Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions
Sebastian Moeller <moeller0@gmx.de> Sat, 09 November 2019 09:37 UTC
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From: Sebastian Moeller <moeller0@gmx.de>
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Date: Sat, 09 Nov 2019 10:36:56 +0100
Cc: Greg White <g.white@CableLabs.com>, tsvwg IETF list <tsvwg@ietf.org>
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To: "Black, David" <David.Black@dell.com>
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Subject: Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions
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Hi David, in short, I guess that would work for me (what ever that is worth), more below. > On Nov 9, 2019, at 00:43, Black, David <David.Black@dell.com> wrote: > > Looks like progress - more inline ... > > Thanks, --David > >> -----Original Message----- >> From: Sebastian Moeller <moeller0@gmx.de> >> Sent: Friday, November 8, 2019 6:23 PM >> To: Black, David >> Cc: Greg White; tsvwg IETF list >> Subject: Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions >> >> >> [EXTERNAL EMAIL] >> >> Hi David, >> >> >>> On Nov 8, 2019, at 20:56, Black, David <David.Black@dell.com> wrote: >>> >>> Hi Greg, >>> >>> Backing up a few messages, I might have found a way out of this debate. >> Sebastian wrote: >>> >>>> [SM] Sorry with source, I was not talking about individual senders, >>>> but about the "NQB/L4S complex" that I expect to cause a lot of NQB marked >>>> traffic to appear on the ingress side of home users once it gets off the >>>> ground. >>> >>> That specific situation appears to be straightforward to address because >> the edge of the ISP network that supports Diffserv is involved. Specifically, >> the specification of the NQB PHB ought to include text to the effect that >> outbound NQB-marked traffic MUST be rate limited at the egress from the >> Diffserv domain/region if the downstream (receiving) network is not known >> to support NQB (this is not the precise language, but should convey the >> concept). >> >> [SM] I like this idea, I just wonder how that is going to work in the >> light of highly variable transmit rates on wifi links? IMHO AP & stations are in >> a better position to meaningfully rate limit than any upstream element. > > [David>] Apply a generous "fudge factor" so that the NQB rate limit is well short of any rate that could cause trouble. My initial sense is that this NQB rate limit limit is a safety limit that does not have an optimization goal, so the rate can be set well short of transmission rates that have a reasonable possibility of causing trouble. As part of, this, I'm hoping that there's limited downside to remarking more NQB traffic to Default (best effort) than necessary in this situation. I understand that the WiFi AP/station would be a more effective location for this sort of functionality, but in this situation, we are able specify the functionality of the immediate upstream ISP element, but not the well-worn WiFi AP that the user bought on eBay last week. [SM] That looks like reasonable compromise for everybody. > > I would leave configuration of NQB rate limits to network operators. Also, in extremis, zero is always a safe NQB egress rate ;-), so would it help to require that the NQB egress rate be configurable to zero? [SM] That is also okay, as an enduser I can (and can be expected to) address my ISP if I have questions/issues with my link's configuration, so making sure the access network provider feels responsible for avoiding NQB flooding would be good. Thanks Sebastian > >> >> >>> In the reverse direction rate limiting NQB traffic on ingress (or outright >> bleaching it to best effort if the subscriber should not be using NQB in the >> first place) seems like a good idea, and may rise to the level of a MUST >> requirement if the NQB-supporting network that the traffic is entering does >> not implement traffic protection for the NQB "queue" at each network node. >> With a little creativity, the necessary rate limiting might be able to take >> advantage of an NQB queue protection mechanism if one is present