4.1.1. ID (Identifier)

IANA has allocated the numeric Identifiers 1 and 2 for the two Named Metric Entries in Section 4. See Section 4.1.2 for mapping to Names.¶

4.1.3. URI

URL: https://www.iana.org/performance-metrics/RTDelay_Active_IP-UDP-Periodic_RFC8912sec4_Seconds_95Percentile¶

URL: https://www.iana.org/performance-metrics/RTLoss_Active_IP-UDP-Periodic_RFC8912sec4_Percent_LossRatio¶

4.1.4. Description

RTDelay:

This metric assesses the delay of a stream of packets exchanged between two hosts (which are the two measurement points). The output is the round-trip delay for all successfully exchanged packets expressed as the 95th percentile of their conditional delay distribution.¶

RTLoss:

This metric assesses the loss ratio of a stream of packets exchanged between two hosts (which are the two measurement points). The output is the round-trip loss ratio for all transmitted packets expressed as a percentage.¶

4.1.5. Change Controller

IETF¶

4.1.6. Version (of Registry Format)

1.0¶

4.2.1. Reference Definition

For delay:¶

Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip Delay Metric for IPPM", RFC 2681, DOI 10.17487/RFC2681, September 1999, <https://www.rfc-editor.org/info/rfc2681>. [RFC2681]¶

Section 2.4 of [RFC2681] provides the reference definition of the singleton (single value) round-trip delay metric. Section 3.4 of [RFC2681] provides the reference definition expanded to cover a multi-singleton sample. Note that terms such as "singleton" and "sample" are defined in Section 11 of [RFC2330].¶

Note that although the definition of round-trip delay between the Source (Src) and the Destination (Dst) as provided in Section 2.4 of [RFC2681] is directionally ambiguous in the text, this metric tightens the definition further to recognize that the host in the Src Role will send the first packet to the host in the Dst Role and will ultimately receive the corresponding return packet from the Dst (when neither is lost).¶

Finally, note that the variable "dT" is used in [RFC2681] to refer to the value of round-trip delay in metric definitions and methods. The variable "dT" has been reused in other IPPM literature to refer to different quantities and cannot be used as a global variable name.¶

For loss:¶

Morton, A., "Round-Trip Packet Loss Metrics", RFC 6673, DOI 10.17487/RFC6673, August 2012, <https://www.rfc-editor.org/info/rfc6673>. [RFC6673]¶

Both Delay and Loss metrics employ a maximum waiting time for received packets, so the count of lost packets to total packets sent is the basis for the loss ratio calculation as per Section 6.1 of [RFC6673].¶

4.2.2. Fixed Parameters

Type-P as defined in Section 13 of [RFC2330]:

IPv4 header values:

DSCP:

Set to 0¶

TTL:

Set to 255¶

Protocol:

Set to 17 (UDP)¶

IPv6 header values:

DSCP:

Set to 0¶

Hop Count:

Set to 255¶

Next Header:

Set to 17 (UDP)¶

Flow Label:

Set to 0¶

Extension Headers:

None¶

UDP header values:

Checksum:

The checksum MUST be calculated and the non-zero checksum included in the header¶

UDP Payload:

Total of 100 bytes

¶

Other measurement Parameters:

Tmax:

A loss threshold waiting time with value 3.0, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms), with lossless conversion to/from the 32-bit NTP timestamp as per Section 6 of [RFC5905].¶

4.3.1. Reference Methods

The methodology for this metric (equivalent to Type-P-Round-trip- Delay and Type-P-Round-trip-Delay-Poisson-Stream) is defined as in Section 2.6 of [RFC2681] (for singletons) and Section 3.6 of [RFC2681] (for samples) using the Type-P and Tmax defined in the Fixed Parameters column. However, the Periodic stream will be generated according to [RFC3432].¶

The reference method distinguishes between long-delayed packets and lost packets by implementing a maximum waiting time for packet arrival. Tmax is the waiting time used as the threshold to declare a packet lost. Lost packets SHALL be designated as having undefined delay and counted for the RTLoss metric [RFC6673].¶

The calculations on the delay (RTT) SHALL be performed on the conditional distribution, conditioned on successful packet arrival within Tmax. Also, when all packet delays are stored, the process that calculates the RTT value MUST enforce the Tmax threshold on stored values before calculations. See Section 4.1 of [RFC3393] for details on the conditional distribution to exclude undefined values of delay, and see Section 5 of [RFC6703] for background on this analysis choice.¶

The reference method requires some way to distinguish between different packets in a stream to establish correspondence between sending times and receiving times for each successfully arriving packet. Sequence numbers or other send-order identification MUST be retained at the Src or included with each packet to disambiguate packet reordering if it occurs.¶

If a standard measurement protocol is employed, then the measurement process will determine the sequence numbers or timestamps applied to test packets after the Fixed and Runtime Parameters are passed to that process. The chosen measurement protocol will dictate the format of sequence numbers and timestamps, if they are conveyed in the packet payload.¶

Refer to Section 4.4 of [RFC6673] for an expanded discussion of the instruction to "send a Type-P packet back to the Src as quickly as possible" in Section 2.6 of [RFC2681]. Section 8 of [RFC6673] presents additional requirements that MUST be included in the Method of Measurement for this metric.¶

4.3.2. Packet Stream Generation

This section provides details regarding packet traffic, which is used as the basis for measurement. In IPPM Metrics, this is called the "stream"; this stream can easily be described by providing the list of stream Parameters.¶

Section 3 of [RFC3432] prescribes the method for generating Periodic streams using associated Parameters.¶

incT:

The nominal duration of the inter-packet interval, first bit to first bit, with value 0.0200, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms).¶

dT:

The duration of the interval for allowed sample start times, with value 1.0, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms).¶

Note: An initiation process with a number of control exchanges resulting in unpredictable start times (within a time interval) may be sufficient to avoid synchronization of periodic streams and is a valid replacement for selecting a start time at random from a fixed interval.¶

The T0 Parameter will be reported as a measured Parameter. Parameters incT and dT are Fixed Parameters.¶

4.3.3. Traffic Filtering (Observation) Details

N/A¶

4.3.4. Sampling Distribution

N/A¶

4.3.5. Runtime Parameters and Data Format

Runtime Parameters are input factors that must be determined, configured into the measurement system, and reported with the results for the context to be complete.¶

Src:

The IP address of the host in the Src Role (format ipv4‑address-no-zone value for IPv4 or ipv6-address-no-zone value for IPv6; see Section 4 of [RFC6991]).¶

Dst:

