Date: Sun, 14 Feb 2010 14:30:05 +0100 From: Alexander Egorenkov <egorenar@googlemail.com> To: Sam Leffler <sam@errno.com> Cc: freebsd-net@freebsd.org Subject: Re: A-MPDU transmission in net80211 on FreeBSD 8 Message-ID: <2d3b7e441002140530m176ccf5csd120f1029263413b@mail.gmail.com> In-Reply-To: <4B65D816.5010709@errno.com> References: <2d3b7e441001271104j14836df4j14428d34561dead1@mail.gmail.com> <2d3b7e441001271108p2a40dbbbwaa6af9679d61ab@mail.gmail.com> <4B64FC76.5060506@errno.com> <2d3b7e441001302334t5baa1102pdd1ee0309d32c2fd@mail.gmail.com> <4B65D816.5010709@errno.com>
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Hi, thanks for your help, I implemented A-MPDU Tx in my Ralink driver now and it works very good. I have average Tx rate about 4.5~5 MBytes/s now :-) The Ralink chip that i have implements the frame queue in hardware so i had only to assign sequence numbers, set BA window size and MPDU density and it worked, lucky me :-) Alex. On Sun, Jan 31, 2010 at 8:20 PM, Sam Leffler <sam@errno.com> wrote: > Alexander Egorenkov wrote: > >> Why doesn't 802.11 stack assign sequence numbers to A-MPDU frames ? >> > > Because if net80211 does the assignment it may be wrong. As the comment > says, if tx aggregation causes frames to be q'd above the h/w then by the > time they are sent OTA the pre-assigned seq# may be invalidated by other > frames going out ahead of it. > > > When sequence numbers are not assigned to A-MPDU frames, then BA doesn't >> work with my AP. >> I tried to assign sequence numbers to A-MPDU frames in my device driver >> and then BAs worked >> with my AP. >> > > That is what the comment says to do. > > > And what is meant by aggregation queue ? Where is that queue anf how do i >> use it ? >> > > The aggregation q is the mechanism used to hold frames waiting for > additional frames to aggregated into an A-MSDU/A-MPDU. The queue is > typically wherever the aggregation work is done. Some devices do this in > h/w, others require the host handle this. When done in the host it can be > done in the driver or above. The intent has always been to have net80211 > implement tx aggregation that a driver can fallback on but I never did the > work. All the 11n drivers I've done have either handled tx aggregation in > h/w or in the driver. > > >> Thanks. >> >> >> On Sun, Jan 31, 2010 at 4:43 AM, Sam Leffler <sam@errno.com <mailto: >> sam@errno.com>> wrote: >> >> Alexander Egorenkov wrote: >> >> Sorry, i posted the wrong comment. >> Here is the comment which i don't understand: >> >> /* >> * NB: don't assign a sequence # to potential >> * aggregates; we expect this happens at the >> * point the frame comes off any aggregation q >> * as otherwise we may introduce holes in the >> * BA sequence space and/or make window accouting >> * more difficult. >> * >> * XXX may want to control this with a driver >> * capability; this may also change when we pull >> * aggregation up into net80211 >> */ >> >> Thanks. >> >> >> What is unclear? >> >> Sam >> >> >> >> On Wed, Jan 27, 2010 at 8:04 PM, Alexander Egorenkov < >> egorenar@googlemail.com <mailto:egorenar@googlemail.com>> wrote: >> >> Hi, >> >> i'm implementing a device driver for a 802.11n NIC under >> FreeBSD 8 >> und experimented with A-MPDU transmission. I looked into >> net80211 code >> and there is some code which implements this feature but it >> worked not very >> well for me. >> I noticed e.g. that sequence numbers are not assigned to >> A-MPDU frames >> and found this comment in file ieee80211_output.c : >> >> >> /* >> * Check if A-MPDU tx aggregation is setup or if we >> * should try to enable it. The sta must be associated >> * with HT and A-MPDU enabled for use. When the policy >> * routine decides we should enable A-MPDU we issue an >> * ADDBA request and wait for a reply. The frame being >> * encapsulated will go out w/o using A-MPDU, or >> possibly >> * it might be collected by the driver and >> held/retransmit. >> * The default ic_ampdu_enable routine handles >> staggering >> * ADDBA requests in case the receiver NAK's us or we >> are >> * otherwise unable to establish a BA stream. >> */ >> >> Can somebody elaborate this description to me please. >> >> Thanks. >> >> ALex. >> >> >> _______________________________________________ >> freebsd-net@freebsd.org <mailto:freebsd-net@freebsd.org> mailing >> >> list >> http://lists.freebsd.org/mailman/listinfo/freebsd-net >> To unsubscribe, send any mail to >> "freebsd-net-unsubscribe@freebsd.org >> <mailto:freebsd-net-unsubscribe@freebsd.org>" >> >> >> >> >> >
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