Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.debian.user > #173713 > unrolled thread

Disabling transmission of beacon frames

Back to article view | Back to linux.debian.user

Contents

  Disabling transmission of beacon frames Jan Bakuwel <jan.bakuwel@gmail.com> - 2016-10-22 06:00 +0200
    Re: Disabling transmission of beacon frames Henrique de Moraes Holschuh <hmh@debian.org> - 2016-10-22 15:50 +0200
      Re: Disabling transmission of beacon frames Henrique de Moraes Holschuh <hmh@debian.org> - 2016-10-22 21:10 +0200
      Re: Disabling transmission of beacon frames Jan Bakuwel <jan.bakuwel@gmail.com> - 2016-10-22 23:10 +0200
        Re: Disabling transmission of beacon frames Henrique de Moraes Holschuh <hmh@debian.org> - 2016-10-23 05:30 +0200
    Re: Disabling transmission of beacon frames Dan Purgert <dan@djph.net> - 2016-10-22 16:10 +0200

#173713 — Disabling transmission of beacon frames

Hi all,

As far as I'm aware, IEEE802.11 defines the two modes a wifi AP and
client can establish communication, passive (AP broadcasts SSID, clients
connects to SSID) and active (AP doesn't broadcast SSID, client
broadcasts SSID probe and AP then sends a probe response).

Does anyone know if it's possible to disable passive mode on an AP? It
is possible to set the SSID to hidden but this does not stop the
broadcasts, it just broadcasts frames with a null SSID. Stopping the
broadcasts altogether (and as a consequence the client must use active
mode, ie. needs to send probes) will result in no EMR when wifi is not
in use, in other words AP will only listen not transmit in that case,
yet wifi is available when needed.

Jan

[toc] | [next] | [standalone]

#173722

On Sat, 22 Oct 2016, Jan Bakuwel wrote:
> Does anyone know if it's possible to disable passive mode on an AP? It
> is possible to set the SSID to hidden but this does not stop the
> broadcasts, it just broadcasts frames with a null SSID. Stopping the
> broadcasts altogether (and as a consequence the client must use active
> mode, ie. needs to send probes) will result in no EMR when wifi is not
> in use, in other words AP will only listen not transmit in that case,
> yet wifi is available when needed.

The AP would have to switch to standard beaconning while *any* station
is associated, otherwise it could have nefarious effects on network
performance.

Also, beacon-less infrasctructure mode CANNOT work on a number of bands
where the stations are forced to operate in passive mode (i.e. they
cannot issue a probe request to a channel where they did not receive an
AP beacon).  It is also likely forbidden in any channels where DSS
(weather radar detection) must be performed, as this is only performed
by APs.

So, in theory this would work provided the adapter firmware allows for
it in the first place, and it is restricted to channels where clients
are allowed to actively probe for APs -- which is information readly
available on the regdb (regulatory database).  However, I see no way to
control this in /sbin/iw for infrastructure mode (but I find iw terribly
confusing, so I might have failed to notice it).

Please ask in the linux-wireless mailinglist at vger.kernel.org.

-- 
  Henrique Holschuh

[toc] | [prev] | [next] | [standalone]

#173739

On Sat, 22 Oct 2016, Henrique de Moraes Holschuh wrote:
> AP beacon).  It is also likely forbidden in any channels where DSS
> (weather radar detection) must be performed, as this is only performed
> by APs.

Make that DFS.  Sorry for the typo.

-- 
  Henrique Holschuh

[toc] | [prev] | [next] | [standalone]

#173747

Hi Henrique,

On 23/10/16 02:40, Henrique de Moraes Holschuh wrote:
> On Sat, 22 Oct 2016, Jan Bakuwel wrote:
>> Does anyone know if it's possible to disable passive mode on an AP? It
>> is possible to set the SSID to hidden but this does not stop the
>> broadcasts, it just broadcasts frames with a null SSID. Stopping the
>> broadcasts altogether (and as a consequence the client must use active
>> mode, ie. needs to send probes) will result in no EMR when wifi is not
>> in use, in other words AP will only listen not transmit in that case,
>> yet wifi is available when needed.
> The AP would have to switch to standard beaconning while *any* station
> is associated, otherwise it could have nefarious effects on network
> performance.

