| Hi Jay, thank you for your clarification on the use case.
The Beacon Measurement and BSS Transition Management (BTM, (not BTW)) request frames are part of the associated STA steering. I agree that associated STA steering is good mechanism. We have spend a lot of time talking on pre-associated STAs steering mechanisms and desires to steer non-associated STAs. It is good, if we can focus only to use case 4.8 on pre-associated steering.
In use case 4.8, an associated STA makes Beacon Measurement, i.e. active scanning of specific SSID, as requested by the AP. Jay is claiming that current Beacon measurement is performing poorly, because CSI Information cannot be reported/obtained from the measurement. Due to lack of CSI information the AP may steer the associated STA to poor AP.
I think it is possible to improve Beacon Measurement without having general pre-associated STA identification mechanism. This will be much more simple and focused operation. - Maybe STA can provide the missing information to the AP in Beacon Report to help AP on associated STA steering? Cheers, Jarkko
Hi Jarkko, Thanks for the comments. But there is still some misunderstanding on your side on the use case 4.8. In short response, the probe response is common for all STAs. I copy all the steps below for the reference. And some clarification inline in blue font. [Network topology] Gateway connects with AP2,AP3 via wired/wireless backhaul. (STA1) connects with Gateway in the initial association. (STA1) moves from L1 to L2 and the GW(Gateway) detects the RSSI lower than a predefined threshold. (GW) sends a Beacon request frame to instruct STA1 to send a probe request frame to AP2 and AP3 on their operating channel respectively. (AP2, AP3) calculate and report the CSI and UL RSSI information of the received probe request frame from STA1 to Gateway respectively .[identified probing] (AP2,AP3) respond with probe response to STA1. (STA1) send Beacon report based on the received probe response frame to the GW Note: the Beacon report has the RSSI information of the target APs, but no CSI information of them. (GW) generates the preference list based on AP2 and AP3’s report, send a BTW request frame containing the prefer list(like AP2) to STA1. (STA1) associates with AP2 via FT based on the preference list(like AP2) in the BTW request frame <image001.png> Thanks Best Regards Jay Yang Hi Jay, thank you for your responses. Yes, it would be great if we can agree to IE instead of STA MAC addresses in device identification schemes. As discussed earlier, the pre-associated STA steering with probes (use case 4.8) has functionality that is not compatible with 802.11 standard. - The 802.11 rules for sending probe response frames do not consider the transmitter of the probe request. -à<Jay> Yes, follow all 802.11 SPEC rule. - Even is STA never changes its MAC address, the STA will learn all available APs by passively scanning. Even bad behaving APs, not compliant with 802.11, cannot steer the STA. à<Jay>Agree, STA can collect the AP’s information by itself, but it’s never know the information around the AP. I guess there is a general common sense in all IEEE group, including 11be group. Seems you also agree this point in the previous mail discussion. the identifiable probe can help the network collect the metrics between the associated STA and candidate APs, the recommendation is done by BTM request/response frame exchange. As a summary "pre-associated STA steering with probes" cannot be fixed in 802.11bh, because: 1) It does not exist in 802.11 à<Jay> ”client/band steering” is the Wi-Fi industry term that is widely adopted by the SPEC published by WFA,WBA group. If you’re not happy to see such term, we can use “AP recommendation” instead. 2) It is not broken by random and changing MAC addresses. à<Jay> I would like to clarify use case 4.8 as “pre-associated STA metrics collection with probes, and then provide the recommended candidate APs via BTM request/response frame exchange based on the metrics and other factors” Probe with RCM makes such implementation broken because there is no way for network collect the metrics between candidate APs operating on other channels and the associated STA. Other WBA or WFA groups may have their own device identifiers, rules and use cases for device identification. - I need more details on this WBA use case to understand and comment it. à<Jay> OK, no problem, if the Chair think we have more time to talk it via the reflector or in the call. There is an use case/requirement defined by WBA pass point white paper that may attack STA vendor’s eyes for pre-association identification schemes, in which the network (including both base station and AP) support for roaming between base station and AP without interruption in voice and video. The general scenario may like this(See the figure below). The network understands the current traffic loading for each UE, based on “I know you” identifier, the network can recommend the suitable candidate AP for each STA, to achieve the traffic seamless roaming from base station to AP. Such frame exchange may be happened via ANQP frame. Form STA/UE side, regardless any recommendation in pre-association, there is no way for STA to understand whether the expected AP can afford current traffic loading requirement, the voice and video service interruption issue may happen. Thanks for your response. At least I see it’s possible that we could reach some consensus and move forward. See my response in blue font. Hi Jay, thank you for your comments. Thanks for the comments, see my response inline. - Are there aspects of e-RRCM that you oppose, and bringing those into the proposal that is put to motion next week would cause you to vote No?
1) RRCM and e-RRCM allow STA to use only MAC addresses that are calculated by using RMAK. - This limits STA operation flexibility to freely select its MAC address. àBased on 11aq, each STA calculates its RMA based on one private equation. In e-RRCM, both side calculate the same RMAs based on the pre-defined equation, it’s easy for implementor to switch from private equation to the pre-defined equation. Anyway, If you have a strong concern on the MAC based solution, we can move it to the IE element. The purpose of the generated RMA is to find the right key on both side in e-RRCM solution, no matter it’s MAC address or other staff.
JKN: IE based solution would be much better than MAC address based solution. The STA has selected its MAC address and this selection is widely deployed. The use of IE would solve this comment.
