From: Krishna Chaitanya <firstname.lastname@example.org> To: Johannes Berg <email@example.com> Cc: Guy Harris <firstname.lastname@example.org>, "email@example.com" <firstname.lastname@example.org>, Simon Barber <email@example.com>, Richard Sharpe <firstname.lastname@example.org>, linux-wireless <email@example.com>, Maya Erez <firstname.lastname@example.org>, email@example.com Subject: Re: Correct radiotap header for 802.11ad Date: Wed, 11 Dec 2019 15:09:19 +0530 Message-ID: <CABPxzY+0v-Rb-GWkL-iwCfefzhFE5AiGBh2xxV_U_OC0Q+eoVQ@mail.gmail.com> (raw) In-Reply-To: <firstname.lastname@example.org> On Wed, Dec 11, 2019 at 2:02 PM Johannes Berg <email@example.com> wrote: > > ++ for the DMG discussion > > On Tue, 2019-12-10 at 15:51 -0800, Guy Harris wrote: > > On Sep 17, 2015, at 9:37 AM, Johannes Berg <firstname.lastname@example.org> wrote: > > Reviving an old thread :-) > > > > Not being familiar with DMG, I can't really comment on this. > > > > > > It does sound like we need *some* new field though, be it either a DMG > > > field or a PLCP SIGNAL field, or perhaps even both. > > > > > > Going back to the original thread though, I think using the MCS field > > > is quite wrong. > > > > But a presumably-Linux system does appear to use it; see Wireshark bug > > > > https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=16272 > > > > For now, I'll throw a hack into Wireshark to treat a signal >= 60 GHz > > as meaning 11ad, > > I don't think that's quite right - you'll need to do something like >= > 56 GHz. > > > but, again, should there be additional fields for 11ad? > > I would think so. > > On the one hand I think (and looking at the spec seems to confirm this) > that basically DMG uses an MCS index. Now, the MCS radiotap field was > designed for HT and has a lot of things that are not applicable (GI, > STBC, etc.) > > OTOH, there are DMG-specific things that probably ought to be captured > by a proper sniffer, like the PPDU type, training length, etc. Also, > there's the thing with the "Extended SC MCS Indication field", which > really also ought to be captured. > > Sadly, the only Linux implementation didn't bother adjusting any of this > even in the Linux general stack (and I didn't pay enough attention to it > at the beginning), so even the rate reporting to userspace is just the > MCS index. This might actually be sufficient for the current uses > (there's a conversion function to bandwidth too), though it doesn't seem > quite applicable to the whole spec. > > For both the Linux userspace reporting and radiotap then, this > completely ignores the existence of the MCSes 9.1 and 12.1-12.6, which > cannot be captured in either format right now. Maybe the extended SC > MCSes are just not used by equipment in the field? > They are used. Unfortunately, Linux-wireless doesn't have native support for DMG wil6210 and our driver has to workaround by using HT IE's (ieee80211_supported_band). > > > In any case, to capture DMG properly I'd say we need a new radiotap > field with at least > * (base) MCS > * Extended SC MCS bit > and it should probably optionally cover the other possible fields as > well > * Scrambler Initialization > * Length (?) > * Additional PPDU bit > * PPDU type bit > * Training Length > * Beam Tracking Request > * Last RSSI > * Turnaround yes, we definitely need this, there are some additional fields in 11ay, but I guess that discussion is for another time.
next prev parent reply index Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-08-22 19:41 Richard Sharpe [not found] ` <CACyXjPzq-ePB1ux6wi_Rv3onPKXomcJcm15XJwA51u0E4W2txw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2015-08-22 20:59 ` Guy Harris [not found] ` <38F46E1D-1C4A-48DC-A906-9522006E8474-FrUbXkNCsVf2fBVCVOL8/A@public.gmane.org> 2015-08-22 22:06 ` Richard Sharpe [not found] ` <CACyXjPx81fh_jeQSUjE-_w8NQ_Jr-ajmnVWSopfzcLPOWoGmGg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2015-08-22 22:24 ` Guy Harris 2015-08-22 23:34 ` Guy Harris [not found] ` <1606812C-649C-4C06-ABE0-AE2F4474BCD0-FrUbXkNCsVf2fBVCVOL8/A@public.gmane.org> 2015-08-24 7:40 ` Johannes Berg [not found] ` <1440402013.3735.1.camel-cdvu00un1VgdHxzADdlk8Q@public.gmane.org> 2015-08-24 16:21 ` Richard Sharpe [not found] ` <CACyXjPwSZPV+U_=zQpDBpeBnhMntzEFhyJnBOw3-N8qPfyHc1A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2015-08-24 16:28 ` Johannes Berg 2015-08-26 22:59 ` Simon Barber [not found] ` <55DE44EB.6080603-vp0mx6+5gkqFX2APIN6yfw@public.gmane.org> 2015-08-27 1:17 ` Guy Harris [not found] ` <126B842D-05EA-4510-BC9B-DB1A4AABEC12-FrUbXkNCsVf2fBVCVOL8/A@public.gmane.org> 2015-09-10 18:25 ` Guy Harris [not found] ` <1135A126-6A5A-4C84-A52D-13C0387609CC-FrUbXkNCsVf2fBVCVOL8/A@public.gmane.org> 2015-09-17 16:37 ` Johannes Berg 2019-12-10 23:51 ` Guy Harris 2019-12-11 8:32 ` Johannes Berg 2019-12-11 9:39 ` Krishna Chaitanya [this message] 2019-12-11 12:57 ` Johannes Berg 2019-12-11 13:20 ` Krishna Chaitanya 2019-12-20 21:56 ` Guy Harris 2015-09-17 16:32 ` Johannes Berg 2015-08-26 22:56 ` Simon Barber
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