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List:       linux-wireless
Subject:    p54: AP mode: no data frame despite traffic indication set in TIM
From:       "Stefan Steuerwald" <salsasepp () googlemail ! com>
Date:       2008-11-21 14:12:19
Message-ID: f76a32050811210612i13ee251ewd6c1cab616a62529 () mail ! gmail ! com
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I got another one to lay out before you for comment:

Setup:
- XG-601 card (ISL3880) with p54pci driver in AP mode
- iPod Touch 2G (firmware 2.1.1) as the only client

The client does an http request and waits for an answer. In this case,
the web server answers, but the answer seemingly is never sent over
the air.

Please see the attached pcap:
- frame 7: http request
- frame 13: iPod goes to sleep
- frame 23: AP beacon indicates traffic for iPod (AID 1 in TIM)
- frame 25: iPod wakes up
- in between: MISSING DATA ???
- frame 27: AP beacon with no traffic indicated ???
- frame 29: iPod goes to sleep again
- subsequent frames: repetitions of this, until the TCP connection is closed

My understanding is that the AP would not indicate any traffic without
actually having some ready to send? Wrong assumption?

Both the iPod and the monitoring device seem to agree the http reply
is not there. This would be a good reason for the application-level
timeouts I'm seeing.

Best wishes,
  Stefan.


See also: previous conversation about app-level timeouts and powersave:
http://article.gmane.org/gmane.linux.kernel.wireless.general/24278

["ipod-no-data-despite-traffic-in-tim.pcap" (application/cap)]
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