+++ /dev/null
----
-title: Multiple Loss Ratio Search for Packet Throughput (MLRsearch)
-abbrev: Multiple Loss Ratio Search
-docname: draft-ietf-bmwg-mlrsearch-02
-date: 2021-11-02
-
-ipr: trust200902
-area: ops
-wg: Benchmarking Working Group
-kw: Internet-Draft
-cat: info
-
-coding: us-ascii
-pi: # can use array (if all yes) or hash here
- toc: yes
- sortrefs: # defaults to yes
- symrefs: yes
-
-author:
- -
- ins: M. Konstantynowicz
- name: Maciek Konstantynowicz
- org: Cisco Systems
- role: editor
- email: mkonstan@cisco.com
- -
- ins: V. Polak
- name: Vratko Polak
- org: Cisco Systems
- email: vrpolak@cisco.com
-
-normative:
- RFC2544:
-
-informative:
- FDio-CSIT-MLRsearch:
- target: https://docs.fd.io/csit/rls2101/report/introduction/methodology_data_plane_throughput/methodology_mlrsearch_tests.html
- title: "FD.io CSIT Test Methodology - MLRsearch"
- date: 2021-02
- PyPI-MLRsearch:
- target: https://pypi.org/project/MLRsearch/0.4.0/
- title: "MLRsearch 0.4.0, Python Package Index"
- date: 2021-04
-
---- abstract
-
-This document proposes changes to [RFC2544], specifically to packet
-throughput search methodology, by defining a new search algorithm
-referred to as Multiple Loss Ratio search (MLRsearch for short). Instead
-of relying on binary search with pre-set starting offered load, it
-proposes a novel approach discovering the starting point in the initial
-phase, and then searching for packet throughput based on defined packet
-loss ratio (PLR) input criteria and defined final trial duration time.
-One of the key design principles behind MLRsearch is minimizing the
-total test duration and searching for multiple packet throughput rates
-(each with a corresponding PLR) concurrently, instead of doing it
-sequentially.
-
-The main motivation behind MLRsearch is the new set of challenges and
-requirements posed by NFV (Network Function Virtualization),
-specifically software based implementations of NFV data planes. Using
-[RFC2544] in the experience of the authors yields often not repetitive
-and not replicable end results due to a large number of factors that are
-out of scope for this draft. MLRsearch aims to address this challenge
-in a simple way of getting the same result sooner, so more repetitions
-can be done to describe the replicability.
-
---- middle
-
-# Terminology
-
-* Frame size: size of an Ethernet Layer-2 frame on the wire, including
- any VLAN tags (dot1q, dot1ad) and Ethernet FCS, but excluding Ethernet
- preamble and inter-frame gap. Measured in bytes (octets).
-* Packet size: same as frame size, both terms used interchangeably.
-* Device Under Test (DUT): In software networking, "device" denotes a
- specific piece of software tasked with packet processing. Such device
- is surrounded with other software components (such as operating system
- kernel). It is not possible to run devices without also running the
- other components, and hardware resources are shared between both. For
- purposes of testing, the whole set of hardware and software components
- is called "system under test" (SUT). As SUT is the part of the whole
- test setup performance of which can be measured by [RFC2544] methods,
- this document uses SUT instead of [RFC2544] DUT. Device under test
- (DUT) can be re-introduced when analysing test results using whitebox
- techniques, but this document sticks to blackbox testing.
-* System Under Test (SUT): System under test (SUT) is a part of the
- whole test setup whose performance is to be benchmarked. The complete
- test setup contains other parts, whose performance is either already
- established, or not affecting the benchmarking result.
-* Bi-directional throughput tests: involve packets/frames flowing in
- both transmit and receive directions over every tested interface of
- SUT/DUT. Packet flow metrics are measured per direction, and can be
- reported as aggregate for both directions and/or separately
- for each measured direction. In most cases bi-directional tests
- use the same (symmetric) load in both directions.
