Now I'm learning something! Seems like Johannes' initial question about powersaving might have been right on the mark, and Holger's explanation set that straight in my brain. Thank you for that! I have attached some traces. Connected my iPod to the XG-601 AP and to my fritzbox 7170. I'm not sure about the interpretation of the beacon flags, but I never see beacon flags other than 0x0, does that mean the AP is saying "stay awake, no sleeping" to the client? The iPod alternates Null Functions with the PWR MGT bit on and off - whatever that means. Is it ignoring the AP and snoring away? @Johannes: I was not able to find any indicated traffic in any of the beacon TIMs. Thank you all for your valuable time with this, Stefan. 2008/11/20 Holger Schurig <hs4233@xxxxxxxxxxxxxxxxxxxx>: >> The gap is filled by some "Null function" packets originating >> on the iPod (maybe it is getting impatient?). This gets me an >> application-level timeout. > > Some comments about your "ipod_http_request_delayed_answer.pcap": > > > Clients use "null functions" to tell the AP that they're going to > sleep --- or that they are now waking up again. You can see this > in wireshark if you open "IEEE802.11", then "Frame Control: > xxxx", then "Flags". Look at the flag "PWR_MGT". > > > While sleeping, the AP should notify the client via a bitmask in > it's beacons that there is traffic for it. As your dump doesn't > include the beacons from the AP, we can't see if the proper bit > is set there. > > At time 36.04 the Ipod WLAN card signals that it woke up and it > got then it's packet at time 36.70, which isn't awfully fast > after the wakeup, but ... > > > Just make a trace with beacons towards your mac80211 based AP and > one trace towards another access points and compare the beacon. >
Attachment:
ipod-xg601-httpget-beacons.pcap
Description: application/cap
Attachment:
ipod-fritzbox-dnsquery-beacons.pcap
Description: application/cap
Attachment:
ipod-fritzbox-httpget-beacons.pcap
Description: application/cap
Attachment:
ipod-fritzbox-httprequests-beacons.pcap
Description: application/cap
