Initial Performance Metrics Registry EntriesAT&T Labs200 Laurel Avenue SouthMiddletownNJ07748United States of America+1 732 420 1571acmorton@att.comUniversidad Carlos III de MadridAv. Universidad 30LeganesMadrid28911Spain34 91 6249500marcelo@it.uc3m.eshttp://www.it.uc3m.esBTAdastral Park, Martlesham HeathIpswichUnited Kingdomphilip.eardley@bt.comAT&T Labs200 Laurel Avenue SouthMiddletownNJ07748United States of America+1 732 420 2514kld@att.com
Transport
IPPMLossDelayDelay VariationICMP pingDNS ResponsePoissonPeriodicTCPThis 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
.
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Table of Contents
. Introduction
. Requirements Language
. Scope
. Registry Categories and Columns
. UDP Round-Trip Latency and Loss Registry Entries
. Summary
. ID (Identifier)
. Name
. URI
. Description
. Change Controller
. Version (of Registry Format)
. Metric Definition
. Reference Definition
. Fixed Parameters
. Method of Measurement
. Reference Methods
. Packet Stream Generation
. Traffic Filtering (Observation) Details
. Sampling Distribution
. Runtime Parameters and Data Format
. Roles
. Output
. Type
. Reference Definition
. Metric Units
. Calibration
. Administrative Items
. Status
. Requester
. Revision
. Revision Date
. Comments and Remarks
. Packet Delay Variation Registry Entry
. Summary
. ID (Identifier)
. Name
. URI
. Description
. Change Controller
. Version (of Registry Format)
. Metric Definition
. Reference Definition
. Fixed Parameters
. Method of Measurement
. Reference Methods
. Packet Stream Generation
. Traffic Filtering (Observation) Details
. Sampling Distribution
. Runtime Parameters and Data Format
. Roles
. Output
. Type
. Reference Definition
. Metric Units
. Calibration
. Administrative Items
. Status
. Requester
. Revision
. Revision Date
. Comments and Remarks
. DNS Response Latency and Loss Registry Entries
. Summary
. ID (Identifier)
. Name
. URI
. Description
. Change Controller
. Version (of Registry Format)
. Metric Definition
. Reference Definition
. Fixed Parameters
. Method of Measurement
. Reference Methods
. Packet Stream Generation
. Traffic Filtering (Observation) Details
. Sampling Distribution
. Runtime Parameters and Data Format
. Roles
. Output
. Type
. Reference Definition
. Metric Units
. Calibration
. Administrative Items
. Status
. Requester
. Revision
. Revision Date
. Comments and Remarks
. UDP Poisson One-Way Delay and Loss Registry Entries
. Summary
. ID (Identifier)
. Name
. URI
. Description
. Change Controller
. Version (of Registry Format)
. Metric Definition
. Reference Definition
. Fixed Parameters
. Method of Measurement
. Reference Methods
. Packet Stream Generation
. Traffic Filtering (Observation) Details
. Sampling Distribution
. Runtime Parameters and Data Format
. Roles
. Output
. Type
. Reference Definition
. Metric Units
. Calibration
. Administrative Items
. Status
. Requester
. Revision
. Revision Date
. Comments and Remarks
. UDP Periodic One-Way Delay and Loss Registry Entries
. Summary
. ID (Identifier)
. Name
. URI
. Description
. Change Controller
. Version (of Registry Format)
. Metric Definition
. Reference Definition
. Fixed Parameters
. Method of Measurement
. Reference Methods
. Packet Stream Generation
. Traffic Filtering (Observation) Details
. Sampling Distribution
. Runtime Parameters and Data Format
. Roles
. Output
. Type
. Reference Definition
. Metric Units
. Calibration
. Administrative Items
. Status
. Requester
. Revision
. Revision Date
. Comments and Remarks
. ICMP Round-Trip Latency and Loss Registry Entries
. Summary
. ID (Identifier)
. Name
. URI
. Description
. Change Controller
. Version (of Registry Format)
. Metric Definition
. Reference Definition
. Fixed Parameters
. Method of Measurement
. Reference Methods
. Packet Stream Generation
. Traffic Filtering (Observation) Details
. Sampling Distribution
. Runtime Parameters and Data Format
. Roles
. Output
. Type
. Reference Definition
. Metric Units
. Calibration
. Administrative Items
. Status
. Requester
. Revision
. Revision Date
. Comments and Remarks
. TCP Round-Trip Delay and Loss Registry Entries
. Summary
. ID (Identifier)
. Name
. URI
. Description
. Change Controller
. Version (of Registry Format)
. Metric Definition
. Reference Definition
. Fixed Parameters
. Method of Measurement
. Reference Methods
. Packet Stream Generation
. Traffic Filtering (Observation) Details
. Sampling Distribution
. Runtime Parameters and Data Format
. Roles
. Output
. Type
. Reference Definition
. Metric Units
. Calibration
. Administrative Items
. Status
. Requester
. Revision
. Revision Date
. Comments and Remarks
. Security Considerations
. IANA Considerations
. References
. Normative References
. Informative References
Acknowledgments
Authors' Addresses
IntroductionThis 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 .Although there are several standard templates for organizing
specifications of Performance Metrics (see for
an example of the traditional IPPM template, based to a large extent on
the Benchmarking Methodology Working Group's traditional template in
, and see 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, defines the
overall format for a Performance Metrics Registry. 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
also requires that new entries be administered by IANA through the
Specification Required policy , which will
ensure that the metrics are tightly defined.Requirements LanguageThe 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
when, and only
when, they appear in all capitals, as shown here.ScopeThis 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 and its updates.Registry Categories and ColumnsThis memo uses the terminology defined in .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
--------------------
UDP Round-Trip Latency and Loss Registry EntriesThis 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 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.SummaryThis category includes multiple indexes to the Registry Entries: the
element ID and Metric Name.ID (Identifier)IANA has allocated the numeric Identifiers 1 and 2 for the two
Named Metric Entries in . See for mapping to Names.
