Network Working Group
Internet Engineering Task Force (IETF) A. Morton
Internet-Draft
Request for Comments: 9097 AT&T Labs
Intended status:
Category: Standards Track R. Geib
Expires: December 11, 2021
ISSN: 2070-1721 Deutsche Telekom
L. Ciavattone
AT&T Labs
June 9,
November 2021
Metrics and Methods for One-way One-Way IP Capacity
draft-ietf-ippm-capacity-metric-method-12
Abstract
This memo revisits the problem of Network Capacity metrics Metrics first
examined in RFC 5136. The This memo specifies a more practical Maximum
IP-Layer Capacity metric Metric definition catering for to measurement
purposes, and
outlines the corresponding methods Methods of measurement. Measurement.
Status of This Memo
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Internet-Drafts are draft documents valid the IETF community. It has
received public review and has been approved for a maximum publication by the
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Internet Standards is available in Section 2 of RFC 7841.
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This Internet-Draft will expire on December 11, 2021.
https://www.rfc-editor.org/info/rfc9097.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Scope, Goals, and Applicability . . . . . . . . . . . . . . . 4
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. General Parameters and Definitions . . . . . . . . . . . . . 6
5. IP-Layer Capacity Singleton Metric Definitions . . . . . . . 8
5.1. Formal Name . . . . . . . . . . . . . . . . . . . . . . . 8
5.2. Parameters . . . . . . . . . . . . . . . . . . . . . . . 8
5.3. Metric Definitions . . . . . . . . . . . . . . . . . . . 8
5.4. Related Round-Trip Delay and One-way One-Way Loss Definitions . . 9
5.5. Discussion . . . . . . . . . . . . . . . . . . . . . . . 10
5.6. Reporting the Metric . . . . . . . . . . . . . . . . . . 10
6. Maximum IP-Layer Capacity Metric Definitions (Statistic) . . 10 (Statistics)
6.1. Formal Name . . . . . . . . . . . . . . . . . . . . . . . 10
6.2. Parameters . . . . . . . . . . . . . . . . . . . . . . . 11
6.3. Metric Definitions . . . . . . . . . . . . . . . . . . . 11
6.4. Related Round-Trip Delay and One-way One-Way Loss Definitions . . 13
6.5. Discussion . . . . . . . . . . . . . . . . . . . . . . . 13
6.6. Reporting the Metric . . . . . . . . . . . . . . . . . . 13
7. IP-Layer Sender Bit Rate Singleton Metric Definitions . . . . 14
7.1. Formal Name . . . . . . . . . . . . . . . . . . . . . . . 14
7.2. Parameters . . . . . . . . . . . . . . . . . . . . . . . 14
7.3. Metric Definition . . . . . . . . . . . . . . . . . . . . 15
7.4. Discussion . . . . . . . . . . . . . . . . . . . . . . . 15
7.5. Reporting the Metric . . . . . . . . . . . . . . . . . . 15
8. Method of Measurement . . . . . . . . . . . . . . . . . . . . 15
8.1. Load Rate Adjustment Algorithm . . . . . . . . . . . . . 16
8.2. Measurement Qualification or Verification . . . . . . . . 21
8.3. Measurement Considerations . . . . . . . . . . . . . . . 22
8.4. Running Code . . . . . . . . . . . . . . . . . . . . . . 24
9. Reporting Formats . . . . . . . . . . . . . . . . . . . . . . 25
9.1. Configuration and Reporting Data Formats . . . . . . . . 27
10. Security Considerations . . . . . . . . . . . . . . . . . . . 27
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 28
13. References
12.1. Normative References
12.2. Informative References
Appendix A - A. Load Rate Adjustment Pseudo Code . . . . . . . . 28
14. Pseudocode
Appendix B - B. RFC 8085 UDP Guidelines Check . . . . . . . . . 29
14.1.
B.1. Assessment of Mandatory Requirements . . . . . . . . . . 29
14.2.
B.2. Assessment of Recommendations . . . . . . . . . . . . . 31
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 34
15.1. Normative References . . . . . . . . . . . . . . . . . . 34
15.2. Informative References . . . . . . . . . . . . . . . . . 35
Acknowledgments
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 37
1. Introduction
The IETF's efforts to define Network Capacity and Bulk Transport
Capacity (BTC) have been chartered and progressed for over twenty
years. Over that time, the performance community has seen the
development of Informative definitions in [RFC3148] for the Framework
for Bulk Transport Capacity
(BTC), RFC 5136 Capacity, [RFC5136] for Network Capacity and
Maximum IP-Layer Capacity, and the Experimental metric definitions
and methods in [RFC8337],
Model-Based "Model-Based Metrics for BTC. Bulk Transport Capacity"
[RFC8337].
This memo revisits the problem of Network Capacity metrics Metrics examined
first in [RFC3148] and later in [RFC5136]. Maximum IP-Layer Capacity
and [RFC3148] Bulk Transfer Capacity [RFC3148] (goodput) are different metrics.
Maximum IP-Layer Capacity is like the theoretical goal for goodput.
There are many metrics in [RFC5136], such as Available Capacity.
Measurements depend on the network path under test and the use case.
Here, the main use case is to assess the maximum capacity Maximum Capacity of one or
more networks where the subscriber receives specific performance
assurances, sometimes referred to as the Internet access, or where a
limit of the technology used on a path is being tested. For example,
when a user subscribes to a 1 Gbps service, then the user, the
service provider,
Service Provider, and possibly other parties want to assure that the
specified performance level is delivered. When a test confirms the
subscribed performance level, then a tester can seek the location of a
bottleneck elsewhere.
This memo recognizes the importance of a definition of a Maximum IP-
Layer Capacity Metric at a time when Internet subscription speeds
have increased dramatically; dramatically -- a definition that is both practical
and effective for the performance community's needs, including
Internet users. The metric definition is definitions are intended to use Active
Methods of Measurement [RFC7799], and a method Method of measurement Measurement is included.
included for each metric.
The most direct active measurement Active Measurement of IP-Layer Capacity would use IP
packets, but in practice a transport header is needed to traverse
address and port translators. UDP offers the most direct assessment
possibility, and in the [copycat] measurement study to investigate whether UDP
is viable as a general Internet transport protocol, protocol [copycat], the
authors found that a high percentage of paths tested support UDP
transport. A number of liaisons liaison statements have been exchanged on
this topic [LS-SG12-A] [LS-SG12-B], discussing the laboratory and
field tests that support the UDP-based approach to IP-Layer Capacity
measurement.
This memo also recognizes the many updates to the IP Performance Metrics
(IPPM) Framework [RFC2330] that have been published over twenty years, and since 1998. In
particular, it makes use of [RFC7312] for the Advanced Stream and
Sampling Framework, Framework and [RFC8468] with for its IPv4, IPv6, and IPv4-IPv6
Coexistence Updates.
Appendix A describes the load rate adjustment algorithm in pseudo-
code. algorithm, using
pseudocode. Appendix B discusses the algorithm's compliance with
[RFC8085].
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP
14[RFC2119] 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Scope, Goals, and Applicability
The scope of this memo is to define Active Measurement metrics and
corresponding methods to unambiguously determine Maximum IP-Layer
Capacity and useful secondary metrics.
Another goal is to harmonize the specified metric Metric and method Method across
the industry, and this memo is the vehicle that captures IETF
consensus, possibly resulting in changes to the specifications of
other Standards Development Organizations (SDO) (SDOs) (through each SDO's
normal contribution process, process or through liaison exchange).
Secondary goals are to add considerations for test procedures, procedures and to
provide interpretation of the Maximum IP-Layer Capacity results (to
identify cases where more testing is warranted, possibly with
alternate configurations). Fostering the development of protocol
support for this metric Metric and method Method of measurement Measurement is also a goal of
this memo (all active testing protocols currently defined by the IPPM
WG are UDP-based, UDP based, meeting a key requirement of these methods). The
supporting protocol development to measure this metric according to
the specified method is a key future contribution to Internet
measurement.
The load rate adjustment algorithm's scope is limited to helping
determine the Maximum IP-Layer Capacity in the context of an
infrequent, diagnostic, short term short-term measurement. It is RECOMMENDED to
discontinue non-measurement traffic that shares a subscriber's
dedicated resources while testing: measurements may not be accurate accurate,
and throughput of competing elastic traffic may be greatly reduced.
The primary application of the metric Metrics and method Methods of measurement Measurement
described here is the same as what is described in Section 2 of [RFC7497]
[RFC7497], where:
o
| The access portion of the network is the focus of this problem
| statement. The user typically subscribes to a service with
| bidirectional Internet [Internet] access partly described by rates in bits
| per second.
In addition, the use of the load rate adjustment algorithm described
in section Section 8.1 has the following additional applicability
limitations:
-
* It MUST only be used in the application of diagnostic and
operations measurements as described in this memo
- memo.
* It MUST only be used in circumstances consistent with Section 10,
Security Considerations
- 10
("Security Considerations").
* If a network operator is certain of the IP-layer capacity IP-Layer Capacity to be
validated, then testing MAY start with a fixed rate fixed-rate test at the IP-
layer capacity
IP-Layer 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 certainty,
and the load adjustment algorithm is RECOMMENDED.
Further, the metric Metrics and method Methods of measurement Measurement are intended for use
where specific exact path information is unknown within a range of
possible values:
- the
* The subscriber's exact Maximum IP-Layer Capacity is unknown (which
is sometimes the case; service rates can be increased due to
upgrades without a subscriber's request, request or increased to provide a
surplus to compensate for possible underestimates of TCP-based
testing).
- the
* The size of the bottleneck buffer is unknown.
Finally, the measurement system's load rate adjustment algorithm
SHALL NOT be provided with the exact capacity value to be validated
a priori. This restriction fosters a fair result, result and removes an
opportunity for bad actors to operate with nefarious operation enabled by knowledge of the "right
answer".
correct answer.
3. Motivation
As with any problem that has been worked on for many years in various
SDOs without any special attempts at coordination, various solutions
for metrics Metrics and methods Methods have emerged.
