Return-path: Received: from xc.sipsolutions.net ([83.246.72.84]:48989 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755416AbYJMSEI (ORCPT ); Mon, 13 Oct 2008 14:04:08 -0400 Subject: Re: [RFC] mac80211: fix short preamble determination From: Johannes Berg To: Jouni Malinen Cc: linux-wireless , Daniel Drake , Felix Fietkau In-Reply-To: <20081013175457.GB30095@jm.kir.nu> References: <1223713593.29811.38.camel@johannes.berg> <20081013155938.GA30095@jm.kir.nu> <1223919110.10113.1.camel@johannes.berg> <20081013175457.GB30095@jm.kir.nu> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-sJdN70Z7ohcxQgkrsRHd" Date: Mon, 13 Oct 2008 20:03:32 +0200 Message-Id: <1223921012.10113.5.camel@johannes.berg> (sfid-20081013_200413_659718_AA561AE4) Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: --=-sJdN70Z7ohcxQgkrsRHd Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Mon, 2008-10-13 at 20:54 +0300, Jouni Malinen wrote: > > I don't see how it cannot be -- you need stations not capable of > > short-preamble to correctly update their NAV, no? >=20 > Well, if you have many such devices, yes, but one might try to live > without such protection if there are some with very limited transmit > needs. Would you then announce short preamble as the AP? That'd mean all other stations would use short preamble and the poor non-short-preamble STA would be left completely in the dark wrt. its NAV. > I don't know whether it would make much sense in most cases and > anyway, it would be possible to make APs reject all associations from > such devices. For example, I could see an attempt to dedicate one > channel for 11g (ERP) and short preamble supported STAs and make the > more modern implementations get somewhat better throughput there. Indeed, that is possible, I think there's even a status code allocated for this. > I'll try to remember to file a comment to TGmb on this (they are still > collecting comments for fixing issues in 802.11 and published > amendments). Probe Request with this does not make much sense (unless > you are either only interested in BSSes that support short preamble > and/or you know that the AP you're interested is able to receive this). > Authentication, association, and public action frames might be more > likely candidates for this. Ohh. Just a few days ago I sent an email with a request for interpretation (there really just is a typo in 802.11-2007 but...) That got forwarded around a lot, but I guess at least TGmb will see it :) johannes --=-sJdN70Z7ohcxQgkrsRHd Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Comment: Johannes Berg (powerbook) iQIcBAABAgAGBQJI841wAAoJEKVg1VMiehFYws8P/12uMjRaoOT2k4E9uYku4iPx /Eoi5ojVzGlkFfj06NN8j/8VNN0W9NLWbFn+5h1YhsbQ4jkoI2i+3z8V7Jy+IoiI v3as1CZnanFHCMUu9vpR9oU3boIcEucJskuHOJSoB43eI4YPLvGxVKKJoCVcazuO cofpr0Eirz57q9wlfspQp/FV4x6tR/JvY4knLBIxiv+oOKKSPYizBz3aNZS1P8Wd cp5+zbHf5Bw11E/BTogULPt3NY6gaKeYyLQHEFpUjt1qzzp3kxuKiYXUI7S9Ae7Z sVhKicAKASi8rpnqVU3JJJs64WVOZtdIv197uG8lN49rj3Zw6f1poCXQS4geLlyT QAjHJlGT3HxeynWC8tmz7ssrnYl6wGkpqSXxm7l3Ee4PQOjZdOyWYx5IpBspFMvE wH+58dny35GIBcDmHQy/TgrCYqLw7QbHXiAJRiX2lEMu7OxsUp0u8ogvTG4Qmf7h pUylM5zF5LMbk7pIt8753JcZzowjLDnjYoGLeun1gdjH2//aeG8ZgQu2sqjGDp7B 5OmGGOWCMRWUeWTzRlVdZgIsQ6LY3Qt5hf7b6eMzTHnerq/+yWSm20bKm9URi8vM vXV5NmZZ7TgEM7U4ZgzBgOsU7PourcZPosR4xpi58q74cPNSHRhFxl4sKlc7g7mV XEAx9hK8a6A8cNgV/BsJ =MyNW -----END PGP SIGNATURE----- --=-sJdN70Z7ohcxQgkrsRHd--