Re: Completely disabling RTS/CTS

From: Ben Greear <greearb@candelatech.com>
To: Krishna Chaitanya <chaitanya.mgit@gmail.com>,
	Raj Joshi <rajjoshi@comp.nus.edu.sg>
Cc: ath10k <ath10k@lists.infradead.org>
Subject: Re: Completely disabling RTS/CTS
Date: Thu, 21 Jul 2016 09:44:32 -0700	[thread overview]
Message-ID: <5790FBF0.2060800@candelatech.com> (raw)
In-Reply-To: <CABPxzY+KHVGAUKjU2kWdKiEPZFV3=sOnWe-qBMDOPffw_vJ0+g@mail.gmail.com>

On 07/21/2016 07:29 AM, Krishna Chaitanya wrote:
> On Thu, Jul 21, 2016 at 7:45 PM, Raj Joshi <rajjoshi@comp.nus.edu.sg> wrote:
>> Hi all,
>>
>> I am trying to "completely" disable RTS/CTS.
>>
>> * Case 1: Using iw/iwconfig when I set the sender's RTS threshold to a
>> very high value (RTS thr=10000 B), I expect that no RTS should be
>> sent. However, it seems that this threshold is not being honored and I
>> can sniff large number of RTS/CTS frames. I verified that no A-MSDU is
>> exceeding 10000 B.
>> * Case 2: Interestingly, when I set the sender's RTS threshold to off
>> (RTS thr:off), compared to case #1 much less number of RTS/CTS frames
>> are seen and throughput is seen to improve. But I can still see
>> RTS/CTS frames being sent.
>> * Since the channel is clear and much isolated, and there is just one
>> AP and one STA, there is negligible chance of other factors playing
>> any role.
>> * There is one change though that I have disabled dynamic bandwidth
>> i.e. ar->wmi.pdev_param->dynamic_bw set zero in mac.c. I believe this
>> is likely not an issue as similar RTS/CTS behavior is seen even with
>> dynamic_bw set to 1 (there are no heterogeneous channel widths in the
>> network in any case).
>> * Another thing I noticed is that the RTS/CTS protection mode if set,
>> it is set to CTS-to-self, rather than "RTS/CTS" i.e.
>> ar->wmi.vdev_param->protection_mode in mac.c is either set to 1 or 0
>> (depending upon use_cts_prot), but not 2. This probably seems not
>> helpful in hidden node scenarios as the CTS frame is unicasted instead
>> broadcasting.
>>
>> I would appreciate any pointers on completely disabling RTS/CTS as
>> well as the ability to choose between complete RTS/CTS versus
>> CTS-to-self whenever RTS/CTS is enabled.
> Which mode is this? For aggregated frames (AMPDU) RTS Threshold is
> not checked, so it can still be enabled

Probably would require firmware changes to fully disable RTS/CTS
from what I recall when I was reading the rate-ctrl code...

Thanks,
Ben

>
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-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

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