-* Uni-directional throughput tests: involve packets/frames flowing in
- only one direction, i.e. either transmit or receive direction, over
- every tested interface of SUT/DUT. Packet flow metrics are measured
- and are reported for measured direction.
-* Packet Loss Ratio (PLR): ratio of packets received relative to packets
- transmitted over the test trial duration, calculated using formula:
- PLR = ( pkts_transmitted - pkts_received ) / pkts_transmitted.
- For bi-directional throughput tests aggregate PLR is calculated based
- on the aggregate number of packets transmitted and received.
-* Effective loss ratio: A corrected value of measured packet loss ratio
- chosen to avoid difficulties if SUT exhibits decreasing loss
- with increasing load. Maximum of packet loss ratios measured at the same
- duration on all loads smaller than (and including) the current one.
-* Target loss ratio: A packet loss ratio value acting as an input for search.
- The search is finding tight enough lower and upper bound in intended load,
- so that the lower bound has smaller or equal loss ratio, and upper bound
- has strictly larger loss ratio. For the tightest upper bound,
- the effective loss ratio is the same as packet loss ratio.
- For the tightest lower bound, the effective loss ratio can be higher
- than the packet loss ratio, but still not larger than the target loss ratio.
-* Packet Throughput Rate: maximum packet offered load DUT/SUT forwards
- within the specified Packet Loss Ratio (PLR). In many cases the rate
- depends on the frame size processed by DUT/SUT. Hence packet
- throughput rate MUST be quoted with specific frame size as received by
- DUT/SUT during the measurement. For bi-directional tests, packet
- throughput rate should be reported as aggregate for both directions.
- Measured in packets-per-second (pps) or frames-per-second (fps),
- equivalent metrics.
-* Bandwidth Throughput Rate: a secondary metric calculated from packet
- throughput rate using formula: bw_rate = pkt_rate * (frame_size +
- L1_overhead) * 8, where L1_overhead for Ethernet includes preamble (8
- octets) and inter-frame gap (12 octets). For bi-directional tests,
- bandwidth throughput rate should be reported as aggregate for both
- directions. Expressed in bits-per-second (bps).
-* Non Drop Rate (NDR): maximum packet/bandwidth throughput rate sustained
- by DUT/SUT at PLR equal zero (zero packet loss) specific to tested
- frame size(s). MUST be quoted with specific packet size as received by
- DUT/SUT during the measurement. Packet NDR measured in
- packets-per-second (or fps), bandwidth NDR expressed in
- bits-per-second (bps).
-* Partial Drop Rate (PDR): maximum packet/bandwidth throughput rate
- sustained by DUT/SUT at PLR greater than zero (non-zero packet loss)
- specific to tested frame size(s). MUST be quoted with specific packet
- size as received by DUT/SUT during the measurement. Packet PDR
- measured in packets-per-second (or fps), bandwidth PDR expressed in
- bits-per-second (bps).
-* Maximum Receive Rate (MRR): packet/bandwidth rate regardless of PLR
- sustained by DUT/SUT under specified Maximum Transmit Rate (MTR)
- packet load offered by traffic generator. MUST be quoted with both
- specific packet size and MTR as received by DUT/SUT during the
- measurement. Packet MRR measured in packets-per-second (or fps),
- bandwidth MRR expressed in bits-per-second (bps).
-* Trial: a single measurement step. See [RFC2544] section 23.
-* Trial duration: amount of time over which packets are transmitted
- in a single measurement step.
-
-# MLRsearch Background
-
-Multiple Loss Ratio search (MLRsearch) is a packet throughput search
-algorithm suitable for deterministic systems (as opposed to
-probabilistic systems). MLRsearch discovers multiple packet throughput
-rates in a single search, each rate is associated with a distinct
-Packet Loss Ratio (PLR) criterion.