The IP address of the host in the Dst Role (format ipv4‑address-no-zone value for IPv4 or ipv6-address-no-zone value for IPv6; see Section 4 of [RFC6991]).¶

T0:

A time, the start of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330]. When T0 is "all-zeros", a start time is unspecified and Tf is to be interpreted as the duration of the measurement interval. The start time is controlled through other means.¶

Tf:

A time, the end of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330]. When T0 is "all-zeros", an ending time and date is ignored and Tf is interpreted as the duration of the measurement interval.¶

4.3.6. Roles

Src:

Launches each packet and waits for return transmissions from the Dst.¶

Dst:

Waits for each packet from the Src and sends a return packet to the Src.¶

4.4.1. Type

Percentile: For the conditional distribution of all packets with a valid value of round-trip delay (undefined delays are excluded), this is a single value corresponding to the 95th percentile, as follows:¶

See Section 4.1 of [RFC3393] for details on the conditional distribution to exclude undefined values of delay, and see Section 5 of [RFC6703] for background on this analysis choice.¶

The percentile = 95, meaning that the reported delay, "95Percentile", is the smallest value of round-trip delay for which the Empirical Distribution Function, EDF(95Percentile), is greater than or equal to 95% of the singleton round-trip delay values in the conditional distribution. See Section 11.3 of [RFC2330] for the definition of the percentile statistic using the EDF.¶

For LossRatio, the count of lost packets to total packets sent is the basis for the loss ratio calculation as per Section 6.1 of [RFC6673].¶

4.4.2. Reference Definition

For all outputs:¶

T0:

The start of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330].¶

Tf:

The end of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330].¶

TotalPkts:

The count of packets sent by the Src to the Dst during the measurement interval.¶

95Percentile:

The time value of the result is expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 9 (see Section 9.3 of [RFC6020]) with a resolution of 0.000000001 seconds (1.0 ns).¶

Percent_LossRatio:

The numeric value of the result is expressed in units of lost packets to total packets times 100%, as a positive value of type decimal64 with fraction digits = 9 (see Section 9.3 of [RFC6020]) with a resolution of 0.0000000001.¶

4.4.3. Metric Units

The 95th percentile of round-trip delay is expressed in seconds.¶

The round-trip loss ratio is expressed as a percentage of lost packets to total packets sent.¶

4.4.4. Calibration

Section 3.7.3 of [RFC7679] provides a means to quantify the systematic and random errors of a time measurement. Calibration in-situ could be enabled with an internal loopback at the Source host that includes as much of the measurement system as possible, performs address manipulation as needed, and provides some form of isolation (e.g., deterministic delay) to avoid send-receive interface contention. Some portion of the random and systematic error can be characterized in this way.¶

When a measurement controller requests a calibration measurement, the loopback is applied and the result is output in the same format as a normal measurement, with an additional indication that it is a calibration result.¶

Both internal loopback calibration and clock synchronization can be used to estimate the available accuracy of the Output Metric Units. For example, repeated loopback delay measurements will reveal the portion of the output result resolution that is the result of system noise and is thus inaccurate.¶

4.5.1. Status

Current¶

4.5.2. Requester

RFC 8912¶

4.5.3. Revision

1.0¶

4.5.4. Revision Date

YYYY-MM-DD¶

5.1.1. ID (Identifier)

IANA has allocated the numeric Identifier 3 for the Named Metric Entry in Section 5. See Section 5.1.2 for mapping to Name.¶

5.1.3. URI

URL: https://www.iana.org/performance-metrics/OWPDV_Active_IP-UDP-Periodic_RFC8912sec5_Seconds_95Percentile¶

5.1.4. Description

This metric assesses packet delay variation with respect to the minimum delay observed on the periodic stream. The output is expressed as the 95th percentile of the packet delay variation distribution.¶

5.1.5. Change Controller

IETF¶

5.1.6. Version (of Registry Format)

1.0¶

5.2.1. Reference Definition

Paxson, V., Almes, G., Mahdavi, J., and M. Mathis, "Framework for IP Performance Metrics", RFC 2330, DOI 10.17487/RFC2330, May 1998, <https://www.rfc-editor.org/info/rfc2330>. [RFC2330]¶

Demichelis, C. and P. Chimento, "IP Packet Delay Variation Metric for IP Performance Metrics (IPPM)", RFC 3393, DOI 10.17487/RFC3393, November 2002, <https://www.rfc-editor.org/info/rfc3393>. [RFC3393]¶

Morton, A. and B. Claise, "Packet Delay Variation Applicability Statement", RFC 5481, DOI 10.17487/RFC5481, March 2009, <https://www.rfc-editor.org/info/rfc5481>. [RFC5481]¶

Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, "Network Time Protocol Version 4: Protocol and Algorithms Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, <https://www.rfc-editor.org/info/rfc5905>. [RFC5905]¶

See Sections 2.4 and 3.4 of [RFC3393]. The measured singleton delay differences are referred to by the variable name "ddT" (applicable to all forms of delay variation). However, this Metric Entry specifies the PDV form defined in Section 4.2 of [RFC5481], where the singleton PDV for packet i is referred to by the variable name "PDV(i)".¶

5.2.2. Fixed Parameters

IPv4 header values:

DSCP:

Set to 0¶

TTL:

Set to 255¶

Protocol:

Set to 17 (UDP)¶

IPv6 header values:

DSCP:

Set to 0¶

Hop Count:

Set to 255¶

Next Header:

Set to 17 (UDP)¶

Flow Label:

Set to 0¶

Extension Headers:

None¶

UDP header values:

Checksum:

The checksum MUST be calculated and the non-zero checksum included in the header¶

UDP Payload:

Total of 200 bytes

¶

Other measurement Parameters:

Tmax:

A loss threshold waiting time with value 3.0, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms), with lossless conversion to/from the 32-bit NTP timestamp as per Section 6 of [RFC5905].¶

F:

A selection function unambiguously defining the packets from the stream selected for the metric. See Section 4.2 of [RFC5481] for the PDV form.¶

See the Packet Stream Generation section for two additional Fixed Parameters.¶

5.3.1. Reference Methods

See Sections 2.6 and 3.6 of [RFC3393] for general singleton element calculations. This Metric Entry requires implementation of the PDV form defined in Section 4.2 of [RFC5481]. Also see measurement considerations in Section 8 of [RFC5481].¶

The reference method distinguishes between long-delayed packets and lost packets by implementing a maximum waiting time for packet arrival. Tmax is the waiting time used as the threshold to declare a packet lost. Lost packets SHALL be designated as having undefined delay.¶