There are five factors that have changed (or begun began to change) in the
2013-2019 time frame, and the presence of any one of them on the path
requires features in the measurement design to account for the
changes:
1. Internet access is no longer the bottleneck for many users (but
subscribers expect network providers to honor contracted
performance).
2. Both transfer rate and latency are important to a user's
satisfaction.
3. UDP's growing role in Transport, transport is growing in areas where TCP once
dominated.
4. Content and applications are moving physically closer to users.
5. There is less emphasis on ISP gateway measurements, possibly due
to less traffic crossing ISP gateways in the future.
4. General Parameters and Definitions
This section lists the REQUIRED input factors to specify a Sender or
Receiver metric.
o Src, one
Src: One of the addresses of a host (such as a globally routable IP
address).
o Dst, one
Dst: One of the addresses of a host (such as a globally routable IP
address).
o MaxHops, the
MaxHops: The limit on the number of Hops a specific packet may visit
as it traverses from the host at Src to the host at Dst
(implemented in the TTL or Hop Limit).
o T0, the
T0: The time at the start of a measurement interval, when packets
are first transmitted from the Source.
o I, the
I: The nominal duration of a measurement interval at the
destination Destination
(default 10 sec)
o dt, the sec).
dt: The nominal duration of m equal sub-intervals in I at the
destination
Destination (default 1 sec)
o dtn, the sec).
dtn: The beginning boundary of a specific sub-interval, n, one of m
sub-intervals in I
o FT, the I.
FT: The feedback time interval between status feedback messages
communicating measurement results, sent from the receiver Receiver to
control the sender. Sender. The results are evaluated throughout the test
to determine how to adjust the current offered load rate at the
sender
Sender (default 50ms)
o Tmax, a 50 msec).
Tmax: A maximum waiting time for test packets to arrive at the
destination,
Destination, set sufficiently long to disambiguate packets with
long delays from packets that are discarded (lost), such that the
distribution of one-way delay is not truncated.
o F, the
F: The number of different flows synthesized by the method (default 1 flow)
o flow, the
one flow).
Flow: The stream of packets with the same n-tuple of designated
header fields that (when held constant) result in identical
treatment in a multi-path multipath decision (such as the decision taken in
load balancing). Note: The IPv6 flow label SHOULD be included in
the flow definition when routers have complied with [RFC6438]
guidelines.
o Type-P, the guidelines
provided in [RFC6438].
Type-P: The complete description of the test packets for which this
assessment applies (including the flow-defining fields). Note
that the UDP transport layer is one requirement for test packets
specified below. Type-P is a parallel concept parallel to "population of
interest" as defined in clause Clause 6.1.1 of[Y.1540].
o of [Y.1540].
Payload Content, this IPPM Framework-conforming metric and method
includes packet payload content as an Content: An aspect of the Type-P
parameter, which Parameter that can help to
improve measurement determinism. Specifying packet payload
content helps to ensure IPPM Framework-conforming Metrics and
Methods. If there is payload compression in the path and tests
intend to characterize a possible advantage due to compression,
then payload content SHOULD be supplied by a pseudo-random pseudorandom sequence
generator, by using part of a compressed file, or by other means.
See Section 3.1.2 of [RFC7312].
o PM, a
PM: A list of fundamental metrics, such as loss, delay, and
reordering, and corresponding target performance threshold. threshold(s). At
least one fundamental metric and target performance threshold MUST
be supplied (such as One-way one-way IP Packet Loss packet loss [RFC7680] equal to
zero).
A non-Parameter which that is required for several metrics is defined
below:
o T, the
T: The host time of the *first* test packet's *arrival* as measured
at the destination Destination Measurement Point, or MP(Dst). There may be
other packets sent between Source and Destination hosts that are
excluded, so this is the time of arrival of the first packet used
for measurement of the metric.
Note that time stamp timestamp format and resolution, sequence numbers, etc.
will be established by the chosen test protocol standard or
implementation.
5. IP-Layer Capacity Singleton Metric Definitions
This section sets requirements for the singleton Singleton metric that supports
the Maximum IP-Layer Capacity Metric definition definitions in Section 6.
5.1. Formal Name
Type-P-One-way-IP-Capacity, or
"Type-P-One-way-IP-Capacity" is the formal name; it is informally
called IP-Layer Capacity. "IP-Layer Capacity".
Note that Type-P depends on the chosen method.
5.2. Parameters
This section lists the REQUIRED input factors to specify the metric,
beyond those listed in Section 4.
No additional Parameters are needed.
5.3. Metric Definitions
This section defines the REQUIRED aspects of the measurable IP-Layer
Capacity metric Metric (unless otherwise indicated) for measurements between
specified Source and Destination hosts:
Define the IP-Layer Capacity, C(T,dt,PM), to be the number of IP-
Layer bits (including header and data fields) in packets that can be
transmitted from the Src host and correctly received by the Dst host
during one contiguous sub-interval, dt in length. The IP-Layer
Capacity depends on the Src and Dst hosts, the host addresses, and
the path between the hosts.
The number of these IP-Layer bits is designated n0[dtn,dtn+1] for a
specific dt.
When the packet size is known and of fixed size, the packet count
during a single sub-interval dt multiplied by the total bits in IP
header and data fields is equal to n0[dtn,dtn+1].
Anticipating a Sample of Singletons, the number of sub-intervals with
duration dt MUST be set to a natural number m, so that T+I = T + m*dt
with dtn+1 - dtn = dt for 1 <= n <= m.
Parameter PM represents other performance metrics [see section (see Section 5.4
below];
below); their measurement results SHALL be collected during
measurement of IP-Layer Capacity and associated with the
corresponding dtn for further evaluation and reporting. Users SHALL
specify the parameter Parameter Tmax as required by each metric's reference
definition.
Mathematically, this definition is represented as (for each n):
( n0[dtn,dtn+1] )
C(T,dt,PM) = -------------------------
dt
Figure 1: Equation for IP-Layer Capacity
and:
o
* n0 is the total number of IP-Layer header and payload bits that
can be transmitted in standard-formed packets [RFC8468] from the
Src host and correctly received by the Dst host during one
contiguous sub-interval, dt in length, during the interval [T,
T+I],
o C(T,dt,PM)
[T,T+I].
* C(T,dt,PM), the IP-Layer Capacity, corresponds to the value of n0
measured in any sub-interval beginning at dtn, divided by the
length of the sub-interval, dt.
o
* PM represents other performance metrics [see section (see Section 5.4 below]; below);
their measurement results SHALL be collected during measurement of
IP-Layer Capacity and associated with the corresponding dtn for
further evaluation and reporting.
o all
* All sub-intervals MUST be of equal duration. Choosing dt as non-
overlapping consecutive time intervals allows for a simple
implementation.
o
* The bit rate of the physical interface of the measurement devices
MUST be higher than the smallest of the links on the path whose
C(T,I,PM) is to be measured (the bottleneck link).
Measurements according to these definitions this definition SHALL use the UDP transport
layer. Standard-formed packets are specified in Section 5 of
[RFC8468]. The measurement SHOULD use a randomized Source port or
equivalent technique, and SHOULD send responses from the Source
address matching the test packet destination Destination address.
Some effects of compression affects on measurement are discussed in Section 6
of [RFC8468].
5.4. Related Round-Trip Delay and One-way One-Way Loss Definitions
RTD[dtn,dtn+1] is defined as a Sample of the [RFC2681] Round-trip Round-Trip Delay
[RFC2681] between the Src host and the Dst host over during the interval
[T,T+I] (that contains equal non-overlapping intervals of dt). The
"reasonable period of time" mentioned in [RFC2681] is the parameter Parameter
Tmax in this memo. The statistics used to summarize RTD[dtn,dtn+1]
MAY include the minimum, maximum, median, and mean, and the range =
(maximum - minimum) is referred to below in Section 8.1 minimum). Some of these statistics are needed for load
adjustment purposes. purposes (Section 8.1), measurement qualification
(Section 8.2), and reporting (Section 9).
OWL[dtn,dtn+1] is defined as a Sample of the [RFC7680] One-way One-Way Loss [RFC7680]
between the Src host and the Dst host over during the interval [T,T+I]
(that contains equal non-overlapping intervals of dt). The
statistics used to summarize OWL[dtn,dtn+1] MAY include the lost packet count of
lost packets and the ratio of lost packet ratio. packets.
Other metrics MAY be measured: one-way reordering, duplication, and
delay variation.
5.5. Discussion
See the corresponding section for Maximum IP-Layer Capacity. Capacity
(Section 6.5).
5.6. Reporting the Metric
The IP-Layer Capacity SHOULD be reported with at least single Megabit single-Megabit
resolution, in units of Megabits per second (Mbps), (which (Mbps) (which, to avoid
any confusion, is 1,000,000 bits per second to avoid any confusion). second).
The related One-way One-Way Loss metric and Round Trip Round-Trip Delay measurements for
the same Singleton SHALL be reported, also with meaningful resolution
for the values measured.
Individual Capacity measurements MAY be reported in a manner
consistent with the Maximum IP-Layer Capacity, Capacity; see Section 9.
6. Maximum IP-Layer Capacity Metric Definitions (Statistic) (Statistics)
This section sets requirements for the following components to
support the Maximum IP-Layer Capacity Metric.
6.1. Formal Name
Type-P-One-way-Max-IP-Capacity, or
"Type-P-One-way-Max-IP-Capacity" is the formal name; it is informally
called Maximum "Maximum IP-Layer
Capacity. Capacity".
Note that Type-P depends on the chosen method.
6.2. Parameters
This section lists the REQUIRED input factors to specify the metric,
beyond those listed in Section 4.
No additional Parameters or definitions are needed.
6.3. Metric Definitions
This section defines the REQUIRED aspects of the Maximum IP-Layer
Capacity metric Metric (unless otherwise indicated) for measurements between
specified Source and Destination hosts:
Define the Maximum IP-Layer Capacity, Maximum_C(T,I,PM), to be the
maximum number of IP-Layer bits n0[dtn,dtn+1] divided by dt that can
be transmitted in packets from the Src host and correctly received by
the Dst host, over all dt length dt-length intervals in [T, T+I], [T,T+I] and meeting the
PM criteria. Equivalently An equivalent definition would be the Maximum maximum of a
Sample of size m of Singletons C(T,I,PM) collected during the
interval [T, T+I] [T,T+I] and meeting the PM criteria.
