high latency due to distant clients

[Adrian Chadd]

Hi,

I think I fixed this in -HEAD.



-adrian

On 18 July 2013 08:52, Petar Bogdanovic <petar at smokva.net> wrote:
> Hi,
>
> for several years now, I've been running an ALIX-AP with a CM9 Atheros
> 5212 card.  The AP covers a whole house which has about 6 flats and the
> average amount of active clients ranges from 10 to 15.
>
> Recently I noticed high latency when pinging the AP itself which happens
> when distant clients (who knows where around the house---could be inside
> or outside) seem to cause "longs" (long on-chip tx retries) and/or
> "xretries" (tx failed 'cuz too many retries).
>
> The Rate, when talking to these distant clients, is usually below 11M
> (sometimes as low as 1M) which is consistent with their low RSSI values
> the AP is reporting.
>
> With high latency I mean continuous bursts of 500-1000ms instead of
> 0.5ms so I wonder if this is normal.
>
> The software is slightly out of date and athstats is not completely in
> sync with the kernel i'm using (therefore its not reporting some values):
>
>         # uname -a
>         FreeBSD parrot.NGC004 8.1-RC2 FreeBSD 8.1-RC2 #2: Thu Aug 16 21:13:54 CEST 2012
>
>         # athstats -i ath0
>         athstats: ath0: Invalid argument
>         athstats: ath0: Invalid argument
>         3181606  data frames transmit
>         45659    tx frames with an alternate rate
>         568149   long on-chip tx retries
>         19091    tx failed 'cuz too many retries
>         0M       current transmit rate
>         25       tx stopped 'cuz no xmit buffer
>         20922    tx frames with no ack marked
>         3039151  tx frames with short preamble
>         362335   rx failed 'cuz of bad CRC
>         1181     rx failed 'cuz of PHY err
>             315      OFDM restart
>             866      CCK restart
>         2        TDMA slot timing updates
>         -0/+0    TDMA slot adjust (usecs, smoothed)
>         26135    TDMA tx failed 'cuz ACK required
>         -74      rx noise floor
>         3070927  tx frames through raw api
>         6299685  fast frames received
>         1328215  fast frames flushed from staging q
>         20835    ANI decrease noise immunity
>         6593     ANI increased spur immunity
>         121582   ANI decrease spur immunity
>         160      ANI decreased first step level
>         2        cumulative OFDM phy error count
>         2        RTS without CTS
>         1360093  beacons received
>         Antenna profile:
>
> Any ideas on how to avoid that?  Of course I could buy better antennas
> but it seems that, generally speaking, this shouldn't happen.
>
> Thanks,
>
>                 Petar Bogdanovic
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