The calculations on the one-way delay SHALL be performed on the conditional distribution, conditioned on successful packet arrival within Tmax. Also, when all packet delays are stored, the process that calculates the one-way delay value MUST enforce the Tmax threshold on stored values before calculations. See Section 4.1 of [RFC3393] for details on the conditional distribution to exclude undefined values of delay, and see Section 5 of [RFC6703] for background on this analysis choice.¶

The reference method requires some way to distinguish between different packets in a stream to establish correspondence between sending times and receiving times for each successfully arriving packet. Sequence numbers or other send-order identification MUST be retained at the Src or included with each packet to disambiguate packet reordering if it occurs.¶

If a standard measurement protocol is employed, then the measurement process will determine the sequence numbers or timestamps applied to test packets after the Fixed and Runtime Parameters are passed to that process. The chosen measurement protocol will dictate the format of sequence numbers and timestamps, if they are conveyed in the packet payload.¶

5.3.2. Packet Stream Generation

This section provides details regarding packet traffic, which is used as the basis for measurement. In IPPM Metrics, this is called the "stream"; this stream can easily be described by providing the list of stream Parameters.¶

Section 3 of [RFC3432] prescribes the method for generating Periodic streams using associated Parameters.¶

incT:

The nominal duration of the inter-packet interval, first bit to first bit, with value 0.0200, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms).¶

dT:

The duration of the interval for allowed sample start times, with value 1.0, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms).¶

Note: An initiation process with a number of control exchanges resulting in unpredictable start times (within a time interval) may be sufficient to avoid synchronization of periodic streams and is a valid replacement for selecting a start time at random from a fixed interval.¶

The T0 Parameter will be reported as a measured Parameter. Parameters incT and dT are Fixed Parameters.¶

5.3.3. Traffic Filtering (Observation) Details

N/A¶

5.3.4. Sampling Distribution

N/A¶

5.3.5. Runtime Parameters and Data Format

Src:

The IP address of the host in the Src Role (format ipv4‑address-no-zone value for IPv4 or ipv6-address-no-zone value for IPv6; see Section 4 of [RFC6991]).¶

Dst:

The IP address of the host in the Dst Role (format ipv4‑address-no-zone value for IPv4 or ipv6-address-no-zone value for IPv6; see Section 4 of [RFC6991]).¶

T0:

A time, the start of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330]. When T0 is "all-zeros", a start time is unspecified and Tf is to be interpreted as the duration of the measurement interval. The start time is controlled through other means.¶

Tf:

A time, the end of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330]. When T0 is "all-zeros", an ending time and date is ignored and Tf is interpreted as the duration of the measurement interval.¶

5.3.6. Roles

Src:

Launches each packet and waits for return transmissions from the Dst.¶

Dst:

Waits for each packet from the Src and sends a return packet to the Src (when required by the test protocol).¶

5.4.1. Type

Percentile: For the conditional distribution of all packets with a valid value of one-way delay (undefined delays are excluded), this is a single value corresponding to the 95th percentile, as follows:¶

See Section 4.1 of [RFC3393] for details on the conditional distribution to exclude undefined values of delay, and see Section 5 of [RFC6703] for background on this analysis choice.¶

The percentile = 95, meaning that the reported delay, "95Percentile", is the smallest value of one-way PDV for which the Empirical Distribution Function, EDF(95Percentile), is greater than or equal to 95% of the singleton one-way PDV values in the conditional distribution. See Section 11.3 of [RFC2330] for the definition of the percentile statistic using the EDF.¶

5.4.2. Reference Definition

T0:

The start of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330].¶

Tf:

The end of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330].¶

95Percentile:

The time value of the result is expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 9 (see Section 9.3 of [RFC6020]) with a resolution of 0.000000001 seconds (1.0 ns), and with lossless conversion to/from the 64-bit NTP timestamp as per Section 6 of [RFC5905].¶

5.4.3. Metric Units

The 95th percentile of one-way PDV is expressed in seconds.¶

5.4.4. Calibration

Section 3.7.3 of [RFC7679] provides a means to quantify the systematic and random errors of a time measurement. Calibration in-situ could be enabled with an internal loopback that includes as much of the measurement system as possible, performs address manipulation as needed, and provides some form of isolation (e.g., deterministic delay) to avoid send-receive interface contention. Some portion of the random and systematic error can be characterized in this way.¶

For one-way delay measurements, the error calibration must include an assessment of the internal clock synchronization with its external reference (this internal clock is supplying timestamps for measurement). In practice, the time offsets [RFC5905] of clocks at both the Source and Destination are needed to estimate the systematic error due to imperfect clock synchronization (the time offsets are smoothed; thus, the random variation is not usually represented in the results).¶

time_offset:

The time value of the result is expressed in units of seconds, as a signed value of type decimal64 with fraction digits = 9 (see Section 9.3 of [RFC6020]) with a resolution of 0.000000001 seconds (1.0 ns), and with lossless conversion to/from the 64-bit NTP timestamp as per Section 6 of [RFC5905].¶

When a measurement controller requests a calibration measurement, the loopback is applied and the result is output in the same format as a normal measurement, with an additional indication that it is a calibration result. In any measurement, the measurement function SHOULD report its current estimate of the time offset [RFC5905] as an indicator of the degree of synchronization.¶

Both internal loopback calibration and clock synchronization can be used to estimate the available accuracy of the Output Metric Units. For example, repeated loopback delay measurements will reveal the portion of the output result resolution that is the result of system noise and is thus inaccurate.¶

5.5.1. Status

Current¶

5.5.2. Requester

RFC 8912¶

5.5.3. Revision

1.0¶

5.5.4. Revision Date

YYYY-MM-DD¶

6.1.1. ID (Identifier)

IANA has allocated the numeric Identifiers 4 and 5 for the two Named Metric Entries in Section 6. See Section 6.1.2 for mapping to Names.¶

6.1.3. URI

URL: https://www.iana.org/performance-metrics/RTDNS_Active_IP-UDP-Poisson_RFC8912sec6_Seconds_Raw¶

URL: https://www.iana.org/performance-metrics/RLDNS_Active_IP-UDP-Poisson_RFC8912sec6_Logical_Raw¶

6.1.4. Description

This is a metric for DNS Response performance from a network user's perspective, for a specific named resource. The metric can be measured repeatedly using different resource names.¶

RTDNS:

This metric assesses the response time, the interval from the query transmission to the response.¶

RLDNS:

This metric indicates that the response was deemed lost. In other words, the response time exceeded the maximum waiting time.¶

6.1.5. Change Controller

IETF¶

6.1.6. Version (of Registry Format)

1.0¶

6.2.1. Reference Definition

For Delay:¶

Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, November 1987, <https://www.rfc-editor.org/info/rfc1035> (and updates). [RFC1035]¶

Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip Delay Metric for IPPM", RFC 2681, DOI 10.17487/RFC2681, September 1999, <https://www.rfc-editor.org/info/rfc2681>. [RFC2681]¶

Section 2.4 of [RFC2681] provides the reference definition of the singleton (single value) round-trip delay metric. Section 3.4 of [RFC2681] provides the reference definition expanded to cover a multi-singleton sample. Note that terms such as "singleton" and "sample" are defined in Section 11 of [RFC2330].¶

For DNS Response Latency, the entities in [RFC1035] must be mapped to [RFC2681]. The Local Host with its User Program and Resolver take the Role of "Src", and the Foreign Name Server takes the Role of "Dst".¶

Note that although the definition of round-trip delay between the Source (Src) and the Destination (Dst) at T as provided in Section 2.4 of [RFC2681] is directionally ambiguous in the text, this metric tightens the definition further to recognize that the host in the Src Role will send the first packet to the host in the Dst Role and will ultimately receive the corresponding return packet from the Dst (when neither is lost).¶

For Loss:¶

Morton, A., "Round-Trip Packet Loss Metrics", RFC 6673, DOI 10.17487/RFC6673, August 2012, <https://www.rfc-editor.org/info/rfc6673>. [RFC6673]¶

For DNS Response Loss, the entities in [RFC1035] must be mapped to [RFC6673]. The Local Host with its User Program and Resolver take the Role of "Src", and the Foreign Name Server takes the Role of "Dst".¶

Both response time and Loss metrics employ a maximum waiting time for received responses, so the count of lost packets to total packets sent is the basis for the loss determination as per Section 4.3 of [RFC6673].¶

6.2.2. Fixed Parameters

Type-P as defined in Section 13 of [RFC2330]:

IPv4 header values:

DSCP:

Set to 0¶

TTL:

Set to 255¶

Protocol:

Set to 17 (UDP)¶

IPv6 header values:

DSCP:

Set to 0¶

Hop Count:

Set to 255¶

Next Header:

Set to 17 (UDP)¶

Flow Label:

Set to 0¶

Extension Headers:

None¶

UDP header values:

Source port:

53¶

Destination port:

53¶

Checksum:

The checksum MUST be calculated and the non-zero checksum included in the header¶

Payload:

The payload contains a DNS message as defined in [RFC1035] with the following values:¶

The DNS header section contains:

Identification (see the Runtime column)

QR:

Set to 0 (Query)¶

OPCODE:

Set to 0 (standard query)¶

AA:

Not set¶

TC:

Not set¶

RD:

Set to 1 (recursion desired)¶

RA:

Not set¶

RCODE:

Not set¶

QDCOUNT:

Set to 1 (only one entry)¶

ANCOUNT:

Not set¶

NSCOUNT:

Not set¶

ARCOUNT:

Not set¶

The Question section contains:

QNAME:

The Fully Qualified Domain Name (FQDN) provided as input for the test; see the Runtime column¶

QTYPE:

The query type provided as input for the test; see the Runtime column¶

QCLASS:

Set to 1 for IN¶

The other sections do not contain any Resource Records (RRs).

Other measurement Parameters:

Tmax:

A loss threshold waiting time (and to help disambiguate queries). The value is 5.0, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms), with lossless conversion to/from the 32-bit NTP timestamp as per Section 6 of [RFC5905].¶

Observation:

Reply packets will contain a DNS Response and may contain RRs.¶

6.3.1. Reference Methods

The methodology for this metric (equivalent to Type-P-Round-trip-Delay-Poisson-Stream) is defined as in Section 2.6 of [RFC2681] (for singletons) and Section 3.6 of [RFC2681] (for samples) using the Type-P and Timeout defined in the Fixed Parameters column.¶

The reference method distinguishes between long-delayed packets and lost packets by implementing a maximum waiting time for packet arrival. Tmax is the waiting time used as the threshold to declare a response packet lost. Lost packets SHALL be designated as having undefined delay and counted for the RLDNS metric.¶

The calculations on the delay (RTT) SHALL be performed on the conditional distribution, conditioned on successful packet arrival within Tmax. Also, when all packet delays are stored, the process that calculates the RTT value MUST enforce the Tmax threshold on stored values before calculations. See Section 4.1 of [RFC3393] for details on the conditional distribution to exclude undefined values of delay, and see Section 5 of [RFC6703] for background on this analysis choice.¶

The reference method requires some way to distinguish between different packets in a stream to establish correspondence between sending times and receiving times for each successfully arriving reply.¶

DNS messages bearing queries provide for random ID Numbers in the Identification header field, so more than one query may be launched while a previous request is outstanding when the ID Number is used. Therefore, the ID Number MUST be retained at the Src and included with each response packet to disambiguate packet reordering if it occurs.¶

If a DNS Response does not arrive within Tmax, the response time RTDNS is undefined, and RLDNS = 1. The Message ID SHALL be used to disambiguate the successive queries that are otherwise identical.¶

Since the ID Number field is only 16 bits in length, it places a limit on the number of simultaneous outstanding DNS queries during a stress test from a single Src address.¶

Refer to Section 4.4 of [RFC6673] for an expanded discussion of the instruction to "send a Type-P packet back to the Src as quickly as possible" in Section 2.6 of [RFC2681]. However, the DNS server is expected to perform all required functions to prepare and send a response, so the response time will include processing time and network delay. Section 8 of [RFC6673] presents additional requirements that SHALL be included in the Method of Measurement for this metric.¶

In addition to operations described in [RFC2681], the Src MUST parse the DNS headers of the reply and prepare the query response information for subsequent reporting as a measured result, along with the round-trip delay.¶

6.3.2. Packet Stream Generation

This section provides details regarding packet traffic, which is used as the basis for measurement. In IPPM Metrics, this is called the "stream"; this stream can easily be described by providing the list of stream Parameters.¶

Section 11.1.3 of [RFC2330] provides three methods to generate Poisson sampling intervals. The reciprocal of lambda is the average packet spacing; thus, the Runtime Parameter is Reciprocal_lambda = 1⁠/lambda, in seconds.¶

Method 3 SHALL be used. Where given a start time (Runtime Parameter), the subsequent send times are all computed prior to measurement by computing the pseudorandom distribution of inter-packet send times (truncating the distribution as specified in the Parameter Trunc), and the Src sends each packet at the computed times.¶

Note that Trunc is the upper limit on inter-packet times in the Poisson distribution. A random value greater than Trunc is set equal to Trunc instead.¶

