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Re: [STDS-802-11-TGBE] CR doc 22/1709 - Requesting feedback on add/delete link procedure

I also support this proposal, and fully agree with Abhi’s comments.

We should keep in mind that many non-AP STA (MLD) devices will need to dynamically adjust usage of their radio resources for many reasons - e.g. concurrent infra + P2P, in-device coex with other technologies, neighbor discovery, ranging/sensing, deeper power save, etc.
If a client device needs to disassociate (and later re-associate) each time its available radio resources become insufficient to operate (in an 802.11-compliant manner) the affiliated non-AP STAs it previously negotiated, it is very disruptive to performance/UX (e.g. due to teardown and recreation of many states including Block acks, QoS, etc). It can also cause unnecessary overhead on the network side (e.g. disassociation might trigger network accounting events etc).

I agree if there are technical concerns they should be discussed on this thread (there is no way to respond to hearsay about concerns expressed offline). The proposal is not particularly complex, so I find it hard to believe we could not find a reasonable consensus on the design that avoids unnecessary performance degradation.

Thanks
Thomas


On Dec 15, 2022 at 1:34:18 PM, Abhishek Patil <appatil@xxxxxxxxxxxxxxxx> wrote:

Hi All,

 

I speak in favor of this proposal and here’s my reasoning:

 

Today, when an AP MLD adds a link (which the non-AP MLD is capable of operating on), there is no mechanism specified in the standard for the non-AP MLD to add that link to its existing ML setup. This is a gap in the spec that needs to be fixed. It is not a new feature. Due to lack of guidance from the spec, the only option available to a non-AP MLD is to disassociate and reassociate with the same AP MLD. Disassociation is very disruptive. It tears-down association, security and block ack context. As a result any on-going session is terminated. This will impact performance.

 

The proposal in 1709 will address the gap and provide a mechanism for a non-AP MLD to seamlessly add a link to an existing ML setup while maintaining association, security and BA context. Furthermore, any on-going sessions will not be interrupted.

 

The 1:1 remove feature has benefits too. In the current spec, an AP MLD is allowed to remove a link (on a global basis). However, the spec fails to provide a mechanism for a non-AP MLD to do the same. There were some arguments made about ‘disabling a link’. Here too, there is asymmetry in the protocol. An AP MLD is allowed to disable a link (on a global basis) if it can’t operate on that link. However from a non-AP MLD point of view, it has to ‘negotiate’ disablement if it cannot use that link. Signaling PM=1 can be a way to address the issue. However, it still keeps the resources (such as memory etc) allocated and blocked on both sides. Deleting a link is a clean solution for scenarios where the non-AP MLD knows it won’t be using the link going forward.

 

We can’t decide to not address an issue because we failed to reach consensus in the past. Instead, I would like to hear technical concerns so that we can work together to solve them and fix the gaps in the TGbe spec.

 

Regards,
Abhi

 

 

From: Yongho Seok <yongho.seok@xxxxxxxxx>
Sent: Thursday, December 15, 2022 12:35 AM
To: STDS-802-11-TGBE@xxxxxxxxxxxxxxxxx
Subject: Re: [STDS-802-11-TGBE] CR doc 22/1709 - Requesting feedback on add/delete link procedure

 

WARNING: This email originated from outside of Qualcomm. Please be wary of any links or attachments, and do not enable macros.

Hi Binita, 

As I commented in an offline discussion, this feature has been discussed for 2 years. 

Based on the SP result from the November meeting, it seems that the result is going worse compared with last year's result. 

20/1554r4 (ML Reconfiguration, Payam Torab, Facebook)

Straw Poll Result: 43 Y/30 N/18 A

22/1709r4 (LB266 CR for ML Reconfiguration Add Delete Link procedure, Binita Gupta, Meta)

Straw Poll Result: 50 Y/47 N/18 A

 

I think that it is late to address in TGbe, like other quarantine documents, 

Rather than a technical advantage, passing the Letter Ballot is more important to me. Actually, that is the goal of the comment resolution. 