-
-For cases when multiple rates need to be found, this property makes
-MLRsearch more efficient in terms of time execution, compared to
-traditional throughput search algorithms that discover a single packet
-rate per defined search criteria (e.g. a binary search specified by
-[RFC2544]). MLRsearch reduces execution time even further by relying on
-shorter trial durations of intermediate steps, with only the final
-measurements conducted at the specified final trial duration. This
-results in the shorter overall search execution time when compared to a
-traditional binary search, while guaranteeing the same results for
-deterministic systems.
-
-In practice, two rates with distinct PLRs are commonly used for packet
-throughput measurements of NFV systems: Non Drop Rate (NDR) with PLR=0
-and Partial Drop Rate (PDR) with PLR>0. The rest of this document
-describes MLRsearch with NDR and PDR pair as an example.
-
-Similarly to other throughput search approaches like binary search,
-MLRsearch is effective for SUTs/DUTs with PLR curve that is
-non-decreasing with growing offered load. It may not be as
-effective for SUTs/DUTs with abnormal PLR curves, although
-it will always converge to some value.
-
-MLRsearch relies on traffic generator to qualify the received packet
-stream as error-free, and invalidate the results if any disqualifying
-errors are present e.g. out-of-sequence frames.
-
-MLRsearch can be applied to both uni-directional and bi-directional
-throughput tests.
-
-For bi-directional tests, MLRsearch rates and ratios are aggregates of
-both directions, based on the following assumptions:
-
-* Traffic transmitted by traffic generator and received by SUT/DUT
- has the same packet rate in each direction,
- in other words the offered load is symmetric.
-* SUT/DUT packet processing capacity is the same in both directions,
- resulting in the same packet loss under load.
-
-MLRsearch can be applied even without those assumptions,
-but in that case the aggregate loss ratio is less useful as a metric.
-
-MLRsearch can be used for network transactions consisting of more than
-just one packet, or anything else that has intended load as input
-and loss ratio as output (duration as input is optional).
-This text uses mostly packet-centric language.
-
-# MLRsearch Overview
-
-The main properties of MLRsearch:
-
-* MLRsearch is a duration aware multi-phase multi-rate search algorithm:
- * Initial Phase determines promising starting interval for the search.
- * Intermediate Phases progress towards defined final search criteria.
- * Final Phase executes measurements according to the final search
- criteria.
- * Final search criteria are defined by following inputs:
- * Target PLRs (e.g. 0.0 and 0.005 when searching for NDR and PDR).
- * Final trial duration.
- * Measurement resolution.
-* Initial Phase:
- * Measure MRR over initial trial duration.
- * Measured MRR is used as an input to the first intermediate phase.
-* Multiple Intermediate Phases:
- * Trial duration:
- * Start with initial trial duration in the first intermediate phase.
- * Converge geometrically towards the final trial duration.
- * Track all previous trial measurement results:
- * Duration, offered load and loss ratio are tracked.
- * Effective loss ratios are tracked.
- * While in practice, real loss ratios can decrease with increasing load,
- effective loss ratios never decrease. This is achieved by sorting
- results by load, and using the effective loss ratio of the previous load
- if the current loss ratio is smaller than that.
- * The algorithm queries the results to find best lower and upper bounds.
- * Effective loss ratios are always used.
- * The phase ends if all target loss ratios have tight enough bounds.
- * Search:
- * Iterate over target loss ratios in increasing order.
- * If both upper and lower bound are in measurement results for this duration,
- apply bisect until the bounds are tight enough,
- and continue with next loss ratio.
- * If a bound is missing for this duration, but there exists a bound
- from the previous duration (compatible with the other bound
- at this duration), re-measure at the current duration.
- * If a bound in one direction (upper or lower) is missing for this duration,
- and the previous duration does not have a compatible bound,
- compute the current "interval size" from the second tightest bound
- in the other direction (lower or upper respectively)
- for the current duration, and choose next offered load for external search.
- * The logic guarantees that a measurement is never repeated with both
- duration and offered load being the same.
- * The logic guarantees that measurements for higher target loss ratio
- iterations (still within the same phase duration) do not affect validity
- and tightness of bounds for previous target loss ratio iterations
- (at the same duration).