Just out of curiosity why is that? I thought beacons were only used
while AP and client get associated?
If wifi is in use, we can accept EMR including beacons. Just not when
it's not (for example during the night).

> Also, beacon-less infrasctructure mode CANNOT work on a number of bands
> where the stations are forced to operate in passive mode (i.e. they
> cannot issue a probe request to a channel where they did not receive an
> AP beacon).  It is also likely forbidden in any channels where DSS
> (weather radar detection) must be performed, as this is only performed
> by APs.
>
> So, in theory this would work provided the adapter firmware allows for
> it in the first place, and it is restricted to channels where clients
> are allowed to actively probe for APs -- which is information readly
> available on the regdb (regulatory database).  However, I see no way to
> control this in /sbin/iw for infrastructure mode (but I find iw terribly
> confusing, so I might have failed to notice it).

I'll need to study that a bit more. My question only concerns the 2.4GHz
band ... as far as i know DFS only applies to the 5GHZ band, correct?

> Please ask in the linux-wireless mailinglist at vger.kernel.org.

Thanks for the suggestion, I'll do that.

Jan

[toc] | [prev] | [next] | [standalone]

#173752

On Sun, 23 Oct 2016, Jan Bakuwel wrote:
> On 23/10/16 02:40, Henrique de Moraes Holschuh wrote:
> > The AP would have to switch to standard beaconning while *any* station
> > is associated, otherwise it could have nefarious effects on network
> > performance.
> 
> Just out of curiosity why is that? I thought beacons were only used
> while AP and client get associated?

No, they're often used when the station is not receiving from the AP,
even when it is already associated.

Also, other receivers (APs and stations) can use them for channel width
management, and for empty channel detection.

> > Also, beacon-less infrasctructure mode CANNOT work on a number of bands
> > where the stations are forced to operate in passive mode (i.e. they
> > cannot issue a probe request to a channel where they did not receive an
> > AP beacon).  It is also likely forbidden in any channels where DSS
> > (weather radar detection) must be performed, as this is only performed
> > by APs.
> >
> > So, in theory this would work provided the adapter firmware allows for
> > it in the first place, and it is restricted to channels where clients
> > are allowed to actively probe for APs -- which is information readly
> > available on the regdb (regulatory database).  However, I see no way to
> > control this in /sbin/iw for infrastructure mode (but I find iw terribly
> > confusing, so I might have failed to notice it).
> 
> I'll need to study that a bit more. My question only concerns the 2.4GHz
> band ... as far as i know DFS only applies to the 5GHZ band, correct?

Well, look at the regulatory database.  Some 2.4GHz channels can end up
forced by the kernel into passive mode, depending on several factors.
It really depends on your radio's firmware, what region it is set to,
and what region is your kernel set to.

> > Please ask in the linux-wireless mailinglist at vger.kernel.org.
> 
> Thanks for the suggestion, I'll do that.

-- 
  Henrique Holschuh

[toc] | [prev] | [next] | [standalone]

#173724

Jan Bakuwel wrote:
> Hi all,
>
> As far as I'm aware, IEEE802.11 defines the two modes a wifi AP and
> client can establish communication, passive (AP broadcasts SSID, clients
> connects to SSID) and active (AP doesn't broadcast SSID, client
> broadcasts SSID probe and AP then sends a probe response).

Have never heard of "active mode" wifi before.  Doubt it'd be supported
on any generic stuff you can get from bestbuy (etc.) though.  Maybe if
you flash to ddwrt / tomato / etc ... but even there, maybe not.


-- 
|_|O|_| Registered Linux user #585947
|_|_|O| Github: https://github.com/dpurgert
|O|O|O| PGP: 05CA 9A50 3F2E 1335 4DC5  4AEE 8E11 DDF3 1279 A281

[toc] | [prev] | [standalone]

Back to top | Article view | linux.debian.user

csiph-web