[STDS-802-11-TGM] CID 3392 (concurrent reception of fragments of at leas

Thread Links	Date Links
Thread Prev	Thread Next	Thread Index	Date Prev	Date Next	Date Index

> 1. Minutes for 802.11 TG REVmc on Friday November 21, 2014 –

> 1.6.2. CID 3392 (MAC)

Namely:

"A STA shall support the concurrent reception of fragments of at least three MSDUs or MMPDUs. [...]
The destination STA shall maintain a Receive Timer for each MSDU or MMPDU being received,

for a minimum of three MSDUs or MMPDUs." -- does this always apply (e.g. DMG STAs -- see end

of 9.5 and 9.22.2.1; also what about the risk of MSDU/MMPDU reordering caused by concurrent

reception causing replay detection to discard MSDUs/MMPDUs)?

> 1.6.2.1. Cited text duplicates text in 9.5.

> 1.6.2.2. Consider deleting text in 9.5

> 1.6.2.3. Review on Dec 12th teleconference.

I think the "text in 9.5" in question is the following:

Except when using block ack, a DMG STA shall complete the transmission of a fragmented MSDU before

starting transmission of another MSDU with the same TID of the fragmented MSDU.

0) Is this being deleted because it is believed to be duplicated by

material elsewhere in the standard? If so, where, exactly?

Furthermore, the commenter specifically mentioned the following

text in 9.6:

A STA shall support the concurrent reception of fragments of at least three MSDUs or MMPDUs.

What does this mean, exactly?

1) Is there an implied "from different peer STAs"?

2) If there isn't, is there an implied "with different TIDs,

if sent in QoS Data MPDUs"? Or is there an implied "as long

as replay counter constraints are met, if sent in an RSNA"?

3) Is there some difference between EDCA and HCCA (and HEMM)

behaviour?

4) Note also the sentence in 11.4.3.4.4 PN and replay detection

at 1895.40:

The receiver shall discard MSDUs and MMPDUs whose constituent MPDU PN values are not

sequential.

which appears for CCMP but not for GCMP.

Asking this in a different way, which of the following would be correct:

a) A STA shall support the concurrent reception of fragments of at least three MSDUs or MMPDUs,

where these are received from different STAs.

NOTE—Fragmented MSDUs/MMPDUs sent by a STA to another STA are not interleaved.

b) A STA shall support the concurrent reception of fragments of at least three MSDUs or MMPDUs,

where these are received from different STAs, and where these are received from the same STA.

NOTE— Fragmented MSDUs with different TIDs, and MMPDUs, sent by a STA to another STA might be interleaved,

subject to the maximum number of replay counters advertised by the receiving STA.

Fragmented MSDUs with a given TID/MMPDUs sent by a STA to another STA are not interleaved.

c) A STA shall support the concurrent reception of fragments of at least three MSDUs or MMPDUs,

where these are received from different STAs, and where these are received from the same STA.

NOTE— Fragmented MSDUs with a given TID/MMPDUs sent by a STA to another STA might be interleaved.

d) Something else (whether to account of HCCA/HEMM differences

or unencrypted/WEP/TKIP/CCMP/GCMP differences or otherwise)?

I also note the following:

9.8 MSDU transmission restrictions

A STA may have any

number (greater than or equal to one) of eligible MSDUs outstanding concurrently, subject to the restrictions

below.

A non-QoS STA shall not have more than one MSDU or MMPDU from a particular SA to a particular

individual RA outstanding at a time.

NOTE 1—A simpler, more restrictive alternative to the rule in the above paragraph that may be used is that no more than

one MSDU with a particular individual RA be outstanding at a time.

For frames that are not sent within the context of a block ack agreement, a QoS STA shall not have more than

one MSDU or A-MSDU for each TID or MMPDU from a particular SA to a particular individual RA

outstanding at any time.

NOTE 2—A simpler, more restrictive alternative to the rule in the above paragraph that may be used is that no more than

one MSDU or A-MSDU with any particular TID with a particular individual RA be outstanding at any time.

[Tsk, tsk, a "may" in a NOTE!]

My interpretation of the NOTEs is that you can end up with interleaved

fragments, as long as the SA (not the TA, obviously) differs, or,

for HCF, the TID differs. [I'm not entirely sure how to parse

the "or MMPDU" in the latter case, though.] But I'm not sure how

that's compatible with the rule on sequential PNs for CCMP.

Mark

P.S.: There's probably at least one egregious error on my part above.

After some time, fragments, TIDs, PNs, replay counters, etc. just

start becoming one big blur.

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

IF YOU WISH to be Removed from this reflector, PLEASE DO NOT send your request to this CLOSED reflector. We use this valuable tool to communicate on the issues at hand.

[STDS-802-11-TGM] CID 3392 (concurrent reception of fragments of at least three MSDUs or MMPDUs)