6.3.3. Traffic Filtering (Observation) Details

N/A¶

6.3.4. Sampling Distribution

N/A¶

6.3.5. Runtime Parameters and Data Format

Runtime Parameters are input factors that must be determined, configured into the measurement system, and reported with the results for the context to be complete.¶

Src:

The IP address of the host in the Src Role (format ipv4‑address-no-zone value for IPv4 or ipv6-address-no-zone value for IPv6; see Section 4 of [RFC6991]).¶

Dst:

The IP address of the host in the Dst Role (format ipv4‑address-no-zone value for IPv4 or ipv6-address-no-zone value for IPv6; see Section 4 of [RFC6991]).¶

T0:

A time, the start of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330]. When T0 is "all-zeros", a start time is unspecified and Tf is to be interpreted as the duration of the measurement interval. The start time is controlled through other means.¶

Tf:

A time, the end of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330]. When T0 is "all-zeros", an ending time and date is ignored and Tf is interpreted as the duration of the measurement interval.¶

Reciprocal_lambda:

Average packet interval for Poisson streams, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) with a resolution of 0.0001 seconds (0.1 ms), and with lossless conversion to/from the 32-bit NTP timestamp as per Section 6 of [RFC5905].¶

Trunc:

Upper limit on Poisson distribution, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) with a resolution of 0.0001 seconds (0.1 ms), and with lossless conversion to/from the 32-bit NTP timestamp as per Section 6 of [RFC5905] (values above this limit will be clipped and set to the limit value).¶

ID:

The 16-bit Identifier assigned by the program that generates the query. The ID value must vary in successive queries (a list of IDs is needed); see Section 4.1.1 of [RFC1035]. This Identifier is copied into the corresponding reply and can be used by the requester (Src) to match replies with any outstanding queries.¶

QNAME:

The domain name of the query, formatted as specified in Section 4 of [RFC6991].¶

QTYPE:

The query type, which will correspond to the IP address family of the query (decimal 1 for IPv4 or 28 for IPv6), formatted as a uint16, as per Section 9.2 of [RFC6020].¶

6.3.6. Roles

Src:

Launches each packet and waits for return transmissions from the Dst.¶

Dst:

Waits for each packet from the Src and sends a return packet to the Src.¶

6.4.1. Type

Raw: For each DNS query packet sent, sets of values as defined in the next column, including the status of the response, only assigning delay values to successful query-response pairs.¶

6.4.2. Reference Definition

For all outputs:¶

T:

The time the DNS query was sent during the measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330].¶

dT:

The time value of the round-trip delay to receive the DNS Response, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 9 (see Section 9.3 of [RFC6020]) with a resolution of 0.000000001 seconds (1.0 ns), and with lossless conversion to/from the 64-bit NTP timestamp as per Section 6 of [RFC5905]. This value is undefined when the response packet is not received at the Src within a waiting time of Tmax seconds.¶

RCODE:

The value of the RCODE field in the DNS Response header, expressed as a uint64 as specified in Section 9.2 of [RFC6020]. Non-zero values convey errors in the response, and such replies must be analyzed separately from successful requests.¶

Logical:

The numeric value of the result is expressed as a Logical value, where 1 = Lost and 0 = Received, as a positive value of type uint8 (represents integer values between 0 and 255, inclusively (see Section 9.2 of [RFC6020]). Note that for queries with outcome 1 = Lost, dT and RCODE will be set to the maximum for decimal64 and uint64, respectively.¶

6.4.3. Metric Units

RTDNS:

Round-trip delay, dT, is expressed in seconds.¶

RLDNS:

The Logical value, where 1 = Lost and 0 = Received.¶

6.4.4. Calibration

Section 3.7.3 of [RFC7679] provides a means to quantify the systematic and random errors of a time measurement. Calibration in-situ could be enabled with an internal loopback at the Source host that includes as much of the measurement system as possible, performs address and payload manipulation as needed, and provides some form of isolation (e.g., deterministic delay) to avoid send-receive interface contention. Some portion of the random and systematic error can be characterized in this way.¶

When a measurement controller requests a calibration measurement, the loopback is applied and the result is output in the same format as a normal measurement, with an additional indication that it is a calibration result.¶

Both internal loopback calibration and clock synchronization can be used to estimate the available accuracy of the Output Metric Units. For example, repeated loopback delay measurements will reveal the portion of the output result resolution that is the result of system noise and is thus inaccurate.¶

6.5.1. Status

Current¶

6.5.2. Requester

RFC 8912¶

6.5.3. Revision

1.0¶

6.5.4. Revision Date

YYYY-MM-DD¶

7.1.1. ID (Identifier)

IANA has allocated the numeric Identifiers 6-11 for the six Named Metric Entries in Section 7 See Section 7.1.2 for mapping to Names.¶

7.1.3. URI

URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-Poisson-Payload250B_RFC8912sec7_Seconds_95Percentile¶

URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-Poisson-Payload250B_RFC8912sec7_Seconds_Mean¶

URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-Poisson-Payload250B_RFC8912sec7_Seconds_Min¶

URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-Poisson-Payload250B_RFC8912sec7_Seconds_Max¶

URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-Poisson-Payload250B_RFC8912sec7_Seconds_StdDev¶

URL: https://www.iana.org/performance-metrics/OWLoss_Active_IP-UDP-Poisson-Payload250B_RFC8912sec7_Percent_LossRatio¶

7.1.4. Description

OWDelay:

This metric assesses the delay of a stream of packets exchanged between two hosts (or measurement points) and reports the <statistic> of one-way delay for all successfully exchanged packets based on their conditional delay distribution.¶

where <statistic> is one of:¶

• 95Percentile¶
• Mean¶
• Min¶
• Max¶
• StdDev¶

OWLoss:

This metric assesses the loss ratio of a stream of packets exchanged between two hosts (which are the two measurement points). The output is the one-way loss ratio for all transmitted packets expressed as a percentage.¶

7.1.5. Change Controller

IETF¶

7.1.6. Version (of Registry Format)

1.0¶

7.2.1. Reference Definition

For delay:¶

Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton, Ed., "A One-Way Delay Metric for IP Performance Metrics (IPPM)", STD 81, RFC 7679, DOI 10.17487/RFC7679, January 2016, <https://www.rfc-editor.org/info/rfc7679>. [RFC7679]¶

Morton, A. and E. Stephan, "Spatial Composition of Metrics", RFC 6049, DOI 10.17487/RFC6049, January 2011, <https://www.rfc-editor.org/info/rfc6049>. [RFC6049]¶