The number of sub-intervals with duration dt MUST be set to a natural
number m, so that T+I = T + m*dt with dtn+1 - dtn = dt for 1 <= n <=
m.
Parameter PM represents the other performance metrics (see
Section 6.4 below) and their measurement results for the Maximum IP-
Layer Capacity. At least one target performance threshold (PM
criterion) MUST be defined. If more than one metric and target
performance threshold are is defined, then the sub-interval with the
maximum number of bits transmitted MUST meet all the target
performance thresholds. Users SHALL specify the parameter Parameter Tmax as
required by each metric's reference definition.
Mathematically, this definition can be represented as:
max ( n0[dtn,dtn+1] )
[T,T+I]
Maximum_C(T,I,PM) = -------------------------
dt
where:
T T+I
_________________________________________
| | | | | | | | | | |
dtn=1 2 3 4 5 6 7 8 9 10 n+1
n=m
Figure 2: Equation for Maximum Capacity
and:
o
* n0 is the total number of IP-Layer header and payload bits that
can be transmitted in standard-formed packets from the Src host
and correctly received by the Dst host during one contiguous sub-
interval, dt in length, during the interval [T, T+I],
o Maximum_C(T,I,PM) [T,T+I].
* Maximum_C(T,I,PM), the Maximum IP-Layer Capacity, corresponds to
the maximum value of n0 measured in any sub-interval beginning at
dtn, divided by the constant length of all sub-intervals, dt.
o
* PM represents the other performance metrics (see Section 5.4) 6.4) and
their measurement results for the Maximum IP-Layer Capacity. At
least one target performance threshold (PM criterion) MUST be
defined.
o all
* All sub-intervals MUST be of equal duration. Choosing dt as non-
overlapping consecutive time intervals allows for a simple
implementation.
o
* The bit rate of the physical interface of the measurement systems
MUST be higher than the smallest of the links on the path whose
Maximum_C(T,I,PM) is to be measured (the bottleneck link).
In this definition, the m sub-intervals can be viewed as trials when
the Src host varies the transmitted packet rate, searching for the
maximum n0 that meets the PM criteria measured at the Dst host in a
test of duration, duration I. When the transmitted packet rate is held
constant at the Src host, the m sub-intervals may also be viewed as
trials to evaluate the stability of n0 and metric(s) in the PM list
over all dt-length intervals in I.
Measurements according to these definitions SHALL use the UDP
transport layer.
6.4. Related Round-Trip Delay and One-way One-Way Loss Definitions
RTD[dtn,dtn+1] and OWL[dtn,dtn+1] are defined in Section 5.4. Here,
the test intervals are increased to match the capacity Samples,
RTD[T,I] and OWL[T,I].
The interval dtn,dtn+1 where Maximum_C[T,I,PM] Maximum_C(T,I,PM) occurs is the
reporting sub-interval for RTD[dtn,dtn+1] and OWL[dtn,dtn+1] within
RTD[T,I] and OWL[T,I].
Other metrics MAY be measured: one-way reordering, duplication, and
delay variation.
6.5. Discussion
If traffic conditioning (e.g., shaping, policing) applies along a
path for which Maximum_C(T,I,PM) is to be determined, different
values for dt SHOULD be picked and measurements be executed during
multiple intervals [T, T+I]. [T,T+I]. Each duration dt SHOULD be chosen so
that it is an integer multiple of increasing values k times
serialization delay of a path Path MTU (PMTU) at the physical interface
speed where traffic conditioning is expected. This should avoid
taking configured burst tolerance singletons Singletons as a valid
Maximum_C(T,I,PM) result.
A Maximum_C(T,I,PM) without any indication of bottleneck congestion,
be that an increasing increased latency, packet loss loss, or ECN Explicit Congestion
Notification (ECN) marks during a measurement interval interval, I, is likely to
an underestimate of Maximum_C(T,I,PM).
6.6. Reporting the Metric
The IP-Layer Capacity SHOULD be reported with at least single Megabit single-Megabit
resolution, in units of Megabits per second (Mbps) (which (which, to avoid
any confusion, is 1,000,000 bits per second to avoid any confusion). second).
The related One-way One-Way Loss metric and Round Trip Round-Trip Delay measurements for
the same Singleton SHALL be reported, also with meaningful resolution
for the values measured.
When there are demonstrated and repeatable Capacity modes in the
Sample, then the Maximum IP-Layer Capacity SHALL be reported for each
mode, along with the relative time from the beginning of the stream
that the mode was observed to be present. Bimodal Maximum IP-Layer
Capacities have been observed with some services, sometimes called a
"turbo mode" intending to deliver short transfers more quickly, quickly or
reduce the initial buffering time for some video streams. Note that
modes lasting less than dt duration dt will not be detected.
Some transmission technologies have multiple methods of operation
that may be activated when channel conditions degrade or improve, and
these transmission methods may determine the Maximum IP-Layer
Capacity. Examples include line-of-sight microwave modulator
constellations, or cellular modem technologies where the changes may
be initiated by a user moving from one coverage area to another.
Operation in the different transmission methods may be observed over
time, but the modes of Maximum IP-Layer Capacity will not be
activated deterministically as with the "turbo mode" described in the
paragraph above.
7. IP-Layer Sender Bit Rate Singleton Metric Definitions
This section sets requirements for the following components to
support the IP-Layer Sender Bitrate Bit Rate Metric. This metric helps to
check that the sender Sender actually generated the desired rates during a
test, and measurement takes place at the interface between the Src
host to and the network path
interface (or as close as practical within the Src
host). It is not a metric for path performance.
7.1. Formal Name
Type-P-IP-Sender-Bit-Rate, or
"Type-P-IP-Sender-Bit-Rate" is the formal name; it is informally
called IP-Layer the "IP-Layer Sender
Bitrate. Bit Rate".
Note that Type-P depends on the chosen method.
7.2. Parameters
This section lists the REQUIRED input factors to specify the metric,
beyond those listed in Section 4.
o S, the
S: The duration of the measurement interval at the Source
o st, the Source.
st: The nominal duration of N sub-intervals in S (default st = 0.05 seconds)
o stn, the
seconds).
stn: The beginning boundary of a specific sub-interval, n, one of N
sub-intervals in S S.
S SHALL be longer than I, primarily to account for on-demand
activation of the path, or any preamble to testing required, and the
delay of the path.
st SHOULD be much smaller than the sub-interval dt and on the same
order as FT, otherwise FT; otherwise, the rate measurement will include many rate
adjustments and include more time smoothing, thus missing possibly smoothing the
interval that contains the Maximum IP-Layer Capacity. Capacity (and therefore
losing relevance). The st parameter Parameter does not have relevance when the
Source is transmitting at a fixed rate throughout S.
7.3. Metric Definition
This section defines the REQUIRED aspects of the IP-Layer Sender
Bitrate metric Bit
Rate Metric (unless otherwise indicated) for measurements at the
specified Source on packets addressed for the intended Destination
host and matching the required Type-P:
Define the IP-Layer Sender Bit Rate, B(S,st), to be the number of IP-
Layer bits (including header and data fields) that are transmitted
from the Source with address pair Src and Dst during one contiguous
sub-interval, st, during the test interval S (where S SHALL be longer
than I), I) and where the fixed-size packet count during that single
sub-interval sub-
interval st also provides the number of IP-Layer bits in any
interval, [stn,stn+1].
Measurements according to these definitions this definition SHALL use the UDP transport
layer. Any feedback from the Dst host to the Src host received by
the Src host during an interval [stn,stn+1] SHOULD NOT result in an
adaptation of the Src host traffic conditioning during this interval
(rate adjustment occurs on st interval boundaries).
7.4. Discussion
Both the Sender and Receiver or (Source (or Source and Destination) bit rates
SHOULD be assessed as part of an IP-Layer Capacity measurement.
Otherwise, an unexpected sending rate limitation could produce an
erroneous Maximum IP-Layer Capacity measurement.
7.5. Reporting the Metric
The IP-Layer Sender Bit Rate SHALL be reported with meaningful
resolution, in units of Megabits per second (which (which, to avoid any
confusion, is 1,000,000 bits per second to avoid any confusion). second).
Individual IP-Layer Sender Bit Rate measurements are discussed
further in Section 9.
8. Method of Measurement
The
It is REQUIRED per the architecture of the method REQUIRES that two
cooperating hosts
operating operate in the roles of Src (test packet sender) Sender)
and Dst
(receiver), (Receiver) with a measured path and return path between them.
The duration of a test, parameter Parameter I, MUST be constrained in a
production network, since this is an active test method and it will
likely cause congestion on the path from the Src host to the Dst host path
during a test.
8.1. Load Rate Adjustment Algorithm
The algorithm described in this section MUST NOT be used as a general
Congestion Control Algorithm (CCA). As stated in the Scope Section 2, 2 ("Scope,
Goals, and Applicability"), the load rate adjustment algorithm's goal
is to help determine the Maximum IP-Layer Capacity in the context of
an infrequent, diagnostic, short term short-term measurement. There is a tradeoff trade-
off between test duration (also the test data volume) and algorithm
aggressiveness (speed of ramp-up and down ramp-down to the Maximum IP-Layer IP-
Layer Capacity). The parameter Parameter values chosen below strike a well-tested well-
tested balance among these factors.
A table SHALL be pre-built (by the test initiator) administrator), defining all
the offered load rates that will be supported (R1 through Rn, in
ascending order, corresponding to indexed rows in the table). It is
RECOMMENDED that rates begin with 0.5 Mbps at index zero, use 1 Mbps
at index one, and then continue in 1 Mbps increments to 1 Gbps.
Above 1 Gbps, and up to 10 Gbps, it is RECOMMENDED that 100 Mbps
increments be used. Above 10 Gbps, increments of 1 Gbps are
RECOMMENDED. A higher initial IP-Layer Sender Bitrate Bit Rate might be
configured when the test operator is certain that the Maximum IP-
Layer Capacity is well-above well above the initial IP-Layer Sender Bitrate Bit Rate and
factors such as test duration and total test traffic play an
important role. The sending rate table SHOULD backet bracket the maximum
capacity Maximum
Capacity where it will make measurements, including constrained rates
less than 500kbps 500 kbps if applicable.
