Internet Engineering Task Force (IETF) A. Morton
Request for Comments: 8912 AT&T Labs
Category: Standards Track M. Bagnulo
ISSN: 2070-1721 UC3M
P. Eardley
BT
K. D'Souza
AT&T Labs
November 2021
Initial Performance Metrics Registry Entries
Abstract
This memo defines the set of initial entries for the IANA Registry of
Performance Metrics. The set includes UDP Round-Trip Latency and
Loss, Packet Delay Variation, DNS Response Latency and Loss, UDP
Poisson One-Way Delay and Loss, UDP Periodic One-Way Delay and Loss,
ICMP Round-Trip Latency and Loss, and TCP Round-Trip Delay and Loss.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8912.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction
1.1. Requirements Language
2. Scope
3. Registry Categories and Columns
4. UDP Round-Trip Latency and Loss Registry Entries
4.1. Summary
4.1.1. ID (Identifier)
4.1.2. Name
4.1.3. URI
4.1.4. Description
4.1.5. Change Controller
4.1.6. Version (of Registry Format)
4.2. Metric Definition
4.2.1. Reference Definition
4.2.2. Fixed Parameters
4.3. Method of Measurement
4.3.1. Reference Methods
4.3.2. Packet Stream Generation
4.3.3. Traffic Filtering (Observation) Details
4.3.4. Sampling Distribution
4.3.5. Runtime Parameters and Data Format
4.3.6. Roles
4.4. Output
4.4.1. Type
4.4.2. Reference Definition
4.4.3. Metric Units
4.4.4. Calibration
4.5. Administrative Items
4.5.1. Status
4.5.2. Requester
4.5.3. Revision
4.5.4. Revision Date
4.6. Comments and Remarks
5. Packet Delay Variation Registry Entry
5.1. Summary
5.1.1. ID (Identifier)
5.1.2. Name
5.1.3. URI
5.1.4. Description
5.1.5. Change Controller
5.1.6. Version (of Registry Format)
5.2. Metric Definition
5.2.1. Reference Definition
5.2.2. Fixed Parameters
5.3. Method of Measurement
5.3.1. Reference Methods
5.3.2. Packet Stream Generation
5.3.3. Traffic Filtering (Observation) Details
5.3.4. Sampling Distribution
5.3.5. Runtime Parameters and Data Format
5.3.6. Roles
5.4. Output
5.4.1. Type
5.4.2. Reference Definition
5.4.3. Metric Units
5.4.4. Calibration
5.5. Administrative Items
5.5.1. Status
5.5.2. Requester
5.5.3. Revision
5.5.4. Revision Date
5.6. Comments and Remarks
6. DNS Response Latency and Loss Registry Entries
6.1. Summary
6.1.1. ID (Identifier)
6.1.2. Name
6.1.3. URI
6.1.4. Description
6.1.5. Change Controller
6.1.6. Version (of Registry Format)
6.2. Metric Definition
6.2.1. Reference Definition
6.2.2. Fixed Parameters
6.3. Method of Measurement
6.3.1. Reference Methods
6.3.2. Packet Stream Generation
6.3.3. Traffic Filtering (Observation) Details
6.3.4. Sampling Distribution
6.3.5. Runtime Parameters and Data Format
6.3.6. Roles
6.4. Output
6.4.1. Type
6.4.2. Reference Definition
6.4.3. Metric Units
6.4.4. Calibration
6.5. Administrative Items
6.5.1. Status
6.5.2. Requester
6.5.3. Revision
6.5.4. Revision Date
6.6. Comments and Remarks
7. UDP Poisson One-Way Delay and Loss Registry Entries
7.1. Summary
7.1.1. ID (Identifier)
7.1.2. Name
7.1.3. URI
7.1.4. Description
7.1.5. Change Controller
7.1.6. Version (of Registry Format)
7.2. Metric Definition
7.2.1. Reference Definition
7.2.2. Fixed Parameters
7.3. Method of Measurement
7.3.1. Reference Methods
7.3.2. Packet Stream Generation
7.3.3. Traffic Filtering (Observation) Details
7.3.4. Sampling Distribution
7.3.5. Runtime Parameters and Data Format
7.3.6. Roles
7.4. Output
7.4.1. Type
7.4.2. Reference Definition
7.4.3. Metric Units
7.4.4. Calibration
7.5. Administrative Items
7.5.1. Status
7.5.2. Requester
7.5.3. Revision
7.5.4. Revision Date
7.6. Comments and Remarks
8. UDP Periodic One-Way Delay and Loss Registry Entries
8.1. Summary
8.1.1. ID (Identifier)
8.1.2. Name
8.1.3. URI
8.1.4. Description
8.1.5. Change Controller
8.1.6. Version (of Registry Format)
8.2. Metric Definition
8.2.1. Reference Definition
8.2.2. Fixed Parameters
8.3. Method of Measurement
8.3.1. Reference Methods
8.3.2. Packet Stream Generation
8.3.3. Traffic Filtering (Observation) Details
8.3.4. Sampling Distribution
8.3.5. Runtime Parameters and Data Format
8.3.6. Roles
8.4. Output
8.4.1. Type
8.4.2. Reference Definition
8.4.3. Metric Units
8.4.4. Calibration
8.5. Administrative Items
8.5.1. Status
8.5.2. Requester
8.5.3. Revision
8.5.4. Revision Date
8.6. Comments and Remarks
9. ICMP Round-Trip Latency and Loss Registry Entries
9.1. Summary
9.1.1. ID (Identifier)
9.1.2. Name
9.1.3. URI
9.1.4. Description
9.1.5. Change Controller
9.1.6. Version (of Registry Format)
9.2. Metric Definition
9.2.1. Reference Definition
9.2.2. Fixed Parameters
9.3. Method of Measurement
9.3.1. Reference Methods
9.3.2. Packet Stream Generation
9.3.3. Traffic Filtering (Observation) Details
9.3.4. Sampling Distribution
9.3.5. Runtime Parameters and Data Format
9.3.6. Roles
9.4. Output
9.4.1. Type
9.4.2. Reference Definition
9.4.3. Metric Units
9.4.4. Calibration
9.5. Administrative Items
9.5.1. Status
9.5.2. Requester
9.5.3. Revision
9.5.4. Revision Date
9.6. Comments and Remarks
10. TCP Round-Trip Delay and Loss Registry Entries
10.1. Summary
10.1.1. ID (Identifier)
10.1.2. Name
10.1.3. URI
10.1.4. Description
10.1.5. Change Controller
10.1.6. Version (of Registry Format)
10.2. Metric Definition
10.2.1. Reference Definition
10.2.2. Fixed Parameters
10.3. Method of Measurement
10.3.1. Reference Methods
10.3.2. Packet Stream Generation
10.3.3. Traffic Filtering (Observation) Details
10.3.4. Sampling Distribution
10.3.5. Runtime Parameters and Data Format
10.3.6. Roles
10.4. Output
10.4.1. Type
10.4.2. Reference Definition
10.4.3. Metric Units
10.4.4. Calibration
10.5. Administrative Items
10.5.1. Status
10.5.2. Requester
10.5.3. Revision
10.5.4. Revision Date
10.6. Comments and Remarks
11. Security Considerations
12. IANA Considerations
13. References
13.1. Normative References
13.2. Informative References
Acknowledgments
Authors' Addresses
1. Introduction
This memo defines an initial set of entries for the Performance
Metrics Registry. It uses terms and definitions from the IP
Performance Metrics (IPPM) literature, primarily [RFC2330].
Although there are several standard templates for organizing
specifications of Performance Metrics (see [RFC7679] for an example
of the traditional IPPM template, based to a large extent on the
Benchmarking Methodology Working Group's traditional template in
[RFC1242], and see [RFC6390] for a similar template), none of these
templates were intended to become the basis for the columns of an
IETF-wide Registry of metrics. While examining aspects of metric
specifications that need to be registered, it became clear that none
of the existing metric templates fully satisfy the particular needs
of a Registry.
Therefore, [RFC8911] defines the overall format for a Performance
Metrics Registry. Section 5 of [RFC8911] also gives guidelines for
those requesting registration of a Metric -- that is, the creation of
one or more entries in the Performance Metrics Registry:
| In essence, there needs to be evidence that (1) a candidate
| Registered Performance Metric has significant industry interest or
| has seen deployment and (2) there is agreement that the candidate
| Registered Performance Metric serves its intended purpose.
The process defined in [RFC8911] also requires that new entries be
administered by IANA through the Specification Required policy
[RFC8126], which will ensure that the metrics are tightly defined.
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] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Scope
This document defines a set of initial Performance Metrics Registry
Entries. Most are Active Performance Metrics, which are based on
RFCs prepared in the IPPM Working Group of the IETF, according to
their framework [RFC2330] and its updates.
3. Registry Categories and Columns
This memo uses the terminology defined in [RFC8911].
This section provides the categories and columns of the Registry, for
easy reference. An entry (row) therefore gives a complete
description of a Registered Metric.
Registry Categories and Columns are shown below in this format:
Category
------------------...
Column | Column |...
Summary
---------------------------------------------------------------
Identifier | Name | URI | Desc. | Reference | Change | Ver |
| | | | | Controller |
Metric Definition
-----------------------------------------
Reference Definition | Fixed Parameters |
Method of Measurement
---------------------------------------------------------------------
Reference | Packet | Traffic | Sampling | Runtime | Role |
Method | Stream | Filter | Distribution | Parameters | |
| Generation |
Output
-----------------------------------------
Type | Reference | Units | Calibration |
| Definition | | |
Administrative Information
-------------------------------------
Status |Requester | Rev | Rev. Date |
Comments and Remarks
--------------------
4. UDP Round-Trip Latency and Loss Registry Entries
This section specifies an initial Registry Entry for UDP Round-Trip
Latency and another entry for the UDP Round-Trip Loss Ratio.
Note: Each Registry Entry only produces a "raw" output or a
statistical summary. To describe both "raw" and one or more
statistics efficiently, the Identifier, Name, and Output
categories can be split, and a single section can specify two or
more closely related metrics. For example, this section specifies
two Registry Entries with many common columns. See Section 7 for
an example specifying multiple Registry Entries with many common
columns.
All column entries besides the ID, Name, Description, and Output
Reference Method categories are the same; thus, this section defines
two closely related Registry Entries. As a result, IANA has also
assigned a corresponding URL to each of the two Named Metrics.
4.1. Summary
This category includes multiple indexes to the Registry Entries: the
element ID and Metric Name.
4.1.1. ID (Identifier)
IANA has allocated the numeric Identifiers 1 and 2 for the two Named
Metric Entries in Section 4. See Section 4.1.2 for mapping to Names.
4.1.2. Name
1: RTDelay_Active_IP-UDP-Periodic_RFC8912sec4_Seconds_95Percentile
2: RTLoss_Active_IP-UDP-Periodic_RFC8912sec4_Percent_LossRatio
4.1.3. URI
URL: https://www.iana.org/performance-metrics/RTDelay_Active_IP-UDP-
Periodic_RFC8912sec4_Seconds_95Percentile
URL: https://www.iana.org/performance-metrics/RTLoss_Active_IP-UDP-
Periodic_RFC8912sec4_Percent_LossRatio
4.1.4. Description
RTDelay: This metric assesses the delay of a stream of packets
exchanged between two hosts (which are the two measurement
points). The output is the round-trip delay for all successfully
exchanged packets expressed as the 95th percentile of their
conditional delay distribution.
RTLoss: This metric assesses the loss ratio of a stream of packets
exchanged between two hosts (which are the two measurement
points). The output is the round-trip loss ratio for all
transmitted packets expressed as a percentage.
4.1.5. Change Controller
IETF
4.1.6. Version (of Registry Format)
1.0
4.2. Metric Definition
This category includes columns to prompt the entry of all necessary
details related to the metric definition, including the RFC reference
and values of input factors, called "Fixed Parameters".
4.2.1. Reference Definition
For delay:
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>. [RFC2681]
Section 2.4 of [RFC2681] provides the reference definition of the
singleton (single value) round-trip delay metric. Section 3.4 of
[RFC2681] provides the reference definition expanded to cover a
multi-singleton sample. Note that terms such as "singleton" and
"sample" are defined in Section 11 of [RFC2330].
Note that although the definition of round-trip delay between the
Source (Src) and the Destination (Dst) as provided in Section 2.4
of [RFC2681] is directionally ambiguous in the text, this metric
tightens the definition further to recognize that the host in the
Src Role will send the first packet to the host in the Dst Role
and will ultimately receive the corresponding return packet from
the Dst (when neither is lost).
Finally, note that the variable "dT" is used in [RFC2681] to refer
to the value of round-trip delay in metric definitions and
methods. The variable "dT" has been reused in other IPPM
literature to refer to different quantities and cannot be used as
a global variable name.
For loss:
Morton, A., "Round-Trip Packet Loss Metrics", RFC 6673, DOI
10.17487/RFC6673, August 2012, <https://www.rfc-editor.org/info/
rfc6673>. [RFC6673]
Both Delay and Loss metrics employ a maximum waiting time for
received packets, so the count of lost packets to total packets sent
is the basis for the loss ratio calculation as per Section 6.1 of
[RFC6673].
4.2.2. Fixed Parameters
Type-P as defined in Section 13 of [RFC2330]:
IPv4 header values:
DSCP: Set to 0
TTL: Set to 255
Protocol: Set to 17 (UDP)
IPv6 header values:
DSCP: Set to 0
Hop Count: Set to 255
Next Header: Set to 17 (UDP)
Flow Label: Set to 0
Extension Headers: None
UDP header values:
Checksum: The checksum MUST be calculated and the non-zero
checksum included in the header
UDP Payload:
Total of 100 bytes
Other measurement Parameters:
Tmax: A loss threshold waiting time with value 3.0, expressed in
units of seconds, as a positive value of type decimal64 with
fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a
resolution of 0.0001 seconds (0.1 ms), with lossless conversion
to/from the 32-bit NTP timestamp as per Section 6 of [RFC5905].
4.3. Method of Measurement
This category includes columns for references to relevant sections of
the RFC(s) and any supplemental information needed to ensure an
unambiguous method for implementations.
4.3.1. Reference Methods
The methodology for this metric (equivalent to Type-P-Round-trip-
Delay and Type-P-Round-trip-Delay-Poisson-Stream) is defined as in
Section 2.6 of [RFC2681] (for singletons) and Section 3.6 of
[RFC2681] (for samples) using the Type-P and Tmax defined in the
Fixed Parameters column. However, the Periodic stream will be
generated according to [RFC3432].