Section 3.4 of [RFC7679] provides the reference definition of the singleton (single value) one-way delay metric. Section 4.4 of [RFC7679] provides the reference definition expanded to cover a multi-value sample. Note that terms such as "singleton" and "sample" are defined in Section 11 of [RFC2330].¶

Only successful packet transfers with finite delay are included in the sample, as prescribed in Section 4.1.2 of [RFC6049].¶

For loss:¶

Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton, Ed., "A One-Way Loss Metric for IP Performance Metrics (IPPM)", STD 82, RFC 7680, DOI 10.17487/RFC7680, January 2016, <https://www.rfc-editor.org/info/rfc7680>. [RFC7680]¶

Section 2.4 of [RFC7680] provides the reference definition of the singleton (single value) one-way Loss metric. Section 3.4 of [RFC7680] provides the reference definition expanded to cover a multi-singleton sample. Note that terms such as "singleton" and "sample" are defined in Section 11 of [RFC2330].¶

7.2.2. Fixed Parameters

Type-P:

IPv4 header values:

DSCP:

Set to 0¶

TTL:

Set to 255¶

Protocol:

Set to 17 (UDP)¶

IPv6 header values:

DSCP:

Set to 0¶

Hop Count:

Set to 255¶

Next Header:

Set to 17 (UDP)¶

Flow Label:

Set to 0¶

Extension Headers:

None¶

UDP header values:

Checksum:

The checksum MUST be calculated and the non-zero checksum included in the header¶

UDP Payload:

TWAMP-Test packet formats (Section 4.1.2 of [RFC5357])¶

• Security features in use influence the number of Padding octets¶
• 250 octets total, including the TWAMP format type, which MUST be reported¶

Other measurement Parameters:

Tmax:

A loss threshold waiting time with value 3.0, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms), with lossless conversion to/from the 32-bit NTP timestamp as per Section 6 of [RFC5905].¶

See the Packet Stream Generation section for two additional Fixed Parameters.¶

7.3.1. Reference Methods

The methodology for this metric (equivalent to Type-P-One-way-Delay-Poisson-Stream) is defined as in Section 3.6 of [RFC7679] (for singletons) and Section 4.6 of [RFC7679] (for samples) using the Type-P and Tmax defined in the Fixed Parameters column.¶

The reference method distinguishes between long-delayed packets and lost packets by implementing a maximum waiting time for packet arrival. Tmax is the waiting time used as the threshold to declare a packet lost. Lost packets SHALL be designated as having undefined delay and counted for the OWLoss metric.¶

The calculations on the one-way delay SHALL be performed on the conditional distribution, conditioned on successful packet arrival within Tmax. Also, when all packet delays are stored, the process that calculates the one-way delay value MUST enforce the Tmax threshold on stored values before calculations. See Section 4.1 of [RFC3393] for details on the conditional distribution to exclude undefined values of delay, and see Section 5 of [RFC6703] for background on this analysis choice.¶

The reference method requires some way to distinguish between different packets in a stream to establish correspondence between sending times and receiving times for each successfully arriving packet.¶

Since a standard measurement protocol is employed [RFC5357], the measurement process will determine the sequence numbers or timestamps applied to test packets after the Fixed and Runtime Parameters are passed to that process. The measurement protocol dictates the format of sequence numbers and timestamps conveyed in the TWAMP-Test packet payload.¶

7.3.2. Packet Stream Generation

This section provides details regarding packet traffic, which is used as the basis for measurement. In IPPM Metrics, this is called the "stream"; this stream can easily be described by providing the list of stream Parameters.¶

Section 11.1.3 of [RFC2330] provides three methods to generate Poisson sampling intervals. The reciprocal of lambda is the average packet spacing; thus, the Runtime Parameter is Reciprocal_lambda = 1⁠/lambda, in seconds.¶

Method 3 SHALL be used. Where given a start time (Runtime Parameter), the subsequent send times are all computed prior to measurement by computing the pseudorandom distribution of inter-packet send times (truncating the distribution as specified in the Parameter Trunc), and the Src sends each packet at the computed times.¶

Note that Trunc is the upper limit on inter-packet times in the Poisson distribution. A random value greater than Trunc is set equal to Trunc instead.¶

Reciprocal_lambda:

Average packet interval for Poisson streams, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) with a resolution of 0.0001 seconds (0.1 ms), and with lossless conversion to/from the 32-bit NTP timestamp as per Section 6 of [RFC5905]. Reciprocal_lambda = 1 second.¶

Trunc:

Upper limit on Poisson distribution, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) with a resolution of 0.0001 seconds (0.1 ms), and with lossless conversion to/from the 32-bit NTP timestamp as per Section 6 of [RFC5905] (values above this limit will be clipped and set to the limit value). Trunc = 30.0000 seconds.¶

7.3.3. Traffic Filtering (Observation) Details

N/A¶

7.3.4. Sampling Distribution

N/A¶

7.3.5. Runtime Parameters and Data Format

Runtime Parameters are input factors that must be determined, configured into the measurement system, and reported with the results for the context to be complete.¶

Src:

The IP address of the host in the Src Role (format ipv4‑address-no-zone value for IPv4 or ipv6-address-no-zone value for IPv6; see Section 4 of [RFC6991]).¶

Dst:

The IP address of the host in the Dst Role (format ipv4‑address-no-zone value for IPv4 or ipv6-address-no-zone value for IPv6; see Section 4 of [RFC6991]).¶

T0:

A time, the start of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330]. When T0 is "all-zeros", a start time is unspecified and Tf is to be interpreted as the duration of the measurement interval. The start time is controlled through other means.¶

Tf:

A time, the end of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330]. When T0 is "all-zeros", an ending time and date is ignored and Tf is interpreted as the duration of the measurement interval.¶

7.3.6. Roles

Src:

Launches each packet and waits for return transmissions from the Dst.  An example is the TWAMP Session-Sender.¶

Dst:

Waits for each packet from the Src and sends a return packet to the Src.  An example is the TWAMP Session-Reflector.¶

7.4.1. Type

Types are discussed in the subsections below.¶

7.4.2. Reference Definition

For all output types:¶

T0:

The start of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330].¶

Tf:

The end of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330].¶

For LossRatio, the count of lost packets to total packets sent is the basis for the loss ratio calculation as per Section 4.1 of [RFC7680].¶

For each <statistic> or Percent_LossRatio, one of the following subsections applies.¶

   Max = (FiniteDelay[j])

                     _                                       _
                    |            N                            |
                    |           ---                           |
                    |     1     \                          2  |
    Std_Dev = SQRT  |  -------   >   (Delay[n] - MeanDelay)   |
                    |    (N)    /                             |
                    |           ---                           |
                    |          n = 1                          |
                    |_                                       _|