Each rate is defined as datagrams of size ss, sent as a burst of
count cc, each time interval tt (default (the default for tt is 1ms, 100 microsec,
a likely system tick-interval). tick interval). While it is advantageous to use
datagrams of as large a size as possible, it may be prudent to use a
slightly smaller maximum that allows for secondary protocol headers
and/or tunneling without resulting in IP-Layer fragmentation.
Selection of a new rate is indicated by a calculation on the current
row, Rx. For example:
"Rx+1": the sender The Sender uses the next higher next-higher rate in the table.
"Rx-10": the sender The Sender uses the rate 10 rows lower in the table.
At the beginning of a test, the sender Sender begins sending at rate R1 and
the receiver Receiver starts a feedback timer of duration FT (while awaiting
inbound datagrams). As datagrams are received received, they are checked for
sequence number anomalies (loss, out-of-order, duplication, etc.) and
the delay range is measured (one-way or round-trip). This
information is accumulated until the feedback timer FT expires and a
status feedback message is sent from the receiver Receiver back to the sender, Sender,
to communicate this information. The accumulated statistics are then
reset by the receiver Receiver for the next feedback interval. As feedback
messages are received back at the sender, Sender, they are evaluated to
determine how to adjust the current offered load rate (Rx).
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 (see below for the method to declare for declaring congestion),
the offered load rate is increased by more than one rate setting
(e.g., Rx+10). This allows the offered load to quickly reach a near-maximum near-
maximum rate. Conversely, if congestion has been previously
confirmed, the offered load rate is only increased by one (Rx+1).
However, if a rate threshold between high and very above a high sending rates rate (such as 1
Gbps) is exceeded, the offered load rate is only increased by one
(Rx+1) above the rate threshold in any congestion state.
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 threshold values are
0
10 for sequence number gaps and 30 ms msec for lower and 90 ms msec for
upper delay thresholds, respectively. Also, if congestion is now
confirmed for the first time by the current feedback message being
processed, then the offered load rate is decreased by more than one
rate setting (e.g., Rx-30). This one-time reduction is intended to
compensate for the fast initial ramp-up. In all other cases, the
offered load rate is only decreased by one (Rx-1).
If the feedback indicates that there were no sequence number
anomalies AND the delay range was above the lower threshold, threshold but below
the upper threshold, the offered load rate is not changed. This
allows time for recent changes in the offered load rate to
stabilize, stabilize
and for the feedback to represent current conditions more accurately.
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 three consecutive feedback intervals. The algorithm
described above is also illustrated in Annex B of ITU-T Rec.
Recommendation Y.1540, 2020
version[Y.1540], in Annex B, version [Y.1540] and is implemented in the
Appendix on Load A ("Load Rate Adjustment Pseudo Code Pseudocode") in this memo.
The load rate adjustment algorithm MUST include timers that stop the
test when received packet streams cease unexpectedly. The timeout
thresholds are provided in the table below, Table 1, along with values for all other parameters
Parameters and variables described in this section. Operation Operations of
non-obvious parameters Parameters appear below:
load packet timeout Operation: timeout:
The load packet timeout SHALL be reset to the configured value
each time a load packet is received. If the timeout expires, the receiver
Receiver SHALL be closed and no further feedback sent.
feedback message timeout Operation: timeout:
The feedback message timeout SHALL be reset to the configured
value each time a feedback message is received. If the timeout
expires, the sender Sender SHALL be closed and no further load packets
sent.
+-------------+-------------+---------------+-----------------------+
+=============+==========+===========+=========================+
| Parameter | Default | Tested Range | Expected Safe Range |
| | | Range or values | (not entirely tested, |
| | | Values | other |
| | | | values NOT |
| | | | RECOMMENDED) |
+-------------+-------------+---------------+-----------------------+
+=============+==========+===========+=========================+
| FT, | 50ms 50 msec | 20ms, 50ms, 20 msec, | 20ms 20 msec <= FT <= 250ms 250 |
| feedback | | 100ms 50 msec, | Larger msec; larger values may |
| time | | 100 msec | slow the rate increase |
| interval | | | increase and fail to find the |
| | | | find the max |
+-------------+-------------+---------------+-----------------------+
+-------------+----------+-----------+-------------------------+
| Feedback | L*FT, L=20 | L=100 with | 0.5sec 0.5 sec <= L*FT <= 30 |
| message | (1sec with L=20 (1 | FT=50ms with | 30sec Upper sec; upper limit for |
| timeout | FT=50ms) sec with | (5sec) FT=50 | very unreliable test |
| (stop test) | FT=50 | msec (5 | test paths only |
+-------------+-------------+---------------+-----------------------+
| load | msec) | sec) | |
+-------------+----------+-----------+-------------------------+
| Load packet | 1sec 1 sec | 5sec 5 sec | 0.250sec - 30sec 0.250-30 sec; upper |
| timeout | | | Upper limit for very |
| (stop test) | | | unreliable test paths |
| | | | only |
+-------------+-------------+---------------+-----------------------+
+-------------+----------+-----------+-------------------------+
| table Table index | 0.5Mbps 0.5 Mbps | 0.5Mbps 0.5 Mbps | when When testing <=10Gbps <= 10 Gbps |
| 0 | | | |
+-------------+-------------+---------------+-----------------------+
+-------------+----------+-----------+-------------------------+
| table Table index | 1Mbps 1 Mbps | 1Mbps 1 Mbps | when When testing <=10Gbps <= 10 Gbps |
| 1 | | | |
+-------------+-------------+---------------+-----------------------+
+-------------+----------+-----------+-------------------------+
| table Table index | 1Mbps 1 Mbps | 1Mbps<=rate<= 1 Mbps <= | same Same as tested |
| (step) size | | 1Gbps rate <= 1 | |
+-------------+-------------+---------------+-----------------------+
| table | | Gbps | |
+-------------+----------+-----------+-------------------------+
| Table index | 100Mbps 100 Mbps | 1Gbps<=rate<= 1 Gbps <= | same Same as tested |
| (step) | | 10Gbps rate <= | |
| size, rate | | 10 Gbps | |
| rate>1Gbps > 1 Gbps | | | |
+-------------+-------------+---------------+-----------------------+
+-------------+----------+-----------+-------------------------+
| table Table index | 1Gbps 1 Gbps | untested Untested | >10Gbps >10 Gbps |
| (step) | | | |
| size, rate | | | |
| rate>10Gbps > 10 Gbps | | | |
+-------------+-------------+---------------+-----------------------+
+-------------+----------+-----------+-------------------------+
| ss, UDP | none None | <=1222 | Recommend max at |
| payload | | | largest value that |
| size, bytes | | | avoids fragmentation; |
| | | | use of too- |
| | | | small using a payload size |
| | | | that is too small might result in |
| | | | result in unexpected sender |
| | | | limitations. Sender limitations |
+-------------+-------------+---------------+-----------------------+
+-------------+----------+-----------+-------------------------+
| cc, burst | none None | 1<=cc<= 100 1 <= cc | same Same as tested. Vary |
| count | | <= 100 | cc as needed to create |
| | | | create the desired |
| | | | maximum |
| | | | sending rate. Sender |
| | | | buffer size may limit |
| | | | cc in implementation. the |
| | | | implementation |
+-------------+-------------+---------------+-----------------------+
+-------------+----------+-----------+-------------------------+
| tt, burst | 100microsec 100 | 100microsec, 100 | available Available range of |
| interval | microsec | 1msec microsec, | "tick" values (HZ |
| | | 1 msec | param) |
+-------------+-------------+---------------+-----------------------+
+-------------+----------+-----------+-------------------------+
| low Low delay | 30ms 30 msec | 5ms, 30ms 5 msec, | same Same as tested |
| range | | 30 msec | |
| threshold | | | |
+-------------+-------------+---------------+-----------------------+
+-------------+----------+-----------+-------------------------+
| high High delay | 90ms 90 msec | 10ms, 90ms 10 msec, | same Same as tested |
| range | | 90 msec | |
| threshold | | | |
+-------------+-------------+---------------+-----------------------+
+-------------+----------+-----------+-------------------------+
| sequence Sequence | 0 10 | 0, 100 1, 5, | same Same as tested |
| error | | 10, 100 | |
| threshold | | | |
+-------------+-------------+---------------+-----------------------+
+-------------+----------+-----------+-------------------------+
| consecutive Consecutive | 2 3 | 2 2, 3, 4, | Use values >1 to avoid |
| errored | | 5 | avoid misinterpreting |
| status | | | transient loss |
| report | | | |
| threshold | | | |
+-------------+-------------+---------------+-----------------------+
+-------------+----------+-----------+-------------------------+
| Fast mode | 10 | 10 | 2 <= steps <= 30 |
| increase, | | | |
| in table | | | |
| index steps | | | |
+-------------+-------------+---------------+-----------------------+
+-------------+----------+-----------+-------------------------+
| Fast mode | 3 * Fast | 3 * Fast mode | same Same as tested |
| decrease, | mode | increase mode | |
| in table | increase | increase | |
| index steps | | | |
+-------------+-------------+---------------+-----------------------+
+-------------+----------+-----------+-------------------------+
Table 1: Parameters for Load Rate Adjustment Algorithm
As a consequence of default parameterization, the Number of table
steps in total for rates <10Gbps less than 10 Gbps is 2000 1090 (excluding index
0).
A related sender Sender backoff response to network conditions occurs when
one or more status feedback messages fail to arrive at the sender. Sender.