- * Use of internal and external searches:
- * External search:
- * It is a variant of "exponential search".
- * The "interval size" is multiplied by a configurable constant
- (powers of two work well with the subsequent internal search).
- * Internal search:
- * A variant of binary search that measures at offered load between
- the previously found bounds.
- * The interval does not need to be split into exact halves,
- if other split can get to the target width goal faster.
- * The idea is to avoid returning interval narrower than the current
- width goal. See sample implementation details, below.
-* Final Phase:
- * Executed with the final test trial duration, and the final width
- goal that determines resolution of the overall search.
-* Intermediate Phases together with the Final Phase are called
- Non-Initial Phases.
-* The returned bounds stay within prescribed min_rate and max_rate.
- * When returning min_rate or max_rate, the returned bounds may be invalid.
- * E.g. upper bound at max_rate may come from a measurement
- with loss ratio still not higher than the target loss ratio.
-
-The main benefits of MLRsearch vs. binary search include:
-
-* In general, MLRsearch is likely to execute more trials overall, but
- likely less trials at a set final trial duration.
-* In well behaving cases, e.g. when results do not depend on trial
- duration, it greatly reduces (>50%) the overall duration compared to a
- single PDR (or NDR) binary search over duration, while finding
- multiple drop rates.
-* In all cases MLRsearch yields the same or similar results to binary
- search.
-* Note: both binary search and MLRsearch are susceptible to reporting
- non-repeatable results across multiple runs for very bad behaving
- cases.
-
-Caveats:
-
-* Worst case MLRsearch can take longer than a binary search, e.g. in case of
- drastic changes in behaviour for trials at varying durations.
- * Re-measurement at higher duration can trigger a long external search.
- That never happens in binary search, which uses the final duration
- from the start.
-
-# Sample Implementation
-
-Following is a brief description of a sample MLRsearch implementation,
-which is a simplified version of the existing implementation.
-
-## Input Parameters
-
-1. **max_rate** - Maximum Transmit Rate (MTR) of packets to
- be used by external traffic generator implementing MLRsearch,
- limited by the actual Ethernet link(s) rate, NIC model or traffic
- generator capabilities.
-2. **min_rate** - minimum packet transmit rate to be used for
- measurements. MLRsearch fails if lower transmit rate needs to be
- used to meet search criteria.
-3. **final_trial_duration** - required trial duration for final rate
- measurements.
-4. **initial_trial_duration** - trial duration for initial MLRsearch phase.
-5. **final_relative_width** - required measurement resolution expressed as
- (lower_bound, upper_bound) interval width relative to upper_bound.
-6. **packet_loss_ratios** - list of maximum acceptable PLR search criteria.
-7. **number_of_intermediate_phases** - number of phases between the initial
- phase and the final phase. Impacts the overall MLRsearch duration.
- Less phases are required for well behaving cases, more phases
- may be needed to reduce the overall search duration for worse behaving cases.
-
-## Initial Phase
-
-1. First trial measures at configured maximum transmit rate (MTR) and
- discovers maximum receive rate (MRR).
- * IN: trial_duration = initial_trial_duration.
- * IN: offered_transmit_rate = maximum_transmit_rate.
- * DO: single trial.
- * OUT: measured loss ratio.
- * OUT: MRR = measured receive rate.
- Received rate is computed as intended load multiplied by pass ratio
- (which is one minus loss ratio). This is useful when loss ratio is computed
- from a different metric than intended load. For example, intended load
- can be in transactions (multiple packets each), but loss ratio is computed
- on level of packets, not transactions.
-
- * Example: If MTR is 10 transactions per second, and each transaction has
- 10 packets, and receive rate is 90 packets per second, then loss rate
- is 10%, and MRR is computed to be 9 transactions per second.
-
- If MRR is too close to MTR, MRR is set below MTR so that interval width
- is equal to the width goal of the first intermediate phase.