The reference method distinguishes between long-delayed packets and
lost packets by implementing a maximum waiting time for packet
arrival. Tmax is the waiting time used as the threshold to declare a
packet lost. Lost packets SHALL be designated as having undefined
delay and counted for the RTLoss metric [RFC6673].
The calculations on the delay (RTT) SHALL be performed on the
conditional distribution, conditioned on successful packet arrival
within Tmax. Also, when all packet delays are stored, the process
that calculates the RTT value MUST enforce the Tmax threshold on
stored values before calculations. See Section 4.1 of [RFC3393] for
details on the conditional distribution to exclude undefined values
of delay, and see Section 5 of [RFC6703] for background on this
analysis choice.
The reference method requires some way to distinguish between
different packets in a stream to establish correspondence between
sending times and receiving times for each successfully arriving
packet. Sequence numbers or other send-order identification MUST be
retained at the Src or included with each packet to disambiguate
packet reordering if it occurs.
If a standard measurement protocol is employed, then the measurement
process will determine the sequence numbers or timestamps applied to
test packets after the Fixed and Runtime Parameters are passed to
that process. The chosen measurement protocol will dictate the
format of sequence numbers and timestamps, if they are conveyed in
the packet payload.
Refer to Section 4.4 of [RFC6673] for an expanded discussion of the
instruction to "send a Type-P packet back to the Src as quickly as
possible" in Section 2.6 of [RFC2681]. Section 8 of [RFC6673]
presents additional requirements that MUST be included in the Method
of Measurement for this metric.
4.3.2. Packet Stream Generation
This section provides details regarding packet traffic, which is used
as the basis for measurement. In IPPM Metrics, this is called the
"stream"; this stream can easily be described by providing the list
of stream Parameters.
Section 3 of [RFC3432] prescribes the method for generating Periodic
streams using associated Parameters.
incT: The nominal duration of the inter-packet interval, first bit
to first bit, with value 0.0200, expressed in units of seconds, as
a positive value of type decimal64 with fraction digits = 4 (see
Section 9.3 of [RFC6020]) and with a resolution of 0.0001 seconds
(0.1 ms).
dT: The duration of the interval for allowed sample start times,
with value 1.0, expressed in units of seconds, as a positive value
of type decimal64 with fraction digits = 4 (see Section 9.3 of
[RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms).
Note: An initiation process with a number of control exchanges
resulting in unpredictable start times (within a time interval)
may be sufficient to avoid synchronization of periodic streams and
is a valid replacement for selecting a start time at random from a
fixed interval.
The T0 Parameter will be reported as a measured Parameter.
Parameters incT and dT are Fixed Parameters.
4.3.3. Traffic Filtering (Observation) Details
N/A
4.3.4. Sampling Distribution
N/A
4.3.5. Runtime Parameters and Data Format
Runtime Parameters are input factors that must be determined,
configured into the measurement system, and reported with the results
for the context to be complete.
Src: The IP address of the host in the Src Role (format
ipv4-address-no-zone value for IPv4 or ipv6-address-no-zone value
for IPv6; see Section 4 of [RFC6991]).
Dst: The IP address of the host in the Dst Role (format
ipv4-address-no-zone value for IPv4 or ipv6-address-no-zone value
for IPv6; see Section 4 of [RFC6991]).
T0: A time, the start of a measurement interval (format "date-time"
as specified in Section 5.6 of [RFC3339]; see also "date-and-time"
in Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330]. When T0 is "all-zeros", a start time is
unspecified and Tf is to be interpreted as the duration of the
measurement interval. The start time is controlled through other
means.
Tf: A time, the end of a measurement interval (format "date-time" as
specified in Section 5.6 of [RFC3339]; see also "date-and-time" in
Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330]. When T0 is "all-zeros", an ending time
and date is ignored and Tf is interpreted as the duration of the
measurement interval.
4.3.6. Roles
Src: Launches each packet and waits for return transmissions from
the Dst.
Dst: Waits for each packet from the Src and sends a return packet to
the Src.
4.4. Output
This category specifies all details of the output of measurements
using the metric.
4.4.1. Type
Percentile: For the conditional distribution of all packets with a
valid value of round-trip delay (undefined delays are excluded), this
is a single value corresponding to the 95th percentile, as follows:
See Section 4.1 of [RFC3393] for details on the conditional
distribution to exclude undefined values of delay, and see Section 5
of [RFC6703] for background on this analysis choice.
The percentile = 95, meaning that the reported delay, "95Percentile",
is the smallest value of round-trip delay for which the Empirical
Distribution Function, EDF(95Percentile), is greater than or equal to
95% of the singleton round-trip delay values in the conditional
distribution. See Section 11.3 of [RFC2330] for the definition of
the percentile statistic using the EDF.
For LossRatio, the count of lost packets to total packets sent is the
basis for the loss ratio calculation as per Section 6.1 of [RFC6673].
4.4.2. Reference Definition
For all outputs:
T0: The start of a measurement interval (format "date-time" as
specified in Section 5.6 of [RFC3339]; see also "date-and-time" in
Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330].
Tf: The end of a measurement interval (format "date-time" as
specified in Section 5.6 of [RFC3339]; see also "date-and-time" in
Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330].
TotalPkts: The count of packets sent by the Src to the Dst during
the measurement interval.
95Percentile: The time value of the result is expressed in units of
seconds, as a positive value of type decimal64 with fraction
digits = 9 (see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns).
Percent_LossRatio: The numeric value of the result is expressed in
units of lost packets to total packets times 100%, as a positive
value of type decimal64 with fraction digits = 9 (see Section 9.3
of [RFC6020]) with a resolution of 0.0000000001.
4.4.3. Metric Units
The 95th percentile of round-trip delay is expressed in seconds.
The round-trip loss ratio is expressed as a percentage of lost
packets to total packets sent.
4.4.4. Calibration
Section 3.7.3 of [RFC7679] provides a means to quantify the
systematic and random errors of a time measurement. Calibration in-
situ could be enabled with an internal loopback at the Source host
that includes as much of the measurement system as possible, performs
address manipulation as needed, and provides some form of isolation
(e.g., deterministic delay) to avoid send-receive interface
contention. Some portion of the random and systematic error can be
characterized in this way.
When a measurement controller requests a calibration measurement, the
loopback is applied and the result is output in the same format as a
normal measurement, with an additional indication that it is a
calibration result.
Both internal loopback calibration and clock synchronization can be
used to estimate the available accuracy of the Output Metric Units.
For example, repeated loopback delay measurements will reveal the
portion of the output result resolution that is the result of system
noise and is thus inaccurate.
4.5. Administrative Items
4.5.1. Status
Current
4.5.2. Requester
RFC 8912
4.5.3. Revision
1.0
4.5.4. Revision Date
YYYY-MM-DD
2021-11-17
4.6. Comments and Remarks
None
5. Packet Delay Variation Registry Entry
This section gives an initial Registry Entry for a Packet Delay
Variation (PDV) metric.
5.1. Summary
This category includes multiple indexes to the Registry Entry: the
element ID and Metric Name.
5.1.1. ID (Identifier)
IANA has allocated the numeric Identifier 3 for the Named Metric
Entry in Section 5. See Section 5.1.2 for mapping to Name.
5.1.2. Name
3: OWPDV_Active_IP-UDP-Periodic_RFC8912sec5_Seconds_95Percentile
5.1.3. URI
URL: https://www.iana.org/performance-metrics/OWPDV_Active_IP-UDP-
Periodic_RFC8912sec5_Seconds_95Percentile
5.1.4. Description
This metric assesses packet delay variation with respect to the
minimum delay observed on the periodic stream. The output is
expressed as the 95th percentile of the one-way packet delay
variation distribution.
5.1.5. Change Controller
IETF
5.1.6. Version (of Registry Format)
1.0
5.2. Metric Definition
This category includes columns to prompt the entry of all necessary
details related to the metric definition, including the RFC reference
and values of input factors, called "Fixed Parameters".
5.2.1. Reference Definition
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>. [RFC2330]
Demichelis, C. and P. Chimento, "IP Packet Delay Variation Metric
for IP Performance Metrics (IPPM)", RFC 3393, DOI 10.17487/RFC3393,
November 2002, <https://www.rfc-editor.org/info/rfc3393>. [RFC3393]
Morton, A. and B. Claise, "Packet Delay Variation Applicability
Statement", RFC 5481, DOI 10.17487/RFC5481, March 2009,
<https://www.rfc-editor.org/info/rfc5481>. [RFC5481]
Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, "Network Time
Protocol Version 4: Protocol and Algorithms Specification", RFC 5905,
DOI 10.17487/RFC5905, June 2010, <https://www.rfc-editor.org/info/
rfc5905>. [RFC5905]
See Sections 2.4 and 3.4 of [RFC3393]. The measured singleton delay
differences are referred to by the variable name "ddT" (applicable to
all forms of delay variation). However, this Metric Entry specifies
the PDV form defined in Section 4.2 of [RFC5481], where the singleton
PDV for packet i is referred to by the variable name "PDV(i)".
5.2.2. Fixed Parameters
IPv4 header values:
DSCP: Set to 0
TTL: Set to 255
Protocol: Set to 17 (UDP)
IPv6 header values:
DSCP: Set to 0
Hop Count: Set to 255
Next Header: Set to 17 (UDP)
Flow Label: Set to 0
Extension Headers: None
UDP header values:
Checksum: The checksum MUST be calculated and the non-zero
checksum included in the header
UDP Payload:
Total of 200 bytes
Other measurement Parameters:
Tmax: A loss threshold waiting time with value 3.0, expressed in
units of seconds, as a positive value of type decimal64 with
fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a
resolution of 0.0001 seconds (0.1 ms), with lossless conversion
to/from the 32-bit NTP timestamp as per Section 6 of [RFC5905].
F: A selection function unambiguously defining the packets from
the stream selected for the metric. See Section 4.2 of
[RFC5481] for the PDV form.
See the Packet Stream Generation section for two additional Fixed
Parameters.
5.3. Method of Measurement
This category includes columns for references to relevant sections of
the RFC(s) and any supplemental information needed to ensure an
unambiguous method for implementations.
5.3.1. Reference Methods
See Sections 2.6 and 3.6 of [RFC3393] for general singleton element
calculations. This Metric Entry requires implementation of the PDV
form defined in Section 4.2 of [RFC5481]. Also see measurement
considerations in Section 8 of [RFC5481].
The reference method distinguishes between long-delayed packets and
lost packets by implementing a maximum waiting time for packet
arrival. Tmax is the waiting time used as the threshold to declare a
packet lost. Lost packets SHALL be designated as having undefined
delay.
The calculations on the one-way delay SHALL be performed on the
conditional distribution, conditioned on successful packet arrival
within Tmax. Also, when all packet delays are stored, the process
that calculates the one-way delay value MUST enforce the Tmax
threshold on stored values before calculations. See Section 4.1 of
[RFC3393] for details on the conditional distribution to exclude
undefined values of delay, and see Section 5 of [RFC6703] for
background on this analysis choice.
The reference method requires some way to distinguish between
different packets in a stream to establish correspondence between
sending times and receiving times for each successfully arriving
packet. Sequence numbers or other send-order identification MUST be
retained at the Src or included with each packet to disambiguate
packet reordering if it occurs.
If a standard measurement protocol is employed, then the measurement
process will determine the sequence numbers or timestamps applied to
test packets after the Fixed and Runtime Parameters are passed to
that process. The chosen measurement protocol will dictate the
format of sequence numbers and timestamps, if they are conveyed in
the packet payload.
5.3.2. Packet Stream Generation
This section provides details regarding packet traffic, which is used
as the basis for measurement. In IPPM Metrics, this is called the
"stream"; this stream can easily be described by providing the list
of stream Parameters.
Section 3 of [RFC3432] prescribes the method for generating Periodic
streams using associated Parameters.
incT: The nominal duration of the inter-packet interval, first bit
to first bit, with value 0.0200, expressed in units of seconds, as
a positive value of type decimal64 with fraction digits = 4 (see
Section 9.3 of [RFC6020]) and with a resolution of 0.0001 seconds
(0.1 ms).
dT: The duration of the interval for allowed sample start times,
with value 1.0, expressed in units of seconds, as a positive value
of type decimal64 with fraction digits = 4 (see Section 9.3 of
[RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms).
Note: An initiation process with a number of control exchanges
resulting in unpredictable start times (within a time interval)
may be sufficient to avoid synchronization of periodic streams and
is a valid replacement for selecting a start time at random from a
fixed interval.
The T0 Parameter will be reported as a measured Parameter.
Parameters incT and dT are Fixed Parameters.
5.3.3. Traffic Filtering (Observation) Details
N/A
5.3.4. Sampling Distribution
N/A
5.3.5. Runtime Parameters and Data Format
Src: The IP address of the host in the Src Role (format
ipv4-address-no-zone value for IPv4 or ipv6-address-no-zone value
for IPv6; see Section 4 of [RFC6991]).
Dst: The IP address of the host in the Dst Role (format
ipv4-address-no-zone value for IPv4 or ipv6-address-no-zone value
for IPv6; see Section 4 of [RFC6991]).
T0: A time, the start of a measurement interval (format "date-time"
as specified in Section 5.6 of [RFC3339]; see also "date-and-time"
in Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330]. When T0 is "all-zeros", a start time is
unspecified and Tf is to be interpreted as the duration of the
measurement interval. The start time is controlled through other
means.
Tf: A time, the end of a measurement interval (format "date-time" as
specified in Section 5.6 of [RFC3339]; see also "date-and-time" in
Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330]. When T0 is "all-zeros", an ending time
and date is ignored and Tf is interpreted as the duration of the
measurement interval.
5.3.6. Roles
Src: Launches each packet and waits for return transmissions from
the Dst.
Dst: Waits for each packet from the Src and sends a return packet to
the Src (when required by the test protocol).
5.4. Output
This category specifies all details of the output of measurements
using the metric.
5.4.1. Type
Percentile: For the conditional distribution of all packets with a
valid value of one-way delay (undefined delays are excluded), this is
a single value corresponding to the 95th percentile, as follows:
See Section 4.1 of [RFC3393] for details on the conditional
distribution to exclude undefined values of delay, and see Section 5
of [RFC6703] for background on this analysis choice.
The percentile = 95, meaning that the reported delay, "95Percentile",
is the smallest value of one-way PDV for which the Empirical
Distribution Function, EDF(95Percentile), is greater than or equal to
95% of the singleton one-way PDV values in the conditional
distribution. See Section 11.3 of [RFC2330] for the definition of
the percentile statistic using the EDF.