If no status feedback messages arrive at the sender Sender for the interval
greater than the Lost Status Backoff timeout:
UDRT + (2+w)*FT = Lost Status Backoff timeout
where:
UDRT = upper delay range threshold (default 90ms) 90 msec)
FT = feedback time interval (default 50ms) 50 msec)
w = number of repeated timeouts (w=0 initially, w++ on each
timeout, and reset to 0 when a message is received)
beginning
Beginning when the last message (of any type) was successfully
received at the sender:
Then the Sender:
The offered load SHALL then be decreased, following the same process
as when the feedback indicates the presence of one or more sequence
number anomalies OR the delay range was above the upper threshold (as
described above), with the same load rate adjustment algorithm
variables in their current state. This means that rate reduction and
congestion confirmation can result from a three-way OR that includes lost status
feedback messages, messages OR sequence errors, or errors OR delay variation. variation can result in
rate reduction and congestion confirmation.
The RECOMMENDED initial value for w is 0, taking Round Trip a Round-Trip Time
(RTT) of less than FT into account. A test with an RTT longer than
FT is a valid reason to increase the initial value of w
appropriately. Variable w SHALL be incremented by 1 one whenever the
Lost Status Backoff timeout is exceeded. So So, with FT = 50ms 50 msec and
UDRT = 90ms, 90 msec, a status feedback message loss would be declared at 190ms
190 msec following a successful message, again at 50ms 50 msec after that (240ms
(240 msec total), and so on.
Also, if congestion is now confirmed for the first time by a Lost
Status Backoff timeout, then the offered load rate is decreased by
more than one rate setting (e.g., Rx-30). This one-time reduction is
intended to compensate for the fast initial ramp-up. In all other
cases, the offered load rate is only decreased by one (Rx-1).
Appendix B discusses compliance with the applicable mandatory
requirements of [RFC8085], consistent with the goals of the IP-Layer
Capacity Metric and Method, including the load rate adjustment
algorithm described in this section.
8.2. Measurement Qualification or Verification
It is of course necessary to calibrate the equipment performing the
IP-Layer Capacity measurement, to ensure that the expected capacity
can be measured accurately, accurately and that equipment choices (processing
speed, interface bandwidth, etc.) are suitably matched to the
measurement range.
When assessing a Maximum maximum rate as the metric specifies, artificially
high (optimistic) values might be measured until some buffer on the
path is filled. Other causes include bursts of back-to-back packets
with idle intervals delivered by a path, while the measurement
interval (dt) is small and aligned with the bursts. The artificial
values might result in an un-sustainable unsustainable Maximum Capacity observed
when the method Method of measurement Measurement is searching for the Maximum, maximum, and that
would not do. This situation is different from the bi-modal bimodal service
rates (discussed under Reporting), in "Reporting the Metric", Section 6.6), which are
characterized by a multi-second duration (much longer than the
measured RTT) and repeatable behavior.
There are many ways that the Method of Measurement could handle this
false-max issue. The default value for measurement of singletons Singletons (dt
= 1 second) has proven to be of practical value during tests of this
method, allows the bimodal service rates to be characterized, and it has
an obvious alignment with the reporting units (Mbps).
Another approach comes from Section 24 of [RFC2544] and its
discussion of Trial trial duration, where relatively short trials conducted
as part of the search are followed by longer trials to make the final
determination. In the production network, measurements of Singletons
and Samples (the terms for trials and tests of Lab Benchmarking) must
be limited in duration because they may be service-affecting. affect service. But there is
sufficient value in repeating a Sample with a fixed sending rate
determined by the previous search for the Maximum IP-Layer Capacity,
to qualify the result in terms of the other performance metrics
measured at the same time.
A qualification Qualification measurement for the search result is a subsequent
measurement, sending at a fixed 99.x % percent of the Maximum IP-Layer
Capacity for I, or an indefinite period. The same Maximum Capacity
Metric is applied, and the Qualification for the result is a Sample
without supra-threshold packet loss losses or a growing minimum delay
trend in subsequent
singletons Singletons (or each dt of the measurement
interval, I). Samples exhibiting supra-threshold packet losses or
increasing queue occupation require a repeated search and/or test at
a reduced fixed sender Sender rate for qualification. Qualification.
Here, as with any Active Capacity test, the test duration must be
kept short. 10 second Ten-second tests for each direction of transmission are
common today. The default measurement interval specified here is I =
10 seconds. The combination of a fast and congestion-aware search
method and user-network coordination make makes a unique contribution to
production testing. The Maximum IP Capacity metric Metric and method Method for
assessing performance is very different from the classic [RFC2544] Throughput metric
Metric and methods : Methods provided in [RFC2544]: it uses near-real-time load
adjustments that are sensitive to loss and delay, similar to other
congestion control algorithms used on the Internet every day, along
with limited duration. On the other hand, [RFC2544] Throughput measurements
[RFC2544] can produce sustained overload conditions for extended
periods of time. Individual trials in a test governed by a binary
search can last 60 seconds for each step, and the final confirmation
trial may be even longer. This is very different from "normal"
traffic levels, but overload conditions are not a concern in the
isolated test environment. The concerns raised in [RFC6815] were
that [RFC2544] the methods discussed in [RFC2544] would be let loose on
production networks, and instead the authors challenged the standards
community to develop
metrics Metrics and methods Methods like those described in this
memo.
8.3. Measurement Considerations
In general, the wide-spread widespread measurements that this memo encourages
will encounter wide-spread widespread behaviors. The bimodal IP Capacity
behaviors already discussed in Section 6.6 are good examples.
In general, it is RECOMMENDED to locate test endpoints as close to
the intended measured link(s) as practical (this (for reasons of scale,
this is not always
possible for reasons of scale; possible; there is a limit on the number of test
endpoints coming from many perspectives, perspectives -- for example, management
and measurement
traffic for example). traffic). The testing operator MUST set a value for
the MaxHops parameter, Parameter, based on the expected path length. This parameter
Parameter can keep measurement traffic from straying too far beyond
the intended path.
The path measured path may be stateful based on many factors, and the
Parameter "Time of day" when a test starts may not be enough
information. Repeatable testing may require knowledge of the time
from the beginning of a measured flow, flow -- and how the flow is constructed
constructed, including how much traffic has already been sent on that
flow when a
state-change state change is observed, observed -- because the state-change state change may
be based on
time or time, bytes sent sent, or both. Both load packets and status
feedback messages MUST contain sequence numbers, which numbers; this helps with
measurements based on those packets.
Many different types of traffic shapers and on-demand communications
access technologies may be encountered, as anticipated in [RFC7312],
and play a key role in measurement results. Methods MUST be prepared
to provide a short preamble transmission to activate on-demand
communications access, access and to discard the preamble from subsequent
test results.
Conditions which
The following conditions might be encountered during measurement,
where packet losses may occur independently of the measurement
sending rate:
1. Congestion of an interconnection or backbone interface may appear
as packet losses distributed over time in the test stream, due to
much higher rate
much-higher-rate interfaces in the backbone.
2. Packet loss due to the use of Random Early Detection (RED) or
other active queue management may or may not affect the
measurement flow if competing background traffic (other flows) are is
simultaneously present.
3. There may be only a small delay variation independent of the
sending rate under these conditions, too. conditions as well.
4. Persistent competing traffic on measurement paths that include
shared transmission media may cause random packet losses in the
test stream.
It is possible to mitigate these conditions using the flexibility of
the load-rate adjusting load rate adjustment algorithm described in Section 8.1 above
(tuning specific parameters). Parameters).
If the measurement flow burst duration happens to be on the order of
or smaller than the burst size of a shaper or a policer in the path,
then the line rate might be measured rather than the bandwidth limit
imposed by the shaper or policer. If this condition is suspected,
alternate configurations SHOULD be used.
In general, results depend on the sending stream stream's characteristics;
the measurement community has known this for a long time, time and needs to
keep it front of foremost in mind. Although the default is a single flow
(F=1) for testing, the use of multiple flows may be advantageous for
the following reasons:
1. the The test hosts may be able to create a higher load than with a
single flow, or parallel test hosts may be used to generate 1 one
flow each.
2. there Link aggregation may be link aggregation present (flow-based load balancing) balancing), and
multiple flows are needed to occupy each member of the aggregate.
3. Internet access policies may limit the IP-Layer Capacity
depending on the Type-P of the packets, possibly reserving
capacity for various stream types.
Each flow would be controlled using its own implementation of the
load rate adjustment (search) algorithm.
It is obviously counter-productive counterproductive to run more than one independent
and concurrent test (regardless of the number of flows in the test
stream) attempting to measure the *maximum* capacity on a single
path. The number of concurrent, independent tests of a path SHALL be
limited to one.
Tests of a v4-v6 transition mechanism might well be the intended
subject of a capacity test. As long as the both IPv4 packets and IPv6
packets sent/received are both standard-formed, this should be allowed
(and the change in header size easily accounted for on a per-packet
basis).
As testing continues, implementers should expect some evolution in the methods. methods to
evolve. The ITU-T has published a Supplement (60) supplement (Supplement 60) to the
Y-series of ITU-T Recommendations, "Interpreting ITU-T Y.1540 Maximum IP-
Layer Capacity measurements", maximum
IP-layer capacity measurements" [Y.Sup60], which is the result of
continued testing with the metric, and those metric. Those results have improved the method described here.
8.4. Running Code
RFC Editor: This section is for the benefit of the Document
Shepherd's form, and will be deleted prior to publication.
Much of the development of the method and comparisons with existing
methods conducted at IETF Hackathons and elsewhere have been based on
the example udpst Linux measurement tool (which is a working
reference for further development) [udpst]. The current project:
o is a utility that can function as a client or server daemon
o requires a successful client-initiated setup handshake between
cooperating hosts and allows firewalls to control inbound
unsolicited UDP which either go to a control port [expected and w/
authentication] or to ephemeral ports that are only created as
needed. Firewalls protecting each host can both continue to do
their job normally. This aspect is similar to many other test
utilities available.
o is written in C, and built with gcc (release 9.3) and its standard
run-time libraries
o allows configuration of most of the parameters described in
Sections 4 and 7.
o supports IPv4 and IPv6 address families.
o supports IP-Layer packet marking. here.
9. Reporting Formats
The singleton Singleton IP-Layer Capacity results SHOULD be accompanied by the
context under which they were measured.
o timestamp
* Timestamp (especially the time when the maximum was observed in
dtn)
o
dtn).
* Source and Destination (by IP or other meaningful ID)
o other ID).