7.4.3. Metric Units

The <statistic> of one-way delay is expressed in seconds, where <statistic> is one of:¶

• 95Percentile¶
• Mean¶
• Min¶
• Max¶
• StdDev¶

The one-way loss ratio is expressed as a percentage of lost packets to total packets sent.¶

7.4.4. Calibration

Section 3.7.3 of [RFC7679] provides a means to quantify the systematic and random errors of a time measurement. Calibration in-situ could be enabled with an internal loopback that includes as much of the measurement system as possible, performs address manipulation as needed, and provides some form of isolation (e.g., deterministic delay) to avoid send-receive interface contention. Some portion of the random and systematic error can be characterized in this way.¶

For one-way delay measurements, the error calibration must include an assessment of the internal clock synchronization with its external reference (this internal clock is supplying timestamps for measurement). In practice, the time offsets [RFC5905] of clocks at both the Source and Destination are needed to estimate the systematic error due to imperfect clock synchronization (the time offsets [RFC5905] are smoothed; thus, the random variation is not usually represented in the results).¶

time_offset:

The time value of the result is expressed in units of seconds, as a signed value of type decimal64 with fraction digits = 9 (see Section 9.3 of [RFC6020]) with a resolution of 0.000000001 seconds (1.0 ns), and with lossless conversion to/from the 64-bit NTP timestamp as per Section 6 of [RFC5905].¶

When a measurement controller requests a calibration measurement, the loopback is applied and the result is output in the same format as a normal measurement, with an additional indication that it is a calibration result. In any measurement, the measurement function SHOULD report its current estimate of the time offset [RFC5905] as an indicator of the degree of synchronization.¶

Both internal loopback calibration and clock synchronization can be used to estimate the available accuracy of the Output Metric Units. For example, repeated loopback delay measurements will reveal the portion of the output result resolution that is the result of system noise and is thus inaccurate.¶

7.5.1. Status

Current¶

7.5.2. Requester

RFC 8912¶

7.5.3. Revision

1.0¶

7.5.4. Revision Date

YYYY-MM-DD¶

8.1.1. ID (Identifier)

IANA has allocated the numeric Identifiers 12-17 for the six Named Metric Entries in Section 8. See Section 8.1.2 for mapping to Names.¶

8.1.3. URI

URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-Periodic20m-Payload142B_RFC8912sec8_Seconds_95Percentile¶

URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-Periodic20m-Payload142B_RFC8912sec8_Seconds_Mean¶

URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-Periodic20m-Payload142B_RFC8912sec8_Seconds_Min¶

URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-Periodic20m-Payload142B_RFC8912sec8_Seconds_Max¶

URL: https://www.iana.org/performance-metrics/OWDelay_Active_IP-UDP-Periodic20m-Payload142B_RFC8912sec8_Seconds_StdDev¶

URL: https://www.iana.org/performance-metrics/OWLoss_Active_IP-UDP-Periodic20m-Payload142B_RFC8912sec8_Percent_LossRatio¶

8.1.4. Description

OWDelay:

This metric assesses the delay of a stream of packets exchanged between two hosts (or measurement points) and reports the <statistic> one-way delay for all successfully exchanged packets based on their conditional delay distribution.¶

where <statistic> is one of:¶

• 95Percentile¶
• Mean¶
• Min¶
• Max¶
• StdDev¶

OWLoss:

This metric assesses the loss ratio of a stream of packets exchanged between two hosts (which are the two measurement points). The output is the one-way loss ratio for all transmitted packets expressed as a percentage.¶

8.1.5. Change Controller

IETF¶

8.1.6. Version (of Registry Format)

1.0¶

8.2.1. Reference Definition

For delay:¶

Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton, Ed., "A One-Way Delay Metric for IP Performance Metrics (IPPM)", STD 81, RFC 7679, DOI 10.17487/RFC7679, January 2016, <https://www.rfc-editor.org/info/rfc7679>. [RFC7679]¶

Morton, A. and E. Stephan, "Spatial Composition of Metrics", RFC 6049, DOI 10.17487/RFC6049, January 2011, <https://www.rfc-editor.org/info/rfc6049>. [RFC6049]¶

Section 3.4 of [RFC7679] provides the reference definition of the singleton (single value) one-way delay metric. Section 4.4 of [RFC7679] provides the reference definition expanded to cover a multi-value sample. Note that terms such as "singleton" and "sample" are defined in Section 11 of [RFC2330].¶

Only successful packet transfers with finite delay are included in the sample, as prescribed in Section 4.1.2 of [RFC6049].¶

For loss:¶

Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton, Ed., "A One-Way Loss Metric for IP Performance Metrics (IPPM)", STD 82, RFC 7680, DOI 10.17487/RFC7680, January 2016, <https://www.rfc-editor.org/info/rfc7680>. [RFC7680]¶

Section 2.4 of [RFC7680] provides the reference definition of the singleton (single value) one-way Loss metric. Section 3.4 of [RFC7680] provides the reference definition expanded to cover a multi-singleton sample. Note that terms such as "singleton" and "sample" are defined in Section 11 of [RFC2330].¶

8.2.2. Fixed Parameters

Type-P:

IPv4 header values:

DSCP:

Set to 0¶

TTL:

Set to 255¶

Protocol:

Set to 17 (UDP)¶

IPv6 header values:

DSCP:

Set to 0¶

Hop Count:

Set to 255¶

Next Header:

Set to 17 (UDP)¶

Flow Label:

Set to 0¶

Extension Headers:

None¶

UDP header values:

Checksum:

The checksum MUST be calculated and the non-zero checksum included in the header¶

UDP Payload:

TWAMP-Test packet formats (Section 4.1.2 of [RFC5357])¶

• Security features in use influence the number of Padding octets¶
• 142 octets total, including the TWAMP format (and format type MUST be reported, if used)¶

Other measurement Parameters:

Tmax:

A loss threshold waiting time with value 3.0, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms), with lossless conversion to/from the 32-bit NTP timestamp as per Section 6 of [RFC5905].¶

See the Packet Stream Generation section for three additional Fixed Parameters.¶

8.3.1. Reference Methods

The methodology for this metric (equivalent to Type-P-One-way-Delay-Poisson-Stream) is defined as in Section 3.6 of [RFC7679] (for singletons) and Section 4.6 of [RFC7679] (for samples) using the Type-P and Tmax defined in the Fixed Parameters column. However, a Periodic stream is used, as defined in [RFC3432].¶