5.4.2. Reference Definition
T0: The start of a measurement interval (format "date-time" as
specified in Section 5.6 of [RFC3339]; see also "date-and-time" in
Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330].
Tf: The end of a measurement interval (format "date-time" as
specified in Section 5.6 of [RFC3339]; see also "date-and-time" in
Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330].
95Percentile: The time value of the result is expressed in units of
seconds, as a positive value of type decimal64 with fraction
digits = 9 (see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
5.4.3. Metric Units
The 95th percentile of one-way PDV is expressed in seconds.
5.4.4. Calibration
Section 3.7.3 of [RFC7679] provides a means to quantify the
systematic and random errors of a time measurement. Calibration in-
situ could be enabled with an internal loopback that includes as much
of the measurement system as possible, performs address manipulation
as needed, and provides some form of isolation (e.g., deterministic
delay) to avoid send-receive interface contention. Some portion of
the random and systematic error can be characterized in this way.
For one-way delay measurements, the error calibration must include an
assessment of the internal clock synchronization with its external
reference (this internal clock is supplying timestamps for
measurement). In practice, the time offsets [RFC5905] of clocks at
both the Source and Destination are needed to estimate the systematic
error due to imperfect clock synchronization (the time offsets are
smoothed; thus, the random variation is not usually represented in
the results).
time_offset: The time value of the result is expressed in units of
seconds, as a signed value of type decimal64 with fraction
digits = 9 (see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
When a measurement controller requests a calibration measurement, the
loopback is applied and the result is output in the same format as a
normal measurement, with an additional indication that it is a
calibration result. In any measurement, the measurement function
SHOULD report its current estimate of the time offset [RFC5905] as an
indicator of the degree of synchronization.
Both internal loopback calibration and clock synchronization can be
used to estimate the available accuracy of the Output Metric Units.
For example, repeated loopback delay measurements will reveal the
portion of the output result resolution that is the result of system
noise and is thus inaccurate.
5.5. Administrative Items
5.5.1. Status
Current
5.5.2. Requester
RFC 8912
5.5.3. Revision
1.0
5.5.4. Revision Date
YYYY-MM-DD
2021-11-17
5.6. Comments and Remarks
Lost packets represent a challenge for delay variation metrics. See
Section 4.1 of [RFC3393] and the delay variation applicability
statement [RFC5481] for extensive analysis and comparison of PDV and
an alternate metric, IPDV (Inter-Packet Delay Variation).
6. DNS Response Latency and Loss Registry Entries
This section gives initial Registry Entries for DNS Response Latency
and Loss from a network user's perspective, for a specific named
resource. The metric can be measured repeatedly for different named
resources. [RFC2681] defines a round-trip delay metric. We build on
that metric by specifying several of the input Parameters to
precisely define two metrics for measuring DNS latency and loss.
All column entries besides the ID, Name, Description, and Output
Reference Method categories are the same; thus, this section defines
two closely related Registry Entries. As a result, IANA has assigned
corresponding URLs to each of the two Named Metrics.
6.1. Summary
This category includes multiple indexes to the Registry Entries: the
element ID and Metric Name.
6.1.1. ID (Identifier)
IANA has allocated the numeric Identifiers 4 and 5 for the two Named
Metric Entries in Section 6. See Section 6.1.2 for mapping to Names.
6.1.2. Name
4: RTDNS_Active_IP-UDP-Poisson_RFC8912sec6_Seconds_Raw
5: RLDNS_Active_IP-UDP-Poisson_RFC8912sec6_Logical_Raw
6.1.3. URI
URL: https://www.iana.org/performance-metrics/RTDNS_Active_IP-UDP-
Poisson_RFC8912sec6_Seconds_Raw
URL: https://www.iana.org/performance-metrics/RLDNS_Active_IP-UDP-
Poisson_RFC8912sec6_Logical_Raw
6.1.4. Description
This is a metric for DNS Response performance from a network user's
perspective, for a specific named resource. The metric can be
measured repeatedly using different resource names.
RTDNS: This metric assesses the response time, the interval from the
query transmission to the response.
RLDNS: This metric indicates that the response was deemed lost. In
other words, the response time exceeded the maximum waiting time.
6.1.5. Change Controller
IETF
6.1.6. Version (of Registry Format)
1.0
6.2. Metric Definition
This category includes columns to prompt the entry of all necessary
details related to the metric definition, including the RFC reference
and values of input factors, called "Fixed Parameters".
6.2.1. Reference Definition
For Delay:
Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, November
1987, <https://www.rfc-editor.org/info/rfc1035> (and updates).
[RFC1035]
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>. [RFC2681]
Section 2.4 of [RFC2681] provides the reference definition of the
singleton (single value) round-trip delay metric. Section 3.4 of
[RFC2681] provides the reference definition expanded to cover a
multi-singleton sample. Note that terms such as "singleton" and
"sample" are defined in Section 11 of [RFC2330].
For DNS Response Latency, the entities in [RFC1035] must be mapped
to [RFC2681]. The Local Host with its User Program and Resolver
take the Role of "Src", and the Foreign Name Server takes the Role
of "Dst".
Note that although the definition of round-trip delay between the
Source (Src) and the Destination (Dst) at T as provided in
Section 2.4 of [RFC2681] is directionally ambiguous in the text,
this metric tightens the definition further to recognize that the
host in the Src Role will send the first packet to the host in the
Dst Role and will ultimately receive the corresponding return
packet from the Dst (when neither is lost).
For Loss:
Morton, A., "Round-Trip Packet Loss Metrics", RFC 6673, DOI
10.17487/RFC6673, August 2012, <https://www.rfc-editor.org/info/
rfc6673>. [RFC6673]
For DNS Response Loss, the entities in [RFC1035] must be mapped to
[RFC6673]. The Local Host with its User Program and Resolver take
the Role of "Src", and the Foreign Name Server takes the Role of
"Dst".
Both response time and Loss metrics employ a maximum waiting time
for received responses, so the count of lost packets to total
packets sent is the basis for the loss determination as per
Section 4.3 of [RFC6673].
6.2.2. Fixed Parameters
Type-P as defined in Section 13 of [RFC2330]:
IPv4 header values:
DSCP: Set to 0
TTL: Set to 255
Protocol: Set to 17 (UDP)
IPv6 header values:
DSCP: Set to 0
Hop Count: Set to 255
Next Header: Set to 17 (UDP)
Flow Label: Set to 0
Extension Headers: None
UDP header values:
Source port: 53
Destination port: 53
Checksum: The checksum MUST be calculated and the non-zero
checksum included in the header
Payload:
The payload contains a DNS message as defined in [RFC1035] with
the following values:
The DNS header section contains:
Identification (see the Runtime column)
QR: Set to 0 (Query)
OPCODE: Set to 0 (standard query)
AA: Not set
TC: Not set
RD: Set to 1 (recursion desired)
RA: Not set
RCODE: Not set
QDCOUNT: Set to 1 (only one entry)
ANCOUNT: Not set
NSCOUNT: Not set
ARCOUNT: Not set
The Question section contains:
QNAME: The Fully Qualified Domain Name (FQDN) provided as
input for the test; see the Runtime column
QTYPE: The query type provided as input for the test; see
the Runtime column
QCLASS: Set to 1 for IN
The other sections do not contain any Resource Records
(RRs).
Other measurement Parameters:
Tmax: A loss threshold waiting time (and to help disambiguate
queries). The value is 5.0, expressed in units of seconds, as
a positive value of type decimal64 with fraction digits = 4
(see Section 9.3 of [RFC6020]) and with a resolution of 0.0001
seconds (0.1 ms), with lossless conversion to/from the 32-bit
NTP timestamp as per Section 6 of [RFC5905].
Observation: Reply packets will contain a DNS Response and may
contain RRs.
6.3. Method of Measurement
This category includes columns for references to relevant sections of
the RFC(s) and any supplemental information needed to ensure an
unambiguous method for implementations.
6.3.1. Reference Methods
The methodology for this metric (equivalent to Type-P-Round-trip-
Delay-Poisson-Stream) is defined as in Section 2.6 of [RFC2681] (for
singletons) and Section 3.6 of [RFC2681] (for samples) using the
Type-P and Timeout defined in the Fixed Parameters column.
The reference method distinguishes between long-delayed packets and
lost packets by implementing a maximum waiting time for packet
arrival. Tmax is the waiting time used as the threshold to declare a
response packet lost. Lost packets SHALL be designated as having
undefined delay and counted for the RLDNS metric.
The calculations on the delay (RTT) SHALL be performed on the
conditional distribution, conditioned on successful packet arrival
within Tmax. Also, when all packet delays are stored, the process
that calculates the RTT value MUST enforce the Tmax threshold on
stored values before calculations. See Section 4.1 of [RFC3393] for
details on the conditional distribution to exclude undefined values
of delay, and see Section 5 of [RFC6703] for background on this
analysis choice.
The reference method requires some way to distinguish between
different packets in a stream to establish correspondence between
sending times and receiving times for each successfully arriving
reply.
DNS messages bearing queries provide for random ID Numbers in the
Identification header field, so more than one query may be launched
while a previous request is outstanding when the ID Number is used.
Therefore, the ID Number MUST be retained at the Src and included
with each response packet to disambiguate packet reordering if it
occurs.
If a DNS Response does not arrive within Tmax, the response time
RTDNS is undefined, and RLDNS = 1. The Message ID SHALL be used to
disambiguate the successive queries that are otherwise identical.
Since the ID Number field is only 16 bits in length, it places a
limit on the number of simultaneous outstanding DNS queries during a
stress test from a single Src address.
Refer to Section 4.4 of [RFC6673] for an expanded discussion of the
instruction to "send a Type-P packet back to the Src as quickly as
possible" in Section 2.6 of [RFC2681]. However, the DNS server is
expected to perform all required functions to prepare and send a
response, so the response time will include processing time and
network delay. Section 8 of [RFC6673] presents additional
requirements that SHALL be included in the Method of Measurement for
this metric.
In addition to operations described in [RFC2681], the Src MUST parse
the DNS headers of the reply and prepare the query response
information for subsequent reporting as a measured result, along with
the round-trip delay.
6.3.2. Packet Stream Generation
This section provides details regarding packet traffic, which is used
as the basis for measurement. In IPPM Metrics, this is called the
"stream"; this stream can easily be described by providing the list
of stream Parameters.
Section 11.1.3 of [RFC2330] provides three methods to generate
Poisson sampling intervals. The reciprocal of lambda is the average
packet spacing; thus, the Runtime Parameter is
Reciprocal_lambda = 1/lambda, in seconds.
Method 3 SHALL be used. Where given a start time (Runtime
Parameter), the subsequent send times are all computed prior to
measurement by computing the pseudorandom distribution of inter-
packet send times (truncating the distribution as specified in the
Parameter Trunc), and the Src sends each packet at the computed
times.
Note that Trunc is the upper limit on inter-packet times in the
Poisson distribution. A random value greater than Trunc is set equal
to Trunc instead.
6.3.3. Traffic Filtering (Observation) Details
N/A
6.3.4. Sampling Distribution
N/A
6.3.5. Runtime Parameters and Data Format
Runtime Parameters are input factors that must be determined,
configured into the measurement system, and reported with the results
for the context to be complete.
Src: The IP address of the host in the Src Role (format
ipv4-address-no-zone value for IPv4 or ipv6-address-no-zone value
for IPv6; see Section 4 of [RFC6991]).
Dst: The IP address of the host in the Dst Role (format
ipv4-address-no-zone value for IPv4 or ipv6-address-no-zone value
for IPv6; see Section 4 of [RFC6991]).
T0: A time, the start of a measurement interval (format "date-time"
as specified in Section 5.6 of [RFC3339]; see also "date-and-time"
in Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330]. When T0 is "all-zeros", a start time is
unspecified and Tf is to be interpreted as the duration of the
measurement interval. The start time is controlled through other
means.
Tf: A time, the end of a measurement interval (format "date-time" as
specified in Section 5.6 of [RFC3339]; see also "date-and-time" in
Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330]. When T0 is "all-zeros", an ending time
and date is ignored and Tf is interpreted as the duration of the
measurement interval.
Reciprocal_lambda: Average packet interval for Poisson streams,
expressed in units of seconds, as a positive value of type
decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020])
with a resolution of 0.0001 seconds (0.1 ms), and with lossless
conversion to/from the 32-bit NTP timestamp as per Section 6 of
[RFC5905].
Trunc: Upper limit on Poisson distribution, expressed in units of
seconds, as a positive value of type decimal64 with fraction
digits = 4 (see Section 9.3 of [RFC6020]) with a resolution of
0.0001 seconds (0.1 ms), and with lossless conversion to/from the
32-bit NTP timestamp as per Section 6 of [RFC5905] (values above
this limit will be clipped and set to the limit value).
ID: The 16-bit Identifier assigned by the program that generates the
query. The ID value must vary in successive queries (a list of
IDs is needed); see Section 4.1.1 of [RFC1035]. This Identifier
is copied into the corresponding reply and can be used by the
requester (Src) to match replies with any outstanding queries.
QNAME: The domain name of the query, formatted as specified in
Section 4 of [RFC6991].
QTYPE: The query type, which will correspond to the IP address
family of the query (decimal 1 for IPv4 or 28 for IPv6), formatted
as a uint16, as per Section 9.2 of [RFC6020].
6.3.6. Roles
Src: Launches each packet and waits for return transmissions from
the Dst.
Dst: Waits for each packet from the Src and sends a return packet to
the Src.
6.4. Output
This category specifies all details of the output of measurements
using the metric.
6.4.1. Type
Raw: For each DNS query packet sent, sets of values as defined in the
next column, including the status of the response, only assigning
delay values to successful query-response pairs.
6.4.2. Reference Definition
For all outputs:
T: The time the DNS query was sent during the measurement interval
(format "date-time" as specified in Section 5.6 of [RFC3339]; see
also "date-and-time" in Section 3 of [RFC6991]). The UTC Time
Zone is required by Section 6.1 of [RFC2330].
dT: The time value of the round-trip delay to receive the DNS
Response, expressed in units of seconds, as a positive value of
type decimal64 with fraction digits = 9 (see Section 9.3 of
[RFC6020]) with a resolution of 0.000000001 seconds (1.0 ns), and
with lossless conversion to/from the 64-bit NTP timestamp as per
Section 6 of [RFC5905]. This value is undefined when the response
packet is not received at the Src within a waiting time of
Tmax seconds.