* Other inner parameters Parameters of the test case (Section 4)
o outer parameters, 4).
* Outer Parameters, such as "test conducted in motion" or other
factors belonging to the context of the measurement
o result measurement.
* Result validity (indicating cases where the process was somehow
interrupted or the attempt failed)
o a failed).
* A field where unusual circumstances could be documented, and
another one for "ignore/mask "ignore / mask out" purposes in further processing
processing.
The Maximum IP-Layer Capacity results SHOULD be reported in the
format of a table with tabular
format. There SHOULD be a row for each of column that identifies the test Phases and Number
of Flows. Phase.
There SHOULD be a column listing the number of flows used in that
Phase. The remaining columns SHOULD report the following results for
the phases with number aggregate of all flows, and for including the resultant Maximum IP-Layer Capacity results for Capacity,
the aggregate Loss Ratio, the RTT minimum, RTT maximum, and each flow tested. other metrics
tested having similar relevance.
As mentioned in Section 6.6, bi-modal bimodal (or multi-modal) maxima SHALL be
reported for each mode separately.
+-------------+-------------------------+----------+----------------+
+========+==========+==================+========+=========+=========+
| Phase, # Phase | Number | Maximum IP-Layer | Loss | RTT min, max, min | RTT |
| | of Flows | Capacity, Mbps Capacity (Mbps) | Ratio | msec (msec) | max |
|
+-------------+-------------------------+----------+----------------+ | Search,1 | | | | (msec) |
+========+==========+==================+========+=========+=========+
| Search | 1 | 967.31 | 0.0002 | 30, 30 | 58 |
+-------------+-------------------------+----------+----------------+
+--------+----------+------------------+--------+---------+---------+
| Verify | Verify,1 1 | 966.00 | 0.0000 | 30, 30 | 38 |
+-------------+-------------------------+----------+----------------+
+--------+----------+------------------+--------+---------+---------+
Table 2: Maximum IP-layer IP-Layer Capacity Results
Static and configuration parameters: Parameters:
The sub-interval time, dt, MUST accompany a report of Maximum IP-
Layer Capacity results, and as well as the remaining Parameters from
Section 4,
General Parameters. 4 ("General Parameters and Definitions").
The PM list metrics corresponding to the sub-interval where the
Maximum Capacity occurred MUST accompany a report of Maximum IP-Layer
Capacity results, for each test phase. Phase.
The IP-Layer Sender Bit rate Rate results SHOULD be reported in the format
of a table with tabular
format. There SHOULD be a row for each of column that identifies the test phases, sub-intervals (st)
and number of flows. Phase.
There SHOULD be columns for a column listing each individual (numbered) flow used
in that Phase, or the phases with
number aggregate of flows, and flows in that Phase. A
corresponding column SHOULD identify the specific sending rate sub-
interval, stn, for each flow and aggregate. A final column SHOULD
report the resultant IP-Layer Sender Bit rate Rate results for the aggregate and each flow tested.
+--------------------------+-------------+----------------------+ used, or
the aggregate of all flows.
+========+==========================+===========+=============+
| Phase | Phase, Flow Number or Aggregate | st, sec stn (sec) | Sender Bitrate, Mbps Bit |
| |
+--------------------------+-------------+----------------------+ | Search,1 | Rate (Mbps) |
+========+==========================+===========+=============+
| Search | 1 | 0.00 - 0.05 | 345 |
+--------------------------+-------------+----------------------+
+--------+--------------------------+-----------+-------------+
| Search | Search,2 2 | 0.00 - 0.05 | 289 |
+--------------------------+-------------+----------------------+
+--------+--------------------------+-----------+-------------+
| Search | Search,Agg Agg | 0.00 - 0.05 | 634 |
+--------------------------+-------------+----------------------+
IP-layer
+--------+--------------------------+-----------+-------------+
| Search | 1 | 0.05 | 499 |
+--------+--------------------------+-----------+-------------+
| Search | ... | 0.05 | ... |
+--------+--------------------------+-----------+-------------+
Table 3: IP-Layer Sender Bit Rate Results (Example with Two
Flows and st = 0.05 (sec))
Static and configuration parameters: Parameters:
The subinterval time, sub-interval duration, st, MUST accompany a report of Sender IP-Layer IP-
Layer Bit Rate results.
Also, the values of the remaining Parameters from Section 4, General
Parameters, 4 ("General
Parameters and Definitions") MUST be reported.
9.1. Configuration and Reporting Data Formats
As a part of the multi-Standards Development Organization (SDO)
harmonization of this metric Metric and method Method of measurement, Measurement, one of the
areas where the Broadband Forum (BBF) contributed its expertise was
in the definition of an information model and data model for
configuration and reporting. These models are consistent with the
metric parameters Parameters and default values specified as lists is in this memo.
[TR-471] provides the Information information model that was used to prepare a
full data model in related BBF work. The BBF has also carefully
considered topics within its purview, such as the placement of
measurement systems within the Internet access architecture. For
example, timestamp resolution requirements that influence the choice
of the test protocol are provided in Table 2 of [TR-471].
10. Security Considerations
Active metrics Metrics and measurements Active Measurements have a long history of
security considerations. The security considerations that apply to
any active
measurement Active Measurement of live paths are relevant here. See
[RFC4656] and [RFC5357].
When considering the privacy of those involved in measurement or
those whose traffic is measured, the sensitive information available
to potential observers is greatly reduced when using active
techniques
which that are within this scope of work. Passive observations
of user traffic for measurement purposes raise many privacy issues.
We refer the reader to the privacy considerations described in the Large Scale
Large-scale Measurement of Broadband Performance (LMAP) Framework
[RFC7594], which covers active and passive techniques.
There are some new considerations for Capacity measurement as
described in this memo.
1. Cooperating Source and Destination hosts and agreements to test
the path between the hosts are REQUIRED. Hosts perform in either
the Src role or the Dst roles. role.
2. It is REQUIRED to have a user client-initiated setup handshake
between cooperating hosts that allows firewalls to control
inbound unsolicited UDP traffic which either that goes to either a control
port [expected (expected and w/authentication] with authentication) or to ephemeral ports that
are only created as needed. Firewalls protecting each host can
both continue to do their job normally.
3. Client-server authentication and integrity protection for
feedback messages conveying measurements is are RECOMMENDED.
4. Hosts MUST limit the number of simultaneous tests to avoid
resource exhaustion and inaccurate results.
5. Senders MUST be rate-limited. rate limited. This can be accomplished using a
pre-built table defining all the offered load rates that will be
supported (Section 8.1). The recommended load-control load control search
algorithm results in "ramp-up" from the lowest rate in the table.
6. Service subscribers with limited data volumes who conduct
extensive capacity testing might experience the effects of
Service Provider controls on their service. Testing with the
Service Provider's measurement hosts SHOULD be limited in
frequency and/or overall volume of test traffic (for example, the
range of duration values, I, SHOULD be limited).
The exact specification of these features is left for the future protocol
development.
11. IANA Considerations
This memo makes document has no requests of IANA.
15. IANA actions.
12. References
15.1.
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
"Framework for IP Performance Metrics", RFC 2330,
DOI 10.17487/RFC2330, May 1998,
<https://www.rfc-editor.org/info/rfc2330>.
[RFC2681] Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip
Delay Metric for IPPM", RFC 2681, DOI 10.17487/RFC2681,
September 1999, <https://www.rfc-editor.org/info/rfc2681>.
[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, DOI 10.17487/RFC4656, September 2006,
<https://www.rfc-editor.org/info/rfc4656>.
[RFC4737] Morton, A., Ciavattone, L., Ramachandran, G., Shalunov,
S., and J. Perser, "Packet Reordering Metrics", RFC 4737,
DOI 10.17487/RFC4737, November 2006,
<https://www.rfc-editor.org/info/rfc4737>.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, DOI 10.17487/RFC5357, October 2008,
<https://www.rfc-editor.org/info/rfc5357>.
[RFC6438] Carpenter, B. and S. Amante, "Using the IPv6 Flow Label
for Equal Cost Multipath Routing and Link Aggregation in
Tunnels", RFC 6438, DOI 10.17487/RFC6438, November 2011,
<https://www.rfc-editor.org/info/rfc6438>.
[RFC7497] Morton, A., "Rate Measurement Test Protocol Problem
Statement and Requirements", RFC 7497,
DOI 10.17487/RFC7497, April 2015,
<https://www.rfc-editor.org/info/rfc7497>.
[RFC7680] Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton,
Ed., "A One-Way Loss Metric for IP Performance Metrics
(IPPM)", STD 82, RFC 7680, DOI 10.17487/RFC7680, January
2016, <https://www.rfc-editor.org/info/rfc7680>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8468] Morton, A., Fabini, J., Elkins, N., Ackermann, M., and V.
Hegde, "IPv4, IPv6, and IPv4-IPv6 Coexistence: Updates for
the IP Performance Metrics (IPPM) Framework", RFC 8468,
DOI 10.17487/RFC8468, November 2018,
<https://www.rfc-editor.org/info/rfc8468>.
15.2.
12.2. Informative References
[copycat] Edleine, K., Kuhlewind, Edeline, K., Kühlewind, M., Trammell, B., and B. Donnet,
"copycat: Testing Differential Treatment of New Transport
Protocols in the Wild (ANRW '17)", Wild", ANRW '17,
DOI 10.1145/3106328.3106330, July 2017,
<https://irtf.org/anrw/2017/anrw17-final5.pdf>.
[LS-SG12-A]
12, I. S., "LS
"Liaison statement: LS - Harmonization of IP Capacity and
Latency Parameters: Revision of Draft Rec. Y.1540 on IP
packet transfer performance parameters and New Annex A
with Lab Evaluation Plan", May From ITU-T SG 12, March 2019,
<https://datatracker.ietf.org/liaison/1632/>.
[LS-SG12-B]
12, I. S., "LS
"Liaison statement: LS on harmonization of IP Capacity and
Latency Parameters: Consent of Draft Rec. Y.1540 on IP
packet transfer performance parameters and New Annex A
with Lab & Field Evaluation Plans", March From ITU-T-SG-12, May
2019, <https://datatracker.ietf.org/liaison/1645/>.
