Re: [ippm] Lars Eggert's Discuss on draft-ietf-ippm-capacity-metric-method-10: (with DISCUSS and COMMENT)
Martin Duke <martin.h.duke@gmail.com> Thu, 20 May 2021 19:03 UTC
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References: <162072161364.15626.11472410331094167599@ietfa.amsl.com> <1764ec14e5394838b2a2802c45561aab@att.com> <6B3E6E27-AE72-4ABB-AE28-0A74B3EE93D0@eggert.org> <CAM4esxQKCooYRGf_+=fxgXNHpAGr69JdavqWX3o0CHiGda+nMw@mail.gmail.com> <98764a1876b047038bc02ae37d5faabd@att.com> <CAM4esxQv3upjAToW-Ph1537VGsb7SbDmSY7FAq2O2JnOqnivWA@mail.gmail.com>
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From: Martin Duke <martin.h.duke@gmail.com>
Date: Thu, 20 May 2021 12:03:31 -0700
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To: "MORTON JR., AL" <acmorton@att.com>
Cc: Lars Eggert <lars@eggert.org>, "ippm-chairs@ietf.org" <ippm-chairs@ietf.org>, "draft-ietf-ippm-capacity-metric-method@ietf.org" <draft-ietf-ippm-capacity-metric-method@ietf.org>, "ippm@ietf.org" <ippm@ietf.org>, Ian Swett <ianswett@google.com>, The IESG <iesg@ietf.org>, "tpauly@apple.com" <tpauly@apple.com>
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Subject: Re: [ippm] Lars Eggert's Discuss on draft-ietf-ippm-capacity-metric-method-10: (with DISCUSS and COMMENT)
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OK, we waived the downref. If 7967 is going to be a perennial problem, I don't see that it meets any of the downref criteria in 3967, and I would encourage the group to consider updating its status to proposed standard. On Wed, May 19, 2021 at 4:17 PM Martin Duke <martin.h.duke@gmail.com> wrote: > Got it. According to RFC 8067, the IESG can just waive it when the AD > review misses it rather than go through another last call. I'll open that > subject at tomorrow's telechat -- unless the smart people in IPPM think > that changes warrant a new IETF Last Call in their own right. > > On Wed, May 19, 2021 at 3:48 PM MORTON JR., AL <acmorton@att.com> wrote: > >> in-line, >> >> Al >> >> >> >> *From:* Martin Duke <martin.h.duke@gmail.com> >> *Sent:* Wednesday, May 19, 2021 6:30 PM >> *To:* Lars Eggert <lars@eggert.org> >> *Cc:* MORTON JR., AL <acmorton@att.com>; ippm-chairs@ietf.org; >> draft-ietf-ippm-capacity-metric-method@ietf.org; ippm@ietf.org; Ian >> Swett <ianswett@google.com>; The IESG <iesg@ietf.org>; tpauly@apple.com >> *Subject:* Re: Lars Eggert's Discuss on >> draft-ietf-ippm-capacity-metric-method-10: (with DISCUSS and COMMENT) >> >> >> >> OK, I've had a look at this, and I don't see why this is a normative >> reference at all! >> >> >> >> The primary application of the metric and method of measurement >> >> described here is the same as in Section 2 of [RFC7497] <https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/html/rfc7497*section-2__;Iw!!BhdT!xlfpewVBdgR2F4flazNgF3Ypkw-6ovu-odnTKamNrSa250ONVpnJdOv2Pnhu$> where: >> >> >> >> o The access portion of the network is the focus of this problem >> >> statement. The user typically subscribes to a service with >> >> bidirectional access partly described by rates in bits per second. >> >> >> >> How is this necessary to implement the draft? >> >> *[acm] * >> >> *For Implementation, Not at all! But we use it to set the Scope and >> Applicability, which is a Normative section by its very nature, IMO. The >> Figure in RFC 7497 limits the applicability to a small number of >> administrative domains at the edge of the Internet, including what most >> people think of when they hear “Internet access”.* >> >> >> >> *So, you can’t implement this RFC *and use it properly* without this >> reference.* >> >> >> >> *Adding the reference to RFC 7497 was a big step in resolving Magnus’ >> comments. He didn’t want the Capacity test used end-to-end on the Internet, >> and RFC 7497 was the perfect solution. But like all our framework RFCs, >> it’s Informational.* >> >> >> >> Happy to be corrected on this! >> >> *[acm] * >> >> *I made my case, it’s your call. We have a working version going for >> Lars’ comments, so it’s an easy fix.* >> >> >> >> [Also, appropriately ashamed to have missed it in my AD review] >> >> *[acm] * >> >> *You didn’t miss it! It wasn’t in the Scope/applicability section at >> that time! This Ref was added for Magnus!