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From: "Luis R. Rodriguez" <mcgrof@frijolero.org>
Date: Tue, 20 Sep 2011 15:37:17 -0700
Message-ID: <CAB=NE6UYY5sbpmkTHPx1LVFh6SC0QebqhKcpYCawZryvttOS=A@mail.gmail.com> (sfid-20110921_003741_217047_C9790D14)
Subject: Re: [PATCH v3 3/3] mac80211: Add HT operation modes for IBSS
To: Felix Fietkau <nbd@openwrt.org>
Cc: Johannes Berg <johannes@sipsolutions.net>,
	Javier Cardona <javier@cozybit.com>,
	Alexander Simon <an.alexsimon@googlemail.com>,
	linux-wireless@vger.kernel.org
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On Tue, Sep 20, 2011 at 2:52 PM, Felix Fietkau <nbd@openwrt.org> wrote:
> On 2011-09-20 11:26 PM, Luis R. Rodriguez wrote:
>>
>> On Tue, Sep 20, 2011 at 2:04 PM, Felix Fietkau<nbd@openwrt.org>  wrote:
>>>
>>>  If we want to properly enforce Annex J channel pairs, this needs to
>>>  be moved to cfg80211.
>>
>> This does not still address the issue of one peer finding out it
>> cannot deal with an HT40 pair and correcting the topology and
>> propagating this out. Not yet sure if for 802.11ac we'll need
>> something similar but its worth considering.
>
> Don't think of it as a topology. Each node makes its own decisions about
> HT40+/HT40-/HT20.

OK lets go with an example.

Node A: HT40+
   Primary: 5785 (157)
   Extension: 5805 (161)

Node B: HT20 as it finds a legacy AP with on 5805.
  Channel: 5785 (157)

Node C: HT40-
  Primary:  5785 (157)
  Extension: 5765 (153)

So we want to support this setup?

What if the network changes and we cannot use the original HT40 pair
now but we can later? This applies even to today's hostapd AP setup
and more rhetorical.

> If modes are incompatible, fallback to HT20  always works
> for communicating with a peer.

Agreed.

  Luis