Wireshark-users: [Wireshark-users] Concerning WMM decoding
From: "zze-Comodo RENAULT M ext RD-BIZZ-ISS" <mrenault.ext@xxxxxxxxxxxxxxxxxx>
Date: Mon, 29 Jan 2007 17:42:59 +0100
Hi everyone, My name is Mathieu. I use Wireshark a lot at my work (and also at home!). My wireshark sniffer is installed on an Ubuntu with a 2.6.15 kernel. I use a netgear WG511T PCMCIA card. The madwifi driver version is 0.9.1. My problem is the following : Iam working with Access Points and stations which implemennt WMM ( "QoS" for wifi). The frame format changes in comparison with 802.11 frame. For a WMM data frame, the format is the following: |Frame_ctrl 2B|Dur 2B|Addr1 6B|Addr2 6B| Addr3 6B| Seq_Ctrl 2B | Addr4 6B or 0B| QoS_Control 2B| Body nB|FCS 4B| The QoS control field is : 15 7|6 5| 4 |3|2 0| -------------------------------- 0 |ack| EOSP |0| UP | When I capture data frames (which carry RTP packets), the decoding of the QoS control field changes depending on whether the frame is sent by the station or the AP Please see the QoS parameter field in these captures ============================================== |WMM Data Frame sent by the station to the AP| ============================================== No. Time Source Destination Protocol Info 9238 41.491213 172.16.0.23 172.16.0.83 RTP Payload type=ITU-T G.711 PCMU, SSRC=1391439426, Seq=64020, Time=2720 Frame 9238 (378 bytes on wire, 378 bytes captured) Prism Monitoring Header IEEE 802.11 Type/Subtype: QoS Data (40) Frame Control: 0x0988 (Normal) Duration: 44 BSS Id: SmcNetwo_57:69:38 (00:13:f7:57:69:38) (DUT) Source address: NokiaDan_41:5c:74 (00:13:fd:41:5c:74) (STA) Destination address: 3Com_ed:91:0e (00:04:75:ed:91:0e) (Asterisk computer) Fragment number: 0 Sequence number: 410 QoS parameters Priority: 5 (Video) (Video) TXOP Limit Requested: 0 Ack Policy: Normal Ack (0x0000) Logical-Link Control Internet Protocol, Src: 172.16.0.23 (172.16.0.23), Dst: 172.16.0.83 (172.16.0.83) User Datagram Protocol, Src Port: 16384 (16384), Dst Port: 10220 (10220) Real-Time Transport Protocol ===================================== |Frame sent by the station to the AP| ===================================== No. Time Source Destination Protocol Info 9249 41.500530 172.16.0.83 172.16.0.23 RTP Payload type=ITU-T G.711 PCMU, SSRC=574060427, Seq=10951, Time=800 Frame 9249 (378 bytes on wire, 378 bytes captured) Prism Monitoring Header IEEE 802.11 Type/Subtype: QoS Data (40) Frame Control: 0x0288 (Normal) Duration: 44 Destination address: NokiaDan_41:5c:74 (00:13:fd:41:5c:74) (STA) BSS Id: SmcNetwo_57:69:38 (00:13:f7:57:69:38) (DUT) Source address: 3Com_ed:91:0e (00:04:75:ed:91:0e) (Asterisk computer) Fragment number: 0 Sequence number: 2222 QoS parameters Priority: 0 (Best Effort) (Best Effort) .... 0... = EOSP: Service period QAP PS Buffer State: 0x0 Ack Policy: Normal Ack (0x0000) Logical-Link Control Internet Protocol, Src: 172.16.0.83 (172.16.0.83), Dst: 172.16.0.23 (172.16.0.23) User Datagram Protocol, Src Port: 10220 (10220), Dst Port: 16384 (16384) Real-Time Transport Protocol But in the WMM specifications, the "meaning" of the QoS Control field is independent from the transmission direction. Do you have an explanation? Thank you for your help Best regards Mathieu Renault
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