at the >> Diffserv edge. >>> >>> The individual sender situation appears to be of less concern, as at least in >> this case it looks like an instance of: >>> >>> If you point the gun at your own foot and pull the trigger, do not ask >> where the hole in your foot came from. >>> >>> As, at least for the home user, the result is only to damage her own WiFi >> network, particularly if the ISP ingress node protects its network from the >> user sending too much NQB-marked traffic. >>> >>> Thanks, --David >>> >>>> -----Original Message----- >>>> From: tsvwg <tsvwg-bounces@ietf.org> On Behalf Of Greg White >>>> Sent: Thursday, November 7, 2019 7:45 PM >>>> To: Sebastian Moeller >>>> Cc: tsvwg IETF list >>>> Subject: Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions >>>> >>>> >>>> [EXTERNAL EMAIL] >>>> >>>> It seems as if you are arguing from religious grounds. There is no >> "NQB/L4S >>>> complex" that is nefariously seeking to saturate your home network. >>>> >>>> So, I will try to ask the question again. >>>> >>>> If the policy that gets written into the RFC is that NQB traffic should not be >>>> high data rate traffic, then this achieves your objective? If we include a >>>> paragraph like that which exists in RFC 8325 that explains why, in the case >> of >>>> WiFi networks, it should not be high data rate traffic, would that be >>>> sufficient? >>>> >>>> -Greg >>>> >>>> >>>> On 11/7/19, 5:09 PM, "Sebastian Moeller" <moeller0@gmx.de> wrote: >>>> >>>> >>>> >>>>> On Nov 8, 2019, at 00:20, Greg White <g.white@CableLabs.com> wrote: >>>>> >>>>> You've still missed the point. >>>>> >>>>> [SM] It will keep one expected major source of DSCP marked traffic >>>> on a sane(r) policy. >>>>> >>>>> No. It won't. >>>>> >>>>> What will keep that source on a sane policy is that they have an interest >>>> in having a sane policy. This IETF draft does not create that interest, nor >>>> would it prevent them from running amok. >>>>> >>>>> -Greg >>>> >>>> [SM] Sorry with source, I was not talking about individual senders, >>>> but about the "NQB/L4S complex" that I expect to cause a lot of NQB >> marked >>>> traffic to appear on the ingress side of home users ionce it gets off the >>>> ground. And my point is very much to give my best arguments to make >> sure >>>> you do not end up writing a bad policy into an RFC. What ever you do in >> the >>>> real world is outside of the scope of the IETF, but taking that as an >> argument >>>> in favor of bad engineering is simply a bad argument. >>>> And regarding your interpretation of individual senders, it is clear that >>>> remote senders have a snowballs chance in hell to react timely to the >>>> variable bitrates on a wifi segment, hence the wifi elements AP (and >> ideally >>>> STAs) will need to enforce sanity and make sure tp avoid starvation. This is >>>> not a new requirement, but the status quo is that most traffic is AC_BE, so >>>> the lack of enforcement was sort of tolerable; but either NQB withers >> away >>>> and will not be used (and all of this discussion does not matter) or it will be >>>> used and then you better make sure that NQB will not be found out as a >>>> reason why non-NQB on-line gaming starts to suck. But really looking at >> the >>>> AC stats from my laptop: >>>> >>>> laptop:~ user$ sudo netstat -I en0 -qq >>>> en0: >>>> [ sched: FQ_CODEL qlength: 0/128 ] >>>> [ pkts: 0 bytes: 0 dropped pkts: 185 bytes: 55724 ] >>>> ===================================================== >>>> [ pri: VO (1) srv_cl: 0x400180 quantum: 600 drr_max: 8 ] >>>> [ queued pkts: 0 bytes: 0 ] >>>> [ dequeued pkts: 171322 bytes: 15967234 ] >>>> [ budget: 0 target qdelay: 10.00 msec update >> interval:100.00 msec ] >>>> [ flow control: 0 feedback: 0 stalls: 0 failed: 0 ] >>>> [ drop overflow: 0 early: 0 memfail: 0 duprexmt:0 ] >>>> [ flows total: 0 new: 0 old: 0 ] >>>> [ throttle on: 0 off: 0 drop: 0 ] >>>> ===================================================== >>>> [ pri: VI (2) srv_cl: 0x380100 quantum: 3000 drr_max: 6 ] >>>> [ queued pkts: 0 bytes: 0 ] >>>> [ dequeued pkts: 1081254 bytes: 95307849 ] >>>> [ budget: 0 target qdelay: 10.00 msec update >> interval:100.00 