[RFC2544] Bradner, S. and J. McQuaid, "Benchmarking Methodology for
Network Interconnect Devices", RFC 2544,
DOI 10.17487/RFC2544, March 1999,
<https://www.rfc-editor.org/info/rfc2544>.
[RFC3148] Mathis, M. and M. Allman, "A Framework for Defining
Empirical Bulk Transfer Capacity Metrics", RFC 3148,
DOI 10.17487/RFC3148, July 2001,
<https://www.rfc-editor.org/info/rfc3148>.
[RFC5136] Chimento, P. and J. Ishac, "Defining Network Capacity",
RFC 5136, DOI 10.17487/RFC5136, February 2008,
<https://www.rfc-editor.org/info/rfc5136>.
[RFC6815] Bradner, S., Dubray, K., McQuaid, J., and A. Morton,
"Applicability Statement for RFC 2544: Use on Production
Networks Considered Harmful", RFC 6815,
DOI 10.17487/RFC6815, November 2012,
<https://www.rfc-editor.org/info/rfc6815>.
[RFC7312] Fabini, J. and A. Morton, "Advanced Stream and Sampling
Framework for IP Performance Metrics (IPPM)", RFC 7312,
DOI 10.17487/RFC7312, August 2014,
<https://www.rfc-editor.org/info/rfc7312>.
[RFC7594] Eardley, P., Morton, A., Bagnulo, M., Burbridge, T.,
Aitken, P., and A. Akhter, "A Framework for Large-Scale
Measurement of Broadband Performance (LMAP)", RFC 7594,
DOI 10.17487/RFC7594, September 2015,
<https://www.rfc-editor.org/info/rfc7594>.
[RFC7799] Morton, A., "Active and Passive Metrics and Methods (with
Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
May 2016, <https://www.rfc-editor.org/info/rfc7799>.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <https://www.rfc-editor.org/info/rfc8085>.
[RFC8337] Mathis, M. and A. Morton, "Model-Based Metrics for Bulk
Transport Capacity", RFC 8337, DOI 10.17487/RFC8337, March
2018, <https://www.rfc-editor.org/info/rfc8337>.
[TR-471] Morton, A., "Broadband Forum TR-471: IP Layer "Maximum IP-Layer Capacity
Metrics Metric, Related
Metrics, and Measurement", July 2020,
<https://www.broadband-forum.org/technical/download/TR-
471.pdf>.
[udpst] udpst Project Collaborators, "UDP Speed Test Open Measurements", Broadband project", December Forum TR-471, July
2020,
<https://github.com/BroadbandForum/obudpst>. <https://www.broadband-forum.org/technical/download/
TR-471.pdf>.
[Y.1540] Y.1540, I. R., ITU-T, "Internet protocol data communication service - IP
packet transfer and availability performance parameters",
ITU-T Recommendation Y.1540, December 2019,
<https://www.itu.int/rec/T-REC-Y.1540-201912-I/en>.
[Y.Sup60] Morton, A., "Recommendation Y.Sup60, (09/20) Interpreting ITU-T, "Interpreting ITU-T Y.1540 maximum IP-layer
capacity measurements, and
Errata", September 2020, measurements", ITU-T Recommendation Y.Sup60,
October 2021, <https://www.itu.int/rec/T-REC-Y.Sup60/en>.
13.
Appendix A - A. Load Rate Adjustment Pseudo Code
The following is Pseudocode
This appendix provides a pseudo-code pseudocode implementation of the algorithm
described in Section 8.1.
Rx = 0 # The current sending rate (equivalent to a row
# of the table)
seqErr = 0 # Measured count of any of that includes Loss or Reordering
# or Duplication impairments (all appear
# initially as errors in the packet sequence
# numbering)
seqErrThresh = 10 # Threshold on seqErr count that includes Loss or
# Reordering or Duplication impairments (all
# appear initially as errors in the packet
# sequence numbering)
delay = 0 # Measured Range of Round Trip Delay, RTD, ms Delay (RTD), msec
lowThresh = 30 # Low threshold on the Range of RTD, ms msec
upperThresh = 90 # Upper threshold on the Range of RTD, ms
hSpeedTresh msec
hSpeedThresh = 1 Gbps # Threshold for transition between sending rate
# step sizes (such as 1 Mbps and 100 Mbps) Mbps), Gbps
slowAdjCount = 0 # Measured Number of consecutive status reports
# indicating loss and/or delay variation above
# upperThresh
slowAdjThresh = 2 3 # Threshold on slowAdjCount used to infer
# congestion. Use values >1 > 1 to avoid
# misinterpreting transient loss loss.
highSpeedDelta = 10 # The number of rows to move in a single
# adjustment when initially increasing offered
# load (to ramp-up ramp up quickly)
maxLoadRates = 2000 # Maximum table index (rows)
if ( seqErr == 0 <= seqErrThresh && delay < lowThresh ) {
if ( Rx < hSpeedTresh hSpeedThresh && slowAdjCount < slowAdjThresh ) {
Rx += highSpeedDelta;
slowAdjCount = 0;
} else {
if ( Rx < maxLoadRates - 1 )
Rx++;
}
} else if ( seqErr > 0 seqErrThresh || delay > upperThresh ) {
slowAdjCount++;
if ( Rx < hSpeedTresh hSpeedThresh && slowAdjCount == slowAdjThresh ) {
if ( Rx > highSpeedDelta * 3 )
Rx -= highSpeedDelta * 3;
else
Rx = 0;
} else {
if ( Rx > 0 )
Rx--;
}
}
14.
Appendix B - B. RFC 8085 UDP Guidelines Check
The BCP on
Section 3.1 of [RFC8085] (BCP 145), which provides UDP usage guidelines [RFC8085]
guidelines, focuses primarily on congestion control in section 3.1. control. The Guidelines guidelines
appear in mandatory (MUST) and recommendation (SHOULD) categories.
14.1.
B.1. Assessment of Mandatory Requirements
The mandatory requirements in Section 3 of [RFC8085] include: include the
following:
| Internet paths can have widely varying characteristics, ...
| Consequently, applications that may be used on the Internet MUST
| NOT make assumptions about specific path characteristics. They
| MUST instead use mechanisms that let them operate safely under
| very different path conditions. Typically, this requires
| conservatively probing the current conditions of the Internet path
| they communicate over to establish a transmission behavior that it
| can sustain and that is reasonably fair to other traffic sharing
| the path.
The purpose of the load rate adjustment algorithm described in
Section 8.1 is to probe the network and enable Maximum IP-Layer
Capacity measurements with as few assumptions about the measured path
as
possible, possible and within the range application of applications described in
Section 2.
The degree of probing conservatism There is in tension with between the need to
minimize goals of probing
conservatism and minimization of both the traffic dedicated to
testing (especially with Gigabit rate measurements) and the duration
of the test (which is one contributing factor to the overall
algorithm fairness).
The text of Section 3 of [RFC8085] goes on to recommend alternatives
to UDP to meet the mandatory requirements, but none are suitable for
the scope and purpose of the metrics Metrics and methods Methods in this memo. In
fact, ad hoc TCP-based methods fail to achieve the measurement
accuracy repeatedly proven in comparison measurements with the
running code [LS-SG12-A] [LS-SG12-B] [Y.Sup60]. Also, the UDP aspect
of these methods is present primarily to support modern Internet
transmission where a transport protocol is required [copycat]; the
metric is based on the IP-Layer IP Layer, and UDP allows simple correlation to
the IP-Layer. IP Layer.
Section 3.1.1 of [RFC8085] discusses protocol timer guidelines:
| Latency samples MUST NOT be derived from ambiguous transactions.
| The canonical example is in a protocol that retransmits data, but
| subsequently cannot determine which copy is being acknowledged.
Both load packets and status feedback messages MUST contain sequence
numbers, which
numbers; this helps with measurements based on those packets, and
there are no retransmissions needed.
| When a latency estimate is used to arm a timer that provides loss
| detection -- with or without retransmission -- expiry of the timer
| MUST be interpreted as an indication of congestion in the network,
| causing the sending rate to be adapted to a safe conservative
rate... rate
| ...
The method methods described in this memo uses use timers for sending rate
backoff when status feedback messages are lost (Lost Status Backoff
timeout),
timeout) and for stopping a test when connectivity is lost for a
longer interval (Feedback (feedback message or load packet timeouts).
There is no
This memo does not foresee any specific benefit foreseen by of using Explicit
Congestion Notification (ECN) in this memo. (ECN).
Section 3.2 of [RFC8085] discusses message size guidelines:
| To determine an appropriate UDP payload size, applications MUST
| subtract the size of the IP header (which includes any IPv4
| optional headers or IPv6 extension headers) as well as the length
| of the UDP header (8 bytes) from the PMTU size.
The method uses a sending rate table with a maximum UDP payload size
that anticipates significant header overhead and avoids
fragmentation.
Section 3.3 of [RFC8085] provides reliability guidelines:
| Applications that do require reliable message delivery MUST
| implement an appropriate mechanism themselves.
The IP-Layer Capacity Metric Metrics and Method Methods do not require reliable
delivery.
| Applications that require ordered delivery MUST reestablish
| datagram ordering themselves.
The IP-Layer Capacity Metric Metrics and Method does Methods do not need to reestablish
packet order; it is preferred preferable to measure packet reordering if it
occurs [RFC4737].
14.2.
B.2. Assessment of Recommendations
The load rate adjustment algorithm's goal is to determine the Maximum
IP-Layer Capacity in the context of an infrequent, diagnostic, short short-
term measurement. This goal is a global exception to many [RFC8085]
SHOULD-level requirements, SHOULD-
level requirements as listed in [RFC8085], of which many are intended
for long-lived flows that must coexist with other traffic in more-or-less a more
or less fair way. However, the algorithm (as specified in
Section 8.1 and Appendix A above) reacts to indications of congestion
in clearly defined ways.
A specific recommendation is provided as an example. Section 3.1.5
of [RFC8085] on (regarding the implications of RTT and Loss Measurements loss measurements
on
Congestion Control congestion control) says:
| A congestion control [algorithm] designed for UDP SHOULD respond
| as quickly as possible when it experiences congestion, and it
| SHOULD take into account both the loss rate and the response time
| when choosing a new rate.