RCODE: The value of the RCODE field in the DNS Response header,
expressed as a uint64 as specified in Section 9.2 of [RFC6020].
Non-zero values convey errors in the response, and such replies
must be analyzed separately from successful requests.
Logical: The numeric value of the result is expressed as a Logical
value, where 1 = Lost and 0 = Received, as a positive value of
type uint8 (represents integer values between 0 and 255,
inclusively (see Section 9.2 of [RFC6020]). Note that for queries
with outcome 1 = Lost, dT and RCODE will be set to the maximum for
decimal64 and uint64, respectively.
6.4.3. Metric Units
RTDNS: Round-trip delay, dT, is expressed in seconds.
RLDNS: The Logical value, where 1 = Lost and 0 = Received.
6.4.4. Calibration
Section 3.7.3 of [RFC7679] provides a means to quantify the
systematic and random errors of a time measurement. Calibration in-
situ could be enabled with an internal loopback at the Source host
that includes as much of the measurement system as possible, performs
address and payload manipulation as needed, and provides some form of
isolation (e.g., deterministic delay) to avoid send-receive interface
contention. Some portion of the random and systematic error can be
characterized in this way.
When a measurement controller requests a calibration measurement, the
loopback is applied and the result is output in the same format as a
normal measurement, with an additional indication that it is a
calibration result.
Both internal loopback calibration and clock synchronization can be
used to estimate the available accuracy of the Output Metric Units.
For example, repeated loopback delay measurements will reveal the
portion of the output result resolution that is the result of system
noise and is thus inaccurate.
6.5. Administrative Items
6.5.1. Status
Current
6.5.2. Requester
RFC 8912
6.5.3. Revision
1.0
6.5.4. Revision Date
YYYY-MM-DD
2021-11-17
6.6. Comments and Remarks
None
7. UDP Poisson One-Way Delay and Loss Registry Entries
This section specifies five initial Registry Entries for UDP Poisson
One-Way Delay and one entry for UDP Poisson One-Way Loss.
All column entries besides the ID, Name, Description, and Output
Reference Method categories are the same; thus, this section defines
six closely related Registry Entries. As a result, IANA has assigned
corresponding URLs to each of the Named Metrics.
7.1. Summary
This category includes multiple indexes to the Registry Entries: the
element ID and Metric Name.
7.1.1. ID (Identifier)
IANA has allocated the numeric Identifiers 6-11 for the six Named
Metric Entries in Section 7. See Section 7.1.2 for mapping to Names.
7.1.2. Name
6:
OWDelay_Active_IP-UDP-Poisson-
Payload250B_RFC8912sec7_Seconds_95Percentile
7: OWDelay_Active_IP-UDP-Poisson-
Payload250B_RFC8912sec7_Seconds_Mean
8: OWDelay_Active_IP-UDP-Poisson-
Payload250B_RFC8912sec7_Seconds_Min
9: OWDelay_Active_IP-UDP-Poisson-
Payload250B_RFC8912sec7_Seconds_Max
10:
OWDelay_Active_IP-UDP-Poisson-
Payload250B_RFC8912sec7_Seconds_StdDev
11:
OWLoss_Active_IP-UDP-Poisson-
Payload250B_RFC8912sec7_Percent_LossRatio
7.1.3. URI
URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-
Poisson-Payload250B_RFC8912sec7_Seconds_95Percentile
URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-
Poisson-Payload250B_RFC8912sec7_Seconds_Mean
URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-
Poisson-Payload250B_RFC8912sec7_Seconds_Min
URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-
Poisson-Payload250B_RFC8912sec7_Seconds_Max
URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-
Poisson-Payload250B_RFC8912sec7_Seconds_StdDev
URL: https://www.iana.org/performance-metrics/OWLoss_Active_IP-UDP-
Poisson-Payload250B_RFC8912sec7_Percent_LossRatio
7.1.4. Description
OWDelay: This metric assesses the delay of a stream of packets
exchanged between two hosts (or measurement points) and reports
the <statistic> of one-way delay for all successfully exchanged
packets based on their conditional delay distribution.
where <statistic> is one of:
* 95Percentile
* Mean
* Min
* Max
* StdDev
OWLoss: This metric assesses the loss ratio of a stream of packets
exchanged between two hosts (which are the two measurement
points). The output is the one-way loss ratio for all transmitted
packets expressed as a percentage.
7.1.5. Change Controller
IETF
7.1.6. Version (of Registry Format)
1.0
7.2. Metric Definition
This category includes columns to prompt the entry of all necessary
details related to the metric definition, including the RFC reference
and values of input factors, called "Fixed Parameters".
7.2.1. Reference Definition
For delay:
Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton, Ed., "A
One-Way Delay Metric for IP Performance Metrics (IPPM)", STD 81,
RFC 7679, DOI 10.17487/RFC7679, January 2016, <https://www.rfc-
editor.org/info/rfc7679>. [RFC7679]
Morton, A. and E. Stephan, "Spatial Composition of Metrics", RFC
6049, DOI 10.17487/RFC6049, January 2011, <https://www.rfc-
editor.org/info/rfc6049>. [RFC6049]
Section 3.4 of [RFC7679] provides the reference definition of the
singleton (single value) one-way delay metric. Section 4.4 of
[RFC7679] provides the reference definition expanded to cover a
multi-value sample. Note that terms such as "singleton" and
"sample" are defined in Section 11 of [RFC2330].
Only successful packet transfers with finite delay are included in
the sample, as prescribed in Section 4.1.2 of [RFC6049].
For loss:
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>. [RFC7680]
Section 2.4 of [RFC7680] provides the reference definition of the
singleton (single value) one-way Loss metric. Section 3.4 of
[RFC7680] provides the reference definition expanded to cover a
multi-singleton sample. Note that terms such as "singleton" and
"sample" are defined in Section 11 of [RFC2330].
7.2.2. Fixed Parameters
Type-P:
IPv4 header values:
DSCP: Set to 0
TTL: Set to 255
Protocol: Set to 17 (UDP)
IPv6 header values:
DSCP: Set to 0
Hop Count: Set to 255
Next Header: Set to 17 (UDP)
Flow Label: Set to 0
Extension Headers: None
UDP header values:
Checksum: The checksum MUST be calculated and the non-zero
checksum included in the header
UDP Payload: TWAMP-Test packet formats (Section 4.1.2 of
[RFC5357])
Security features in use influence the number of Padding
octets
250 octets total, including the TWAMP format type, which
MUST be reported
Other measurement Parameters:
Tmax: A loss threshold waiting time with value 3.0, expressed in
units of seconds, as a positive value of type decimal64 with
fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a
resolution of 0.0001 seconds (0.1 ms), with lossless conversion
to/from the 32-bit NTP timestamp as per Section 6 of [RFC5905].
See the Packet Stream Generation section for two additional Fixed
Parameters.
7.3. Method of Measurement
This category includes columns for references to relevant sections of
the RFC(s) and any supplemental information needed to ensure an
unambiguous method for implementations.
7.3.1. Reference Methods
The methodology for this metric (equivalent to Type-P-One-way-Delay-
Poisson-Stream) is defined as in Section 3.6 of [RFC7679] (for
singletons) and Section 4.6 of [RFC7679] (for samples) using the
Type-P and Tmax defined in the Fixed Parameters column.
The reference method distinguishes between long-delayed packets and
lost packets by implementing a maximum waiting time for packet
arrival. Tmax is the waiting time used as the threshold to declare a
packet lost. Lost packets SHALL be designated as having undefined
delay and counted for the OWLoss metric.
The calculations on the one-way delay SHALL be performed on the
conditional distribution, conditioned on successful packet arrival
within Tmax. Also, when all packet delays are stored, the process
that calculates the one-way delay value MUST enforce the Tmax
threshold on stored values before calculations. See Section 4.1 of
[RFC3393] for details on the conditional distribution to exclude
undefined values of delay, and see Section 5 of [RFC6703] for
background on this analysis choice.
The reference method requires some way to distinguish between
different packets in a stream to establish correspondence between
sending times and receiving times for each successfully arriving
packet.
Since a standard measurement protocol is employed [RFC5357], the
measurement process will determine the sequence numbers or timestamps
applied to test packets after the Fixed and Runtime Parameters are
passed to that process. The measurement protocol dictates the format
of sequence numbers and timestamps conveyed in the TWAMP-Test packet
payload.
7.3.2. Packet Stream Generation
This section provides details regarding packet traffic, which is used
as the basis for measurement. In IPPM Metrics, this is called the
"stream"; this stream can easily be described by providing the list
of stream Parameters.
Section 11.1.3 of [RFC2330] provides three methods to generate
Poisson sampling intervals. The reciprocal of lambda is the average
packet spacing; thus, the Runtime Parameter is
Reciprocal_lambda = 1/lambda, in seconds.
Method 3 SHALL be used. Where given a start time (Runtime
Parameter), the subsequent send times are all computed prior to
measurement by computing the pseudorandom distribution of inter-
packet send times (truncating the distribution as specified in the
Parameter Trunc), and the Src sends each packet at the computed
times.
Note that Trunc is the upper limit on inter-packet times in the
Poisson distribution. A random value greater than Trunc is set equal
to Trunc instead.
Reciprocal_lambda: Average packet interval for Poisson streams,
expressed in units of seconds, as a positive value of type
decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020])
with a resolution of 0.0001 seconds (0.1 ms), and with lossless
conversion to/from the 32-bit NTP timestamp as per Section 6 of
[RFC5905]. Reciprocal_lambda = 1 second.
Trunc: Upper limit on Poisson distribution, expressed in units of
seconds, as a positive value of type decimal64 with fraction
digits = 4 (see Section 9.3 of [RFC6020]) with a resolution of
0.0001 seconds (0.1 ms), and with lossless conversion to/from the
32-bit NTP timestamp as per Section 6 of [RFC5905] (values above
this limit will be clipped and set to the limit value).
Trunc = 30.0000 seconds.
7.3.3. Traffic Filtering (Observation) Details
N/A
7.3.4. Sampling Distribution
N/A
7.3.5. Runtime Parameters and Data Format
Runtime Parameters are input factors that must be determined,
configured into the measurement system, and reported with the results
for the context to be complete.
Src: The IP address of the host in the Src Role (format
ipv4-address-no-zone value for IPv4 or ipv6-address-no-zone value
for IPv6; see Section 4 of [RFC6991]).
Dst: The IP address of the host in the Dst Role (format
ipv4-address-no-zone value for IPv4 or ipv6-address-no-zone value
for IPv6; see Section 4 of [RFC6991]).
T0: A time, the start of a measurement interval (format "date-time"
as specified in Section 5.6 of [RFC3339]; see also "date-and-time"
in Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330]. When T0 is "all-zeros", a start time is
unspecified and Tf is to be interpreted as the duration of the
measurement interval. The start time is controlled through other
means.
Tf: A time, the end of a measurement interval (format "date-time" as
specified in Section 5.6 of [RFC3339]; see also "date-and-time" in
Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330]. When T0 is "all-zeros", an ending time
and date is ignored and Tf is interpreted as the duration of the
measurement interval.
7.3.6. Roles
Src: Launches each packet and waits for return transmissions from
the Dst. An example is the TWAMP Session-Sender.
Dst: Waits for each packet from the Src and sends a return packet to
the Src. An example is the TWAMP Session-Reflector.
7.4. Output
This category specifies all details of the output of measurements
using the metric.
7.4.1. Type
Types are discussed in the subsections below.
7.4.2. Reference Definition
For all output types:
T0: The start of a measurement interval (format "date-time" as
specified in Section 5.6 of [RFC3339]; see also "date-and-time" in
Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330].
Tf: The end of a measurement interval (format "date-time" as
specified in Section 5.6 of [RFC3339]; see also "date-and-time" in
Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330].
For LossRatio, the count of lost packets to total packets sent is the
basis for the loss ratio calculation as per Section 4.1 of [RFC7680].
For each <statistic> or Percent_LossRatio, one of the following
subsections applies.
7.4.2.1. Percentile95
The 95th percentile SHALL be calculated using the conditional
distribution of all packets with a finite value of one-way delay
(undefined delays are excluded) -- a single value, as follows:
See Section 4.1 of [RFC3393] for details on the conditional
distribution to exclude undefined values of delay, and see Section 5
of [RFC6703] for background on this analysis choice.
See Section 4.3 of [RFC3393] for details on the percentile statistic
(where round-trip delay should be substituted for "ipdv").
The percentile = 95, meaning that the reported delay, "95Percentile",
is the smallest value of one-way delay for which the Empirical
Distribution Function, EDF(95Percentile), is greater than or equal to
95% of the singleton one-way delay values in the conditional
distribution. See Section 11.3 of [RFC2330] for the definition of
the percentile statistic using the EDF.
95Percentile: The time value of the result is expressed in units of
seconds, as a positive value of type decimal64 with fraction
digits = 9 (see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
7.4.2.2. Mean
The mean SHALL be calculated using the conditional distribution of
all packets with a finite value of one-way delay (undefined delays
are excluded) -- a single value, as follows:
See Section 4.1 of [RFC3393] for details on the conditional
distribution to exclude undefined values of delay, and see Section 5
of [RFC6703] for background on this analysis choice.
See Section 4.2.2 of [RFC6049] for details on calculating this
statistic; see also Section 4.2.3 of [RFC6049].
Mean: The time value of the result is expressed in units of seconds,
as a positive value of type decimal64 with fraction digits = 9
(see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
7.4.2.3. Min
The minimum SHALL be calculated using the conditional distribution of
all packets with a finite value of one-way delay (undefined delays
are excluded) -- a single value, as follows:
See Section 4.1 of [RFC3393] for details on the conditional
distribution to exclude undefined values of delay, and see Section 5
of [RFC6703] for background on this analysis choice.
See Section 4.3.2 of [RFC6049] for details on calculating this
statistic; see also Section 4.3.3 of [RFC6049].
Min: The time value of the result is expressed in units of seconds,
as a positive value of type decimal64 with fraction digits = 9
(see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
7.4.2.4. Max
The maximum SHALL be calculated using the conditional distribution of
all packets with a finite value of one-way delay (undefined delays
are excluded) -- a single value, as follows:
See Section 4.1 of [RFC3393] for details on the conditional
distribution to exclude undefined values of delay, and see Section 5
of [RFC6703] for background on this analysis choice.