Name
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.
Change ControllerIETFVersion (of Registry Format)1.0Metric DefinitionThis 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".Reference DefinitionFor 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>.
provides the reference
definition of the singleton (single value) round-trip delay metric.
provides the reference
definition expanded to cover a multi-singleton sample. Note that
terms such as "singleton" and "sample" are defined in .Note that although the definition of round-trip delay between the
Source (Src) and the Destination (Dst) as provided in
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 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>.
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 .Fixed Parameters
Type-P as defined in :
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 ) and with a resolution of 0.0001
seconds (0.1 ms), with lossless conversion to/from the
32-bit NTP timestamp as per .
Method of MeasurementThis category includes columns for references to relevant sections
of the RFC(s) and any supplemental information needed to ensure
an unambiguous method for implementations.Reference MethodsThe methodology for this metric (equivalent to Type-P-Round-trip-
Delay and Type-P-Round-trip-Delay-Poisson-Stream) is defined as in
(for
singletons) and
(for samples) using the Type-P and Tmax defined in the
Fixed Parameters column. However, the Periodic stream will be
generated according to .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 (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 for details on the conditional distribution to
exclude undefined values of delay, and see 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
for an expanded
discussion of the instruction to "send a Type-P packet back to the
Src as quickly as possible" in .
presents additional requirements that MUST be
included in the Method of Measurement for this metric.Packet Stream GenerationThis 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. 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 ) 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
) 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.Traffic Filtering (Observation) DetailsN/ASampling DistributionN/ARuntime Parameters and Data FormatRuntime 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 ).
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 ).
T0:
A time, the start of a measurement interval
(format "date‑time" as specified in ; see also
"date‑and‑time" in ). The
UTC Time Zone is required by . 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 ; see also
"date‑and‑time" in ). The UTC Time Zone is required by . When T0 is "all-zeros", an ending
time and date is ignored and Tf is interpreted as the duration of
the measurement interval.
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.
OutputThis category specifies all details of the output of measurements
using the metric.TypePercentile: 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 for details on the
conditional distribution to exclude undefined values of delay, and see
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 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 .Reference DefinitionFor all outputs:
T0:
The start of a measurement interval (format
"date‑time" as specified in ; see also
"date‑and‑time" in ). The UTC Time Zone is required by .
Tf:
The end of a measurement interval (format
"date‑time" as specified in ; see also
"date‑and‑time" in ). The UTC Time Zone is required by .
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 ) 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 ) with a resolution of
0.0000000001.
Metric UnitsThe 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.Calibration 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.Administrative ItemsStatusCurrentRequesterRFC 8912Revision1.0Revision Date2021-11-17Comments and RemarksNonePacket Delay Variation Registry EntryThis section gives an initial Registry Entry for a Packet Delay
Variation (PDV) metric.SummaryThis category includes multiple indexes to the Registry Entry:
the element ID and Metric Name.ID (Identifier)IANA has allocated the numeric Identifier 3 for the
Named Metric Entry in . See for mapping to Name.Name
URIURL: DescriptionThis 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.Change ControllerIETFVersion (of Registry Format)1.0Metric DefinitionThis 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".Reference DefinitionPaxson, 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>. 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>. 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>. 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>.
See Sections and of . 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 , where the singleton PDV for packet i is referred
to by the variable name "PDV(i)".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 ) and with a resolution of 0.0001 seconds (0.1
ms), with lossless conversion to/from the 32-bit NTP timestamp
as per .
F:
A selection function unambiguously defining the
packets from the stream selected for the metric. See for the PDV form.
See the Packet Stream Generation section for two
additional Fixed Parameters.Method of MeasurementThis category includes columns for references to relevant sections
of the RFC(s) and any supplemental information needed to ensure
an unambiguous method for implementations.Reference MethodsSee Sections and of for general
singleton element calculations. This Metric Entry requires
implementation of the PDV form defined in . Also see measurement considerations in .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 for details on the conditional distribution
to exclude undefined values of delay, and see 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.Packet Stream GenerationThis 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. 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 ) 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
) 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.Traffic Filtering (Observation) DetailsN/ASampling DistributionN/ARuntime 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 ).
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 ).
T0:
A time, the start of a measurement interval
(format "date‑time" as specified in ; see also
"date‑and‑time" in ). The UTC Time Zone is required by . 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 ; see also
"date‑and‑time" in ). The UTC Time Zone is required by . When T0 is "all-zeros", an ending
time and date is ignored and Tf is interpreted as the duration of
the measurement interval.
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).
