Re: [B.A.T.M.A.N.] batman-adv: ap mode with isolation enabled

[Antonio Quartulli <ordex@autistici.org>]

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On Fri, Oct 12, 2012 at 09:54:53AM -0300, NicoEchániz wrote:
> On 10/12/12 04:15, Antonio Quartulli wrote:
> > On Fri, Oct 12, 2012 at 02:15:39 -0300, NicoEchániz wrote:
> >>
> >> Is the setup clear enough now? or am I missing the point as to what is
> >> unclear? Please ask whatever needs to be clarified.
> >>
> > 
> > Hello Nicolás,
> > 
> > I think I got your point. First, you are talking about the "normal" AP isolation
> > feature that you can enable in hostapd, right? Because in batman-adv we have our
> > own (Distributed) AP-isolation but it has different effects and behaviours.
> 
> exactly, it is the "normal" AP isolation feature.
> 
> 
> > The behaviour is correct: OGMs are broadcast packets. In infrastructure mode,
> > whatever broadcast packet a station sends gets to the AP which will re-broadcast
> > it again. In this way every station gets it and from the batman-adv point of
> > view it is like the packet was received directly from the other sta (the MAC
> > addresses in the packet say so). Therefore you must enable ap-isolation in
> > hostapd if you want batman-adv to behave as you expect.
> 
> Does this mean that with isolation turned off stations will try to
> communincate directly if they can? Say, if we have two stations that are
> far from the AP but very near each other, will they actually send
> (unicast) packets to each other without going through the AP at all? If
> so, activating isolation might be eliminating real possible paths, all
> for the sake of sane originator tables.

First, this is not related to batman-adv. We are discussing something "below"
the batman-adv layer. In infrastructure mode unicast packet from station A to
station B will pass through the AP. This behaviour has been changed by 802.11e
and (T)DLS (you can have a look at the 802.11 standard if you want more details
about that). But, again, this is not related to batman-adv.

If you use infrastructure mode without AP isolation, batman-adv will consider
all the other STAs as direct neighbours. But, due to infrastructure mode,
packets from STA1 to STA2 will always pass through the AP. This is also why I
would suggest to keep AP-isolation ON if you want to run batman-adv on the
stations and on the AP, but then it depends on what you want to get.

> 
> 
> I believe our mixed setup is not standard practice, that's why I wanted
> to share this real-world results.

not standard, but common (there are many -closed- drivers that work better in
infrastructure than adhoc mode. but this is normally used in PtP links only due
to asymmetry problems on the link (see 802.11 standard for more :-))

Cheers!


-- 
Antonio Quartulli

..each of us alone is worth nothing..
Ernesto "Che" Guevara

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