msec ] >>>> [ flow control: 0 feedback: 0 stalls: 0 failed: 0 ] >>>> [ drop overflow: 0 early: 0 memfail: 0 duprexmt:0 ] >>>> [ flows total: 0 new: 0 old: 0 ] >>>> [ throttle on: 0 off: 0 drop: 0 ] >>>> ===================================================== >>>> [ pri: BE (7) srv_cl: 0x0 quantum: 1500 drr_max: 4 ] >>>> [ queued pkts: 0 bytes: 0 ] >>>> [ dequeued pkts: 41792980 bytes: 10120070005 ] >>>> [ budget: 0 target qdelay: 10.00 msec update >> interval:100.00 msec ] >>>> [ flow control: 9 feedback: 9 stalls: 8 failed: 0 ] >>>> [ drop overflow: 0 early: 5 memfail: 0 duprexmt:0 ] >>>> [ flows total: 0 new: 0 old: 0 ] >>>> [ throttle on: 0 off: 0 drop: 0 ] >>>> ===================================================== >>>> [ pri: BK (8) srv_cl: 0x100080 quantum: 1500 drr_max: 2 ] >>>> [ queued pkts: 0 bytes: 0 ] >>>> [ dequeued pkts: 4392109 bytes: 1258595132 ] >>>> [ budget: 0 target qdelay: 10.00 msec update >> interval:100.00 msec ] >>>> [ flow control: 2 feedback: 2 stalls: 2 failed: 0 ] >>>> [ drop overflow: 0 early: 0 memfail: 0 duprexmt:0 ] >>>> [ flows total: 0 new: 0 old: 0 ] >>>> [ throttle on: 0 off: 0 drop: 0 ] >>>> >>>> >>>> >>>> >>>> and my OpenWrt router: >>>> >>>> root@router:~# cat /sys/kernel/debug/ieee80211/phy1/ath9k/xmit >>>> BE BK VI VO >>>> >>>> MPDUs Queued: 4933 120 595 47628 >>>> MPDUs Completed: 2765 331 1045 110627 >>>> MPDUs XRetried: 2792 30 381 216 >>>> Aggregates: 4053416 109096 11152 0 >>>> AMPDUs Queued HW: 0 0 0 0 >>>> AMPDUs Completed: 29761018 931822 280598 0 >>>> AMPDUs Retried: 484203 23327 4543 0 >>>> AMPDUs XRetried: 8606 149 754 0 >>>> TXERR Filtered: 97 7 32 37 >>>> FIFO Underrun: 0 0 0 0 >>>> TXOP Exceeded: 0 0 0 0 >>>> TXTIMER Expiry: 0 0 0 0 >>>> DESC CFG Error: 0 0 0 0 >>>> DATA Underrun: 0 0 0 0 >>>> DELIM Underrun: 0 0 0 0 >>>> TX-Pkts-All: 29775181 932332 282778 110843 >>>> TX-Bytes-All: 672115293 1008162267 199579558 20417055 >>>> HW-put-tx-buf: 8 8 8 8 >>>> HW-tx-start: 21266021 570626 256944 110799 >>>> HW-tx-proc-desc: 21266026 570629 257004 110839 >>>> TX-Failed: 0 0 0 0 >>>> >>>> >>>> Summary packet numbers: >>>> AC Laptop >>>> BE: 41792980 29775181 >>>> BK: 4392109 932332 >>>> VI: 1081254 282778 >>>> VO: 171322 110843 >>>> Total: 47437665 31101134 >>>> >>>> >>>> So my status quo is that all four AC are used with the fraction of >>>> AC_VI+AC_VO at >>>> 100*(1081254+ 171322)/47437665 = 2.6 % (laptop) >>>> 100*(282778 + 110843)/31101134 = 1.3 % (router) >>>> >>>> This is with relative high streaming media usage. >>>> >>>> >>>> Best Regards >>>> Sebastian >>>> >>>> >>>> >>>> >>>> >>>> >>>>> >>>>> >>>>> >>>>> On 11/7/19, 4:12 PM, "Sebastian Moeller" <moeller0@gmx.de> wrote: >>>>> >>>>> Hi Greg, >>>>> >>>>> >>>>>> On Nov 7, 2019, at 23:44, Greg White <g.white@CableLabs.com> wrote: >>>>>> >>>>>> Sebastian, >>>>>> >>>>>> I agree that this isn't rocket science. In the existing WiFi systems that >>>> we're discussing, there are 16 DSCPs that get mapped to AC_VI, and 16 >>>> DSCPs that get mapped to AC_VO. No one polices any of them in >> residential >>>> WiFi networks! There is nothing that prevents anyone from writing an >>>> application today that sends bulk traffic marked as CS7 (a value that the >> IETF >>>> considers to be reserved). >>>>> >>>>> [SM] Sure, but thanks to ISP often bleaching DSCPs there currently is >>>> very little in and outgoing traffic that actually maps to anything but AC_BE, >>>> you propose to change that in a major way, with your attempt at making >> NQB >>>> end to end (with one end potentially being in a close data center with an >> SLA >>>> allowing for NQB survival). Just because no one has massively abused this >> so >>>> far, is NOT a justification to do so now. >>>>> >>>>> >>>>>> >>>>>> I believe that the reason that RFC 8325 simply wrings its hands over this >>>> issue, as opposed to solving it, is that A) it is a *really* hard problem to >> solve >>>> in an unmanaged network, and B) while it is certainly a problem in theory, >>>> there is no evidence that it is a real problem in practice. >>>>> >>>>> [SM] The problem is that there is simply no data, and interpreting this >>>> as there is no problem is