Re: [Bluez-devel] Piconet Routing

M RISON
2004-10-21T09:51:13Z

> > > > Since Bluetooth uses Time Division Duplex, a slave is not allowed to
> > > > talk to another slave in the same Piconet. The logical consequence
>must
> > > > be that the data is routed over the master. I've used l2test to
>check if
> > > > l2cap does this kind of routing automatically. It doesn't but rather
> > > > creates a new, direct acl link to the remote slave device
>(scatternet).
> > > > I don't know how it is with rfcomm, but I suppose it's the same. My
> > > > question: Is there any automatic Piconet Routing inside BlueZ or
>does
> > > > one have to implement it by oneself?
> > > you must do it by yourself, because even if the master manages to put
> > > all devices into the same piconet the connections are point to point.
> > TCP connections are also point to point, but since it's built on top
> > of IP, it goes (transparently) over many routers. Before I tested it,
> > I thought the link manager would take care of this. How does the
> > communiction of many BT devices work in practice? Who manages this
> > routing, since one device can only be point-to-point-connected to 2
> > devices (an this doesn't work really smooth)?

[No, a master can be P2P-connected to up to 7 active slaves in a piconet,
and if you support scatternets then you can in theory also be P2P-connected
to several masters (although this is indeed not very smooth in BT1.2).]

> > There must be one
> > controlling instance. One cannot let the different applications handle
> > this, can one?
>this is true, but the problem is, that a slave does not know to which
>other slaves a master is connected. There is no routing stuff like in IP
>and you can't retrieve these information from the HCI layer.

A solution to the OP's problem is to use the PAN profile. The master (GN)
will then automatically "route" (bridge, actually) BNEP (Ethernet) packets
between the slaves (PANUs).

Mark

--
CPC/IP - A TCP/IP stack for Amstrad CPCs
-- http://www.nenie.org/cpcip/
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