- If MRR is less than min_rate, min_rate is used.
-2. Second trial measures at MRR and discovers MRR2.
- * IN: trial_duration = initial_trial_duration.
- * IN: offered_transmit_rate = MRR.
- * DO: single trial.
- * OUT: measured loss ratio.
- * OUT: MRR2 = measured receive rate.
- If MRR2 is less than min_rate, min_rate is used.
- If loss ratio is less or equal to the smallest target loss ratio,
- MRR2 is set to a value above MRR, so that interval width is equal
- to the width goal of the first intermediate phase.
- MRR2 could end up being equal to MTR (for example if both measurements so far
- had zero loss), which was already measured, step 3 is skipped in that case.
-3. Third trial measures at MRR2.
- * IN: trial_duration = initial_trial_duration.
- * IN: offered_transmit_rate = MRR2.
- * DO: single trial.
- * OUT: measured loss ratio.
- * OUT: MRR3 = measured receive rate.
- If MRR3 is less than min_rate, min_rate is used.
- If step 3 is not skipped, the first trial measurement is forgotten.
- This is done because in practice (if MRR2 is above MRR), external search
- from MRR and MRR2 is likely to lead to a faster intermediate phase
- than a bisect between MRR2 and MTR.
-
-## Non-Initial Phases
-
-1. Main phase loop:
- 1. IN: trial_duration for the current phase. Set to
- initial_trial_duration for the first intermediate phase; to
- final_trial_duration for the final phase; or to the element of
- interpolating geometric sequence for other intermediate phases.
- For example with two intermediate phases, trial_duration of the
- second intermediate phase is the geometric average of
- initial_trial_duration and final_trial_duration.
- 2. IN: relative_width_goal for the current phase. Set to
- final_relative_width for the final phase; doubled for each
- preceding phase. For example with two intermediate phases, the
- first intermediate phase uses quadruple of final_relative_width
- and the second intermediate phase uses double of
- final_relative_width.
- 3. IN: Measurement results from the previous phase (previous duration).
- 4. Internal target ratio loop:
- 1. IN: Target loss ratio for this iteration of ratio loop.
- 2. IN: Measurement results from all previous ratio loop iterations
- of current phase (current duration).
- 3. DO: According to the procedure described in point 2:
- 1. either exit the phase (by jumping to 1.5),
- 2. or exit loop iteration (by continuing with next target loss ratio,
- jumping to 1.4.1),
- 3. or calculate new transmit rate to measure with.
- 4. DO: Perform the trial measurement at the new transmit rate and
- current trial duration, compute its loss ratio.
- 5. DO: Add the result and go to next iteration (1.4.1),
- including the added trial result in 1.4.2.
- 5. OUT: Measurement results from this phase.
- 6. OUT: In the final phase, bounds for each target loss ratio
- are extracted and returned.
- 1. If a valid bound does not exist, use min_rate or max_rate.
-2. New transmit rate (or exit) calculation (for point 1.4.3):
- 1. If the previous duration has the best upper and lower bound,
- select the middle point as the new transmit rate.
- 1. See 2.5.3. below for the exact splitting logic.
- 2. This can be a no-op if interval is narrow enough already,
- in that case continue with 2.2.
- 3. Discussion, assuming the middle point is selected and measured:
- 1. Regardless of loss rate measured, the result becomes
- either best upper or best lower bound at current duration.
- 2. So this condition is satisfied at most once per iteration.
- 3. This also explains why previous phase has double width goal:
- 1. We avoid one more bisection at previous phase.
- 2. At most one bound (per iteration) is re-measured
- with current duration.
- 3. Each re-measurement can trigger an external search.
- 4. Such surprising external searches are the main hurdle
- in achieving low overall search durations.
- 5. Even without 1.1, there is at most one external search
- per phase and target loss ratio.
- 6. But without 1.1 there can be two re-measurements,
- each coming with a risk of triggering external search.
- 2. If the previous duration has one bound best, select its transmit rate.
