radiotap.netbsd.org archive mirror
 help / color / mirror / Atom feed
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: Mon, 20 Feb 2012 12:03:29 +0100	[thread overview]
Message-ID: <1329735809.3458.14.camel@jlt3.sipsolutions.net> (raw)
In-Reply-To: <21E1C3B49A18BA428D58607D5EEA5398C3D354-RqevaKtL5OWBP98+muIrrKRtKmQZhJ7pQQ4Iyu8u01E@public.gmane.org>

Hi,

Sorry for the delay in reviewing this.

> >But now imagine a device misses a frame due to decode problem or so ...
> >then which one would you want:
> >1) subframe index skips that one
> >2) subframe index just increases
> >
> >Say
> >   [mpdu][pad][pad][----][pad][mpdu]
> >1) 0     1    2    (3)   4    5
> >2) 0     1    2          3    4
> >
> >but then the driver would have to guess at the padding? Not sure. In any case, we need to nail
> >this down, because in the case 2) the driver can number the subframes (but it's less useful),
> >and in the case 1) the device has to provide it (and not all do -- so we need a separate valid bit).
> >In the case 1), even the application (wireshark) could provide the subframe index?
> 
> Good you brought this up.
> 
> I had basically case 2) in mind. Even the device itself may not always
> be able to provide the index for subframes totally skipped due to
> decode problems. 

Yes, good point.

> It may sometimes be able to pass to the driver subframes with bad
> delimiter CRC and these would get indexed by the driver (with flag
> 0x10 set). So the principle is that only whatever subframes the device
> can pass to the driver, good or bad, get indexed.
> 
> But I now feel the application itself can provide the subframe
> indexing (as in case 2). It can use the subframe reference number and
> timestamp for this. The burden on the driver would be decreased, and
> we also save space in the Radiotap header by removing this field.

Makes sense to me. I guess that means we just remove the ampdu subframe
index from the proposal, so we have this?


 A-MPDU radiotap field
-----------------------
bit index: TBD
alignment: 4 bytes (u32)

 * ampdu reference number (u32)
 * flags (u16)
   - 0x01: driver reports 0-length subframes
   - 0x02: is 0-length subframe (valid if 0x01 set)
   - 0x04: last subframe known
           (should be set for all subframes if driver knows)
   - 0x08: is last subframe in ampdu (valid if 0x04 set)
           (clear for all but last subframe)
   - 0x10: delimiter CRC error
   - 0x20: delimiter CRC value known
 * delimiter CRC value (u8) (valid if flag 0x20 set)
 * u8 (reserved)


(I added the reserved field and changed the flags to u16, it seems
relatively likely that other fields will need u32 alignment so it seems
reasonable to reserve a byte here, maybe for VHT extensions?)

johannes

  parent reply	other threads:[~2012-02-20 11:03 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
     [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 [this message]
     [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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1329735809.3458.14.camel@jlt3.sipsolutions.net \
    --to=johannes-cdvu00un1vgdhxzaddlk8q@public.gmane.org \
    --cc=kcrao-A+ZNKFmMK5xy9aJCnZT0Uw@public.gmane.org \
    --cc=radiotap-sUITvd46vNxg9hUCZPvPmw@public.gmane.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).