OutputThis category specifies all details of the output of measurements
using the metric.TypePercentile: 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 for details on the
conditional distribution to exclude undefined values of delay, and see
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 for the definition of
the percentile statistic using the EDF.Reference Definition
T0:
The start of a measurement interval (format
"date‑time" as specified in ; see also
"date‑and‑time" in ). The UTC Time Zone is required by .
Tf:
The end of a measurement interval (format
"date‑time" as specified in ; see also
"date‑and‑time" in ). The UTC Time Zone is required by .
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 ) with a resolution of 0.000000001 seconds (1.0
ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
Metric UnitsThe 95th percentile of one-way PDV is expressed in seconds.Calibration 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
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 ) with a resolution of 0.000000001 seconds (1.0
ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
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 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.Administrative ItemsStatusCurrentRequesterRFC 8912Revision1.0Revision Date2021-11-17Comments and RemarksLost packets represent a challenge for delay variation metrics. See
and the delay variation
applicability statement for extensive analysis
and comparison of PDV and an alternate metric, IPDV (Inter-Packet
Delay Variation).DNS Response Latency and Loss Registry EntriesThis 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.
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.SummaryThis category includes multiple indexes to the Registry Entries:
the element ID and Metric Name.ID (Identifier)IANA has allocated the numeric Identifiers 4 and 5 for the two
Named Metric Entries in . See
for mapping to Names.Name
URIURL: URL: DescriptionThis 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.
Change ControllerIETFVersion (of Registry Format)1.0Metric DefinitionThis 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".Reference DefinitionFor 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).
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>.
provides the reference
definition of the singleton (single value) round-trip delay metric.
provides the reference
definition expanded to cover a multi-singleton sample. Note that
terms such as "singleton" and "sample" are defined in .For DNS Response Latency, the entities in must be mapped to . 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
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>.
For DNS Response Loss, the entities in must be mapped
to . 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 .Fixed Parameters
Type-P as defined in :
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
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 ) and with a resolution of 0.0001
seconds (0.1 ms), with lossless conversion to/from the
32-bit NTP timestamp as per .
Observation:
Reply packets will contain a DNS Response and
may contain RRs.
Method of MeasurementThis category includes columns for references to relevant sections
of the RFC(s) and any supplemental information needed to ensure
an unambiguous method for implementations.Reference MethodsThe methodology for this metric (equivalent to
Type-P-Round-trip-Delay-Poisson-Stream) is defined as in (for singletons) and (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 for details on the conditional distribution to
exclude undefined values of delay, and see 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 for an expanded
discussion of the instruction to "send a Type-P packet back to the
Src as quickly as possible" in . 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. presents
additional requirements that SHALL be included in the Method of
Measurement for this metric.In addition to operations described in ,
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.Packet Stream GenerationThis 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.
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.Traffic Filtering (Observation) DetailsN/ASampling DistributionN/ARuntime Parameters and Data FormatRuntime 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 ).
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 ).
T0:
A time, the start of a measurement interval
(format "date‑time" as specified in ; see also
"date‑and‑time" in ). The UTC Time Zone is required by . 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 ; see also
"date‑and‑time" in ). The UTC Time Zone is required by . 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 ) with a resolution of 0.0001
seconds (0.1 ms), and with lossless conversion to/from the
32-bit NTP timestamp as per .
Trunc:
Upper limit on Poisson distribution,
expressed in units of seconds, as a positive value of type
decimal64 with fraction digits = 4 (see ) with a resolution of 0.0001 seconds (0.1 ms),
and with lossless conversion to/from the 32-bit NTP timestamp as
per (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 . 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 .
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 .
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.
OutputThis category specifies all details of the output of measurements
using the metric.TypeRaw: 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.Reference DefinitionFor all outputs:
T:
The time the DNS query was sent during the
measurement interval (format "date‑time" as specified in
; see
also "date‑and‑time" in ). The UTC Time Zone is required by
.
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
) with a resolution of
0.000000001 seconds (1.0 ns), and with lossless conversion
to/from the 64-bit NTP timestamp as per . 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 . 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 ). Note that for queries with outcome 1 = Lost,
dT and RCODE will be set to the maximum for decimal64 and uint64, respectively.
Metric Units
RTDNS:
Round-trip delay, dT, is expressed in seconds.
RLDNS:
The Logical value, where 1 = Lost and 0 =
Received.
Calibration 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.Administrative ItemsStatusCurrentRequesterRFC 8912Revision1.0Revision Date2021-11-17Comments and RemarksNoneUDP Poisson One-Way Delay and Loss Registry EntriesThis 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.SummaryThis category includes multiple indexes to the Registry Entries:
the element ID and Metric Name.ID (Identifier)IANA has allocated the numeric Identifiers 6-11 for the six
Named Metric Entries in . See for mapping to Names.Name
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.
Change ControllerIETFVersion (of Registry Format)1.0Metric DefinitionThis 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".Reference DefinitionFor 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>.
Morton, A. and E. Stephan, "Spatial Composition of Metrics", RFC
6049, DOI 10.17487/RFC6049, January 2011,
<https://www.rfc-editor.org/info/rfc6049>.
provides the reference
definition of the singleton (single value) one-way delay metric.
provides the reference
definition expanded to cover a multi-value sample. Note that terms
such as "singleton" and "sample" are defined in .Only successful packet transfers with finite delay are included
in the sample, as prescribed in .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>.
provides the reference
definition of the singleton (single value) one-way Loss metric.
provides the reference
definition expanded to cover a multi-singleton sample. Note that
terms such as "singleton" and "sample" are defined in .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 ()
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 ) and with a resolution of 0.0001 seconds (0.1
ms), with lossless conversion to/from the 32-bit NTP timestamp
as per .
