Date: Thu, 31 Jan 2013 17:01:45 -0800 From: Adrian Chadd <adrian@freebsd.org> To: Ramanujan Seshadri <ksramanujan@gmail.com> Cc: FreeBSD Net <freebsd-net@freebsd.org>, PseudoCylon <moonlightakkiy@yahoo.ca>, freebsd-wireless@freebsd.org Subject: Re: Block ACK in Ralink RT2860 Message-ID: <CAJ-VmokRO0rTXMgmusmMmo%2B9OpbRyNqjkuyZzOJkuRYwqkUc-Q@mail.gmail.com> In-Reply-To: <CAK=C58LqgYYLrFZv-s%2BDHYYjFNjP%2BpQJXF3FnRhgWnHwvG_4eA@mail.gmail.com> References: <CAFZ_MYL6qsDCar-mLPsJDziB996LE=sXhLkAxBA8VSn3wemXmw@mail.gmail.com> <CAK=C58LcRhAeERbSiX60DMA-7MAmGgiwPqT9Y=5rd9b6k=uXug@mail.gmail.com> <CAFZ_MYL6v6FqsKrkh1SvZb9Krp8M4YFKobQ83WMx0Si%2Bu0rcXg@mail.gmail.com> <CAK=C58LqgYYLrFZv-s%2BDHYYjFNjP%2BpQJXF3FnRhgWnHwvG_4eA@mail.gmail.com>
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Hi, So the 30 second version: * the maximum aggregation size in 802.11n is 65536 bytes, including the between-frame delimiters; * mpdu density defines how big those delimiters are - they're calculated either in bytes or as a function of the currently selected rate and duration, which ends up being a set of bytes anyway; * some hardware may require extra delimiter time between frames to "reset" internal frame processing between MPDUs. The atheros hardware, for examples, sets the default mpdu density to 8 microseconds to allow the encryption hardware to reset fully. It's only needed at the higher rates, but I've not sat down and totally mapped out what behaviour is there so I do it for all rates; * .. and later atheros hardware has a minimum per-MPDU timing and delimiters are added to that to "pad" out a frame to a minimum duration in microseconds. Again, to meet timing requirements in the chip; * bawinsize is negotiated during ADDBA negotiation. The maximum window size is 64 frames but devices may negotiate smaller window sizes if they like; * some hardware / drivers may limit the size of aggregates anyway - eg, the ath(4) aggregation code limits the per-AMPDU size to 32 frames even if the window is 64 frames. This is done to limit the effects of poor reception. Again, I could do a smarter job of it in ideal(er) situations but I've been focusing on other things. HTH, adrian On 31 January 2013 16:48, Ramanujan Seshadri <ksramanujan@gmail.com> wrote: > I am testing the driver code witht he ralink nic. Yes the frame > aggregation works, since i get higher throughput. I am actually tryign to > know how many frames (MPDU's) are aggregated each time in an AMPDU. > > Regarding the MPDU density - i was wondering how it should affect the Frame > aggregation. Since MPDU density is the time duration between each MPDU sent > within the AMPDU. So, how does this matter to the hardware for aggregating > the number of frames. It just sends MPDU's with the set interval. > > The other two limits make sense, the BAWinSize and the MAX_LEN_CFG. > > Ram > > On Wed, Jan 30, 2013 at 5:45 PM, PseudoCylon <moonlightakkiy@yahoo.ca>wrote: > >> On Wed, Jan 30, 2013 at 1:20 PM, Ramanujan Seshadri >> <ksramanujan@gmail.com> wrote: >> > Thank you. I also wanted to know the function where the Block ACK Window >> > will be decided. is it decided during the ADDBA session establishment or >> > does it change dynamically. >> >> The hardware will aggregate packets until any of following limits hit max >> http://fxr.watson.org/fxr/source/dev/ral/rt2860reg.h#L782 >> * rt2860_txwi.flags >> RT2860_TX_MPDU_DSITY_SHIFT >> 000 == no restriction >> 001 == 1/4 us >> 010 == 1/2 us >> ... >> 111 == 16 us >> * rt2860_txwi.xflags >> RT2860_TX_BAWINSIZE_SHIFT (frame count) >> >> http://fxr.watson.org/fxr/source/dev/ral/rt2860reg.h#L93 >> * RT2860_MAX_LEN_CFG bit 12:13 >> 00 == 8k bytes >> 01 == 16k >> 10 == 32k >> 11 == 64k >> >> At a quick look, none of them is set in current code. Also, >> RT2860_TX_AMPDU flag need to be set to make the h/w aggregate packets. >> >> How is ampdu working on ral(4)? I cannot test because I do not have >> any ral(4) nic (only have run(4) nics). >> >> >> AK >> >> > >> > >> > On Thu, Jan 24, 2013 at 5:13 PM, PseudoCylon <moonlightakkiy@yahoo.ca> >> > wrote: >> >> >> >> > Message: 6 >> >> > Date: Thu, 24 Jan 2013 12:23:55 -0500 >> >> > From: Ramanujan Seshadri <ksramanujan@gmail.com> >> >> > To: freebsd-net@freebsd.org >> >> > Subject: Block ACK in Ralink RT2860 >> >> > Message-ID: >> >> > >> >> > <CAK=C58KyA80kgVqenHj8xEkmkKDNHnmbQkZoyKQ-K6r_7V4GGA@mail.gmail.com> >> >> > Content-Type: text/plain; charset=ISO-8859-1 >> >> > >> >> > Hi all, >> >> > I am trying to read the contents of block ack's in a Ralink RT2860 >> >> > driver. >> >> > Can you please help me to know which function i should be looking >> into ? >> >> >> >> At default, all BA packets are dropped by h/w. Clear RT2860_DROP_BA flag >> >> at >> >> http://fxr.watson.org/fxr/source/dev/ral/rt2860.c#L3559 >> >> >> >> Then, the diver should receive BA packets, and you can read them. >> >> >> >> >> >> AK >> > >> > >> > _______________________________________________ > 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"
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