* >> >> >> >> Martni >> >> >> >> On Tue, May 18, 2021 at 12:05 AM Lars Eggert <lars@eggert.org> wrote: >> >> Hi Al, >> >> On 2021-5-17, at 21:00, MORTON JR., AL <acmorton@att.com> wrote: >> >> DOWNREF from this Standards Track doc to Informational RFC7497. >> >> I didn't see this called out in the Last Call, and it's also not a >> >> document we have in the DOWNREF registry already. >> > [acm] >> > Ok, I think this means another IETF Last Call? It's not the first time >> > we've been tripped-up by keeping IPPM's Framework+updates and other >> > requirements docs off the Standards-Track. >> > >> > I also think that https://datatracker.ietf.org/doc/html/rfc7497 >> <https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/html/rfc7497__;!!BhdT!xlfpewVBdgR2F4flazNgF3Ypkw-6ovu-odnTKamNrSa250ONVpnJdPOyZrAO$> >> will figure >> > prominently in future work on the Capacity topic, such as a test >> protocol, so we >> > should add it to the DOWNREF registry. >> > >> > @@@@ Is the DOWNREF registry an action item for chairs or AD/Martin? >> >> yes, another LC will unfortunately be needed. It's an action item for >> Martin. >> >> Note that everything below was comments, which are not blocking the >> document: >> >> >> Section 1, paragraph 3, comment: >> >>> Here, the main use case is to assess the maximum capacity of the >> >>> access network, with specific performance criteria used in the >> >>> measurement. >> >> >> >> If the main use case is to measure access network paths, that >> applicability >> >> should be made very explicit, i.e., in the title and abstract. >> > >> > Two things: >> > >> > 1. The term "access" doesn't have a universally agreed definition >> regarding the portion of the network it covers, and that's partly because >> there are many architectures in use. >> > >> > 2. If we add access to the title or abstract, we are unnecessarily >> limiting the scope that we define later. We refer to section of RFC 7497 >> where the figure includes the subscriber's device, multiple private >> networks, and various devices and gateways ending at a transit gateway. >> > >> > So, I don't want to emphasize the term "access" as you propose. >> >> That's fine, too. When reading the document, I came away with the >> impression that it did want to focus on measuring access networks, because >> it actually says that in several places (e.g., the quote above.) If the >> intent is for this to be a general metric for IP paths, maybe review the >> places where the document talks about "access" to make sure they are not >> giving the wrong impression. >> >> > Perhaps we can clarify this further in the Intro, because the Scope >> says: >> > >> > The primary application of the metric and method of measurement >> > described here is the same as in Section 2 of [RFC7497]... >> > >> > How about: >> > Here, the main use case is to assess the maximum capacity of one or >> more networks >> > where the subscriber receives specific performance assurances, sometimes >> > referred to as the Internet access. >> >> It's not only the intro, though. There is text talking about "access" >> throughout the document. >> >> >> Section 2, paragraph 2, comment: >> >>> The scope of this memo is to define a metric and corresponding >> method >> >>> to unambiguously perform Active measurements of Maximum IP-Layer >> >>> Capacity, along with related metrics and methods. >> >> >> >> I'm not sure what "unambiguously perform" is meant to express? >> > >> > [RG] is it unambiguously measure...? If yes roughly: >> > "The scope of this memo is to define Active Measurement metrics and >> corresponding methods >> > to unambiguously determine Maximum IP-Layer Capacity and useful >> secondary evaluations." >> > >> > [acm] With s/evaluations/metrics/ this WFM. >> >> WFM >> >> >> Section 2, paragraph 3, comment: >> >>> A local goal is to aid efficient test procedures where possible, and >> >>> to recommend reporting with additional interpretation of the >> results. >> >> >> >> What is this goal "local" to - the IETF? >> > [acm] Yes IETF, but that word choice seems unclear now. >> > >> > [RG] further s/aid/add?? >> > >> >> Also, I'm unclear what "reporting >> >> with additional interpretation of the results" is supposed to express. >> > >> > [acm] Let's try: >> > >> > Secondary goals are to add considerations for test procedures, and >> > to provide interpretation of the Maximum IP-Layer Capacity results (to >> > identify cases where more testing is warranted, possibly with alternate >> > configurations). >> >> WFM >> >> >> Section 