See the Packet Stream Generation section for two additional
Fixed Parameters.Method of MeasurementThis category includes columns for references to relevant sections
of the RFC(s) and any supplemental information needed to ensure
an unambiguous method for implementations.Reference MethodsThe methodology for this metric (equivalent to
Type-P-One-way-Delay-Poisson-Stream) is defined as in (for singletons) and (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 for details on the conditional distribution
to exclude undefined values of delay, and see 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 , 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.Packet Stream GenerationThis 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.
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 ) with a resolution of 0.0001
seconds (0.1 ms), and with lossless conversion to/from the
32-bit NTP timestamp as per . 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 ) with a resolution of 0.0001 seconds (0.1 ms),
and with lossless conversion to/from the 32-bit NTP timestamp as
per (values above this
limit will be clipped and set to the limit value).
Trunc = 30.0000 seconds.
Traffic Filtering (Observation) DetailsN/ASampling DistributionN/ARuntime Parameters and Data FormatRuntime 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 ).
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 ).
T0:
A time, the start of a measurement interval
(format "date‑time" as specified in ; see also
"date‑and‑time" in ). The UTC Time Zone is required by . 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 ; see also
"date‑and‑time" in ). The UTC Time Zone is required by . When T0 is "all-zeros", an ending
time and date is ignored and Tf is interpreted as the duration of
the measurement interval.
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.
OutputThis category specifies all details of the output of measurements
using the metric.TypeTypes are discussed in the subsections below.Reference DefinitionFor all output types:
T0:
The start of a measurement interval (format
"date‑time" as specified in ; see also
"date‑and‑time" in ). The UTC Time Zone is required by .
Tf:
The end of a measurement interval (format
"date‑time" as specified in ; see also
"date‑and‑time" in ). The UTC Time Zone is required by .
For LossRatio, the count of lost packets to total packets sent
is the basis for the loss ratio calculation as per .For each <statistic> or Percent_LossRatio, one of the following subsections
applies.Percentile95The 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 for details on the
conditional distribution to exclude undefined values of delay, and
see for background on this
analysis choice.See 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 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 ) with a resolution of 0.000000001 seconds
(1.0 ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
MeanThe 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 for details on the
conditional distribution to exclude undefined values of delay, and
see for background on this
analysis choice.See for details on
calculating this statistic; see also .
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 ) with a resolution of 0.000000001 seconds
(1.0 ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
MinThe 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 for details on the
conditional distribution to exclude undefined values of delay, and
see for background on this
analysis choice.See for details on
calculating this statistic; see also .
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 ) with a resolution of 0.000000001 seconds
(1.0 ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
MaxThe 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 for details on the
conditional distribution to exclude undefined values of delay, and
see for background on this
analysis choice.See for a closely
related method for calculating this statistic; see also . 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 ) with a resolution of 0.000000001 seconds
(1.0 ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
Std_DevThe 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 for details on the
conditional distribution to exclude undefined values of delay, and
see for background on this
analysis choice.See 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 ,
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 ) with a resolution of 0.000000001 seconds
(1.0 ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
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
) with a
resolution of 0.0000000001.
Metric UnitsThe <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.Calibration 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
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 ) with a resolution of 0.000000001 seconds (1.0
ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
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 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.Administrative ItemsStatusCurrentRequesterRFC 8912Revision1.0Revision Date2021-11-17Comments and RemarksNoneUDP Periodic One-Way Delay and Loss Registry EntriesThis 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.SummaryThis category includes multiple indexes to the Registry Entries:
the element ID and Metric Name.ID (Identifier)IANA has allocated the numeric Identifiers 12-17 for the six
Named Metric Entries in . See
for mapping to Names.Name
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.
Change ControllerIETFVersion (of Registry Format)1.0Metric DefinitionThis 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".Reference DefinitionFor 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>.
Morton, A. and E. Stephan, "Spatial Composition of Metrics", RFC
6049, DOI 10.17487/RFC6049, January 2011,
<https://www.rfc-editor.org/info/rfc6049>.
provides the reference
definition of the singleton (single value) one-way delay metric.
provides the reference
definition expanded to cover a multi-value sample. Note that terms
such as "singleton" and "sample" are defined in .Only successful packet transfers with finite delay are included
in the sample, as prescribed in .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>.
provides the reference
definition of the singleton (single value) one-way Loss metric.
provides the reference
definition expanded to cover a multi-singleton sample. Note that
terms such as "singleton" and "sample" are defined in .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 ()
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 ) and with a resolution of 0.0001 seconds (0.1
ms), with lossless conversion to/from the 32-bit NTP timestamp
as per .
See the Packet Stream Generation section for three additional
Fixed Parameters.Method of MeasurementThis category includes columns for references to relevant sections
of the RFC(s) and any supplemental information needed to ensure
an unambiguous method for implementations.Reference MethodsThe methodology for this metric (equivalent to
Type-P-One-way-Delay-Poisson-Stream) is defined as in (for singletons) and (for samples) using
the Type-P and Tmax defined in the Fixed Parameters column. However, a
Periodic stream is used, as defined in .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 for details on the conditional distribution
to exclude undefined values of delay, and see 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 , 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.Packet Stream GenerationThis 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. 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 ) and with a resolution of 0.0001 seconds (0.1 ms), with lossless conversion to/from the 32-bit NTP timestamp
as per .