The load rate adjustment algorithm responds to loss and RTT
measurements with a clear and concise rate reduction when warranted,
and the response makes use of direct measurements (more exact than
can be inferred from TCP ACKs).
Section 3.1.5 of [RFC8085] goes on to specify: specify the following:
| The implemented congestion control scheme SHOULD result in
| bandwidth (capacity) use that is comparable to that of TCP within
| an order of magnitude, so that it does not starve other flows
| sharing a common bottleneck.
This is a requirement for coexistent streams, and not for diagnostic
and infrequent measurements using short durations. The rate
oscillations during short tests allow other packets to pass, pass and don't
starve other flows.
Ironically, ad hoc TCP-based measurements of "Internet Speed" are
also designed to work around this SHOULD-level requirement, by
launching many flows (9, for example) to increase the outstanding
data dedicated to testing.
The load rate adjustment algorithm cannot become a TCP-like
congestion control, or it will have the same weaknesses of TCP when
trying to make a Maximum IP-Layer Capacity measurement, measurement and will not
achieve the goal. The results of the referenced testing [LS-SG12-A]
[LS-SG12-B] [Y.Sup60] supported this statement hundreds of times,
with comparisons to multi-connection TCP-based measurements.
A brief review of some other SHOULD-level requirements from [RFC8085] follows (Yes (marked "Yes"
when this memo is compliant, or Not applicable = NA) :
+--+---------------------------------------------------------+---------+
|Y?| "NA" (Not Applicable)):
+======+============================================+=========+
| Yes? | Recommendation in RFC 8085 Recommendation | Section |
+--+---------------------------------------------------------+---------+
Yes|
+======+============================================+=========+
| Yes | MUST tolerate a wide range of Internet | 3 |
| | path conditions | 3 |
+------+--------------------------------------------+---------+
| NA | SHOULD use a full-featured transport | |
| | (e.g., TCP) | |
+------+--------------------------------------------+---------+
+------+--------------------------------------------+---------+
| Yes | |
Yes| SHOULD control rate of transmission | 3.1 |
+------+--------------------------------------------+---------+
| NA | SHOULD perform congestion control over all traffic | |
| | traffic | | for
+------+--------------------------------------------+---------+
+======+============================================+=========+
| | For bulk transfers, | 3.1.2 |
+======+============================================+=========+
| NA | SHOULD consider implementing TFRC | |
+------+--------------------------------------------+---------+
| NA | else, SHOULD in other ways use bandwidth | |
| | similar to TCP | |
+------+--------------------------------------------+---------+
+======+============================================+=========+
| | |
| for For non-bulk transfers, | 3.1.3 |
+======+============================================+=========+
| NA | SHOULD measure RTT and transmit max. 1 datagram/RTT | 3.1.1 |
| | datagram/RTT | |
+------+--------------------------------------------+---------+
| NA | else, SHOULD send at most 1 datagram every | |
| | 3 seconds | |
+------+--------------------------------------------+---------+
| NA | SHOULD back-off retransmission timers | |
| | following loss | |
+------+--------------------------------------------+---------+
+------+--------------------------------------------+---------+
| Yes | |
Yes| SHOULD provide mechanisms to regulate the bursts of | 3.1.6 |
| transmission | | bursts of transmission | |
+------+--------------------------------------------+---------+
+------+--------------------------------------------+---------+
| NA | MAY implement ECN; a specific set of application | 3.1.7 |
| | application mechanisms are REQUIRED if ECN is used. | |
| | is used | |
Yes| for
+------+--------------------------------------------+---------+
+------+--------------------------------------------+---------+
| Yes | For DiffServ, SHOULD NOT rely on | 3.1.8 |
| | implementation of PHBs | 3.1.8 | |
+------+--------------------------------------------+---------+
+------+--------------------------------------------+---------+
| Yes |
Yes| for For QoS-enabled paths, MAY choose not to use CC | 3.1.9 |
| | use CC | |
+------+--------------------------------------------+---------+
+------+--------------------------------------------+---------+
| Yes |
Yes| SHOULD NOT rely solely on QoS for their capacity | 3.1.10 |
| | capacity | |
+------+--------------------------------------------+---------+
| NA | non-CC controlled flows SHOULD implement a transport | |
| | transport circuit breaker | |
+------+--------------------------------------------+---------+
| Yes | MAY implement a circuit breaker for other applications | |
| | applications | | for
+------+--------------------------------------------+---------+
+======+============================================+=========+
| | For tunnels carrying IP traffic, | 3.1.11 |
+======+============================================+=========+
| NA | SHOULD NOT perform congestion control | |
+------+--------------------------------------------+---------+
| NA | MUST correctly process the IP ECN field | |
+------+--------------------------------------------+---------+
+======+============================================+=========+
| | |
| for For non-IP tunnels or rate not determined | 3.1.11 |
| | by traffic, | |
+======+============================================+=========+
| NA | SHOULD perform CC or use circuit breaker | 3.1.11 |
+------+--------------------------------------------+---------+
| NA | SHOULD restrict types of traffic transported by the | |
| tunnel | transported by the tunnel | |
+------+--------------------------------------------+---------+
+------+--------------------------------------------+---------+
| Yes |
Yes| SHOULD NOT send datagrams that exceed the | 3.2 |
| | PMTU, i.e., | 3.2 |
Yes|
+------+--------------------------------------------+---------+
| Yes | SHOULD discover PMTU or send datagrams < | |
| | minimum PMTU; PMTU | |
+------+--------------------------------------------+---------+
| NA | Specific application mechanisms are REQUIRED if PLPMTUD | |
| is used. | REQUIRED if PLPMTUD is used | |
+------+--------------------------------------------+---------+
+------+--------------------------------------------+---------+
| Yes |
Yes| SHOULD handle datagram loss, duplication, reordering | 3.3 |
| | reordering | |
+------+--------------------------------------------+---------+
| NA | SHOULD be robust to delivery delays up to | |
| | 2 minutes | |
+------+--------------------------------------------+---------+
+------+--------------------------------------------+---------+
| Yes | |
Yes| SHOULD enable IPv4 UDP checksum | 3.4 |
Yes|
+------+--------------------------------------------+---------+
| Yes | SHOULD enable IPv6 UDP checksum; Specific application specific | 3.4.1 |
| | application mechanisms are REQUIRED if a | |
| | zero IPv6 UDP checksum is used | |
| used. | |
| |
+------+--------------------------------------------+---------+
+------+--------------------------------------------+---------+
| NA | SHOULD provide protection from off-path attacks | 5.1 |
| | attacks | |
+------+--------------------------------------------+---------+
| | else, MAY use UDP-Lite with suitable checksum coverage | 3.4.2 |
| | checksum coverage | |
+------+--------------------------------------------+---------+
+------+--------------------------------------------+---------+
| NA | SHOULD NOT always send middlebox keep-alive messages keep- | 3.5 |
| | alive messages | |
+------+--------------------------------------------+---------+
| NA | MAY use keep-alives when needed (min. | |
| | interval 15 sec) | |
+------+--------------------------------------------+---------+
+------+--------------------------------------------+---------+
| Yes | |
Yes| Applications specified for use in limited use (or | 3.6 |
| | use (or controlled environments) SHOULD identify equivalent | |
| | identify equivalent mechanisms and | |
| | describe their use case. | | case | |
+------+--------------------------------------------+---------+
+------+--------------------------------------------+---------+
| NA | Bulk-multicast apps SHOULD implement congestion control | 4.1.1 |
| | congestion control | |
+------+--------------------------------------------+---------+
+------+--------------------------------------------+---------+
| NA | Low volume multicast apps SHOULD implement congestion | 4.1.2 |
| control | | congestion control | |
+------+--------------------------------------------+---------+
+------+--------------------------------------------+---------+
| NA | Multicast apps SHOULD use a safe PMTU | 4.2 |
+------+--------------------------------------------+---------+
+------+--------------------------------------------+---------+
| Yes | |
Yes| SHOULD avoid using multiple ports | 5.1.2 |
Yes|
+------+--------------------------------------------+---------+
| Yes | MUST check received IP source address | |
| |
+------+--------------------------------------------+---------+
+------+--------------------------------------------+---------+
| NA | SHOULD validate payload in ICMP messages | 5.2 |
+------+--------------------------------------------+---------+
+------+--------------------------------------------+---------+
| Yes | |
Yes| SHOULD use a randomized source Source port or equivalent | 6 |
| | equivalent technique, and, for client/server applications, SHOULD client/ | |
| | server applications, SHOULD send responses | |
| | from source address matching request | |
| 5.1 |
+------+--------------------------------------------+---------+
| NA | SHOULD use standard IETF security | 6 |
| | protocols when needed | 6 |
+---------------------------------------------------------+---------+
12.
+------+--------------------------------------------+---------+
Table 4: Summary of Key Guidelines from RFC 8085
Acknowledgments
Thanks to Joachim Fabini, Matt Mathis, J.Ignacio J. Ignacio Alvarez-Hamelin,
Wolfgang Balzer, Frank Brockners, Greg Mirsky, Martin Duke, Murray
Kucherawy, and Benjamin Kaduk for their extensive comments on the this
memo and related topics. In a second round of reviews, we
acknowledge Magnus Westerlund, Lars Eggert, and Zahed Sarkar. Zaheduzzaman Sarker.
Authors' Addresses
Al Morton
AT&T Labs
200 Laurel Avenue South
Middletown, NJ 07748
USA
United States of America
Phone: +1 732 420 1571
Fax: +1 732 368 1192
Email: acm@research.att.com
Ruediger
Rüdiger Geib
Deutsche Telekom
Heinrich Hertz Str. 3-7
Darmstadt
64295 Darmstadt
Germany
Phone: +49 6151 5812747
Email: Ruediger.Geib@telekom.de
Len Ciavattone
AT&T Labs
200 Laurel Avenue South
Middletown, NJ 07748
USA
United States of America
Phone: +1 732 420 1239
Email: lencia@att.com