2, paragraph 10, comment: >> >>> - If a network operator is certain of the access capacity to be >> >>> validated, then testing MAY start with a fixed rate test at the >> >>> access capacity and avoid activating the load adjustment algorithm. >> >>> However, the stimulus for a diagnostic test (such as a subscriber >> >>> request) strongly implies that there is no certainty and the load >> >>> adjustment algorithm will be needed. >> >> >> >> Since the first sentence of this paragraph uses a RFC2119 MAY, I'd >> suggest >> >> rephrasing the second sentence to end with "there is no certainty and >> use >> >> of the load adjustment algorithm is RECOMMENDED." >> > >> > [RG] sounds good to me. >> > [acm] WFM >> >> WFM >> >> >> Section 3, paragraph 4, comment: >> >>> 1. Internet access is no longer the bottleneck for many users. >> >> >> >> What is the bottleneck then, and if it's not the access bandwidth, why >> is >> >> a new metric for it helpful? >> > >> > [RG]+[acm] 1. Internet access is no longer the bottleneck for many >> users, but subscribers expect network providers to honor contracted access >> performance. >> > >> > [acm] IOW, when you subscribe to a 1 Gbps service, then your ISP, you, >> and possibly other parties want to assure that performance level is >> delivered. If you test and confirm the subscribed performance level, then >> you can seek the location of the bottleneck elsewhere. >> >> That context would be helpful to have in the document in some form, IMO. >> >> > Section 4, paragraph 4, comment: >> >>> o Src, the address of a host (such as the globally routable IP >> >>> address). >> >>> >> >>> o Dst, the address of a host (such as the globally routable IP >> >>> address). >> >> >> >> For many hosts, their IP address is not globally routable, and hasn't >> been >> >> for decades. Or did you mean CPE? >> > >> > [acm] I think *host* is general-enough to include CPE that is the >> source or destination of test packets. Also, "globally routable" is part of >> an example. >> >> I still wonder if removing "globally routable" would reduce confusion >> here, but OK. >> >> > Section 8.1, paragraph 1, comment: >> >>> 8.1. Load Rate Adjustment Algorithm >> >> >> >> I wonder why this section is trying to define a crude new AIMD scheme, >> when we >> >> have lots of good experience with TCP's AIMD approach, which converges >> on >> >> the available bandwidth relatively well? >> > >> > [acm] "crude"?? Our algorithm has the advantage of receiver >> measurements of rate, >> > loss, and delay. So, we aren't making inferences based on ACKs, we >> communicate >> > measurement feedback instead. >> >> Maybe I should have said "complex" :-) >> >> > This is not a new AIMD. I'm sure you haven't had time to review >> > hundreds of test results where we compare our load adjustment algorithm >> to >> > TCP's AIMDs when seeking to measure the maximum IP-layer capacity. >> > >> > Please see section 4 of https://datatracker.ietf.org/doc/html/rfc8337 >> <https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/html/rfc8337__;!!BhdT!xlfpewVBdgR2F4flazNgF3Ypkw-6ovu-odnTKamNrSa250ONVpnJdMQ2_xii$> >> > particularly the list of section 4.1 where Matt Mathis wrote: >> > >> > o TCP is a control system with circular dependencies -- everything >> > affects performance, including components that are explicitly not >> > part of the test (for example, the host processing power is not >> > in-scope of path performance tests). >> > >> > and this is similar to the statements I have heard for >20 years in >> IETF, >> > where the conclusion is that TCP was not designed as a measurement tool. >> > >> > So, it was a goal to avoid the limitations of TCP (windows, ACK >> feedback, >> > retransmissions, and the CCA that were available, including BBR and >> BBRv2). >> > The algorithm we defined is intended to be fast, adjustable in >> straightforward >> > ways, and (most important to Magnus) not to be deployed as a >> general-purpose >> > CCA in TCP. Our scope is infrequent, diagnostic measurements. >> >> Point taken. >> >> >> Section 8.1, paragraph 7, comment: >> >>> If the feedback indicates that no sequence number anomalies were >> >>> detected AND the delay range was below the lower threshold, the >> >>> offered load rate is increased. If congestion has not been >> confirmed >> >>> up to this point, the offered load rate is increased by more than >> one >> >>> rate (e.g., Rx+10). This allows the offered load to quickly reach a >> >>> near-maximum rate. Conversely, if congestion has been previously >> >>> confirmed, the offered load rate is only increased by one (Rx+1). >> >> >> >> The first sentence talks about sequence number anomalies and delay >> ranges. >> >> The rest of the paragraph then talks about whether congestion and >> whether it >> >> was confirmed or not. Does this mean that (some amount of) sequence >> number >> >> anomalies and/or delay indicates congestion? Is that defined somewhere? >> > >> > [acm] Yes, in a paragraph that begins: >> > Lastly, the method for inferring congestion is that there were... >> > >> > I'll add a forward reference: >> > ... If congestion has not been confirmed up to this point (see below >> > for the method to declare congestion), the offered load rate is >> increased ... >> >> WFM >> >> >> Section 8.1, paragraph 7, comment: >> >>> If the feedback indicates that sequence number anomalies were >> >>> detected OR the delay range was above the upper threshold, the >> >>> offered load rate is decreased. The RECOMMENDED values are 0 for >> >> >> >> This doesn't agree with the previous paragraph, which says >> "Conversely, if >> >> congestion has been previously confirmed, the offered load rate is only >> >> increased by one (Rx+1)." (Or I don't understand the difference between >> >> congestion and sequence number anomalies/delay ranges; see previous >> >> comment.) >> > >> > [acm] Your "(Or ...)" is correct, we deferred the description of >> congestion >> > declaration to a later paragraph, where we require 2 feedback messages >> at least: >> > >> > Lastly, the method for inferring congestion is that there were >> sequence >> > number anomalies AND/OR the delay range was above the upper threshold >> > for two consecutive feedback intervals. ... >> >> WFM >> >> > Section 8.4, paragraph 2, comment: >> >>> This section is for the benefit of the Document Shepherd's form, and >> >>> will be deleted prior to final review. >> >> >> >> Should this section have been deleted before the IESG review then? >> Would >> >> you like the IESG to ignore it? >> > >> > [acm] I think that during the February review, that's exactly what the >> IESG did: >> > ignore the section. We would have happily supported any AD who wanted >> to review >> > or try the code by allowing access to our server. >> > >> >> You probably also need to instruct the RFC >> >> Editor to remove it before publication? >> > >> > [acm] OK >> > RFC Editor: This section is for the benefit of the Document Shepherd's >> form, >> > and will be deleted prior to publication. >> > >> >>>> I don't think this material from 8.4 made it into the Doc Shepherd's >> form, >> > which is one reason it's still hanging around... >> >> WFM >> >> > This document uses RFC2119 keywords, but does not contain the >> recommended >> >> RFC8174 boilerplate. (It contains some text with a similar beginning.) >> > [acm] I think this is covered, section 1.1. >> >> WFM >> >> >> >> >> >> -------------------------------------------------------------------------- >> >> ----- >> >> All comments below are about very minor potential issues that you may >> choose to >> >> address in some way - or ignore - as you see fit. Some were flagged by >> >> automated tools, so there will likely be some false positives. There >> is no need >> >> to let me know what you did with these suggestions. >> > >> > Ok, thanks. I would like to know which tool(s) you used (and if free, >> > even on a trial basis). Seemed to do a decent job. >> >> https://github.com/larseggert/ietf-reviewtool >> <https://urldefense.com/v3/__https:/github.com/larseggert/ietf-reviewtool__;!!BhdT!xlfpewVBdgR2F4flazNgF3Ypkw-6ovu-odnTKamNrSa250ONVpnJdGUm8Z7Q$> >> >> Thanks, >> Lars >> >>
- [ippm] Lars Eggert's Discuss on draft-ietf-ippm-c… Lars Eggert via Datatracker
- Re: [ippm] Lars Eggert's Discuss on draft-ietf-ip… MORTON JR., AL
- Re: [ippm] Lars Eggert's Discuss on draft-ietf-ip… Lars Eggert
- Re: [ippm] Lars Eggert's Discuss on draft-ietf-ip… Martin Duke
- Re: [ippm] Lars Eggert's Discuss on draft-ietf-ip… MORTON JR., AL
- Re: [ippm] Lars Eggert's Discuss on draft-ietf-ip… Martin Duke
- Re: [ippm] Lars Eggert's Discuss on draft-ietf-ip… Martin Duke
- Re: [ippm] Lars Eggert's Discuss on draft-ietf-ip… Lars Eggert
- Re: [ippm] Lars Eggert's Discuss on draft-ietf-ip… MORTON JR., AL