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 )
and with a resolution of 0.0001 seconds (0.1 ms), with lossless conversion
to/from the 32-bit NTP timestamp as per .
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.Traffic Filtering (Observation) DetailsN/ASampling DistributionN/ARuntime Parameters and Data FormatRuntime 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 ).
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 ).
T0:
A time, the start of a measurement interval
(format "date‑time" as specified in ; see also
"date‑and‑time" in ). The UTC Time Zone is required by . 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 ; see also
"date‑and‑time" in ). The UTC Time Zone is required by . When T0 is "all-zeros", an ending
time and date is ignored and Tf is interpreted as the duration of
the measurement interval.
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.
OutputThis category specifies all details of the output of measurements
using the metric.TypeLatency and Loss Types are discussed in the subsections below.Reference DefinitionFor all output types:
T0:
The start of a measurement interval (format
"date‑time" as specified in ; see also
"date‑and‑time" in ). The UTC Time Zone is required by .
Tf:
The end of a measurement interval (format
"date‑time" as specified in ; see also
"date‑and‑time" in ). The UTC Time Zone is required by .
For LossRatio, the count of lost packets to total packets sent
is the basis for the loss ratio calculation as per .For each <statistic> or Percent_LossRatio, one of the following subsections
applies.Percentile95The 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 for details on the
conditional distribution to exclude undefined values of delay, and
see for background on this
analysis choice.See 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 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 ) with a resolution of 0.000000001 seconds
(1.0 ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
MeanThe 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 for details on the
conditional distribution to exclude undefined values of delay, and
see for background on this
analysis choice.See for details on
calculating this statistic; see also .
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 ) with a resolution of 0.000000001 seconds
(1.0 ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
MinThe 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 for details on the
conditional distribution to exclude undefined values of delay, and
see for background on this
analysis choice.See for details on
calculating this statistic; see also .
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 ) with a resolution of 0.000000001 seconds
(1.0 ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
MaxThe 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 for details on the
conditional distribution to exclude undefined values of delay, and
see for background on this
analysis choice.See for a closely
related method for calculating this statistic; see also . 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 ) with a resolution of 0.000000001 seconds
(1.0 ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
Std_DevStd_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 for details on the
conditional distribution to exclude undefined values of delay, and
see for background on this
analysis choice.See 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 ,
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 ) with a resolution of 0.000000001 seconds
(1.0 ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
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
with a
resolution of 0.0000000001.
Metric UnitsThe <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.Calibration 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
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 ) with a resolution of 0.000000001 seconds (1.0
ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
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 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.Administrative ItemsStatusCurrentRequesterRFC 8912Revision1.0Revision Date2021-11-17Comments and RemarksNoneICMP Round-Trip Latency and Loss Registry EntriesThis 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.SummaryThis category includes multiple indexes to the Registry Entries: the
element ID and Metric Name.ID (Identifier)IANA has allocated the numeric Identifiers 18-21 for the four
Named Metric Entries in .
See for mapping to Names.Name
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.
Change ControllerIETFVersion (of Registry Format)1.0Metric DefinitionThis 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".Reference DefinitionFor 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>.
provides the reference
definition of the singleton (single value) round-trip delay metric.
provides the reference
definition expanded to cover a multi-singleton sample. Note that
terms such as "singleton" and "sample" are defined in .Note that although the definition of round-trip delay between the
Source (Src) and the Destination (Dst) as provided in
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 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>.
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 .Fixed Parameters
Type-P as defined in :
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 ) and with a resolution of 0.0001
seconds (0.1 ms), with lossless conversion to/from the
32-bit NTP timestamp as per .
Method of MeasurementThis category includes columns for references to relevant sections
of the RFC(s) and any supplemental information needed to ensure
an unambiguous method for implementations.Reference MethodsThe methodology for this metric (equivalent to
Type-P-Round-trip-Delay-Poisson-Stream) is defined as in (for singletons) and (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 for details on the conditional distribution to
exclude undefined values of delay, and see 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 for an expanded
discussion of the instruction to "send a Type-P packet back to the
Src as quickly as possible" in . presents additional requirements that MUST be
included in the Method of Measurement for this metric.Packet Stream GenerationThis 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 , 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.Traffic Filtering (Observation) DetailsN/ASampling DistributionN/ARuntime Parameters and Data FormatRuntime 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 ).
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 ).
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 )
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 ; see also
"date‑and‑time" in ). The UTC Time Zone is required by . 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 .
See the Packet Stream Generation section for
additional Runtime Parameters.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).
OutputThis category specifies all details of the output of measurements
using the metric.TypeLatency and Loss Types are discussed in the subsections below.Reference DefinitionFor all output types:
T0:
The start of a measurement interval (format
"date‑time" as specified in ; see also
"date‑and‑time" in ). The UTC Time Zone is required by .
Tf:
The end of a measurement interval (format
"date‑time" as specified in ; see also
"date‑and‑time" in ). The UTC Time Zone is required by .