See Section 4.3.2 of [RFC6049] for a closely related method for
calculating this statistic; see also Section 4.3.3 of [RFC6049]. The
formula is as follows:
Max = (FiniteDelay[j])
such that for some index, j, where 1 <= j <= N
FiniteDelay[j] >= FiniteDelay[n] for all n
Max: The time value of the result is expressed in units of seconds,
as a positive value of type decimal64 with fraction digits = 9
(see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
7.4.2.5. Std_Dev
The standard deviation (Std_Dev) SHALL be calculated using the
conditional distribution of all packets with a finite value of
one-way delay (undefined delays are excluded) -- a single value, as
follows:
See Section 4.1 of [RFC3393] for details on the conditional
distribution to exclude undefined values of delay, and see Section 5
of [RFC6703] for background on this analysis choice.
See Section 6.1.4 of [RFC6049] for a closely related method for
calculating this statistic. The formula is the classic calculation
for the standard deviation of a population.
Define Population Std_Dev_Delay as follows:
_ _
| N |
| --- |
| 1 \ 2 |
Std_Dev = SQRT | ------- > (Delay[n] - MeanDelay) |
| (N) / |
| --- |
| n = 1 |
|_ _|
where all packets n = 1 through N have a value for Delay[n],
MeanDelay is calculated per Section 7.4.2.2, and SQRT[] is the Square
Root function:
Std_Dev: The time value of the result is expressed in units of
seconds, as a positive value of type decimal64 with fraction
digits = 9 (see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
7.4.2.6. Percent_LossRatio
Percent_LossRatio: The numeric value of the result is expressed in
units of lost packets to total packets times 100%, as a positive
value of type decimal64 with fraction digits = 9 (see Section 9.3
of [RFC6020]) with a resolution of 0.0000000001.
7.4.3. Metric Units
The <statistic> of one-way delay is expressed in seconds, where
<statistic> is one of:
* 95Percentile
* Mean
* Min
* Max
* StdDev
The one-way loss ratio is expressed as a percentage of lost packets
to total packets sent.
7.4.4. Calibration
Section 3.7.3 of [RFC7679] provides a means to quantify the
systematic and random errors of a time measurement. Calibration in-
situ could be enabled with an internal loopback that includes as much
of the measurement system as possible, performs address manipulation
as needed, and provides some form of isolation (e.g., deterministic
delay) to avoid send-receive interface contention. Some portion of
the random and systematic error can be characterized in this way.
For one-way delay measurements, the error calibration must include an
assessment of the internal clock synchronization with its external
reference (this internal clock is supplying timestamps for
measurement). In practice, the time offsets [RFC5905] of clocks at
both the Source and Destination are needed to estimate the systematic
error due to imperfect clock synchronization (the time offsets
[RFC5905] are smoothed; thus, the random variation is not usually
represented in the results).
time_offset: The time value of the result is expressed in units of
seconds, as a signed value of type decimal64 with fraction
digits = 9 (see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
When a measurement controller requests a calibration measurement, the
loopback is applied and the result is output in the same format as a
normal measurement, with an additional indication that it is a
calibration result. In any measurement, the measurement function
SHOULD report its current estimate of the time offset [RFC5905] as an
indicator of the degree of synchronization.
Both internal loopback calibration and clock synchronization can be
used to estimate the available accuracy of the Output Metric Units.
For example, repeated loopback delay measurements will reveal the
portion of the output result resolution that is the result of system
noise and is thus inaccurate.
7.5. Administrative Items
7.5.1. Status
Current
7.5.2. Requester
RFC 8912
7.5.3. Revision
1.0
7.5.4. Revision Date
YYYY-MM-DD
2021-11-17
7.6. Comments and Remarks
None
8. UDP Periodic One-Way Delay and Loss Registry Entries
This section specifies five initial Registry Entries for UDP Periodic
One-Way Delay and one entry for UDP Periodic One-Way Loss.
All column entries besides the ID, Name, Description, and Output
Reference Method categories are the same; thus, this section defines
six closely related Registry Entries. As a result, IANA has assigned
corresponding URLs to each of the six Named Metrics.
8.1. Summary
This category includes multiple indexes to the Registry Entries: the
element ID and Metric Name.
8.1.1. ID (Identifier)
IANA has allocated the numeric Identifiers 12-17 for the six Named
Metric Entries in Section 8. See Section 8.1.2 for mapping to Names.
8.1.2. Name
12:
OWDelay_Active_IP-UDP-Periodic20m-
Payload142B_RFC8912sec8_Seconds_95Percentile
13:
OWDelay_Active_IP-UDP-Periodic20m-
Payload142B_RFC8912sec8_Seconds_Mean
14:
OWDelay_Active_IP-UDP-Periodic20m-
Payload142B_RFC8912sec8_Seconds_Min
15:
OWDelay_Active_IP-UDP-Periodic20m-
Payload142B_RFC8912sec8_Seconds_Max
16:
OWDelay_Active_IP-UDP-Periodic20m-
Payload142B_RFC8912sec8_Seconds_StdDev
17:
OWLoss_Active_IP-UDP-Periodic20m-
Payload142B_RFC8912sec8_Percent_LossRatio
8.1.3. URI
URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-
Periodic20m-Payload142B_RFC8912sec8_Seconds_95Percentile
URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-
Periodic20m-Payload142B_RFC8912sec8_Seconds_Mean
URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-
Periodic20m-Payload142B_RFC8912sec8_Seconds_Min
URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-
Periodic20m-Payload142B_RFC8912sec8_Seconds_Max
URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-
Periodic20m-Payload142B_RFC8912sec8_Seconds_StdDev
URL: https://www.iana.org/performance-metrics/OWLoss_Active_IP-UDP-
Periodic20m-Payload142B_RFC8912sec8_Percent_LossRatio
8.1.4. Description
OWDelay: This metric assesses the delay of a stream of packets
exchanged between two hosts (or measurement points) and reports
the <statistic> of one-way delay for all successfully exchanged
packets based on their conditional delay distribution.
where <statistic> is one of:
* 95Percentile
* Mean
* Min
* Max
* StdDev
OWLoss: This metric assesses the loss ratio of a stream of packets
exchanged between two hosts (which are the two measurement
points). The output is the one-way loss ratio for all transmitted
packets expressed as a percentage.
8.1.5. Change Controller
IETF
8.1.6. Version (of Registry Format)
1.0
8.2. Metric Definition
This category includes columns to prompt the entry of all necessary
details related to the metric definition, including the RFC reference
and values of input factors, called "Fixed Parameters".
8.2.1. Reference Definition
For delay:
Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton, Ed., "A
One-Way Delay Metric for IP Performance Metrics (IPPM)", STD 81,
RFC 7679, DOI 10.17487/RFC7679, January 2016, <https://www.rfc-
editor.org/info/rfc7679>. [RFC7679]
Morton, A. and E. Stephan, "Spatial Composition of Metrics", RFC
6049, DOI 10.17487/RFC6049, January 2011, <https://www.rfc-
editor.org/info/rfc6049>. [RFC6049]
Section 3.4 of [RFC7679] provides the reference definition of the
singleton (single value) one-way delay metric. Section 4.4 of
[RFC7679] provides the reference definition expanded to cover a
multi-value sample. Note that terms such as "singleton" and
"sample" are defined in Section 11 of [RFC2330].
Only successful packet transfers with finite delay are included in
the sample, as prescribed in Section 4.1.2 of [RFC6049].
For loss:
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>. [RFC7680]
Section 2.4 of [RFC7680] provides the reference definition of the
singleton (single value) one-way Loss metric. Section 3.4 of
[RFC7680] provides the reference definition expanded to cover a
multi-singleton sample. Note that terms such as "singleton" and
"sample" are defined in Section 11 of [RFC2330].
8.2.2. Fixed Parameters
Type-P:
IPv4 header values:
DSCP: Set to 0
TTL: Set to 255
Protocol: Set to 17 (UDP)
IPv6 header values:
DSCP: Set to 0
Hop Count: Set to 255
Next Header: Set to 17 (UDP)
Flow Label: Set to 0
Extension Headers: None
UDP header values:
Checksum: The checksum MUST be calculated and the non-zero
checksum included in the header
UDP Payload: TWAMP-Test packet formats (Section 4.1.2 of
[RFC5357])
Security features in use influence the number of Padding
octets
142 octets total, including the TWAMP format (and format
type MUST be reported, if used)
Other measurement Parameters:
Tmax: A loss threshold waiting time with value 3.0, expressed in
units of seconds, as a positive value of type decimal64 with
fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a
resolution of 0.0001 seconds (0.1 ms), with lossless conversion
to/from the 32-bit NTP timestamp as per Section 6 of [RFC5905].
See the Packet Stream Generation section for three additional Fixed
Parameters.
8.3. Method of Measurement
This category includes columns for references to relevant sections of
the RFC(s) and any supplemental information needed to ensure an
unambiguous method for implementations.
8.3.1. Reference Methods
The methodology for this metric (equivalent to Type-P-One-way-Delay-
Poisson-Stream) is defined as in Section 3.6 of [RFC7679] (for
singletons) and Section 4.6 of [RFC7679] (for samples) using the
Type-P and Tmax defined in the Fixed Parameters column. However, a
Periodic stream is used, as defined in [RFC3432].
The reference method distinguishes between long-delayed packets and
lost packets by implementing a maximum waiting time for packet
arrival. Tmax is the waiting time used as the threshold to declare a
packet lost. Lost packets SHALL be designated as having undefined
delay and counted for the OWLoss metric.
The calculations on the one-way delay SHALL be performed on the
conditional distribution, conditioned on successful packet arrival
within Tmax. Also, when all packet delays are stored, the process
that calculates the one-way delay value MUST enforce the Tmax
threshold on stored values before calculations. See Section 4.1 of
[RFC3393] for details on the conditional distribution to exclude
undefined values of delay, and see Section 5 of [RFC6703] for
background on this analysis choice.
The reference method requires some way to distinguish between
different packets in a stream to establish correspondence between
sending times and receiving times for each successfully arriving
packet.
Since a standard measurement protocol is employed [RFC5357], the
measurement process will determine the sequence numbers or timestamps
applied to test packets after the Fixed and Runtime Parameters are
passed to that process. The measurement protocol dictates the format
of sequence numbers and timestamps conveyed in the TWAMP-Test packet
payload.
8.3.2. Packet Stream Generation
This section provides details regarding packet traffic, which is used
as the basis for measurement. In IPPM Metrics, this is called the
"stream"; this stream can easily be described by providing the list
of stream Parameters.
Section 3 of [RFC3432] prescribes the method for generating Periodic
streams using associated Parameters.
incT: The nominal duration of the inter-packet interval, first bit
to first bit, with value 0.0200, expressed in units of seconds, as
a positive value of type decimal64 with fraction digits = 4 (see
Section 9.3 of [RFC6020]) and with a resolution of 0.0001 seconds
(0.1 ms), with lossless conversion to/from the 32-bit NTP
timestamp as per Section 6 of [RFC5905].
dT: The duration of the interval for allowed sample start times,
with value 1.0000, expressed in units of seconds, as a positive
value of type decimal64 with fraction digits = 4 (see Section 9.3
of [RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms),
with lossless conversion to/from the 32-bit NTP timestamp as per
Section 6 of [RFC5905].
T0: The actual start time of the periodic stream, determined from T0
and dT.
Note: An initiation process with a number of control exchanges
resulting in unpredictable start times (within a time interval)
may be sufficient to avoid synchronization of periodic streams and
is a valid replacement for selecting a start time at random from a
fixed interval.
These stream Parameters will be specified as Runtime Parameters.
8.3.3. Traffic Filtering (Observation) Details
N/A
8.3.4. Sampling Distribution
N/A
8.3.5. Runtime Parameters and Data Format
Runtime Parameters are input factors that must be determined,
configured into the measurement system, and reported with the results
for the context to be complete.
Src: The IP address of the host in the Src Role (format
ipv4-address-no-zone value for IPv4 or ipv6-address-no-zone value
for IPv6; see Section 4 of [RFC6991]).
Dst: The IP address of the host in the Dst Role (format
ipv4-address-no-zone value for IPv4 or ipv6-address-no-zone value
for IPv6; see Section 4 of [RFC6991]).
T0: A time, the start of a measurement interval (format "date-time"
as specified in Section 5.6 of [RFC3339]; see also "date-and-time"
in Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330]. When T0 is "all-zeros", a start time is
unspecified and Tf is to be interpreted as the duration of the
measurement interval. The start time is controlled through other
means.
Tf: A time, the end of a measurement interval (format "date-time" as
specified in Section 5.6 of [RFC3339]; see also "date-and-time" in
Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330]. When T0 is "all-zeros", an ending time
and date is ignored and Tf is interpreted as the duration of the
measurement interval.
8.3.6. Roles
Src: Launches each packet and waits for return transmissions from
the Dst. An example is the TWAMP Session-Sender.
Dst: Waits for each packet from the Src and sends a return packet to
the Src. An example is the TWAMP Session-Reflector.
8.4. Output
This category specifies all details of the output of measurements
using the metric.
8.4.1. Type
Latency and Loss Types are discussed in the subsections below.
8.4.2. Reference Definition
For all output types:
T0: The start of a measurement interval (format "date-time" as
specified in Section 5.6 of [RFC3339]; see also "date-and-time" in
Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330].
Tf: The end of a measurement interval (format "date-time" as
specified in Section 5.6 of [RFC3339]; see also "date-and-time" in
Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330].
For LossRatio, the count of lost packets to total packets sent is the
basis for the loss ratio calculation as per Section 4.1 of [RFC7680].
For each <statistic> or Percent_LossRatio, one of the following
subsections applies.
8.4.2.1. Percentile95
The 95th percentile SHALL be calculated using the conditional
distribution of all packets with a finite value of one-way delay
(undefined delays are excluded) -- a single value, as follows:
See Section 4.1 of [RFC3393] for details on the conditional
distribution to exclude undefined values of delay, and see Section 5
of [RFC6703] for background on this analysis choice.
See Section 4.3 of [RFC3393] for details on the percentile statistic
(where round-trip delay should be substituted for "ipdv").
The percentile = 95, meaning that the reported delay, "95Percentile",
is the smallest value of one-way delay for which the Empirical
Distribution Function, EDF(95Percentile), is greater than or equal to
95% of the singleton one-way delay values in the conditional
distribution. See Section 11.3 of [RFC2330] for the definition of
the percentile statistic using the EDF.
