[serval-project-dev] Re: Serval mesh multicast non-functional

[Paul Gardner-Stephen]

Hello,

On Dec 1, 10:45 pm, "L. Martin Ringler" <l.martin.ring... at gmail.com>
wrote:
> It appears Serval doesn't handle multicast UDP messages. Is this
> deliberate or broken?

It is not deliberate on our part.
A number of complications are likely to be present when trying to do
multicast:

1. The phones may not have kernel support for it compiled in (or more
likely, some models will, while others wont).
2. I don't know if BATMAN does multicast (I suspect OLSR might, but I
really don't know).

> Why muticast messages are important...
>
> 1. To maintain a routing table for non pure mesh where some of the
> nodes are seperated by a functional backbone the mesh messages will
> have to be multicast since broadcast messages will be restricted to
> the local subnet. Most modern routers block IP broadcast traffic.

I agree multicast is good here, but there are ways around this, even
if they aren't ideal.
In particular, if there is a mesh node at either end, then they can
(eventually) bridge traffic.
Some of this will become much simpler once we move to the overlay
mesh, at which point multicast will not be sensibly possible, anyway.

> 2. Some applications that could use the ad-hoc mesh are Position
> Location type apps. You and your friends are skiing and you get
> seperated, your app would tell you where they are etc. I think you
> would need to multicast the Position Location Information and
> broadcast wouldn't work if 2 or more discreet groups were on the same
> Serval mesh.

Actually, there are ways around this, and we are currently working on
exactly this kind of groups of people sharing information problem that
you mention.  We see no reason why our planned protocols shouldn't
work with multiple groups in the same physical area, even with
overlapping membership.

> Is the Ad-hoc mesh encryted? Seems to be in the clear.

It is all in the clear at present.  We have plans to add voice, SMS
etc encryption and authentication in over coming months.
Mesh management traffic will remain en claire, but the overlay mesh
will increase the ability to authenticate even that.

Paul.

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