neither solid science nor engineering. If you have >>>> measurements showing that this is no problem with the expected traffic >>>> rates with the NQB marking, please feel free to post them to the list or as >>>> PM. >>>>> >>>>>> >>>>>> >>>>>> Blocking the IETF from assigning NQB the 0x2A value does *nothing* to >>>> prevent an application from using 0x2A (or any of the other 31 code points >>>> that you are concerned about) for *any* purpose that the application >>>> developer sees fit, it does *nothing* to prevent a network operator from >>>> using 0x2A for NQB traffic, and it does *nothing* to help solve the main >> issue >>>> that you are concerned about. >>>>> >>>>> [SM] It will keep one expected major source of DSCP marked traffic >>>> on a sane(r) policy. Most users and applications do not bother paying with >>>> dscps so the current amount of abuse is limited (and if I configure my >> internal >>>> skype and ssh applications to even use AC_VO I can control their activity >> and >>>> usage much better than I can traffic rushing in from the internet). Sure I >> can >>>> re-map 0x2A to a sane value on ingress to my network, but that is not >> going >>>> to help that much if my neighbors do not do this, and their APs start >> hogging >>>> all tx_ops on the shared channel. >>>>> >>>>>> >>>>>> If you want to solve this problem, my suggestion is that you start a new >>>> draft proposing a technology that will holistically protect WiFi networks >> from >>>> all potential DSCP abuses. >>>>> >>>>> [SM] First rule of holes, put the shovel away when you find yourself >>>> inside one. Here, I am not concerned so much in fixing all wifi AC abuse >> and >>>> more in giving my best to avoid this unfortunate and undesirable >> condition >>>> getting worse. >>>>> >>>>> >>>>> >>>>> Sebastian >>>>> >>>>> >>>>> >>>>>> >>>>>> Greg >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> On 11/7/19, 3:00 PM, "Sebastian Moeller" <moeller0@gmx.de> wrote: >>>>>> >>>>>> Greg, >>>>>> >>>>>>> On Nov 7, 2019, at 22:11, Greg White <g.white@CableLabs.com> >>>> wrote: >>>>>>> >>>>>>> Sebastian, >>>>>>> >>>>>>> In the interest of moving this forward and not going in circles, >>>>>> >>>>>> [SM] My impression is not that we going in circles, it is a rather slow >>>> road to understanding and accepting the properties and limitations of >> wifi's >>>> unfortunate prioritization scheme in conjunction with your intended use >> of >>>> the NQB dscp. Me shutting up, would not change the underlaying facts >> that >>>> need to be considered here if the issue is to be solved. >>>>>> >>>>>> >>>>>>> I think you summarized your position as: "To be explicit, I do not >> object >>>> on principle to using AC_VI or even AC_VO as long as this does not eat >>>> significantly into the tx_ops for AC_BE, the current draft improves in that >>>> direction. Would it be possible to make this point even stronger?" >>>>>>> >>>>>>> In my view, as long as the applications that we're recommending to be >>>> marked NQB are no more bandwidth intensive than video conferencing >> (the >>>> applications that the IETF already recommends be marked with a DSCP >> that >>>> maps to AC_VI), then we have achieved what is needed. Do you agree? >>>>>> >>>>>> To state the obvious, "no more bandwidth intensive than video >>>> conferencing" is virtually meaningless as it will give very little guidance on >>>> acceptable either single flow nor aggregate NQB traffic share or absolute >>>> bandwidth (yes rfc8325 is also pretty silent on this, but "look mum, the >> other >>>> guys are doing it too" is not the best of defenses IMHO). I realize that this >> is >>>> an issue for you as you explicitly target NQB as requiring no prioritization >> or >>>> rate-limiting, I get that; but I believe that on wifi since you effectively >>>> propose to use a prioritization system you really really should require >> rate- >>>> limiting. >>>>>> >>>>>> rfc8325, section 8.2: >>>>>> "The wireless LAN presents a unique DoS attack vector, as endpoint >>>>>> devices contend for the shared media on a completely egalitarian >>>>>> basis with the network (as represented by the AP). This