[Bluez-devel] Piconet Routing

[Bluez-devel] Piconet Routing

[Stefan Mischke]

Hello!

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?

Regards
Stefan



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Re: [Bluez-devel] Piconet Routing

[Marcel Holtmann]

Hi Stefan,

> 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.

Regards

Marcel




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Re: [Bluez-devel] Piconet Routing

[Marcel Holtmann]

Hi Stefan,

> > > 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)? 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.

Regards

Marcel




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Re: [Bluez-devel] Piconet Routing

[GUILLON Gabriel]

Take a look at btchat: it does routing through bluetooth

Stefan Mischke a =E9crit :
> Hello!
>=20
> Since Bluetooth uses Time Division Duplex, a slave is not allowed to=20
> talk to another slave in the same Piconet. The logical consequence must=
=20
> be that the data is routed over the master. I've used l2test to check i=
f=20
> l2cap does this kind of routing automatically. It doesn't but rather=20
> creates a new, direct acl link to the remote slave device (scatternet).=
=20
> I don't know how it is with rfcomm, but I suppose it's the same. My=20
> question: Is there any automatic Piconet Routing inside BlueZ or does=20
> one have to implement it by oneself?
>=20
> Regards
> Stefan
>=20
>=20
>=20
> -------------------------------------------------------
> This SF.net email is sponsored by: IT Product Guide on ITManagersJourna=
l
> Use IT products in your business? Tell us what you think of them. Give =
us
> Your Opinions, Get Free ThinkGeek Gift Certificates! Click to find out =
more
> http://productguide.itmanagersjournal.com/guidepromo.tmpl
> _______________________________________________
> Bluez-devel mailing list
> Bluez-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bluez-devel
>=20

--=20
"Everything is funny, if you wait long enough"

Gab

Dieu, dans sa grande cl=E9mence, a invent=E9 l'alcool pour que les moches
aussi puissent baiser.
- Woody Allen -


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Re: [Bluez-devel] Piconet Routing

[M RISON]

> > > > 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/
"Z88 vs CPC? Christ. How did we miss that platform war?"
-- http://www.ntk.net/index.cgi?back=archive00/now0128.txt&line=110#l