possibly both.
>
> the supernodes are likely to have more than 2 mesh radios as some of
> these could be direction antennas.  A supernode might have 3x 2.4Ghz
> radios for mesh, 2x 5Ghz radios for mesh, and a 2.4Ghz radio for
> non-mesh clients.  These would most likely all be connected to a
> switch port and only be on a single ethernet interface as far as
> batman-adv is concerned.
>


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