From: Johannes Berg <johannes-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>
To: "Rao, Krishna" <kcrao-A+ZNKFmMK5xy9aJCnZT0Uw@public.gmane.org>
Cc: "radiotap-sUITvd46vNxg9hUCZPvPmw@public.gmane.org"
<radiotap-sUITvd46vNxg9hUCZPvPmw@public.gmane.org>
Subject: RE: Regarding A-MPDU status field
Date: Wed, 09 Nov 2011 15:02:46 +0100 [thread overview]
Message-ID: <1320847366.3845.72.camel@jlt3.sipsolutions.net> (raw)
In-Reply-To: <21E1C3B49A18BA428D58607D5EEA5398BB67FA-RqevaKtL5OWBP98+muIrrKRtKmQZhJ7pQQ4Iyu8u01E@public.gmane.org>
Hi,
> > -- it might also be helpful to know the padding length before/after
> (?) the packet for example.
> We can add
> 1) Padding length information
> a) value of padding length after the MPDU, and
> b) (debatable) total padding length before the subframe for the
> special case of preceding delimiters with MPDU length zero used to
> meet minimum MPDU start spacing requirements. All the octets of the
> preceding 'zero delimiters' together form the pad, as I understand.
> Note that this information might not be provided by some hardware.
> If an MPDU (not 'zero delimiter') is actually present prior to the
> current subframe for which radiotap info is being displayed, 1b)
> should be zero for the current subframe. Post MPDU pad length
> information for the prior MPDU would anyway be available (assuming the
> containing subframe of the prior MPDU is not corrupted).
So what I wanted here was to be able to reconstruct what happened on the
air as precisely as possible. I don't think the length of the padding is
actually needed -- it can be calculated after the fact since it is
always 0-3 bytes up to a multiple of 4. The number of zero delimiters
would be more interesting.
I'm not sure how to deal with the corruption case.
> Additionally:
> 2) A bit to indicate if this is the last subframe in the A-MPDU.
> Though there might be other ways to infer this information, having it
> as an explicit field would provide convenience.
That seems useful, although I'm not even sure how you would even know
that it is the last one?
> 3) A bit to indicate if the Delimiter CRC is in error.
That's useful, but in that case are you even decoding the MPDU and
passing it up? Also what if a zero delimiter has a bad CRC? Or what if
it just got corrupted and you have to recover parsing? I'm not sure we
can cover all these cases.
> 4) (Debatable) Delimiter CRC value itself. I don't know if there is
> any hardware which returns the actual value to software. Anyway,
> having it as part of the field will allow platforms which do possess
> the capability, to provide this information. It may come in handy for
> some users.
That seems a bit of a stretch, but it's only 8 bits so I wouldn't mind
adding it.
johannes
next prev parent reply other threads:[~2011-11-09 14:02 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-31 9:13 Regarding A-MPDU status field Rao, Krishna
[not found] ` <21E1C3B49A18BA428D58607D5EEA5398BB2E90-RqevaKtL5OWBP98+muIrrKRtKmQZhJ7pQQ4Iyu8u01E@public.gmane.org>
2011-11-02 8:42 ` Johannes Berg
[not found] ` <1320223343.3950.29.camel-8upI4CBIZJIJvtFkdXX2HixXY32XiHfO@public.gmane.org>
2011-11-03 15:02 ` Rao, Krishna
[not found] ` <21E1C3B49A18BA428D58607D5EEA5398BB67FA-RqevaKtL5OWBP98+muIrrKRtKmQZhJ7pQQ4Iyu8u01E@public.gmane.org>
2011-11-09 14:02 ` Johannes Berg [this message]
[not found] ` <1320847366.3845.72.camel-8upI4CBIZJIJvtFkdXX2HixXY32XiHfO@public.gmane.org>
2011-11-09 20:45 ` David Young
2011-11-13 16:49 ` Rao, Krishna
[not found] ` <21E1C3B49A18BA428D58607D5EEA5398BBBD18-RqevaKtL5OWBP98+muIrrKRtKmQZhJ7pQQ4Iyu8u01E@public.gmane.org>
2011-11-14 8:26 ` Johannes Berg
[not found] ` <1321259214.4472.16.camel-8upI4CBIZJIJvtFkdXX2HixXY32XiHfO@public.gmane.org>
2011-11-20 16:37 ` Rao, Krishna
[not found] ` <21E1C3B49A18BA428D58607D5EEA5398BC8C00-RqevaKtL5OWBP98+muIrrKRtKmQZhJ7pQQ4Iyu8u01E@public.gmane.org>
2011-11-21 9:27 ` Johannes Berg
[not found] ` <1321867620.3999.7.camel-8upI4CBIZJIJvtFkdXX2HixXY32XiHfO@public.gmane.org>
2011-11-22 14:27 ` Rao, Krishna
[not found] ` <21E1C3B49A18BA428D58607D5EEA5398BC971A-RqevaKtL5OWBP98+muIrrKRtKmQZhJ7pQQ4Iyu8u01E@public.gmane.org>
2011-11-22 17:06 ` David Young
2011-11-22 14:33 ` Rao, Krishna
2011-11-23 15:23 ` Rao, Krishna
2012-01-03 17:25 ` Rao, Krishna
[not found] ` <21E1C3B49A18BA428D58607D5EEA5398C1F289-RqevaKtL5OWBP98+muIrrKRtKmQZhJ7pQQ4Iyu8u01E@public.gmane.org>
2012-01-04 10:42 ` Johannes Berg
[not found] ` <1325673736.3339.27.camel-8upI4CBIZJIJvtFkdXX2HixXY32XiHfO@public.gmane.org>
2012-01-08 13:43 ` Rao, Krishna
[not found] ` <21E1C3B49A18BA428D58607D5EEA5398C20149-RqevaKtL5OWBP98+muIrrKRtKmQZhJ7pQQ4Iyu8u01E@public.gmane.org>
2012-01-09 10:16 ` Johannes Berg
[not found] ` <1326104166.3451.21.camel-8upI4CBIZJIJvtFkdXX2HixXY32XiHfO@public.gmane.org>
2012-01-15 19:14 ` Rao, Krishna
[not found] ` <21E1C3B49A18BA428D58607D5EEA5398C36652-RqevaKtL5OWBP98+muIrrKRtKmQZhJ7pQQ4Iyu8u01E@public.gmane.org>
2012-01-16 13:46 ` Johannes Berg
[not found] ` <1326721599.3510.18.camel-8upI4CBIZJIJvtFkdXX2HixXY32XiHfO@public.gmane.org>
2012-01-23 16:16 ` Rao, Krishna
[not found] ` <21E1C3B49A18BA428D58607D5EEA5398C3D354-RqevaKtL5OWBP98+muIrrKRtKmQZhJ7pQQ4Iyu8u01E@public.gmane.org>
2012-02-20 11:03 ` Johannes Berg
[not found] ` <1329735809.3458.14.camel-8upI4CBIZJIJvtFkdXX2HixXY32XiHfO@public.gmane.org>
2012-02-22 1:14 ` Rao, Krishna
[not found] ` <21E1C3B49A18BA428D58607D5EEA5398C55E21-RqevaKtL5OWBP98+muIrrKRtKmQZhJ7pQQ4Iyu8u01E@public.gmane.org>
2012-02-23 15:48 ` Johannes Berg
2012-07-05 9:49 ` Johannes Berg
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