<Jay> it will be grateful if the group can reach the consensus on this direction. 2) The use case for pre-association STA identification is not clear to me. - What benefits does STA get if it identifies itself before association? àWhen we talk some use cases like use case 4.8 and use case 4.26 etc. in last year, your guys also agree these cases should be addressed and updated them into the latest use case tracking document, which is approved by the group with unanimous consensus. Anyway, I’m happy to explain the benefit to the STA again, in order to get some STA vendor’s support. If you look Link recommendation feature defined in the latest 11be draft, in which “An AP MLD may also use Multi-Link Traffic Indication element and AID Bitmap element in a Link Recommendation frame to recommend a non-AP MLD to use one or more enabled links for all exchanges both for DL and UL”. Actually, Link recommendation inherits the spirt from Client steering/band steering function, in which AP provides the recommended candidate bands or Neighbor APs, so that STA can obtain the better services on that AP/band. However, the Client steering/band steering is based on the BTM request/response frame change, while allow STA make the final decision. Please see the details in 818r2 “P5, Client steering”
JKN: If I understand your response correctly, you are saying that main benefit of pre-associated STA identification is that network can steer the STA to operate on a network selected BSS, right? - STA may have reasons to select a network that is not obvious for the AP. For instance, STA may have co-ex issues or operate P2P connection. <Jay> The term of client steering or band steering is widely used in Wi-Fi industry, but the basic principle is that network provides the recommendation of the candidate AP. E.g. In our implementation, The network will provide the candidate APs for mobility STA, It’s up to the STA to follow such recommendation or not. The Link Recommendation and BSS Transition Management (BTM) can be used to steer associated STAs. Steering in associated state is much better for the STA, because the STA can send data and have time to select the AP for its association. <Jay> The use case 4.8 is aligned what you are talking, it’s a post-association client steering case indeed. I do not know how the pre-associated STA steering will be done. I think 802.11 specification has no feature or signaling to steer such pre-associated STA. - Only steering mechanism I can think is to fail the identified STA association. This is bad for the STA, because: - STA does not know to which BSS it should associate - Some networks may require STA identification to get access to the network. The device identification should be always optional. <Jay> I see the similar concern from other members, I think we can drop this use case in this round, maybe need further talk in the feature. Do you have some suggestion to avoid AP/ESS to have such implantation? - What benefits does STA get if it identifies itself before association?
-I do not see any response to this question. It seems that there are no benefits for the STA to be identified before association. <Jay> use case 4.8 is an instance of BTM for associated STA, seems you don’t object this use case, could you check that use case step by step, let we know which step is unreasonable or unacceptable? 3) RRCM, e-RRCM and Device ID are alternative, non-interworking, protocols to identify a device. - Why Device ID is not enough? Device ID has been long time in 802.11bh draft. àThe current Device ID is only carried in 4-WAY handshake, if the Device ID or other identifier can be carried in other frame, like triggered probe, it will address a lot of implementation broken issue.
- STAs do a lot of passive scanning, so limiting probe responses does not work <Jay> I don’t remember this group have such use case in the use case tracking document. Maybe some members mentioned it during the call, I saw other members also against it. I also hope the group drop this use case in this round. - The probe responses should be common for all STAs. Probe Responses may select the APs they advertise in Reduced Neighbor Report, but this information is common for all STAs. <Jay> It’s case by case, if we’re talking use case 4.8, the candidate APs only collect the metric based on the *-LTF filed in the probe request, while the information in the probe response is common for all STAs. Further, for broadcast probe response, I agree all information should be same for all STAs. For unicast probe response, there may be some difference for each STAs due to some security concern on AP side. E.g. In some mesh network, the SSID information is only seen for candidate backhaul STAs in the unicast probe response. Further, Our chair Mark made a lot of interpretation on the use cases defined in 11bh PAR in the previous meeting, and seems the current Device ID approach can’t meet the requirement on any of them. It’s decided by whether you want to see the group to finish the task group job in the following plenary meeting. Or we still have enough time, like use more than 1 years to analysis the PAR, analysis the use case from End to End perspective as Sid proposed during the call.
After the down-select procedure, Sid provided 4 extra requirements for pre-association identification scheme in the last call. Suppose some of “Apple funs” keep this position as well. If we insist to working on RRCM solution, I believe “Apple funs” will strong against the down-select results. And the expected motion will be failure definitely. May I request to go with e-RRCM solution which may meet the 4 extra requirements listed by Sid? I would like to hear the group’s opinion. - Consent
- Unauthenticated environment
- Malicious 3rd party protection
- What is identifier used for
I took an action item to start this discussion on the reflector… On today’s call, we completed our down-selection process and settled on RRCM as the favored solution to work on, to try to get any additional solution into the Draft (or agree that we are not adding anything else). However, in discussion following the down-selection process, it seems that some of the objection that might exist and prevent RRCM from passing such a motion, *might* be resolved by aspects of what’s in e-RRCM. So, we are left in a quandary – do we modify RRCM to include some/all e-RRCM extensions to satisfy the concerns, or is that reversing our straw poll guidance that RRCM is preferred over e-RRCM, and therefore we’ll lose some RRCM supporting voters if we do so? So, I’d like to start this thread to see if there is a sense in the group: - Can those who preferred RRCM over e-RRCM provide an understanding of what made that decision for you?
- Are there aspects of e-RRCM that we can add to RRCM (to satisfy those who expressed concerns with RRCM as-is) and still hold your approval of RRCM going forward into the Draft?
- Are there aspects of e-RRCM that you oppose, and bringing those into the proposal that is put to motion next week would cause you to vote No?
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