Re: [bmwg] An Upgrade to Benchmarking Methodology for Network Interconnect Devices -- Fwd: New Version Notification for draft-lencse-bmwg-rfc2544-bis-00.txt
Lencse Gábor <lencse@hit.bme.hu> Mon, 01 June 2020 09:44 UTC
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From: Lencse Gábor <lencse@hit.bme.hu>
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Date: Mon, 01 Jun 2020 11:43:50 +0200
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Subject: Re: [bmwg] An Upgrade to Benchmarking Methodology for Network Interconnect Devices -- Fwd: New Version Notification for draft-lencse-bmwg-rfc2544-bis-00.txt
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Dear Al, Thank you very much for your reply. Please see my answers inline. (I keep only those parts of the text that I reply to.) 2020.05.23. 19:40 keltezéssel, MORTON, ALFRED C (AL) írta: > >> As for the non-overlapping areas of our draft and the documents you >> cited, I have not found anything in them about our suggestion for >> "Improved Throughput and Frame Loss Rate Measurement Procedures using >> Individual Frame Timeout". >> >> If you think this one joins well into your efforts to update RFC 2544, >> then we could focus on this one first, and deal with some others later >> one by one in (in different documents). >> >> What do you think of it? > [acm] > Using a constant frame timeout for declaration of Loss (and delay) is > much like the IPPM WG metrics and methods (see RFC 7679 and RFC 7680) > for the production network measurements (Tmax). A constant waiting time for > frames to arrive at the receiver simply excludes frames on an on-going > basis. RFC 2544 has a waiting time at the end of the trial, where the > tester must wait for 2 seconds for buffers to clear but the first frame > sent has the entire trial duration+2sec to arrive. > Yes, this is why I feel that some of the frames we count as "received" may be completely useless for the applications. > Perhaps the biggest potential change to the Throughput definition is > whether or not we demand frame correspondence between sender and receiver, > so that we can calculate one-way delay. RFC 2544 and ETSI NFV TST009 only > require equal send and receive frame counts to satisfy the zero loss > criteria in the Throughput benchmark definition. But in ETSI NFV TST009, > the Capacity at X% Loss Ratio metric-variant definition begins to infer > frame correspondence. Later, the definitions of (one-way) Latency and > Delay Variation and Loss allow a Sample Filter, which could be a constant > maximum time-out for individual frames, as you suggest. Note that a Sample > Filter could be applied in post-measurement processing, assuming all the > delays are available. I have implemented siitperf-pdv (part of siitpef, available from: https://github.com/lencsegabor/siitperf ) in a way that depending on the value of its last parameter (*frame timeout*), it can do the post-processing in two different ways: - If the value of *frame timeout* is 0, then proper PDV measurement is done. - If the value of *frame timeout* is higher than zero, then rather a special throughput (or frame loss rate) measurement is performed, where the tester checks *frame timeout* for each frame individually: if the measured delay of a frame is longer than the timeout, then the frame is reclassified as lost. > But the real question in my mind now, after looking into the possibilities > to take frame correspondence with a fixed timeout into account, is whether > we can find some examples where adding timeout criteria makes a significant > difference for Throughput measurements that would not be accounted for by > revised/modernized Latency and new Delay Variation Benchmarks and > metric variants? With other words (as my co-author, Keiichi Shima expressed): "Can defining a per-frame timeout test provide more sense than the delay variation test?" IMHO, we can answer "yes". Let us consider the following example. A delay sensitive application can tolerate at most 100ms delay and 0.01% frame loss. (The "lost" frames include also frames with higher than 100ms delay.) Section 7.3.1. of RFC 8219 ( https://tools.ietf.org/html/rfc8219#section-7.3.1) defines PDV as follows: PDV = D99.9thPercentile - Dmin Where: o D99.9thPercentile = the 99.9th percentile (as described in [RFC5481 <https://tools.ietf.org/html/rfc5481>]) of the one-way delay for the stream o Dmin = the minimum one-way delay in the stream There can be two problems with using PDV: - As PDV uses 99.9th percentile, and even if we measure PDV as 99ms, it gives a guarantee for 99.9% of the frames and 0.1% of them may have higher than 100ms latency, whereas our system tolerates only 0.01% frame loss (including frames with higher latency than 100ms) - Dmin is subtracted from the 99.9th percentile, thus the final result of the PDV measurement is not exactly, what we need. IMHO, our suggested method can provide a better solution: - The *frame timeout* parameter of siitperf-pdv should be set to 100ms - The bash shell script that performs the binary search (and executes siitperf-pdv in every single step) should allow 0.01% frame loss. Thus the measurement can be easily performed. What do you think of it? Best regards, Gábor
- [bmwg] An Upgrade to Benchmarking Methodology for… Lencse Gábor
- Re: [bmwg] An Upgrade to Benchmarking Methodology… MORTON, ALFRED C (AL)
- Re: [bmwg] An Upgrade to Benchmarking Methodology… Lencse Gábor
- Re: [bmwg] An Upgrade to Benchmarking Methodology… MORTON, ALFRED C (AL)
- Re: [bmwg] An Upgrade to Benchmarking Methodology… tom petch
- Re: [bmwg] An Upgrade to Benchmarking Methodology… Lencse Gábor
- [bmwg] Question regarding source and destination … Gábor LENCSE
- Re: [bmwg] Question regarding source and destinat… MORTON, ALFRED C (AL)
- Re: [bmwg] An Upgrade to Benchmarking Methodology… MORTON, ALFRED C (AL)
- Re: [bmwg] Question regarding source and destinat… Lencse Gábor