title: Multiple Loss Ratio Search
abbrev: MLRsearch
-docname: draft-ietf-bmwg-mlrsearch-12
-date: 2025-09-04
+docname: draft-ietf-bmwg-mlrsearch-13
+date: 2025-09-16
submissionType: IETF
ipr: trust200902
standalone hardware device) or as virtual appliance (e.g., Virtual
Network Function running on shared servers in the compute cloud).
+This document tightly couples terminology and methodology aspects.
+Instead of a separate terminology section, Table of Contents
+subsections of [MLRsearch Specification](#mlrsearch-specification)
+act as list of newly defined terms.
+If a phrase appears with first letters capitalized, it likely refers
+to a specific term defined in eponymous subsection
+of [MLRsearch Specification](#mlrsearch-specification).
+
## Purpose
The purpose of this document is to describe the Multiple Loss Ratio search
data plane throughput in software-based networking devices and functions.
Applying the vanilla throughput binary search,
-as specified for example in [TST009] and [RFC2544]
+as specified for example in Section 12.3.2 of [TST009]
to software devices under test (DUTs) results in several problems:
- Binary search takes long as most trials are done far from the
1. Allow multiple short trials instead of one big trial per load.
- Optionally, tolerate a percentage of trial results with higher loss.
-2. Allow searching for multiple Search Goals, with differing loss ratios.
+2. Allow searching for multiple [Search Goal](#search-goal)s, with differing loss ratios.
- Any trial result can affect each Search Goal in principle.
3. Insert multiple coarse targets for each Search Goal, earlier ones need
to spend less time on trials.
- Earlier targets also aim for lesser precision.
- Use Forwarding Rate (FR) at Maximum Offered Load (FRMOL), as defined
in Section 3.6.2 of [RFC2285], to initialize bounds.
-4. Be careful when dealing with inconsistent trial results.
- - Reported throughput is smaller than the smallest load with high loss.
- - Smaller load candidates are measured first.
+4. Process of inconsistent trial results carefully.
+ - Reported throughput should be smaller than the smallest load with high loss.
+ - Measure smaller load candidates first.
5. Apply several time-saving load selection heuristics that deliberately
prevent the bounds from narrowing unnecessarily.
The remaining enhancements are treated as implementation details,
thus achieving high comparability without limiting future improvements.
-MLRsearch configuration
-supports both conservative settings and aggressive settings.
-Conservative enough settings lead to results
-unconditionally compliant with [RFC2544],
+MLRsearch configuration supports both conservative settings
+and aggressive settings. Results unconditionally compliant with [RFC2544]
+are possible with conservative enough settings,
but without much improvement on search duration and repeatability - see
[MLRsearch Compliant with RFC 2544](#mlrsearch-compliant-with-rfc-2544).
Conversely, aggressive settings lead to shorter search durations
## DUT in SUT
+Section 19 of [RFC2544] specifies a test setup with an external tester
+stimulating the networking system, treating it either as a single
+Device Under Test (DUT), or as a system of devices, a System Under
+Test (SUT).
+
[RFC2285] defines:
DUT as:
- The collective set of network devices as a single entity to which
stimulus is offered and response measured Section 3.1.2 of [RFC2285].
-Section 19 of [RFC2544] specifies a test setup with an external tester
-stimulating the networking system, treating it either as a single
-Device Under Test (DUT), or as a system of devices, a System Under
-Test (SUT).
-
For software-based data-plane forwarding running on commodity x86/ARM
CPUs, the SUT comprises not only the forwarding application itself, the
DUT, but the entire execution environment: host hardware, firmware and
it can be set as the Goal Loss Ratio (see definitions of
Trial and Goal terms in [Trial Terms](#trial-terms) and [Goal Terms](#goal-terms)).
-- For more information, see an earlier draft [Lencze-Shima] (Section 5)
- and references there.
+For more information, see Section 5 of an earlier draft [Lencze-Shima]
+and references there.
Regardless of the validity of all similar motivations,
support for non-zero loss goals makes a
hence the support for multiple Search Goals remains a problem.
At the time of writing there does not seem to be a consensus in the industry
-on which ratio value is the best.
+on which loss ratio value is the best.
For users, performance of higher protocol layers is important, for
example, goodput of TCP connection (TCP throughput, [RFC6349]), but relationship
between goodput and loss ratio is not simple. Refer to
Except for one phenomenon: Loss Inversion.
Depending on Search Goal attributes, Load Classification results may be resistant
-to small amounts of Section [Inconsistent Trial Results](#inconsistent-trial-results).
+to small amounts of [Inconsistent Trial Results](#inconsistent-trial-results).
However, for larger amounts, a Load that is classified
as an Upper Bound for one Search Goal
may still be a Lower Bound for another Search Goal.
Code Review / csit.git / commitdiff