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.MeanThe 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 for details on the
conditional distribution to exclude undefined values of delay, and
see for background on this
analysis choice.See for details on
calculating this statistic; see also .
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 ) with a resolution of 0.000000001 seconds
(1.0 ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
MinThe 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 for details on the
conditional distribution to exclude undefined values of delay, and
see for background on this
analysis choice.See for details on
calculating this statistic; see also .
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 ) with a resolution of 0.000000001 seconds
(1.0 ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
MaxThe 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 for details on the
conditional distribution to exclude undefined values of delay, and
see for background on this
analysis choice.See for a closely
related method for calculating this statistic; see also . 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 ) with a resolution of 0.000000001 seconds
(1.0 ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
Percent_LossRatioFor LossRatio, the count of lost packets to total packets sent is the basis for the loss ratio calculation as per .
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 ) with a
resolution of 0.0000000001.
Metric UnitsThe <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.Calibration 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.Administrative ItemsStatusCurrentRequesterRFC 8912Revision1.0Revision Date2021-11-17Comments and RemarksNoneTCP Round-Trip Delay and Loss Registry EntriesThis 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.SummaryThis category includes multiple indexes to the Registry Entries: the
element ID and Metric Name.ID (Identifier)IANA has allocated the numeric Identifiers 22-26 for the five
Named Metric Entries in . See
for mapping to Names.Name
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
URIURL: URL: URL: URL: URL: 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) 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) 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 somewhere in the
network. The output is the estimated loss count for the measurement
interval.
Change ControllerIETFVersion (of Registry Format)1.0Metric DefinitionThis 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".Reference DefinitionAlmes, 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>.
Although there is no RFC that describes Passive Measurement of
round-trip delay, the parallel definition for Active Measurement
is provided in .This metric definition uses the term "wire time" as defined in , and the terms "singleton" and "sample" as
defined in .
(
provides the reference definition of the
singleton (single value) round-trip delay metric. provides the reference definition expanded
to cover a multi-singleton sample.)With the OP
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 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_revNote 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_revThe 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. 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:
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_revFixed 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
Method of MeasurementThis category includes columns for references to relevant sections
of the RFC(s) and any supplemental information needed to ensure
an unambiguous method for implementations.Reference MethodsThe foundational methodology for this metric is defined in using the Timestamps option with
modifications that allow application at a mid-path OP . Further details and applicable
heuristics were derived from and .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 , 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 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 ).
A different heuristic from 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
and . Loss is
inferred from out-of-order segments and duplicate segments.
Loss Measurement Filtering Heuristics:
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 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 .
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 .
Packet Stream GenerationN/ATraffic Filtering (Observation) DetailsThe Fixed Parameters above give a portion of the Traffic Filter.
Other aspects will be supplied as Runtime Parameters (below).Sampling DistributionThis metric requires a complete sample of all packets that
qualify according to the Traffic Filter criteria.Runtime Parameters and Data FormatRuntime 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 ).
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 ).
T0:
A time, the start of a measurement interval
(format "date‑time" as specified in ; see also
"date‑and‑time" in ). The UTC Time Zone is required by . 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 ; see also
"date‑and‑time" in ), or the duration (see T0). The UTC Time Zone
is required by .
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.
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.
OutputThis category specifies all details of the output of measurements
using the metric.TypeRTDelay Types are discussed in the subsections below.For RTLoss: The count of lost packets.Reference DefinitionFor all output types:
T0:
The start of a measurement interval (format
"date‑time" as specified in ; see also
"date‑and‑time" in ). The UTC Time Zone is required by .
Tf:
The end of a measurement interval (format
"date‑time" as specified in ; see also
"date‑and‑time" in ). The UTC Time Zone is required by . 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.MeanThe 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 for details on the
conditional distribution to exclude undefined values of delay, and
see for background on this
analysis choice.See for details on
calculating this statistic; see also .
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 ) with a resolution of 0.000000001 seconds
(1.0 ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
MinThe 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 for details on the
conditional distribution to exclude undefined values of delay, and
see for background on this
analysis choice.See for details on
calculating this statistic; see also .
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 ) with a resolution of 0.000000001 seconds
(1.0 ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
MaxThe 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 for details on the
conditional distribution to exclude undefined values of delay, and
see for background on this
analysis choice.See for a closely
related method for calculating this statistic; see also . 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 ) with a resolution of 0.000000001 seconds
(1.0 ns), and with lossless conversion to/from the 64-bit NTP
timestamp as per .
SingletonThe 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 .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 ) with resolution of 0.000000001
seconds (1.0 ns), and with lossless conversion to/from the 64-bit
NTP timestamp as per .Loss CountsRTLoss_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 and the Loss Measurement Filtering Heuristics of . 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 ).
