Thanks, Ganesh and Matt.
I would suggest TGax to just focus on the definition of the management frames from transmitter point of view. Taking the Association Request frame as an example, REVmd 5.0 + 11ax D7.0 would result in (RED
are the ones added by 11ax)
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Order
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Information
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Notes
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44
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Suplemental Cass 2 Capabilities
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The Supplemental Class 2 Capabilities element is present when
dot11Class2CapabilitiesOptionImplemented is true; otherwise not
present.
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45
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MSCS Descriptor
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The MSCS Descriptor element is optionally present if
dot11MSCSActivated is true; otherwise not present.
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45
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HE Capabilities
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The HE Capabilities element is present if dot11HEOptionImplemented is true; otherwise it is not present.
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46
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Channel Switch Timing
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The HE Capabilities element is present if dot11HEOptionImplemented is true; otherwise it is not present.
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…
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So, if a transmitter wanted to include both the MSCS Descriptor and the HE Capabilities in an Association Request frame, then the standard is ambiguous on which should be included first. That is what TGax should resolve – by shifting the
order of the information being added by TGax by 1 (e.g. “45 HE Capabilities”
à “46 HE Capabilities”, “46 Channel Switch Timing”
à “47 Channel Switch Timing”, …)
Regards,
Youhan
From: *** 802.11 TGax - HEW - High Efficiency WLAN *** <STDS-802-11-TGAX@xxxxxxxxxxxxxxxxx>
On Behalf Of Matthew Fischer
Sent: Wednesday, October 28, 2020 3:20 PM
To: STDS-802-11-TGAX@xxxxxxxxxxxxxxxxx
Subject: Re: [STDS-802-11-TGAX] Order of information in some management frames
The standard says that the order is strict:
Fields and elements appear in the specified, relative order, skipping fields or elements that are not present.(#1500)(#185) STAs that encounter an
element ID they do not recognize in the frame body of a received Management frame ignore that element
and continue to parse the remainder of the management frame body (if any) for additional elements with
recognizable element IDs.
But it also says that receivers are supposed to examine the entire frame.
I have heard of implementations in the past which discard everything after they see the highest ordered item of which they are familiar.
I guess that you could say that those implementations are not compliant with the language quoted above, even though that language is not exactly normative.
But you could also say that mis-ordered elements are not compliant.
Hello Youhan:
I think you comment on the order is strictly from a spec-consistency perspective (not to have contradictory order in REVmd versus .11ax). However, the order in which elements are
included in a frame is generally not an issue – as implementation would be parsing elements based element id (and extended element id, if it applies) and not based on the order.
Cheers --
ganesh
“It is amazing what you can accomplish if you don’t care who gets the credit.” – Harry Truman
Hi, Osama, Robert,
11ax D7.0 is adding new information/elements to AssocReq frames, etc., whose order is overlapping w/ those in REVmd D5.0.
For example, 11ax D7.0 is adding the HE Capabilities element is at order #45, Channel Switch Timing is at order #46, etc to the AssocReq frame. But REVmd D5.0 already has MSCS
Descriptor as order #45.
Similar issues exist in AssocResp, ReassocReq and ReassocResp.
While there aren’t any comments submitted on D7.0 for these, I would suggest the group to address these issues for a smooth publication of IEEE 802.11ax. Is this something the
Editor (Robert) could address as an editorial update, or do you need someone to submit a formal text update request document?
Thanks.
Youhan
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