[Commotion-dev] Roaming between nodes

[Mikael "MMN-o" Nordfeldth]

On 2013-07-03 16:07, Dan Staples wrote:> I assume you mean
roaming/handoff of non-mesh clients connected to
> access points on mesh nodes, yes? Unfortunately, this is currently not
> possible, without the type of coordination you describe.

Ah, yes. Handoff/-over is what I mean.

> As I understand
> it, it is a limitation of a layer-3 mesh, such as OLSRd, which we use.
> I've heard that a layer-2 mesh, such as Batman-Adv, *can* do seamless
> handover of access point clients. But of course, there are lots of other
> tradeoffs between layer-2 and layer-3 meshes.

I was thinking that if I am given an IP address unique for the mesh, and
I could keep this whilst connected to any node, wouldn't it be possible
to have packets originating from me be properly routed regardless of
which node I am connected to?

I.e. if when connecting to a wifi node I generate my local IPv6 address
incorporating my MAC address, which can be assumed to be unique. And
when I am then walking to a second access point, losing connection with
the first, I would resend whatever TCP packets not properly sent to the
new AP, effectively re-establishing my connection on the new route.

Though I guess this is where I run into trouble in my train of thought,
as it would perhaps mean that each and every route to each connected
client would have to be propagated over the mesh network in order for
the "return route" to my machine to be properly updated.

Sorry if I haven't fully understood low-level implementations of the OSI
model, feel free to point me to documentation if it's too much. I'm
mostly trying to walk myself through the complexities of mesh networking
and asking for some help along the path ;)

> A while ago, I came upon a solution for doing seamless handover for
> access point clients, developed by folks at the Distributed System and
> Networks Lab @ Johns Hopkins. It's called Smesh: http://www.smesh.org/.
> I would love to try to implement this in Commotion, but it would be a
> long-term project that we currently don't have anyone working on.

No rush in my opinion at least. Seamless handoff is a luxury feature, so
there's no rush in getting it working before anything else .)

> But keep in mind that we are currently ramping up development of
> Commotion desktop/mobile mesh client software (linux, android, mac,
> windows, iOS), that will let mobile phones and laptops and such become
> full-fledged mesh nodes, which will allow for theoretically seamless
> roaming, as they will use ad-hoc links instead of access point
connections.

Absolutely, I'm following the development closely as we're trying out
the firmware builds here in Umeå, Sweden. .)

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