means that >>>>>> any wireless client could potentially monopolize the air by sending >>>>>> packets marked to preferred UP values (i.e., UP values 4-7) in the >>>>>> upstream direction. Similarly, airtime could be monopolized if >>>>>> excessive amounts of downstream traffic were marked/mapped to >>>> these >>>>>> same preferred UP values. As such, the ability to mark/map to these >>>>>> preferred UP values (of UP 4-7) should be controlled. >>>>>> >>>>>> If such marking/mapping were not controlled, then, for example, a >>>>>> malicious user could cause WLAN DoS by flooding traffic marked CS7 >>>>>> DSCP downstream. This codepoint would map by default (as >>>> described >>>>>> in Section 2.3) to UP 7 and would be assigned to the Voice Access >>>>>> Category (AC_VO). Such a flood could cause Denial-of-Service to not >>>>>> only wireless voice applications, but also to all other traffic >>>>>> classes. Similarly, an uninformed application developer may request >>>>>> all traffic from his/her application be marked CS7 or CS6, thinking >>>>>> this would achieve the best overall servicing of their application >>>>>> traffic, while not realizing that such a marking (if honored by the >>>>>> client operating system) could cause not only WLAN DoS, but also IP >>>>>> network instability, as the traffic marked CS7 or CS6 finds its way >>>>>> into queues intended for servicing (relatively low-bandwidth) >>>> network >>>>>> control protocols, potentially starving legitimate network control >>>>>> protocols in the process." >>>>>> >>>>>> To me this clearly indicates that the achievable wifi rate betwnn AP and >>>> each station needs to be taken into account when considering which >> fraction >>>> of > AC_BE traffic is acceptable. So very much incompatible with your goal >> of >>>> having endpoints set the NQB dscp based on their own best assessment >> of >>>> traffic type without some sanitization at the AP level (only the AP will >> have a >>>> reasonable chance of predicting immediate achievable rates with some >>>> confidence, neither endpoints nor intermediate low latency queue >> enabled >>>> AQMs have sufficient knowledge to judge what traffic rate is acceptable >> for >>>> AC_VI). I consider it to be quite unfortunate that rfc8325 has no >> references >>>> to research on real-world data on the consequences of actually following >>>> through with its recommendations, nor that it has robust >> recommendations >>>> of recommended maximal fractions of the achievable rate each AC should >> be >>>> constrained to. >>>>>> >>>>>> All of this is not really rocket science, and the obvious solution, >>>> following both the principle of least surprise and a "first, do no harm" >> maxim >>>> is to select the NQB dscp such that the unfortunate default DSCP to AC >>>> mappings keep NQB marked traffic in the AC_BE queue, UNLESS the AP is >>>> NQB-aware in which case the AP should be mandated to at least reliably >>>> avoid starvation of ACs. >>>>>> The amount of back and forth seems to indicate that this is not an >>>> outcome you consider desirable. >>>>>> >>>>>> >>>>>> Sebastian >>>>>> >>>>>>> >>>>>>> -Greg >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> On 11/5/19, 1:58 AM, "Sebastian Moeller" <moeller0@gmx.de> >> wrote: >>>>>>> >>>>>>> Hi Greg, >>>>>>> >>>>>>> >>>>>>>> On Nov 5, 2019, at 01:28, Greg White <g.white@CableLabs.com> >>>> wrote: >>>>>>>> >>>>>>>> Hi Sebastian, >>>>>>>> >>>>>>>> Interoperability with existing WiFi equipment is an important aspect, >>>> since WiFi latency can be considerable. By default, many existing APs only >>>> support 4 priority queues, and thus it is not possible to meet all of the >>>> requirements of the NQB PHB (at least in this default configuration). >>>>>>> >>>>>>> [SM] I agree the question is how to deal with that "impedance >>>> mismatch". >>>>>>> >>>>>>>> Nonetheless, it is possible to utilize two of the four queues in order >>>> to meet some of the requirements, and thus provide some of the >> benefits of >>>> the NQB PHB. >>>>>>> >>>>>>> [SM] Unless you opt for selecting AC_BK for the NQB traffic, for most >>>> users the value of NQB will be mostly in the