95Percentile: The time value of the result is expressed in units of
seconds, as a positive value of type decimal64 with fraction
digits = 9 (see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
8.4.2.2. Mean
The mean SHALL be calculated using the conditional distribution of
all packets with a finite value of one-way delay (undefined delays
are excluded) -- a single value, as follows:
See Section 4.1 of [RFC3393] for details on the conditional
distribution to exclude undefined values of delay, and see Section 5
of [RFC6703] for background on this analysis choice.
See Section 4.2.2 of [RFC6049] for details on calculating this
statistic; see also Section 4.2.3 of [RFC6049].
Mean: The time value of the result is expressed in units of seconds,
as a positive value of type decimal64 with fraction digits = 9
(see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
8.4.2.3. Min
The minimum SHALL be calculated using the conditional distribution of
all packets with a finite value of one-way delay (undefined delays
are excluded) -- a single value, as follows:
See Section 4.1 of [RFC3393] for details on the conditional
distribution to exclude undefined values of delay, and see Section 5
of [RFC6703] for background on this analysis choice.
See Section 4.3.2 of [RFC6049] for details on calculating this
statistic; see also Section 4.3.3 of [RFC6049].
Min: The time value of the result is expressed in units of seconds,
as a positive value of type decimal64 with fraction digits = 9
(see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
8.4.2.4. Max
The maximum SHALL be calculated using the conditional distribution of
all packets with a finite value of one-way delay (undefined delays
are excluded) -- a single value, as follows:
See Section 4.1 of [RFC3393] for details on the conditional
distribution to exclude undefined values of delay, and see Section 5
of [RFC6703] for background on this analysis choice.
See Section 4.3.2 of [RFC6049] for a closely related method for
calculating this statistic; see also Section 4.3.3 of [RFC6049]. The
formula is as follows:
Max = (FiniteDelay[j])
such that for some index, j, where 1 <= j <= N
FiniteDelay[j] >= FiniteDelay[n] for all n
Max: The time value of the result is expressed in units of seconds,
as a positive value of type decimal64 with fraction digits = 9
(see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
8.4.2.5. Std_Dev
Std_Dev SHALL be calculated using the conditional distribution of all
packets with a finite value of one-way delay (undefined delays are
excluded) -- a single value, as follows:
See Section 4.1 of [RFC3393] for details on the conditional
distribution to exclude undefined values of delay, and see Section 5
of [RFC6703] for background on this analysis choice.
See Section 6.1.4 of [RFC6049] for a closely related method for
calculating this statistic. The formula is the classic calculation
for the standard deviation of a population.
Define Population Std_Dev_Delay as follows:
_ _
| N |
| --- |
| 1 \ 2 |
Std_Dev = SQRT | ------- > (Delay[n] - MeanDelay) |
| (N) / |
| --- |
| n = 1 |
|_ _|
where all packets n = 1 through N have a value for Delay[n],
MeanDelay is calculated per Section 8.4.2.2, and SQRT[] is the Square
Root function:
Std_Dev: The time value of the result is expressed in units of
seconds, as a positive value of type decimal64 with fraction
digits = 9 (see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
8.4.2.6. Percent_LossRatio
Percent_LossRatio: The numeric value of the result is expressed in
units of lost packets to total packets times 100%, as a positive
value of type decimal64 with fraction digits = 9 (see Section 9.3
of [RFC6020] with a resolution of 0.0000000001.
8.4.3. Metric Units
The <statistic> of one-way delay is expressed in seconds, where
<statistic> is one of:
* 95Percentile
* Mean
* Min
* Max
* StdDev
The one-way loss ratio is expressed as a percentage of lost packets
to total packets sent.
8.4.4. Calibration
Section 3.7.3 of [RFC7679] provides a means to quantify the
systematic and random errors of a time measurement. Calibration in-
situ could be enabled with an internal loopback that includes as much
of the measurement system as possible, performs address manipulation
as needed, and provides some form of isolation (e.g., deterministic
delay) to avoid send-receive interface contention. Some portion of
the random and systematic error can be characterized in this way.
For one-way delay measurements, the error calibration must include an
assessment of the internal clock synchronization with its external
reference (this internal clock is supplying timestamps for
measurement). In practice, the time offsets [RFC5905] of clocks at
both the Source and Destination are needed to estimate the systematic
error due to imperfect clock synchronization (the time offsets
[RFC5905] are smoothed; thus, the random variation is not usually
represented in the results).
time_offset: The time value of the result is expressed in units of
seconds, as a signed value of type decimal64 with fraction
digits = 9 (see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
When a measurement controller requests a calibration measurement, the
loopback is applied and the result is output in the same format as a
normal measurement, with an additional indication that it is a
calibration result. In any measurement, the measurement function
SHOULD report its current estimate of the time offset [RFC5905] as an
indicator of the degree of synchronization.
Both internal loopback calibration and clock synchronization can be
used to estimate the available accuracy of the Output Metric Units.
For example, repeated loopback delay measurements will reveal the
portion of the output result resolution that is the result of system
noise and is thus inaccurate.
8.5. Administrative Items
8.5.1. Status
Current
8.5.2. Requester
RFC 8912
8.5.3. Revision
1.0
8.5.4. Revision Date
YYYY-MM-DD
2021-11-17
8.6. Comments and Remarks
None
9. ICMP Round-Trip Latency and Loss Registry Entries
This section specifies three initial Registry Entries for ICMP
Round-Trip Latency and another entry for the ICMP Round-Trip Loss
Ratio.
All column entries besides the ID, Name, Description, and Output
Reference Method categories are the same; thus, this section defines
four closely related Registry Entries. As a result, IANA has
assigned corresponding URLs to each of the four Named Metrics.
9.1. Summary
This category includes multiple indexes to the Registry Entries: the
element ID and Metric Name.
9.1.1. ID (Identifier)
IANA has allocated the numeric Identifiers 18-21 for the four Named
Metric Entries in Section 9. See Section 9.1.2 for mapping to Names.
9.1.2. Name
18: RTDelay_Active_IP-ICMP-SendOnRcv_RFC8912sec9_Seconds_Mean
19: RTDelay_Active_IP-ICMP-SendOnRcv_RFC8912sec9_Seconds_Min
20: RTDelay_Active_IP-ICMP-SendOnRcv_RFC8912sec9_Seconds_Max
21: RTLoss_Active_IP-ICMP-SendOnRcv_RFC8912sec9_Percent_LossRatio
9.1.3. URI
URL: https://www.iana.org/performance-metrics/RTDelay_Active_IP-ICMP-
SendOnRcv_RFC8912sec9_Seconds_Mean
URL: https://www.iana.org/performance-metrics/RTDelay_Active_IP-ICMP-
SendOnRcv_RFC8912sec9_Seconds_Min
URL: https://www.iana.org/performance-metrics/RTDelay_Active_IP-ICMP-
SendOnRcv_RFC8912sec9_Seconds_Max
URL: https://www.iana.org/performance-metrics/RTLoss_Active_IP-ICMP-
SendOnRcv_RFC8912sec9_Percent_LossRatio
9.1.4. Description
RTDelay: This metric assesses the delay of a stream of ICMP packets
exchanged between two hosts (which are the two measurement
points). The output is the round-trip delay for all successfully
exchanged packets expressed as the <statistic> of their
conditional delay distribution, where <statistic> is one of:
* Mean
* Min
* Max
RTLoss: This metric assesses the loss ratio of a stream of ICMP
packets exchanged between two hosts (which are the two measurement
points). The output is the round-trip loss ratio for all
transmitted packets expressed as a percentage.
9.1.5. Change Controller
IETF
9.1.6. Version (of Registry Format)
1.0
9.2. Metric Definition
This category includes columns to prompt the entry of all necessary
details related to the metric definition, including the RFC reference
and values of input factors, called "Fixed Parameters".
9.2.1. Reference Definition
For delay:
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>. [RFC2681]
Section 2.4 of [RFC2681] provides the reference definition of the
singleton (single value) round-trip delay metric. Section 3.4 of
[RFC2681] provides the reference definition expanded to cover a
multi-singleton sample. Note that terms such as "singleton" and
"sample" are defined in Section 11 of [RFC2330].
Note that although the definition of round-trip delay between the
Source (Src) and the Destination (Dst) as provided in Section 2.4
of [RFC2681] is directionally ambiguous in the text, this metric
tightens the definition further to recognize that the host in the
Src Role will send the first packet to the host in the Dst Role
and will ultimately receive the corresponding return packet from
the Dst (when neither is lost).
Finally, note that the variable "dT" is used in [RFC2681] to refer
to the value of round-trip delay in metric definitions and
methods. The variable "dT" has been reused in other IPPM
literature to refer to different quantities and cannot be used as
a global variable name.
For loss:
Morton, A., "Round-Trip Packet Loss Metrics", RFC 6673, DOI
10.17487/RFC6673, August 2012, <https://www.rfc-editor.org/info/
rfc6673>. [RFC6673]
Both Delay and Loss metrics employ a maximum waiting time for
received packets, so the count of lost packets to total packets sent
is the basis for the loss ratio calculation as per Section 6.1 of
[RFC6673].
9.2.2. Fixed Parameters
Type-P as defined in Section 13 of [RFC2330]:
IPv4 header values:
DSCP: Set to 0
TTL: Set to 255
Protocol: Set to 01 (ICMP)
IPv6 header values:
DSCP: Set to 0
Hop Count: Set to 255
Next Header: Set to 128 decimal (ICMP)
Flow Label: Set to 0
Extension Headers: None
ICMP header values:
Type: 8 (Echo Request)
Code: 0
Checksum: The checksum MUST be calculated and the non-zero
checksum included in the header
(Identifier and sequence number set at runtime)
ICMP Payload:
Total of 32 bytes of random information, constant per test
Other measurement Parameters:
Tmax: A loss threshold waiting time with value 3.0, expressed in
units of seconds, as a positive value of type decimal64 with
fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a
resolution of 0.0001 seconds (0.1 ms), with lossless conversion
to/from the 32-bit NTP timestamp as per Section 6 of [RFC5905].
9.3. Method of Measurement
This category includes columns for references to relevant sections of
the RFC(s) and any supplemental information needed to ensure an
unambiguous method for implementations.
9.3.1. Reference Methods
The methodology for this metric (equivalent to Type-P-Round-trip-
Delay-Poisson-Stream) is defined as in Section 2.6 of [RFC2681] (for
singletons) and Section 3.6 of [RFC2681] (for samples) using the
Type-P and Tmax defined in the Fixed Parameters column.
The reference method distinguishes between long-delayed packets and
lost packets by implementing a maximum waiting time for packet
arrival. Tmax is the waiting time used as the threshold to declare a
packet lost. Lost packets SHALL be designated as having undefined
delay and counted for the RTLoss metric.
The calculations on the delay (RTD) SHALL be performed on the
conditional distribution, conditioned on successful packet arrival
within Tmax. Also, when all packet delays are stored, the process
that calculates the RTD value MUST enforce the Tmax threshold on
stored values before calculations. See Section 4.1 of [RFC3393] for
details on the conditional distribution to exclude undefined values
of delay, and see Section 5 of [RFC6703] for background on this
analysis choice.
The reference method requires some way to distinguish between
different packets in a stream to establish correspondence between
sending times and receiving times for each successfully arriving
packet. Sequence numbers or other send-order identification MUST be
retained at the Src or included with each packet to disambiguate
packet reordering if it occurs.
The measurement process will determine the sequence numbers applied
to test packets after the Fixed and Runtime Parameters are passed to
that process. The ICMP measurement process and protocol will dictate
the format of sequence numbers and other Identifiers.
Refer to Section 4.4 of [RFC6673] for an expanded discussion of the
instruction to "send a Type-P packet back to the Src as quickly as
possible" in Section 2.6 of [RFC2681]. Section 8 of [RFC6673]
presents additional requirements that MUST be included in the Method
of Measurement for this metric.
9.3.2. Packet Stream Generation
This section provides details regarding packet traffic, which is used
as the basis for measurement. In IPPM Metrics, this is called the
"stream"; this stream can easily be described by providing the list
of stream Parameters.
The ICMP metrics use a sending discipline called "SendOnRcv" or Send
On Receive. This is a modification of Section 3 of [RFC3432], which
prescribes the method for generating Periodic streams using
associated Parameters as defined below for this description:
incT: The nominal duration of the inter-packet interval, first bit
to first bit.
dT: The duration of the interval for allowed sample start times.
The incT stream Parameter will be specified as a Runtime Parameter,
and dT is not used in SendOnRcv.
A SendOnRcv sender behaves exactly like a Periodic stream generator
while all reply packets arrive with RTD < incT, and the inter-packet
interval will be constant.
If a reply packet arrives with RTD >= incT, then the inter-packet
interval for the next sending time is nominally RTD.
If a reply packet fails to arrive within Tmax, then the inter-packet
interval for the next sending time is nominally Tmax.
If an immediate Send On Reply arrival is desired, then set incT = 0.
9.3.3. Traffic Filtering (Observation) Details
N/A
9.3.4. Sampling Distribution
N/A
9.3.5. Runtime Parameters and Data Format
Runtime Parameters are input factors that must be determined,
configured into the measurement system, and reported with the results
for the context to be complete.
Src: The IP address of the host in the Src Role (format
ipv4-address-no-zone value for IPv4 or ipv6-address-no-zone value
for IPv6; see Section 4 of [RFC6991]).
Dst: The IP address of the host in the Dst Role (format
ipv4-address-no-zone value for IPv4 or ipv6-address-no-zone value
for IPv6; see Section 4 of [RFC6991]).
incT: The nominal duration of the inter-packet interval, first bit
to first bit, expressed in units of seconds, as a positive value
of type decimal64 with fraction digits = 4 (see Section 9.3 of
[RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms).
T0: A time, the start of a measurement interval (format "date-time"
as specified in Section 5.6 of [RFC3339]; see also "date-and-time"
in Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330]. When T0 is "all-zeros", a start time is
unspecified and Tf is to be interpreted as the duration of the
measurement interval. The start time is controlled through other
means.
Count: The total count of ICMP Echo Requests to send, formatted as a
uint16, as per Section 9.2 of [RFC6020].
See the Packet Stream Generation section for additional Runtime
Parameters.
9.3.6. Roles
Src: Launches each packet and waits for return transmissions from
the Dst.
Dst: Waits for each packet from the Src and sends a return packet to
the Src (ICMP Echo Reply, Type 0).
9.4. Output
This category specifies all details of the output of measurements
using the metric.
9.4.1. Type
Latency and Loss Types are discussed in the subsections below.
