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| -rw-r--r-- | docs/ietf/draft-vpolak-bmwg-plrsearch-03.md (renamed from docs/ietf/draft-vpolak-bmwg-plrsearch-02.md) | 44 |
1 files changed, 30 insertions, 14 deletions
diff --git a/docs/ietf/draft-vpolak-bmwg-plrsearch-02.md b/docs/ietf/draft-vpolak-bmwg-plrsearch-03.md index f725024d28..b09b5ce0be 100644 --- a/docs/ietf/draft-vpolak-bmwg-plrsearch-02.md +++ b/docs/ietf/draft-vpolak-bmwg-plrsearch-03.md @@ -1,8 +1,8 @@ --- title: Probabilistic Loss Ratio Search for Packet Throughput (PLRsearch) # abbrev: PLRsearch -docname: draft-vpolak-bmwg-plrsearch-02 -date: 2019-07-08 +docname: draft-vpolak-bmwg-plrsearch-03 +date: 2020-03-06 ipr: trust200902 area: ops @@ -38,10 +38,16 @@ normative: RFC8174: informative: + + FDio-CSIT-PLRsearch: + target: https://docs.fd.io/csit/rls2001/report/introduction/methodology_data_plane_throughput/methodology_plrsearch.html + title: "FD.io CSIT Test Methodology - PLRsearch" + date: 2020-02 + draft-vpolak-mkonstan-bmwg-mlrsearch: target: https://tools.ietf.org/html/draft-vpolak-mkonstan-bmwg-mlrsearch title: "Multiple Loss Ratio Search for Packet Throughput (MLRsearch)" - date: 2019-07 + date: 2020-02 --- abstract @@ -56,7 +62,8 @@ probabilistic in nature, and not deterministic. # Motivation -Network providers are interested in throughput a system can sustain. +Network providers are interested in throughput a networking system can +sustain. [RFC2544] assumes loss ratio is given by a deterministic function of offered load. But NFV software systems are not deterministic enough. @@ -74,6 +81,10 @@ for benchmarking networking setups such as software based NFV systems. # Terms And Assumptions +Due to the indeterministic nature of certain NFV systems that are the +targetted by PLRsearch algorithm, existing network benchmarking terms +are explicated and a number of new terms and assumptions are introduced. + ## Device Under Test In software networking, "device" denotes a specific piece of software @@ -647,7 +658,12 @@ direct critical load estimate, so users can draw their own conclusion. Alternatively, trend analysis may be a part of exit conditions, requiring longer searches for systems displaying trends. -# Sample Implementation Specifics: FD.io CSIT +# Known Implementations + +The only known working implementation of PLRsearch is in Linux +Foundation FD.io CSIT open-source project [FDio-CSIT-PLRsearch]. + +## FD.io CSIT Implementation Specifics The search receives min_rate and max_rate values, to avoid measurements at offered loads not supporeted by the traffic generator. @@ -658,7 +674,7 @@ agnostic to flows and directions, it only cares about overall counts of packets sent and packets lost), but debug output from traffic generator lists unidirectional values. -## Measurement Delay +### Measurement Delay In a sample implemenation in FD.io CSIT project, there is roughly 0.5 second delay between trials due to restrictons imposed by packet traffic @@ -679,7 +695,7 @@ increasing trial durations with configurable coefficients (currently 5.1 seconds for the first trial, each subsequent trial being 0.1 second longer). -## Rounding Errors and Underflows +### Rounding Errors and Underflows In order to avoid them, the current implementation tracks natural logarithm (instead of the original quantity) for any quantity which is @@ -688,7 +704,7 @@ Python), so special value "None" is used instead. Specific functions for frequent operations (such as "logarithm of sum of exponentials") are defined to handle None correctly. -## Fitting Functions +### Fitting Functions Current implementation uses two fitting functions. In general, their estimates for critical rate differ, which adds a simple source of @@ -735,7 +751,7 @@ compute. At the end, both fitting function implementations contain multiple "if" branches, discontinuities are a possibility at range boundaries. -### Stretch Function +#### Stretch Function The original function (before applying logarithm) is Primitive Function to Logistic Function. The name "stretch" is used for related a function @@ -747,7 +763,7 @@ given as InputForm of Wolfram language: r = (a*(1 + E^(m/a))*Log[(E^(b/a) + E^(m/a))/(1 + E^(m/a))])/E^(m/a) -### Erf Function +#### Erf Function The original function is double Primitive Function to Gaussian Function. The name "erf" comes from error function, the first primitive to @@ -760,7 +776,7 @@ given as InputForm of Wolfram language: r = ((a*(E^(-((b - m)^2/a^2)) - E^(-(m^2/a^2))))/Sqrt[Pi] + m*Erfc[m/a] + (b - m)*Erfc[(-b + m)/a])/(1 + Erf[m/a]) -## Prior Distributions +### Prior Distributions The numeric integrator expects all the parameters to be distributed (independently and) uniformly on an interval (-1, 1). @@ -776,7 +792,7 @@ The "stretch" parameter is generated simply as the "mrr" value raised to a random power between zero and one; thus it follows a Reciprocal Distribution. -## Integrator +### Integrator After few measurements, the posterior distribution of fitting function arguments gets quite concentrated into a small area. The integrator is @@ -809,7 +825,7 @@ new area the posterior distribution is concentrated at. The second phase (dominated by whole sample population) is actually relevant for the critical rate estimation. -## Offered Load Selection +### Offered Load Selection First two measurements are hardcoded to happen at the middle of rate interval and at max_rate. Next two measurements follow MRR-like logic, @@ -865,6 +881,6 @@ networks. # Acknowledgements -.. +To be added. --- back
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