Metric UnitsThe <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.CalibrationPassive 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.Administrative ItemsStatusCurrentRequesterRFC 8912Revision1.0Revision Date2021-11-17Comments and RemarksNoneSecurity ConsiderationsThese Registry Entries represent no known implications for Internet
security. With the exception of , each RFC referenced above contains a Security Considerations
section. Further, the Large-scale Measurement of Broadband Performance (LMAP) framework provides
both security and privacy considerations for measurements.There are potential privacy considerations for observed traffic,
particularly for Passive Metrics as discussed in . An attacker that knows
that its TCP connection is being measured can modify its behavior to
skew the measurement results.IANA ConsiderationsIANA has populated the Performance Metrics Registry
defined in with the
values defined in Sections
through .See the IANA Considerations section of for additional considerations.ReferencesNormative ReferencesDomain names - implementation and specificationThis RFC is the revised specification of the protocol and format used in the implementation of the Domain Name System. It obsoletes RFC-883. This memo documents the details of the domain name client - server communication.Key words for use in RFCs to Indicate Requirement LevelsIn many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.Framework for IP Performance MetricsThe purpose of this memo is to define a general framework for particular metrics to be developed by the IETF's IP Performance Metrics effort. This memo provides information for the Internet community. It does not specify an Internet standard of any kind.A Round-trip Delay Metric for IPPMThis memo defines a metric for round-trip delay of packets across Internet paths. [STANDARDS-TRACK]Date and Time on the Internet: TimestampsThis document defines a date and time format for use in Internet protocols that is a profile of the ISO 8601 standard for representation of dates and times using the Gregorian calendar.IP Packet Delay Variation Metric for IP Performance Metrics (IPPM)Network performance measurement with periodic streamsThis memo describes a periodic sampling method and relevant metrics for assessing the performance of IP networks. First, the memo motivates periodic sampling and addresses the question of its value as an alternative to the Poisson sampling described in RFC 2330. The benefits include applicability to active and passive measurements, simulation of constant bit rate (CBR) traffic (typical of multimedia communication, or nearly CBR, as found with voice activity detection), and several instances in which analysis can be simplified. The sampling method avoids predictability by mandating random start times and finite length tests. Following descriptions of the sampling method and sample metric parameters, measurement methods and errors are discussed. Finally, we give additional information on periodic measurements, including security considerations. [STANDARDS-TRACK]Packet Reordering MetricsThis memo defines metrics to evaluate whether a network has maintained packet order on a packet-by-packet basis. It provides motivations for the new metrics and discusses the measurement issues, including the context information required for all metrics. The memo first defines a reordered singleton, and then uses it as the basis for sample metrics to quantify the extent of reordering in several useful dimensions for network characterization or receiver design. Additional metrics quantify the frequency of reordering and the distance between separate occurrences. We then define a metric oriented toward assessment of reordering effects on TCP. Several examples of evaluation using the various sample metrics are included. An appendix gives extended definitions for evaluating order with packet fragmentation. [STANDARDS-TRACK]A Two-Way Active Measurement Protocol (TWAMP)The One-way Active Measurement Protocol (OWAMP), specified in RFC 4656, provides a common protocol for measuring one-way metrics between network devices. OWAMP can be used bi-directionally to measure one-way metrics in both directions between two network elements. However, it does not accommodate round-trip or two-way measurements. This memo specifies a Two-Way Active Measurement Protocol (TWAMP), based on the OWAMP, that adds two-way or round-trip measurement capabilities. The TWAMP measurement architecture is usually comprised of two hosts with specific roles, and this allows for some protocol simplifications, making it an attractive alternative in some circumstances. [STANDARDS-TRACK]Packet Delay Variation Applicability StatementPacket delay variation metrics appear in many different standards documents. The metric definition in RFC 3393 has considerable flexibility, and it allows multiple formulations of delay variation through the specification of different packet selection functions.Although flexibility provides wide coverage and room for new ideas, it can make comparisons of independent implementations more difficult. Two different formulations of delay variation have come into wide use in the context of active measurements. This memo examines a range of circumstances for active measurements of delay variation and their uses, and recommends which of the two forms is best matched to particular conditions and tasks. This memo provides information for the Internet community.A One-Way Packet Duplication MetricWhen a packet is sent from one host to the other, one normally expects that exactly one copy of the packet that was sent arrives at the destination. It is, however, possible that a packet is either lost or that multiple copies arrive.In earlier work, a metric for packet loss was defined. This metric quantifies the case where a packet that is sent does not arrive at its destination within a reasonable time. In this memo, a metric for another case is defined: a packet is sent, but multiple copies arrive. The document also discusses streams and methods to summarize the results of streams. [STANDARDS-TRACK]Network Time Protocol Version 4: Protocol and Algorithms SpecificationThe Network Time Protocol (NTP) is widely used to synchronize computer clocks in the Internet. This document describes NTP version 4 (NTPv4), which is backwards compatible with NTP version 3 (NTPv3), described in RFC 1305, as well as previous versions of the protocol. NTPv4 includes a modified protocol header to accommodate the Internet Protocol version 6 address family. NTPv4 includes fundamental improvements in the mitigation and discipline algorithms that extend the potential accuracy to the tens of microseconds with modern workstations and fast LANs. It includes a dynamic server discovery scheme, so that in many cases, specific server configuration is not required. It corrects certain errors in the NTPv3 design and implementation and includes an optional extension mechanism. [STANDARDS-TRACK]YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)YANG