9.4.2. Reference Definition
For all output types:
T0: The start of a measurement interval (format "date-time" as
specified in Section 5.6 of [RFC3339]; see also "date-and-time" in
Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330].
Tf: The end of a measurement interval (format "date-time" as
specified in Section 5.6 of [RFC3339]; see also "date-and-time" in
Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330].
TotalCount: The count of packets actually sent by the Src to the Dst
during the measurement interval.
For each <statistic> or Percent_LossRatio, one of the following
subsections applies.
9.4.2.1. Mean
The mean SHALL be calculated using the conditional distribution of
all packets with a finite value of round-trip delay (undefined delays
are excluded) -- a single value, as follows:
See Section 4.1 of [RFC3393] for details on the conditional
distribution to exclude undefined values of delay, and see Section 5
of [RFC6703] for background on this analysis choice.
See Section 4.2.2 of [RFC6049] for details on calculating this
statistic; see also Section 4.2.3 of [RFC6049].
Mean: The time value of the result is expressed in units of seconds,
as a positive value of type decimal64 with fraction digits = 9
(see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
9.4.2.2. Min
The minimum SHALL be calculated using the conditional distribution of
all packets with a finite value of round-trip delay (undefined delays
are excluded) -- a single value, as follows:
See Section 4.1 of [RFC3393] for details on the conditional
distribution to exclude undefined values of delay, and see Section 5
of [RFC6703] for background on this analysis choice.
See Section 4.3.2 of [RFC6049] for details on calculating this
statistic; see also Section 4.3.3 of [RFC6049].
Min: The time value of the result is expressed in units of seconds,
as a positive value of type decimal64 with fraction digits = 9
(see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
9.4.2.3. Max
The maximum SHALL be calculated using the conditional distribution of
all packets with a finite value of round-trip delay (undefined delays
are excluded) -- a single value, as follows:
See Section 4.1 of [RFC3393] for details on the conditional
distribution to exclude undefined values of delay, and see Section 5
of [RFC6703] for background on this analysis choice.
See Section 4.3.2 of [RFC6049] for a closely related method for
calculating this statistic; see also Section 4.3.3 of [RFC6049]. The
formula is as follows:
Max = (FiniteDelay[j])
such that for some index, j, where 1 <= j <= N
FiniteDelay[j] >= FiniteDelay[n] for all n
Max: The time value of the result is expressed in units of seconds,
as a positive value of type decimal64 with fraction digits = 9
(see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
9.4.2.4. Percent_LossRatio
For LossRatio, the count of lost packets to total packets sent is the
basis for the loss ratio calculation as per Section 4.1 of [RFC7680].
Percent_LossRatio: The numeric value of the result is expressed in
units of lost packets to total packets times 100%, as a positive
value of type decimal64 with fraction digits = 9 (see Section 9.3
of [RFC6020]) with a resolution of 0.0000000001.
9.4.3. Metric Units
The <statistic> of round-trip delay is expressed in seconds, where
<statistic> is one of:
* Mean
* Min
* Max
The round-trip loss ratio is expressed as a percentage of lost
packets to total packets sent.
9.4.4. Calibration
Section 3.7.3 of [RFC7679] provides a means to quantify the
systematic and random errors of a time measurement. Calibration in-
situ could be enabled with an internal loopback at the Source host
that includes as much of the measurement system as possible, performs
address manipulation as needed, and provides some form of isolation
(e.g., deterministic delay) to avoid send-receive interface
contention. Some portion of the random and systematic error can be
characterized in this way.
When a measurement controller requests a calibration measurement, the
loopback is applied and the result is output in the same format as a
normal measurement, with an additional indication that it is a
calibration result.
Both internal loopback calibration and clock synchronization can be
used to estimate the available accuracy of the Output Metric Units.
For example, repeated loopback delay measurements will reveal the
portion of the output result resolution that is the result of system
noise and is thus inaccurate.
9.5. Administrative Items
9.5.1. Status
Current
9.5.2. Requester
RFC 8912
9.5.3. Revision
1.0
9.5.4. Revision Date
YYYY-MM-DD
2021-11-17
9.6. Comments and Remarks
None
10. TCP Round-Trip Delay and Loss Registry Entries
This section specifies four initial Registry Entries for the Passive
assessment of TCP Round-Trip Delay (RTD) and another entry for the
TCP Round-Trip Loss Count.
All column entries besides the ID, Name, Description, and Output
Reference Method categories are the same; thus, this section defines
four closely related Registry Entries. As a result, IANA has
assigned corresponding URLs to each of the four Named Metrics.
10.1. Summary
This category includes multiple indexes to the Registry Entries: the
element ID and Metric Name.
10.1.1. ID (Identifier)
IANA has allocated the numeric Identifiers 22-26 for the five Named
Metric Entries in Section 10. See Section 10.1.2 for mapping to
Names.
10.1.2. Name
22: RTDelay_Passive_IP-TCP_RFC8912sec10_Seconds_Mean
23: RTDelay_Passive_IP-TCP_RFC8912sec10_Seconds_Min
24: RTDelay_Passive_IP-TCP_RFC8912sec10_Seconds_Max
25: RTDelay_Passive_IP-TCP-HS_RFC8912sec10_Seconds_Singleton
Note that a midpoint observer only has the opportunity to compose a
single RTDelay on the TCP handshake.
26: RTLoss_Passive_IP-TCP_RFC8912sec10_Packet_Count
10.1.3. URI
URL: https://www.iana.org/performance-metrics/RTDelay_Passive_IP-
TCP_RFC8912sec10_Seconds_Mean
URL: https://www.iana.org/performance-metrics/RTDelay_Passive_IP-
TCP_RFC8912sec10_Seconds_Min
URL: https://www.iana.org/performance-metrics/RTDelay_Passive_IP-
TCP_RFC8912sec10_Seconds_Max
URL: https://www.iana.org/performance-metrics/RTDelay_Passive_IP-TCP-
HS_RFC8912sec10_Seconds_Singleton
URL: https://www.iana.org/performance-metrics/RTLoss_Passive_IP-
TCP_RFC8912sec10_Packet_Count
10.1.4. Description
RTDelay: This metric assesses the round-trip delay of TCP packets
constituting a single connection, exchanged between two hosts. We
consider the measurement of round-trip delay based on a single
Observation Point (OP) [RFC7011] somewhere in the network. The
output is the round-trip delay for all successfully exchanged
packets expressed as the <statistic> of their conditional delay
distribution, where <statistic> is one of:
* Mean
* Min
* Max
RTDelay Singleton: This metric assesses the round-trip delay of TCP
packets initiating a single connection (or 3-way handshake),
exchanged between two hosts. We consider the measurement of
round-trip delay based on a single Observation Point (OP)
[RFC7011] somewhere in the network. The output is the single
measurement of Round-trip delay, or Singleton.
RTLoss: This metric assesses the estimated loss count for TCP
packets constituting a single connection, exchanged between two
hosts. We consider the measurement of round-trip delay based on a
single OP [RFC7011] somewhere in the network. The output is the
estimated loss count for the measurement interval.
10.1.5. Change Controller
IETF
10.1.6. Version (of Registry Format)
1.0
10.2. Metric Definition
This category includes columns to prompt the entry of all necessary
details related to the metric definition, including the RFC reference
and values of input factors, called "Fixed Parameters".
10.2.1. Reference Definition
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>. [RFC2681]
Although there is no RFC that describes Passive Measurement of round-
trip delay, the parallel definition for Active Measurement is
provided in [RFC2681].
This metric definition uses the term "wire time" as defined in
Section 10.2 of [RFC2330], and the terms "singleton" and "sample" as
defined in Section 11 of [RFC2330]. (Section 2.4 of [RFC2681]
provides the reference definition of the singleton (single value)
round-trip delay metric. Section 3.4 of [RFC2681] provides the
reference definition expanded to cover a multi-singleton sample.)
With the OP [RFC7011] typically located between the hosts
participating in the TCP connection, the round-trip delay metric
requires two individual measurements between the OP and each host,
such that the Spatial Composition [RFC6049] of the measurements
yields a round-trip delay singleton (we are extending the composition
of one-way subpath delays to subpath round-trip delay).
Using the direction of TCP SYN transmission to anchor the
nomenclature, host A sends the SYN, and host B replies with SYN-ACK
during connection establishment. The direction of SYN transfer is
considered the Forward direction of transmission, from A through the
OP to B (the Reverse direction is B through the OP to A).
Traffic Filters reduce the packet streams at the OP to a Qualified
bidirectional flow of packets.
In the definitions below, Corresponding Packets are transferred in
different directions and convey a common value in a TCP header field
that establishes correspondence (to the extent possible). Examples
may be found in the TCP timestamp fields.
For a real number, RTD_fwd, >> the round-trip delay in the Forward
direction from the OP to host B at time T' is RTD_fwd << it is
REQUIRED that the OP observed a Qualified Packet to host B at wire
time T', that host B received that packet and sent a Corresponding
Packet back to host A, and the OP observed the Corresponding Packet
at wire time T' + RTD_fwd.
For a real number, RTD_rev, >> the round-trip delay in the Reverse
direction from the OP to host A at time T'' is RTD_rev << it is
REQUIRED that the OP observed a Qualified Packet to host A at wire
time T'', that host A received that packet and sent a Corresponding
Packet back to host B, and that the OP observed the Corresponding
Packet at wire time T'' + RTD_rev.
Ideally, the packet sent from host B to host A in both definitions
above SHOULD be the same packet (or, when measuring RTD_rev first,
the packet from host A to host B in both definitions should be the
same).
The REQUIRED Composition Function for a singleton of round-trip delay
at time T (where T is the earliest of T' and T'' above) is:
RTDelay = RTD_fwd + RTD_rev
Note that when the OP is located at host A or host B, one of the
terms composing RTDelay will be zero or negligible.
Using the abbreviation HS to refer to the TCP handshake: when the
Qualified and Corresponding Packets are a TCP-SYN and a TCP-SYN-ACK,
RTD_fwd == RTD_HS_fwd.
When the Qualified and Corresponding Packets are a TCP-SYN-ACK and a
TCP-ACK, RTD_rev == RTD_HS_rev.
The REQUIRED Composition Function for a singleton of round-trip delay
for the connection handshake is:
RTDelay_HS = RTD_HS_fwd + RTD_HS_rev
The definition of round-trip loss count uses the nomenclature
developed above, based on observation of the TCP header sequence
numbers and storing the sequence number gaps observed. Packet losses
can be inferred from:
Out-of-order segments: TCP segments are transmitted with
monotonically increasing sequence numbers, but these segments may
be received out of order. Section 3 of [RFC4737] describes the
notion of "next expected" sequence numbers, which can be adapted
to TCP segments (for the purpose of detecting reordered packets).
Observation of out-of-order segments indicates loss on the path
prior to the OP and creates a gap.
Duplicate segments: Section 2 of [RFC5560] defines identical packets
and is suitable for evaluation of TCP packets to detect
duplication. Observation of a segment duplicates a segment
previously observed (and thus no corresponding observed segment
gap) indicates loss on the path following the OP (e.g., the
segment overlaps part of the octet stream already observed at the
OP).
Each observation of an out-of-order or duplicate segment infers a
singleton of loss, but the composition of round-trip loss counts will
be conducted over a measurement interval that is synonymous with a
single TCP connection.
With the above observations in the Forward direction over a
measurement interval, the count of out-of-order and duplicate
segments is defined as RTL_fwd. Comparable observations in the
Reverse direction are defined as RTL_rev.
For a measurement interval (corresponding to a single TCP connection)
T0 to Tf, the REQUIRED Composition Function for the two single-
direction counts of inferred loss is:
RTLoss = RTL_fwd + RTL_rev
10.2.2. Fixed Parameters
Traffic Filters:
IPv4 header values:
DSCP: Set to 0
Protocol: Set to 06 (TCP)
IPv6 header values:
DSCP: Set to 0
Hop Count: Set to 255
Next Header: Set to 6 (TCP)
Flow Label: Set to 0
Extension Headers: None
TCP header values:
Flags: ACK, SYN, FIN, set as required
Timestamps Option (TSopt): Set. See Section 3.2 of [RFC7323]
10.3. Method of Measurement
This category includes columns for references to relevant sections of
the RFC(s) and any supplemental information needed to ensure an
unambiguous method for implementations.
10.3.1. Reference Methods
The foundational methodology for this metric is defined in Section 4
of [RFC7323] using the Timestamps option with modifications that
allow application at a mid-path OP [RFC7011]. Further details and
applicable heuristics were derived from [Strowes] and [Trammell-14].
The Traffic Filter at the OP is configured to observe a single TCP
connection. When the SYN/SYN-ACK/ACK handshake occurs, it offers the
first opportunity to measure both RTD_fwd (on the SYN to SYN-ACK
pair) and RTD_rev (on the SYN-ACK to ACK pair). Label this singleton
of RTDelay as RTDelay_HS (composed using the Forward and Reverse
measurement pair). RTDelay_HS SHALL be treated separately from other
RTDelays on data-bearing packets and their ACKs. The RTDelay_HS
value MAY be used as a consistency check on the composed values of
RTDelay for payload-bearing packets.
For payload-bearing packets, the OP measures the time interval
between observation of a packet with sequence number "s" and the
corresponding ACK with the same sequence number. When the payload is
transferred from host A to host B, the observed interval is RTD_fwd.
For payload-bearing packets, each observation of an out-of-order or
duplicate segment infers a loss count, but the composition of round-
trip loss counts will be conducted over a measurement interval that
is synonymous with a single TCP connection.
Because many data transfers are unidirectional (say, in the Forward
direction from host A to host B), it is necessary to use pure ACK
packets with Timestamp (TSval) and packets with the Timestamp value
echo to perform a RTD_rev measurement. The time interval between
observation of the ACK from B to A, and the Corresponding Packet with
a Timestamp Echo Reply (TSecr) field [RFC7323], is the RTD_rev.
Delay Measurement Filtering Heuristics:
* If data payloads were transferred in both Forward and Reverse
directions, then the Round-Trip Time Measurement rule in
Section 4.1 of [RFC7323] could be applied. This rule essentially
excludes any measurement using a packet unless it makes progress
in the transfer (advances the left edge of the send window,
consistent with [Strowes]).
* A different heuristic from [Trammell-14] is to exclude any RTD_rev
that is larger than previously observed values. This would tend
to exclude Reverse measurements taken when the application has no
data ready to send, because considerable time could be added to
RTD_rev from this source of error.
* Note that the above heuristic assumes that host A is sending data.