In that context, I checked the comment spreadsheet, I know that this CR document may address 8 NO voters' concerns. But, I heard concerns from tens of other NO voters about this feature in the offline discussion. So, I believe that adding this feature is not helpful to make the approved TG draft in the next LB because they will not change their vote to Approve and will submit more technical comments. 

 

So, as I said in an offline discussion, I like to reject those CIDs for the same reason as other quarantine documents. And, please refer to the rejection document (11-22/2042) for the motion in the next joint meeting.

 

Thanks, 

Yongho Seok 

 

2022년 12월 11일 (일) 오후 6:20, Binita Gupta <00001d96db2c011d-dmarc-request@xxxxxxxxxxxxxxxxx>님이 작성:

Hi all,

 

I presented CR doc 22/1709r4 during the TGbe Nov plenary session which proposes add/delete link procedures for dynamically adding a link to the ML setup or deleting a link from the ML setup of a non-AP MLD.

 

There were some concerns raised by Ming and Yongho on the proposal. I tried to initiate small group discussions to understand and address their concerns, however due to holidays time, it is hard to find a suitable time slot which works for most.

Hence, I am initiating this discussion on the reflector to hear their concerns and make progress on this CR doc.

 

I would like to briefly summarize below the reasons/benefits for this proposal, to help the group better understand.

  • Add Link - Currently the spec does not define any action for the non-AP MLD to take when a new affiliated AP is added to the AP MLD. If the non-AP MLD wants to add a link to the new AP it is forced to do a re-association, which is very disruptive as it clears all the context on BA, security etc. and interrupts ongoing transmissions on existing links. The add link procedure in 22/1709 proposal a mechanism for seamlessly adding a link to the ML setup of the non-AP MLD without requiring a re-association - it maintains current BA and security context and does not cause any interruption to ongoing transmission on existing links. This is a highly desirable behavior for adding a link to an ML setup.
  • Delete Link – In current spec if a non-AP MLD intends to delete a link from its ML setup, there is no procedure defined for it to do that. It still has to keep using resources for maintaining the link as part of ML setup even if it moves that link to Power save or negotiate a TID-to-link mapping excluding that link. The delete link procedure in 22/1709 allows explicit deletion of a link from the ML setup and frees up resources for both the non-AP MLD and AP MLD and simplifies link management.

 

@Ming – please provide your specific concerns on the add link and delete link procedure. You expressed some concerns on delete link procedure during the call and below are my responses on those. You didn’t express any technical concerns on the add link part, so are you fine with the proposed add link procedure?

  • You mentioned that non-AP MLD can use the power save or negotiate a new T2L mapping for disabling a link from its ML setup. That is possible but that still requires both sides to keep using resources to maintain the disabled link as I mention above. It is desirable to provide an explicit mechanism to remove the link to simplify the link management for both sides.
  • You also mentioned that Advertised T2LM can be used for deleting a link. That feature is defined for disabling a link for the entire AP MLD level and not for deleting a link from the ML setup of a specific non-AP MLD. So, the Advertised T2LM can’t be used for deleting a link from the ML setup of a non-AP MLD.

 

@Yongho – please provide your specific concerns on the add/delete link procedure. The main concern I heard from you is that this is a new feature, and it could impact other parts of the spec and hence should be addressed in UHR timeframe. I think this feature is pretty self-contained and if there is any impact on some other part of the spec, it would be minor clarification, not any big technical change. Please let me know what specific spec impact you are concerned about (if any). BTW, this feature has been discussed in the group previously in 11-21/0534 CR doc, so this is not a new feature being discussed first time. I also understand that at that time the group’s direction was that this feature could be brought back in D2.0, and that’s what we are doing here. So, shouldn’t reject this feature saying that this is a new feature.  

 

Again, I would like to understand your specific concerns and find ways to address those to make progress on this proposal in D2.0 timeframe.

 

Others – please let me know if you have any feedback/comments on the proposal.

 

Thanks,

Binita

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