Hello all,
sometime ago I asked about a way to configure the multicast
data rate for mac80211 based drivers. At the time the answer
was, that the groundwork was in place but that this still
needed an API that would make this feature accessible for
users.
Is there any progress in this regard? What needs to be done?
--
Regards
Joerg
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On Thu, Apr 08, 2010 at 01:07:36PM -0700, Joerg Pommnitz wrote:
> do you mean that I can't configure a separate rate
> for multicast frames? I thought that the rate bitmask
> was a way to tell the RC algorithm what rates to
> consider. Since multicast frames do not get acknowledged
> they are not subject to the automatic rate selection.
At least for now, there is no separate configuration option for
multicast frames, i.e., the same TX rate mask will apply to rate
selection for both unicast and multicast frames. Multicast frames are
subject to rate selection; the current mac80211 rate algorithms may not
do much in that area, though, apart from letting the lowest available
rate be selected. By changing which rates are enabled, you can change
that lowest rate..
> In fact, I'm perfectly happy to leave the rate selection
> for unicast frames in the capable hands of Minstrel, but
> I need something better than 1Mb/s for multicast. The
> lowest data rate just isn't enough for live video feeds.
Like I said in the previous mail, as long as you are fine dropping 1
Mbps from unicast rates, you can get higher rate for multicast..
> What I need is a way to tell mac80211 to use one specific
> basic rate for broadcast and multicast.
Why would the currently available mechanism not work for you?
--
Jouni Malinen PGP id EFC895FA
On Thu, Apr 08, 2010 at 06:45:15AM -0700, Joerg Pommnitz wrote:
> sometime ago I asked about a way to configure the multicast
> data rate for mac80211 based drivers. At the time the answer
> was, that the groundwork was in place but that this still
> needed an API that would make this feature accessible for
> users.
> Is there any progress in this regard? What needs to be done?
If you are fine with disabling the lowest rates for both unicast and
multicast frames, then yes, you should be able to do this with
NL80211_CMD_SET_TX_BITRATE_MASK. As an example, removing rates 1, 2,
5.5, and 11 Mbps from the mask would make multicast frames go out at 6
Mbps in case of 802.11g.
--
Jouni Malinen PGP id EFC895FA
--- Jouni Malinen <[email protected]> wrote:
>
> At least for now, there is no separate configuration option for
> multicast frames, i.e., the same TX rate mask will apply to rate
> selection for both unicast and multicast frames. Multicast frames are
> subject to rate selection; the current mac80211 rate algorithms may not
> do much in that area, though, apart from letting the lowest available
> rate be selected. By changing which rates are enabled, you can change
> that lowest rate..
I think there is a serious problem. Unicast and multicast have
different characteristics and should have different "rate pools"
to select rates from.
>
> Why would the currently available mechanism not work for
> you?
For multicast the situation is the following: the selection of available
data rates affects all stations. If I drop the lower data rates to force
multicast traffic at 11Mbit/s, then the stations close to the sender will
be able to receive a video feed. Stations further away won't get it, but
this is a trade off between data rate (e.g. quality) and coverage.
However, I'd still like to reach them over unicast, even if the data
rate is only 1Mb/s. The current approach would prevent this, despite
the fact that it would be physically possible.
So, I would really prefer a solution were multicast and unicast data
rates can be selected independently of each other.
Kind regards
Joerg
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Jouni,
do you mean that I can't configure a separate rate
for multicast frames? I thought that the rate bitmask
was a way to tell the RC algorithm what rates to
consider. Since multicast frames do not get acknowledged
they are not subject to the automatic rate selection.
In fact, I'm perfectly happy to leave the rate selection
for unicast frames in the capable hands of Minstrel, but
I need something better than 1Mb/s for multicast. The
lowest data rate just isn't enough for live video feeds.
What I need is a way to tell mac80211 to use one specific
basic rate for broadcast and multicast.
--
Regards
Joerg
----- Urspr?ngliche Mail ----
> Von: Jouni Malinen <[email protected]>
> An: Joerg Pommnitz <[email protected]>
> CC: [email protected]
> Gesendet: Donnerstag, den 8. April 2010, 21:43:49 Uhr
> Betreff: Re: Any news regarding multicast rate configuration?
>
> On Thu, Apr 08, 2010 at 06:45:15AM -0700, Joerg Pommnitz wrote:
> sometime
> ago I asked about a way to configure the multicast
> data rate for
> mac80211 based drivers. At the time the answer
> was, that the groundwork
> was in place but that this still
> needed an API that would make this
> feature accessible for
> users.
> Is there any progress in this
> regard? What needs to be done?
If you are fine with disabling the lowest
> rates for both unicast and
multicast frames, then yes, you should be able to
> do this with
NL80211_CMD_SET_TX_BITRATE_MASK. As an example, removing rates
> 1, 2,
5.5, and 11 Mbps from the mask would make multicast frames go out at
> 6
Mbps in case of 802.11g.
--
Jouni Malinen
>
> PGP id EFC895FA
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