priority boost on wifi and the >>>> resulting air-time access advantage (which results in both lower latency >> and >>>> potentially higher bandwidth). >>>>>>> >>>>>>>> With proper configuration and/or policies, this can be done safely. >>>>>>> >>>>>>> [SM] Sure, I am concerned about the status quo wich does not entail >>>> "proper configuration and/or policies", and hence I believe the NQB >> special >>>> treatment on WIFI should be opt-in and not "opt-out" (in quotes as most >>>> endusers will not be able to opt-out). For thid reaon I believe that the >>>> proposal to use a code point that by default is mapped to AC_BK is the >> only >>>> correct solution (as a bonus it seems that such a code point also has a >> better >>>> chance to survive transit over the internet). NQB-aware APs then simply >>>> treat that NQB-codepoint however they want. If for example a priority >> boost >>>> is desired such an AP can easily implement the required rate-limiting so >> that >>>> AC_BE traffic does not get starved out. In short, I fully agree that special >>>> treatment requires "proper configuration and/or policies" and the >> desirable >>>> strategy if that can not guaranteed should be "do no harm". >>>>>>> >>>>>>>> The final SHOULD is intended to address your concern about >>>> prioritization (since it results in segregation without prioritization). >>>>>>> >>>>>>> [SM] Ah, in that case the AP needs to be be NQB aware anyway, >>>> would it then not be better to use an appropriate scheduler/AQM in front >> of >>>> the AC_BE queue and keep all traffic in the same priority class? The >>>> disadvantage of setting AC_VI to the same EDCA values as AC_BE is then >> that >>>> applicatons that expect an airtime access boost from using AC_VI will not >> get >>>> it any more (not necessarily a deal-breaker but certainly unexpected >> enough >>>> to merit clear communication of that side-effect). >>>>>>> >>>>>>>> Absent this requirement (or the ability to comply with it >>>> operationally), the operator would need to consider (and perhaps limit) >>>> which applications are allowed to be marked as NQB. This aspect isn't >>>> discussed in the draft, but I will add it based on your input. >>>>>>> >>>>>>> [SM] Great! I would guess the safest would be to have the NQB- >>>> aware scheduler in an AP apply some (proportional) rate-limiting if NQB >>>> traffic is getting preferential air-time access. >>>>>>> >>>>>>>> >>>>>>>> Network operators understand the value of segregating NQB traffic >>>> on WiFi links, and will almost certainly select a DSCP in practice that >> achieves >>>> that goal. >>>>>>> >>>>>>> [SM] That is exactly part of my concern with the default mapping to >>>> AC_VI approach, I expect that very quickly a lot of traffic will utilize the >> AC_VI >>>> queue potentially starving normal AC_BE traffic in the process. >>>>>>> >>>>>>>> Assigning a different DSCP in this draft would do nothing to prevent >>>> them from doing so. >>>>>>> >>>>>>> [SM] Sure, but is that really a good justification for proposing a DSCP >>>> with known side-effects? As far as I am concerned an RFC should propose >>>> sane defaults and hope for the best. >>>>>>> >>>>>>>> Instead, what we need to do is clearly articulate how to make best >>>> use of the existing WiFi tools, and how to avoid conflicts. >>>>>>> >>>>>>> [SM] I believe the last two are mutually exclusive... >>>>>>> >>>>>>>> >>>>>>>> In existing RFCs, the IETF already recommends that video >>>> conferencing applications mark their traffic as either AF4x or CS4, all of >> which >>>> get mapped to AC_VI. The remaining language in the NQB draft describes >>>> sparser flows than these. >>>>>>> >>>>>>> [SM] as an implementer I read "relatively low data rates", without >>>> further guidance I have very little intuition what to use as reference. >> Could >>>> this be made more explicit? This is orthogonal to the question whether >> such >>>> a limit should be enforced in any way, here the question really is about >>>> getting a feel what is considered acceptable for NQB treatment. >>>>>>> >>>>>>>> >>>>>>>> Based on your comments, I attempted to remove all text that could >>>> be interpreted as recommending that high-data-rate traffic be marked >> NQB. >>>>>>> >>>>>>> [SM] Thanks, as long as the aggregate NQB traffic is relative sparse >>>> compared to the available WiFi bandwidth (or the number of tx_ops) >> most of >>>> my WiFi concerns get less and less relevant. To be explicit, I do not object >> on >>>> principle to using AC_VI or even AC_VO as long as this does not eat >>>> significantly into the tx_ops for AC_BE, the current draft improves in that >>>> direction. Would it be possible to make this point even stronger? >>>>>>> >>>>>>>> It appears that I missed one instance (in the Introduction it gives >>>> "interactive voice and video" as an example). Aside from this (which I can >>>> correct), I think the draft currently recommends that NQB only be used >> for >>>> sparse traffic. That said, the section where this guidance is intended to be >>>> given is still lacking in specificity, and poses some open questions that may >>>> need to be addressed in a subsequent revision. >>>>>>> >>>>>>> [SM] Sounds great. Now this then cycles back to one of the other >>>> open topics, "enforcement". Ideally NQB-aware APs should monitor both >>>> queues and re-assign flows between them based on flow-behavior in >>>> relation to time-variant bandwidth experienced by that flow. >>>>>>> >>>>>>> Best Regards >>>>>>> Sebastian >>>>>>> >>>>>>>> >>>>>>>> Best Regards, >>>>>>>> Greg >>>>>>>> >>>>>>>> >>>>>>>> On 11/4/19, 3:25 PM, "tsvwg on behalf of Sebastian Moeller" >> <tsvwg- >>>> bounces@ietf.org on behalf of moeller0@gmx.de> wrote: >>>>>>>> >>>>>>>> Regarding https://datatracker.ietf.org/doc/draft-ietf-tsvwg- >>>> nqb/?include_text=1 >>>>>>>> >>>>>>>> 7.3. WiFi Networks >>>>>>>> >>>>>>>> WiFi networking equipment compliant with 802.11e generally >>>> supports >>>>>>>> either four or eight transmit queues and four sets of associated >>>> EDCA >>>>>>>> parameters (corresponding to the four WiFi Multimedia Access >>>>>>>> Categories) that are used to enable differentiated media access >>>>>>>> characteristics. Implementations typically utilize the IP DSCP field >>>>>>>> to select a transmit queue, but should be considered as Non- >>>>>>>> Differentiated Services-Compliant Nodes as described in Section 4 >>>> of >>>>>>>> [RFC2475]. As a result this document discusses interoperability with >>>>>>>> WiFi networks, as opposed to PHB compliance. >>>>>>>> >>>>>>>> As discussed in [RFC8325], most existing implementations use a >>>>>>>> default DSCP to User Priority mapping that utilizes the most >>>>>>>> significant three bits of the DiffServ Field to select "User >>>>>>>> Priority" which is then mapped to the four WMM Access >> Categories. >>>> In >>>>>>>> order to increase the likelihood that NQB traffic is provided a >>>>>>>> separate queue from QB traffic in existing WiFi equipment, the >>>> 0x2A >>>>>>>> codepoint is preferred for NQB. This would map NQB to UP_5 >>>> which is >>>>>>>> in the "Video" Access Category. >>>>>>>> >>>>>>>> Systems that utilize [RFC8325], SHOULD map the NQB codepoint to >>>> UP_5 >>>>>>>> in the "Video" Access Category. >>>>>>>> >>>>>>>> In order to preserve the incentives principle, WiFi systems SHOULD >>>>>>>> configure the EDCA parameters for the Video Access Category to >>>> match >>>>>>>> those of the Best Effort Access Category. >>>>>>>> >>>>>>>> >>>>>>>> [SM] This last section is puzzling: if the wifi system configures AC_VI >>>> with EDCA parameters that match the AC_BE parameters, AC_VI ceases >> to >>>> be different from AC_BE, in that case picking a codepoint that >> automatically >>>> maps to CS0 and hence to AC_BE seems much safer, simpler and straight >>>> forward to me. >>>>>>>> Especially since essentially none of the millions deployed WiFi APs >> out >>>> there will a) have this configured like proposed already and b) none of the >>>> consumer APs I know actually allow to easily adjust EDCA parameters at >> all. I >>>> guess I must be missing something and would be delighted to be shown >> why >>>> the proposed text is the right thing. >>>>>>>> My take on this still is, if NQB traffic is sufficiently sparse using AC_VI >>>> can be