- In deterministic case this is the last measurement needed this iteration.
- 3. If only upper bound exists in current duration results:
- 1. This can only happen for the smallest target loss ratio.
- 2. If the upper bound was measured at min_rate,
- exit the whole phase early (not investigating other target loss ratios).
- 3. Select new transmit rate using external search:
- 1. For computing previous interval size, use:
- 1. second tightest bound at current duration,
- 2. or tightest bound of previous duration,
- if compatible and giving a more narrow interval,
- 3. or target interval width if none of the above is available.
- 4. In any case increase to target interval width if smaller.
- 2. Quadruple the interval width.
- 3. Use min_rate if the new transmit rate is lower.
- 4. If only lower bound exists in current duration results:
- 1. If the lower bound was measured at max_rate,
- exit this iteration (continue with next lowest target loss ratio).
- 2. Select new transmit rate using external search:
- 1. For computing previous interval size, use:
- 1. second tightest bound at current duration,
- 2. or tightest bound of previous duration,
- if compatible and giving a more narrow interval,
- 3. or target interval width if none of the above is available.
- 4. In any case increase to target interval width if smaller.
- 2. Quadruple the interval width.
- 3. Use max_rate if the new transmit rate is higher.
- 5. The only remaining option is both bounds in current duration results.
- 1. This can happen in two ways, depending on how the lower bound
- was chosen.
- 1. It could have been selected for the current loss ratio,
- e.g. in re-measurement (2.2) or in initial bisect (2.1).
- 2. It could have been found as an upper bound for the previous smaller
- target loss ratio, in which case it might be too low.
- 3. The algorithm does not track which one is the case,
- as the decision logic works well regardless.
- 2. Compute "extending down" candidate transmit rate exactly as in 2.3.
- 3. Compute "bisecting" candidate transmit rate:
- 1. Compute the current interval width from the two bounds.
- 2. Express the width as a (float) multiple of the target width goal
- for this phase.
- 3. If the multiple is not higher than one, it means the width goal
- is met. Exit this iteration and continue with next higher
- target loss ratio.
- 4. If the multiple is two or less, use half of that
- for new width if the lower subinterval.
- 5. Round the multiple up to nearest even integer.
- 6. Use half of that for new width if the lower subinterval.
- 7. Example: If lower bound is 2.0 and upper bound is 5.0, and width
- goal is 1.0, the new candidate transmit rate will be 4.0.
- This can save a measurement when 4.0 has small loss.
- Selecting the average (3.5) would never save a measurement,
- giving more narrow bounds instead.
- 4. If either candidate computation want to exit the iteration,
- do as bisecting candidate computation says.
- 5. The remaining case is both candidates wanting to measure at some rate.
- Use the higher rate. This prefers external search down narrow enough
- interval, competing with perfectly sized lower bisect subinterval.
-
-# FD.io CSIT Implementation
-
-The only known working implementation of MLRsearch is in
-the open-source code running in Linux Foundation
-FD.io CSIT project [FDio-CSIT-MLRsearch] as part of
-a Continuous Integration / Continuous Development (CI/CD) framework.
-
-MLRsearch is also available as a Python package in [PyPI-MLRsearch].
-
-## Additional details
-
-This document so far has been describing a simplified version of
-MLRsearch algorithm. The full algorithm as implemented in CSIT contains
-additional logic, which makes some of the details (but not general
-ideas) above incorrect. Here is a short description of the additional
-logic as a list of principles, explaining their main differences from
-(or additions to) the simplified description, but without detailing
-their mutual interaction.
-
-1. Logarithmic transmit rate.
- * In order to better fit the relative width goal, the interval
- doubling and halving is done differently.
- * For example, the middle of 2 and 8 is 4, not 5.
-2. Timeout for bad cases.
- * The worst case for MLRsearch is when each phase converges to
- intervals way different than the results of the previous phase.
- * Rather than suffer total search time several times larger than pure
- binary search, the implemented tests fail themselves when the
- search takes too long (given by argument *timeout*).
