That's the point: it's not at all obvious exactly what the behaviour
is if all the classifier mask bits are 0!
One interpretation (yours) is:
# if no frame classifiers fail, we have a match
for classifier in
frame_classifiers:
if not match (frame, classifier):
return false
return true
But another equally valid one is:
# if we have no frame classifiers, we're not matching anything
if
len (frame_classifiers) == 0:
return false
# else if no frame classifiers fail, we have a match
for classifier in
frame_classifiers:
if not match (frame, classifier):
return false
return true
So the NOTE is to give an example of a TCLAS element that would
trigger this ambiguity.
I'm happy to word it differently if you have a better proposal,
but we do need to be clear on the need to have at least one
classifier in a TCLAS, so there won't be differing receiver
interpretations of the TCLAS.
Thanks,
Mark
--
Mark RISON, Standards Architect, WLAN English/Esperanto/Français
Samsung Cambridge Solution Centre Tel: +44 1223 434600
Innovation Park, Cambridge CB4 0DS Fax: +44 1223 434601
ROYAUME UNI WWW:
http://www.samsung.com/uk
From:
Stephen McCann <mccann.stephen@xxxxxxxxx>
Sent: Thursday, 17 February 2022 14:48
To: Mark Rison <m.rison@xxxxxxxxxxx>
Cc: STDS-802-11-TGM@xxxxxxxxxxxxxxxxx
Subject: Re: [STDS-802-11-TGM] 11me/D1.0 CID 1859 (all-zero Classifier Mask fields)
Mark,
thanks for this.
I think it's obvious that if all of the classifier bits are zero then there will be no matches. Why do we have to spell this out in a note?
Kind regards
Stephen
On Thu, 17 Feb 2022 at 10:53, Mark Rison <m.rison@xxxxxxxxxxx> wrote:
--- This message came from the IEEE 802.11 Task Group M Technical Reflector ---
I haven't seen any response to this post, so should I conclude that
there is no objection to resolving this comment as:
REVISED
At the end of 9.4.2.30 add:
A classifier classifies on the basis of at least one match.
NOTE---For example, when the Classifier Mask field is present and
not reserved, at least one bit of this field that is not reserved is set to 1.
?
Thanks,
Mark
--
Mark RISON, Standards Architect, WLAN English/Esperanto/Français
Samsung Cambridge Solution Centre Tel: +44 1223 434600
Innovation Park, Cambridge CB4 0DS Fax: +44 1223 434601
ROYAUME UNI WWW: http://www.samsung.com/uk
From: Mark Rison
Sent: Friday, 21 January 2022 21:00
To: 'STDS-802-11-TGM@xxxxxxxxxxxxxxxxx' <stds-802-11-tgm@xxxxxxxxxxxxxxxxx>
Cc: Thomas Derham (thomas.derham@xxxxxxxxxxxx) <thomas.derham@xxxxxxxxxxxx>; Jouni Malinen (jouni@xxxxxxxxxxxxxxxx) <jouni@xxxxxxxxxxxxxxxx>
Subject: 11me/D1.0 CID 1859 (all-zero Classifier Mask fields)
I was asked to start a thread on this comment:
CID 1859
9.4.2.30
It is not clear whether it is OK to have a Classifier Mask field (where it is not reserved) that is all-0, and if so whether that is an "always matches" or a "never matches"
At the end of the subclause add "If a Classifier Mask field is present and all bits that are not reserved are 0, then this classifier never matches."
As far as I can tell, the classifiers have the following classifier
masks:
0, 1, 2, 4, 5: bitmap indicating parameters that need to match
6, 7, 8, 9: bitmap with 2-bit subbitmaps
3: reserved
10: not present (despite what Figure 9-364—Frame Classifier field format says -- see CID 1856)
The direction of the group was to specify that classifiers that
don't classify anything shall not be transmitted, rather than
trying to specify that they never or always match.
Because there are so many classifiers, and they classify in quite
significantly different ways, I propose adding this general statement
at the end of 9.4.2.30:
A classifier classifies on the basis of at least one match.
NOTE---For example, when the Classifier Mask field is present and
not reserved, at least one bit of this field that is not reserved is set to 1.
Thanks,
Mark
--
Mark RISON, Standards Architect, WLAN English/Esperanto/Français
Samsung Cambridge Solution Centre Tel: +44 1223 434600
Innovation Park, Cambridge CB4 0DS Fax: +44 1223 434601
ROYAUME UNI WWW: http://www.samsung.com/uk
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