justified, but without any rate limits this has the potential of being >>>> quite unfair to concurrent APs on the same channel (as well as the >>>> neighboring channels that overlap with the selected). >>>>>>>> I do not want to sound alarmist, but given the number of cable-ISP >>>> WiFi-APs (as indicated by a SSID containing the ISPs name) in my city, I >>>> believe making sure that those APs will not basically start hogging most >>>> airtime seems the prudent thing to do. If there are sufficient backstops in >>>> place (like rate limiting or automatic down-marking if the traffic is not >> sparse >>>> enough) to avoid the described situation, I am all for it. >>>>>>>> >>>>>>>> The text probably should also openly discuss that in WiFi/WMM the >>>> four available queues by design have different priorities, and by moving >> NQB >>>> out of the default AC_BE while leaving QB flows in there, this effectively >> runs >>>> against the following text in the draft: "The NQB queue SHOULD be given >>>> equal priority compared to queue-building traffic of equivalent >> importance." >>>> (leaving alone the question how an AP or a station is supposed to >> measure >>>> importance) >>>>>>>> >>>>>>>> >>>>>>>> Sebastian >>>>>>>> >>>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>> >>>>>> >>>>>> >>>>> >>>>> >>>>> >>>> >>>> >>> >
- [tsvwg] draft-ietf-tsvwg-nqb, more questions Sebastian Moeller
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Greg White
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Sebastian Moeller
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Black, David
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Sebastian Moeller
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Greg White
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Sebastian Moeller
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Black, David
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Greg White
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Greg White
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Sebastian Moeller
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Dave Taht
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Greg White
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Greg White
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Sebastian Moeller
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Greg White
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Sebastian Moeller
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Greg White
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Sebastian Moeller
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Sebastian Moeller
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Greg White
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Sebastian Moeller
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Black, David
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Black, David
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Sebastian Moeller
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Sebastian Moeller
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Black, David
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Sebastian Moeller
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Greg White
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Sebastian Moeller
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Sebastian Moeller
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Black, David
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Black, David
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Greg White
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Black, David
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Sebastian Moeller
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Greg White
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Black, David
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Greg White
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Sebastian Moeller
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Sebastian Moeller
- Re: [tsvwg] draft-ietf-tsvwg-nqb, more questions Ruediger.Geib