-3. Intended count.
- * The number of packets to send during the trial should be equal to
- the intended load multiplied by the duration.
- * Also multiplied by a coefficient, if loss ratio is calculated
- from a different metric.
- * Example: If a successful transaction uses 10 packets,
- load is given in transactions per second, but loss ratio is calculated
- from packets, so the coefficient to get intended count of packets
- is 10.
- * But in practice that does not work.
- * It could result in a fractional number of packets,
- * so it has to be rounded in a way traffic generator chooses,
- * which may depend on the number of traffic flows
- and traffic generator worker threads.
-4. Attempted count. As the real number of intended packets is not known exactly,
- the computation uses the number of packets traffic generator reports as sent.
- Unless overridden by the next point.
-5. Duration stretching.
- * In some cases, traffic generator may get overloaded,
- causing it to take significantly longer (than duration) to send all packets.
- * The implementation uses an explicit stop,
- * causing lower attempted count in those cases.
- * The implementation tolerates some small difference between
- attempted count and intended count.
- * 10 microseconds worth of traffic is sufficient for our tests.
- * If the difference is higher, the unsent packets are counted as lost.
- * This forces the search to avoid the regions of high duration stretching.
- * The final bounds describe the performance of not just SUT,
- but of the whole system, including the traffic generator.
-6. Excess packets.
- * In some test (e.g. using TCP flows) Traffic generator reacts to packet loss
- by retransmission. Usually, such packet loss is already affecting loss ratio.
- If a test also wants to treat retransmissions due to heavily delayed packets
- also as a failure, this is once again visible as a mismatch between
- the intended count and the attempted count.
- * The CSIT implementation simply looks at absolute value of the difference,
- so it offers the same small tolerance before it starts marking a "loss".
-7. For result processing, we use lower bounds and ignore upper bounds.
-
-### FD.io CSIT Input Parameters
-
-1. **max_rate** - Typical values: 2 * 14.88 Mpps for 64B
- 10GE link rate, 2 * 18.75 Mpps for 64B 40GE NIC (specific model).
-2. **min_rate** - Value: 2 * 9001 pps (we reserve 9000 pps
- for latency measurements).
-3. **final_trial_duration** - Value: 30.0 seconds.
-4. **initial_trial_duration** - Value: 1.0 second.
-5. **final_relative_width** - Value: 0.005 (0.5%).
-6. **packet_loss_ratios** - Value: 0.0, 0.005 (0.0% for NDR, 0.5% for PDR).
-7. **number_of_intermediate_phases** - Value: 2.
- The value has been chosen based on limited experimentation to date.
- More experimentation needed to arrive to clearer guidelines.
-8. **timeout** - Limit for the overall search duration (for one search).
- If MLRsearch oversteps this limit, it immediately declares the test failed,
- to avoid wasting even more time on a misbehaving SUT.
- Value: 600.0 (seconds).
-9. **expansion_coefficient** - Width multiplier for external search.
- Value: 4.0 (interval width is quadroupled).
- Value of 2.0 is best for well-behaved SUTs, but value of 4.0 has been found
- to decrease overall search time for worse-behaved SUT configurations,
- contributing more to the overall set of different SUT configurations tested.
-
-
-## Example MLRsearch Run
-
-
-The following list describes a search from a real test run in CSIT
-(using the default input values as above).
-
-* Initial phase, trial duration 1.0 second.
-
-Measurement 1, intended load 18750000.0 pps (MTR),
-measured loss ratio 0.7089514628479618 (valid upper bound for both NDR and PDR).
-
-Measurement 2, intended load 5457160.071600716 pps (MRR),
-measured loss ratio 0.018650817320118702 (new tightest upper bounds).
-
-Measurement 3, intended load 5348832.933500009 pps (slightly less than MRR2
-in preparation for first intermediate phase target interval width),
-measured loss ratio 0.00964383362905351 (new tightest upper bounds).