is a data modeling language used to model configuration and state data manipulated by the Network Configuration Protocol (NETCONF), NETCONF remote procedure calls, and NETCONF notifications. [STANDARDS-TRACK]Spatial Composition of MetricsThis memo utilizes IP performance metrics that are applicable to both complete paths and sub-paths, and it defines relationships to compose a complete path metric from the sub-path metrics with some accuracy with regard to the actual metrics. This is called "spatial composition" in RFC 2330. The memo refers to the framework for metric composition, and provides background and motivation for combining metrics to derive others. The descriptions of several composed metrics and statistics follow. [STANDARDS-TRACK]Round-Trip Packet Loss MetricsMany user applications (and the transport protocols that make them possible) require two-way communications. To assess this capability, and to achieve test system simplicity, round-trip loss measurements are frequently conducted in practice. The Two-Way Active Measurement Protocol specified in RFC 5357 establishes a round-trip loss measurement capability for the Internet. However, there is currently no round-trip packet loss metric specified according to the RFC 2330 framework.This memo adds round-trip loss to the set of IP Performance Metrics (IPPM). [STANDARDS-TRACK]Common YANG Data TypesThis document introduces a collection of common data types to be used with the YANG data modeling language. This document obsoletes RFC 6021.Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of Flow InformationThis document specifies the IP Flow Information Export (IPFIX) protocol, which serves as a means for transmitting Traffic Flow information over the network. In order to transmit Traffic Flow information from an Exporting Process to a Collecting Process, a common representation of flow data and a standard means of communicating them are required. This document describes how the IPFIX Data and Template Records are carried over a number of transport protocols from an IPFIX Exporting Process to an IPFIX Collecting Process. This document obsoletes RFC 5101.TCP Extensions for High PerformanceThis document specifies a set of TCP extensions to improve performance over paths with a large bandwidth * delay product and to provide reliable operation over very high-speed paths. It defines the TCP Window Scale (WS) option and the TCP Timestamps (TS) option and their semantics. The Window Scale option is used to support larger receive windows, while the Timestamps option can be used for at least two distinct mechanisms, Protection Against Wrapped Sequences (PAWS) and Round-Trip Time Measurement (RTTM), that are also described herein.This document obsoletes RFC 1323 and describes changes from it.A One-Way Delay Metric for IP Performance Metrics (IPPM)This memo defines a metric for one-way delay of packets across Internet paths. It builds on notions introduced and discussed in the IP Performance Metrics (IPPM) Framework document, RFC 2330; the reader is assumed to be familiar with that document. This memo makes RFC 2679 obsolete.A One-Way Loss Metric for IP Performance Metrics (IPPM)This memo defines a metric for one-way loss of packets across Internet paths. It builds on notions introduced and discussed in the IP Performance Metrics (IPPM) Framework document, RFC 2330; the reader is assumed to be familiar with that document. This memo makes RFC 2680 obsolete.Ambiguity of Uppercase vs Lowercase in RFC 2119 Key WordsRFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.Registry for Performance MetricsPassively Measuring TCP Round-Trip TimesCommunications of the ACM, Vol. 56 No. 10, Pages 57-64Inline Data Integrity Signals for Passive MeasurementIn: Dainotti A., Mahanti A., Uhlig S. (eds)
Traffic Monitoring and Analysis. TMA 2014. Lecture Notes in
Computer Science, vol 8406. Springer, Berlin, HeidelbergInformative ReferencesBenchmarking Terminology for Network Interconnection DevicesThis memo discusses and defines a number of terms that are used in describing performance benchmarking tests and the results of such tests. This memo provides information for the Internet community. It does not specify an Internet standard.Guidelines for Considering New Performance Metric DevelopmentThis document describes a framework and a process for developing Performance Metrics of protocols and applications transported over IETF-specified protocols. These metrics can be used to characterize traffic on live networks and services. This memo documents an Internet Best Current Practice.Reporting IP Network Performance Metrics: Different Points of ViewConsumers of IP network performance metrics have many different uses in mind. This memo provides "long-term" reporting considerations (e.g., hours, days, weeks, or months, as opposed to 10 seconds), based on analysis of the points of view of two key audiences. It describes how these audience categories affect the selection of metric parameters and options when seeking information that serves their needs. This document is not an Internet Standards Track specification; it is published for informational purposes.A Framework for Large-Scale Measurement of Broadband Performance (LMAP)Measuring broadband service on a large scale requires a description of the logical architecture and standardisation of the key protocols that coordinate interactions between the components. This document presents an overall framework for large-scale measurements. It also defines terminology for LMAP (Large-Scale Measurement of Broadband Performance).Guidelines for Writing an IANA Considerations Section in RFCsMany protocols make use of points of extensibility that use constants to identify various protocol parameters. To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper. For IETF protocols, that role is filled by the Internet Assigned Numbers Authority (IANA).To make assignments in a given registry prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed. This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the provided guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry.This is the third edition of this document; it obsoletes RFC 5226.AcknowledgmentsThe authors thank 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 , 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 , , , , and participants in the LMAP Working Group. Thanks to for her early IANA reviews, and to for answering
questions related to the presentation of the Registry and accessibility
of the complete template via URL.Authors' AddressesAT&T Labs200 Laurel Avenue SouthMiddletownNJ07748United States of America+1 732 420 1571acmorton@att.comUniversidad Carlos III de MadridAv. Universidad 30LeganesMadrid28911Spain34 91 6249500marcelo@it.uc3m.eshttp://www.it.uc3m.esBTAdastral Park, Martlesham HeathIpswichUnited Kingdomphilip.eardley@bt.comAT&T Labs200 Laurel Avenue SouthMiddletownNJ07748United States of America+1 732 420 2514kld@att.com