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Management Frames Priorities and Broadcast Storm

Management Frames Priorities and Broadcast Storm. Date: 2011-02-14. Authors:. Abstract. This presentation attempts to get TGae’s attention on the problem of increased collision probability resulting from management frames priorities. Management Frames Priorities. IEEE 802.11, 2007 Std.

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Management Frames Priorities and Broadcast Storm

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  1. Management Frames Priorities and Broadcast Storm Date: 2011-02-14 Authors: Ashish Shukla, Marvell

  2. Abstract This presentation attempts to get TGae’s attention on the problem of increased collision probability resulting from management frames priorities Ashish Shukla, Marvell

  3. Management Frames Priorities • IEEE 802.11, 2007 Std. • All management frames are assigned priority AC_VO • Given lots of applications coming up with more and more usage of management frames, it may not be efficient to use AC_VO for all management frames. • IEEE 802.11ae (draft) • Attempts to address inefficiencies resulted with uniform usage of AC_VO for all management frames. • defines policies to have different priorities based on management frame type (for Action frames Category, Action value), individual or group addressed. Ashish Shukla, Marvell

  4. What is missing? • A given management frame may be used in different contexts • Certain management frames may trigger multiple responses from peer STAs when used in a particular fashion. • e.g., a Probe Request may solicit response from one STA (directed) or from multiple STAs (broadcast with wildcard BSSID and SSID). • Example in the next slide. Ashish Shukla, Marvell

  5. Broadcast Storm • A 11s Mesh STA performs device discovery by sending a broadcastt Probe Request with wildcard Mesh ID • Probe Request sent using AC_VO (non-11ae) or AC_BE (11ae 2.0D) and all the peer STAs replies to it with a Probe Response sent using AC_VO • Given AC_VO backoff parameters (CWmin 3, CWmax 7) when there are more than 3 STAs there is very high probability that Probe Responses would collide, examples include a dense mesh of say 10 STAs, or multiple APs on same channel, it would be a significant wastage of medium time (a typical 256B probe response @1mbps ~2ms airtime + Channel access overhead). • Therefore, when multiple response to Probe Request is expected, e.g., in the Mesh STA case, or multiple APs on the same channel, Probe Response should rather use AC_BE. • It would not be detrimental to device discovery, given that at least some of the STAs would be able to successfully transmit Probe Response. Ashish Shukla, Marvell

  6. Conclusion • A STA should use AC_BE for a Management frame transmission that is sent in response to a previously received management frame and it is expected that more than one STA might be transmitting the frame. • Inset the following in 10.ae1.1.1, of 802.11ae 2.0D (table 10.ae1 Default MFQ Policy): • When dot11MFQActivated is true, a Probe Response sent in response to a broadcast Probe Request with either wildcard SSID or wildcard Mesh ID shall be sent using AC_BE. • Need more investigation for other frame usage and a similar approach should be used for the frames resulting similar problems. Ashish Shukla, Marvell

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