-
-* First intermediate phase starts, trial duration still 1.0 seconds.
-
-Measurement 4, intended load 4936605.579021453 pps (no lower bound,
-performing external search downwards, for NDR),
-measured loss ratio 0.0 (valid lower bound for both NDR and PDR).
-
-Measurement 5, intended load 5138587.208637197 pps (bisecting for NDR),
-measured loss ratio 0.0 (new tightest lower bounds).
-
-Measurement 6, intended load 5242656.244044665 pps (bisecting),
-measured loss ratio 0.013523745379347257 (new tightest upper bounds).
-
-* Both intervals are narrow enough.
-* Second intermediate phase starts, trial duration 5.477225575051661 seconds.
-
-Measurement 7, intended load 5190360.904111567 pps (initial bisect for NDR),
-measured loss ratio 0.0023533920869969953 (NDR upper bound, PDR lower bound).
-
-Measurement 8, intended load 5138587.208637197 pps (re-measuring NDR lower bound),
-measured loss ratio 1.2080222912800403e-06 (new tightest NDR upper bound).
-
-* The two intervals have separate bounds from now on.
-
-Measurement 9, intended load 4936605.381062318 pps (external NDR search down),
-measured loss ratio 0.0 (new valid NDR lower bound).
-
-Measurement 10, intended load 5036583.888432355 pps (NDR bisect),
-measured loss ratio 0.0 (new tightest NDR lower bound).
-
-Measurement 11, intended load 5087329.903232804 pps (NDR bisect),
-measured loss ratio 0.0 (new tightest NDR lower bound).
-
-* NDR interval is narrow enough, PDR interval not ready yet.
-
-Measurement 12, intended load 5242656.244044665 pps (re-measuring PDR upper bound),
-measured loss ratio 0.0101174866190136 (still valid PDR upper bound).
-
-* Also PDR interval is narrow enough, with valid bounds for this duration.
-* Final phase starts, trial duration 30.0 seconds.
-
-Measurement 13, intended load 5112894.3238511775 pps (initial bisect for NDR),
-measured loss ratio 0.0 (new tightest NDR lower bound).
-
-Measurement 14, intended load 5138587.208637197 (re-measuring NDR upper bound),
-measured loss ratio 2.030389804256833e-06 (still valid PDR upper bound).
-
-* NDR interval is narrow enough, PDR interval not yet.
-
-Measurement 15, intended load 5216443.04126728 pps (initial bisect for PDR),
-measured loss ratio 0.005620871287975237 (new tightest PDR upper bound).
-
-Measurement 16, intended load 5190360.904111567 (re-measuring PDR lower bound),
-measured loss ratio 0.0027629971184465604 (still valid PDR lower bound).
-
-* PDR interval is also narrow enough.
-* Returning bounds:
-* NDR_LOWER = 5112894.3238511775 pps; NDR_UPPER = 5138587.208637197 pps;
-* PDR_LOWER = 5190360.904111567 pps; PDR_UPPER = 5216443.04126728 pps.
-
-# IANA Considerations
-
-No requests of IANA.
-
-# Security Considerations
-
-Benchmarking activities as described in this memo are limited to
-technology characterization of a DUT/SUT using controlled stimuli in a
-laboratory environment, with dedicated address space and the constraints
-specified in the sections above.
-
-The benchmarking network topology will be an independent test setup and
-MUST NOT be connected to devices that may forward the test traffic into
-a production network or misroute traffic to the test management network.
-
-Further, benchmarking is performed on a "black-box" basis, relying
-solely on measurements observable external to the DUT/SUT.
-
-Special capabilities SHOULD NOT exist in the DUT/SUT specifically for
-benchmarking purposes. Any implications for network security arising
-from the DUT/SUT SHOULD be identical in the lab and in production
-networks.
-
-# Acknowledgements
-
-Many thanks to Alec Hothan of OPNFV NFVbench project for thorough
-review and numerous useful comments and suggestions.
-
---- back
Code Review / csit.git / blobdiff