Host A expecting a download would mean that this heuristic should
be applied to RTD_fwd.
* The statistic calculations to summarize the delay (RTDelay) SHALL
be performed on the conditional distribution, conditioned on
successful Forward and Reverse measurements that follow the
heuristics.
Method for Inferring Loss:
* The OP tracks sequence numbers and stores gaps for each direction
of transmission, as well as the next expected sequence number as
discussed in [Trammell-14] and [RFC4737]. Loss is inferred from
out-of-order segments and duplicate segments.
Loss Measurement Filtering Heuristics:
* [Trammell-14] adds a window of evaluation based on the RTDelay.
* Distinguish reordered packets from out-of-order segments due to
loss, because the sequence number gap is filled during the same
RTDelay window. Segments detected as reordered according to
[RFC4737] MUST reduce the loss count inferred from out-of-order
segments.
* Spurious (unneeded) retransmissions (observed as duplicates) can
also be reduced in this way, as described in [Trammell-14].
Sources of Error:
* The principal source of RTDelay error is the host processing time
to return a packet that defines the termination of a time
interval. The heuristics above intend to mitigate these errors by
excluding measurements where host processing time is a significant
part of RTD_fwd or RTD_rev.
* A key source of RTLoss error is observation loss, as described in
Section 3 of [Trammell-14].
10.3.2. Packet Stream Generation
N/A
10.3.3. Traffic Filtering (Observation) Details
The Fixed Parameters above give a portion of the Traffic Filter.
Other aspects will be supplied as Runtime Parameters (below).
10.3.4. Sampling Distribution
This metric requires a complete sample of all packets that qualify
according to the Traffic Filter criteria.
10.3.5. Runtime Parameters and Data Format
Runtime Parameters are input factors that must be determined,
configured into the measurement system, and reported with the results
for the context to be complete.
Src: The IP address of the host in the host A Role (format
ipv4-address-no-zone value for IPv4 or ipv6-address-no-zone value
for IPv6; see Section 4 of [RFC6991]).
Dst: The IP address of the host in the host B Role (format
ipv4-address-no-zone value for IPv4 or ipv6-address-no-zone value
for IPv6; see Section 4 of [RFC6991]).
T0: A time, the start of a measurement interval (format "date-time"
as specified in Section 5.6 of [RFC3339]; see also "date-and-time"
in Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330]. When T0 is "all-zeros", a start time is
unspecified and Tf is to be interpreted as the duration of the
measurement interval. The start time is controlled through other
means.
Tf: Optionally, the end of a measurement interval (format
"date-time" as specified in Section 5.6 of [RFC3339]; see also
"date-and-time" in Section 3 of [RFC6991]), or the duration (see
T0). The UTC Time Zone is required by Section 6.1 of [RFC2330].
Alternatively, the end of the measurement interval MAY be
controlled by the measured connection, where the second pair of
FIN and ACK packets exchanged between host A and host B
effectively ends the interval.
TTL or Hop Limit: Set at desired value.
10.3.6. Roles
host A: Launches the SYN packet to open the connection. The Role of
"host A" is synonymous with the IP address used at host A.
host B: Replies with the SYN-ACK packet to open the connection. The
Role of "host B" is synonymous with the IP address used at host B.
10.4. Output
This category specifies all details of the output of measurements
using the metric.
10.4.1. Type
RTDelay Types are discussed in the subsections below.
For RTLoss: The count of lost packets.
10.4.2. Reference Definition
For all output types:
T0: The start of a measurement interval (format "date-time" as
specified in Section 5.6 of [RFC3339]; see also "date-and-time" in
Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330].
Tf: The end of a measurement interval (format "date-time" as
specified in Section 5.6 of [RFC3339]; see also "date-and-time" in
Section 3 of [RFC6991]). The UTC Time Zone is required by
Section 6.1 of [RFC2330]. The end of the measurement interval MAY
be controlled by the measured connection, where the second pair of
FIN and ACK packets exchanged between host A and host B
effectively ends the interval.
RTDelay_Passive_IP-TCP-HS: The round-trip delay of the handshake is
a Singleton.
RTLoss: The count of lost packets.
For each <statistic>, Singleton, or Loss Count, one of the following
subsections applies.
10.4.2.1. Mean
The mean SHALL be calculated using the conditional distribution of
all packets with a finite value of round-trip delay (undefined delays
are excluded) -- a single value, as follows:
See Section 4.1 of [RFC3393] for details on the conditional
distribution to exclude undefined values of delay, and see Section 5
of [RFC6703] for background on this analysis choice.
See Section 4.2.2 of [RFC6049] for details on calculating this
statistic; see also Section 4.2.3 of [RFC6049].
Mean: The time value of the result is expressed in units of seconds,
as a positive value of type decimal64 with fraction digits = 9
(see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
10.4.2.2. Min
The minimum SHALL be calculated using the conditional distribution of
all packets with a finite value of round-trip delay (undefined delays
are excluded) -- a single value, as follows:
See Section 4.1 of [RFC3393] for details on the conditional
distribution to exclude undefined values of delay, and see Section 5
of [RFC6703] for background on this analysis choice.
See Section 4.3.2 of [RFC6049] for details on calculating this
statistic; see also Section 4.3.3 of [RFC6049].
Min: The time value of the result is expressed in units of seconds,
as a positive value of type decimal64 with fraction digits = 9
(see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
10.4.2.3. Max
The maximum SHALL be calculated using the conditional distribution of
all packets with a finite value of round-trip delay (undefined delays
are excluded) -- a single value, as follows:
See Section 4.1 of [RFC3393] for details on the conditional
distribution to exclude undefined values of delay, and see Section 5
of [RFC6703] for background on this analysis choice.
See Section 4.3.2 of [RFC6049] for a closely related method for
calculating this statistic; see also Section 4.3.3 of [RFC6049]. The
formula is as follows:
Max = (FiniteDelay[j])
such that for some index, j, where 1 <= j <= N
FiniteDelay[j] >= FiniteDelay[n] for all n
Max: The time value of the result is expressed in units of seconds,
as a positive value of type decimal64 with fraction digits = 9
(see Section 9.3 of [RFC6020]) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion to/from
the 64-bit NTP timestamp as per Section 6 of [RFC5905].
10.4.2.4. Singleton
The singleton SHALL be calculated using the successful RTD_fwd (on
the SYN to SYN-ACK pair) and RTD_rev (on the SYN-ACK to ACK pair),
see Section 10.3.1.
The singleton time value of the result is expressed in units of
seconds, as a positive value of type decimal64 with fraction digits =
9 (see Section 9.3 of [RFC6020]) with resolution of 0.000000001
seconds (1.0 ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per Section 6 of [RFC5905].
10.4.2.5. Loss Counts
RTLoss_Passive_IP-TCP_RFC8912sec10_Packet_Count: The count of lost
packets.
Observation of an out-of-order segment or duplicate segment infers a
loss count, after application of the Definitions of Section 10.2.1
and the Loss Measurement Filtering Heuristics of Section 10.3.1. The
composition of round-trip loss counts will be conducted over a
measurement interval that is synonymous with a single TCP connection.
For a measurement interval (corresponding to a single TCP connection)
T0 to Tf, the REQUIRED Composition Function for the two single-
direction counts of inferred loss is:
RTLoss = RTL_fwd + RTL_rev
Packet count: The numeric value of the result is expressed in units
of lost packets, as a positive value of type uint64 (represents
integer values between 0 and 18446744073709551615, inclusively
(see Section 9.2 of [RFC6020]).
10.4.3. Metric Units
The <statistic> of round-trip delay is expressed in seconds, where
<statistic> is one of:
* Mean
* Min
* Max
The round-trip delay of the TCP handshake singleton is expressed in
seconds.
The round-trip loss count is expressed as a number of packets.
10.4.4. Calibration
Passive Measurements at an OP could be calibrated against an Active
Measurement (with loss emulation) at host A or host B, where the
Active Measurement represents the ground truth.
10.5. Administrative Items
10.5.1. Status
Current
10.5.2. Requester
RFC 8912
10.5.3. Revision
1.0
10.5.4. Revision Date
YYYY-MM-DD
2021-11-17
10.6. Comments and Remarks
None
11. Security Considerations
These Registry Entries represent no known implications for Internet
security. With the exception of [RFC1035], each RFC referenced above
contains a Security Considerations section. Further, the Large-scale
Measurement of Broadband Performance (LMAP) framework [RFC7594]
provides both security and privacy considerations for measurements.
There are potential privacy considerations for observed traffic,
particularly for Passive Metrics as discussed in Section 10. An
attacker that knows that its TCP connection is being measured can
modify its behavior to skew the measurement results.
12. IANA Considerations
IANA has populated the Performance Metrics Registry defined in
[RFC8911] with the values defined in Sections 4 through 10.
See the IANA Considerations section of [RFC8911] for additional
considerations.
13. References
13.1. Normative References
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[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>.
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
<https://www.rfc-editor.org/info/rfc3339>.
[RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation
Metric for IP Performance Metrics (IPPM)", RFC 3393,
DOI 10.17487/RFC3393, November 2002,
<https://www.rfc-editor.org/info/rfc3393>.
[RFC3432] Raisanen, V., Grotefeld, G., and A. Morton, "Network
performance measurement with periodic streams", RFC 3432,
DOI 10.17487/RFC3432, November 2002,
<https://www.rfc-editor.org/info/rfc3432>.
[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>.
[RFC5481] Morton, A. and B. Claise, "Packet Delay Variation
Applicability Statement", RFC 5481, DOI 10.17487/RFC5481,
March 2009, <https://www.rfc-editor.org/info/rfc5481>.
[RFC5560] Uijterwaal, H., "A One-Way Packet Duplication Metric",
RFC 5560, DOI 10.17487/RFC5560, May 2009,
<https://www.rfc-editor.org/info/rfc5560>.
[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
"Network Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
<https://www.rfc-editor.org/info/rfc5905>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.
[RFC6049] Morton, A. and E. Stephan, "Spatial Composition of
Metrics", RFC 6049, DOI 10.17487/RFC6049, January 2011,
<https://www.rfc-editor.org/info/rfc6049>.
[RFC6673] Morton, A., "Round-Trip Packet Loss Metrics", RFC 6673,
DOI 10.17487/RFC6673, August 2012,
<https://www.rfc-editor.org/info/rfc6673>.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC6991, July 2013,
<https://www.rfc-editor.org/info/rfc6991>.
[RFC7011] Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
"Specification of the IP Flow Information Export (IPFIX)
Protocol for the Exchange of Flow Information", STD 77,
RFC 7011, DOI 10.17487/RFC7011, September 2013,
<https://www.rfc-editor.org/info/rfc7011>.
[RFC7323] Borman, D., Braden, B., Jacobson, V., and R.
Scheffenegger, Ed., "TCP Extensions for High Performance",
RFC 7323, DOI 10.17487/RFC7323, September 2014,
<https://www.rfc-editor.org/info/rfc7323>.
[RFC7679] Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton,
Ed., "A One-Way Delay Metric for IP Performance Metrics
(IPPM)", STD 81, RFC 7679, DOI 10.17487/RFC7679, January
2016, <https://www.rfc-editor.org/info/rfc7679>.
[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>.
[RFC8911] Bagnulo, M., Claise, B., Eardley, P., Morton, A., and A.
Akhter, "Registry for Performance Metrics", RFC 8911,
DOI 10.17487/RFC8911, November 2021,
<https://www.rfc-editor.org/info/rfc8911>.
[Strowes] Strowes, S., "Passively Measuring TCP Round-Trip Times",
Communications of the ACM, Vol. 56 No. 10, Pages 57-64,
DOI 10.1145/2507771.2507781, October 2013,
<https://dl.acm.org/doi/10.1145/2507771.2507781>.
[Trammell-14]
Trammell, B., Gugelmann, D., and N. Brownlee, "Inline Data
Integrity Signals for Passive Measurement", In: Dainotti
A., Mahanti A., Uhlig S. (eds) Traffic Monitoring and
Analysis. TMA 2014. Lecture Notes in Computer Science,
vol 8406. Springer, Berlin, Heidelberg,
DOI 10.1007/978-3-642-54999-1_2, March 2014,
<https://link.springer.com/
chapter/10.1007/978-3-642-54999-1_2>.
13.2. Informative References
[RFC1242] Bradner, S., "Benchmarking Terminology for Network
Interconnection Devices", RFC 1242, DOI 10.17487/RFC1242,
July 1991, <https://www.rfc-editor.org/info/rfc1242>.
[RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New
Performance Metric Development", BCP 170, RFC 6390,
DOI 10.17487/RFC6390, October 2011,
<https://www.rfc-editor.org/info/rfc6390>.
[RFC6703] Morton, A., Ramachandran, G., and G. Maguluri, "Reporting
IP Network Performance Metrics: Different Points of View",
RFC 6703, DOI 10.17487/RFC6703, August 2012,
<https://www.rfc-editor.org/info/rfc6703>.
[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>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
Acknowledgments
The authors thank Brian Trammell for suggesting the term "Runtime
Parameters", which led to the distinction between Runtime and Fixed
Parameters implemented in this memo, for identifying the IP Flow
Information Export (IPFIX) metric with Flow Key as an example, for
suggesting the Passive TCP RTD Metric and supporting references, and
for many other productive suggestions. Thanks to Peter Koch, who
provided several useful suggestions for disambiguating successive DNS
queries in the DNS Response time metric.
The authors also acknowledge the constructive reviews and helpful
suggestions from Barbara Stark, Juergen Schoenwaelder, Tim Carey,
Yaakov Stein, and participants in the LMAP Working Group. Thanks to
Michelle Cotton for her early IANA reviews, and to Amanda Baber for
answering questions related to the presentation of the Registry and
accessibility of the complete template via URL.
Authors' Addresses
Al Morton
AT&T Labs
200 Laurel Avenue South
Middletown, NJ 07748
United States of America
Phone: +1 732 420 1571
Email: acmorton@att.com
Marcelo Bagnulo
Universidad Carlos III de Madrid
Av. Universidad 30
28911 Leganes Madrid
Spain
Phone: 34 91 6249500
Email: marcelo@it.uc3m.es
URI: http://www.it.uc3m.es
Philip Eardley
BT
Adastral Park, Martlesham Heath
Ipswich
United Kingdom
Email: philip.eardley@bt.com
Kevin D'Souza
AT&T Labs
200 Laurel Avenue South
Middletown, NJ 07748
United States of America
Phone: +1 732 420 2514
Email: kld@att.com