The reference method distinguishes between long-delayed packets and lost packets by implementing a maximum waiting time for packet arrival. Tmax is the waiting time used as the threshold to declare a packet lost. Lost packets SHALL be designated as having undefined delay and counted for the OWLoss metric.¶

The calculations on the one-way delay SHALL be performed on the conditional distribution, conditioned on successful packet arrival within Tmax. Also, when all packet delays are stored, the process that calculates the one-way delay value MUST enforce the Tmax threshold on stored values before calculations. See Section 4.1 of [RFC3393] for details on the conditional distribution to exclude undefined values of delay, and see Section 5 of [RFC6703] for background on this analysis choice.¶

The reference method requires some way to distinguish between different packets in a stream to establish correspondence between sending times and receiving times for each successfully arriving packet.¶

Since a standard measurement protocol is employed [RFC5357], the measurement process will determine the sequence numbers or timestamps applied to test packets after the Fixed and Runtime Parameters are passed to that process. The measurement protocol dictates the format of sequence numbers and timestamps conveyed in the TWAMP-Test packet payload.¶

8.3.2. Packet Stream Generation

This section provides details regarding packet traffic, which is used as the basis for measurement. In IPPM Metrics, this is called the "stream"; this stream can easily be described by providing the list of stream Parameters.¶

Section 3 of [RFC3432] prescribes the method for generating Periodic streams using associated Parameters.¶

incT:

The nominal duration of the inter-packet interval, first bit to first bit, with value 0.0200, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms), with lossless conversion to/from the 32-bit NTP timestamp as per Section 6 of [RFC5905].¶

dT:

The duration of the interval for allowed sample start times, with value 1.0000, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms), with lossless conversion to/from the 32-bit NTP timestamp as per Section 6 of [RFC5905].¶

T0:

The actual start time of the periodic stream, determined from T0 and dT.¶

Note: An initiation process with a number of control exchanges resulting in unpredictable start times (within a time interval) may be sufficient to avoid synchronization of periodic streams and is a valid replacement for selecting a start time at random from a fixed interval.¶

These stream Parameters will be specified as Runtime Parameters.¶

8.3.3. Traffic Filtering (Observation) Details

N/A¶

8.3.4. Sampling Distribution

N/A¶

8.3.5. Runtime Parameters and Data Format

Runtime Parameters are input factors that must be determined, configured into the measurement system, and reported with the results for the context to be complete.¶

Src:

The IP address of the host in the Src Role (format ipv4‑address-no-zone value for IPv4 or ipv6-address-no-zone value for IPv6; see Section 4 of [RFC6991]).¶

Dst:

The IP address of the host in the Dst Role (format ipv4‑address-no-zone value for IPv4 or ipv6-address-no-zone value for IPv6; see Section 4 of [RFC6991]).¶

T0:

A time, the start of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330]. When T0 is "all-zeros", a start time is unspecified and Tf is to be interpreted as the duration of the measurement interval. The start time is controlled through other means.¶

Tf:

A time, the end of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330]. When T0 is "all-zeros", an ending time and date is ignored and Tf is interpreted as the duration of the measurement interval.¶

8.3.6. Roles

Src:

Launches each packet and waits for return transmissions from the Dst.  An example is the TWAMP Session-Sender.¶

Dst:

Waits for each packet from the Src and sends a return packet to the Src.  An example is the TWAMP Session-Reflector.¶

8.4.1. Type

Latency and Loss Types are discussed in the subsections below.¶

8.4.2. Reference Definition

For all output types:¶

T0:

The start of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330].¶

Tf:

The end of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330].¶

For LossRatio, the count of lost packets to total packets sent is the basis for the loss ratio calculation as per Section 4.1 of [RFC7680].¶

For each <statistic> or Percent_LossRatio, one of the following subsections applies.¶

   Max = (FiniteDelay[j])

                     _                                       _
                    |            N                            |
                    |           ---                           |
                    |     1     \                          2  |
    Std_Dev = SQRT  |  -------   >   (Delay[n] - MeanDelay)   |
                    |    (N)    /                             |
                    |           ---                           |
                    |          n = 1                          |
                    |_                                       _|

8.4.3. Metric Units

The <statistic> of one-way delay is expressed in seconds, where <statistic> is one of:¶

• 95Percentile¶
• Mean¶
• Min¶
• Max¶
• StdDev¶

The one-way loss ratio is expressed as a percentage of lost packets to total packets sent.¶

8.4.4. Calibration

Section 3.7.3 of [RFC7679] provides a means to quantify the systematic and random errors of a time measurement. Calibration in-situ could be enabled with an internal loopback that includes as much of the measurement system as possible, performs address manipulation as needed, and provides some form of isolation (e.g., deterministic delay) to avoid send-receive interface contention. Some portion of the random and systematic error can be characterized in this way.¶

For one-way delay measurements, the error calibration must include an assessment of the internal clock synchronization with its external reference (this internal clock is supplying timestamps for measurement). In practice, the time offsets [RFC5905] of clocks at both the Source and Destination are needed to estimate the systematic error due to imperfect clock synchronization (the time offsets [RFC5905] are smoothed; thus, the random variation is not usually represented in the results).¶

time_offset:

The time value of the result is expressed in units of seconds, as a signed value of type decimal64 with fraction digits = 9 (see Section 9.3 of [RFC6020]) with a resolution of 0.000000001 seconds (1.0 ns), and with lossless conversion to/from the 64-bit NTP timestamp as per Section 6 of [RFC5905].¶

When a measurement controller requests a calibration measurement, the loopback is applied and the result is output in the same format as a normal measurement, with an additional indication that it is a calibration result. In any measurement, the measurement function SHOULD report its current estimate of the time offset [RFC5905] as an indicator of the degree of synchronization.¶

Both internal loopback calibration and clock synchronization can be used to estimate the available accuracy of the Output Metric Units. For example, repeated loopback delay measurements will reveal the portion of the output result resolution that is the result of system noise and is thus inaccurate.¶

8.5.1. Status

Current¶

8.5.2. Requester

RFC 8912¶

8.5.3. Revision

1.0¶

8.5.4. Revision Date

YYYY-MM-DD¶

9.1.1. ID (Identifier)

IANA has allocated the numeric Identifiers 18-21 for the four Named Metric Entries in Section 9. See Section 9.1.2 for mapping to Names.¶

9.1.3. URI

URL: https://www.iana.org/performance-metrics/RTDelay_Active_IP-ICMP-SendOnRcv_RFC8912sec9_Seconds_Mean¶

URL: https://www.iana.org/performance-metrics/RTDelay_Active_IP-ICMP-SendOnRcv_RFC8912sec9_Seconds_Min¶

URL: https://www.iana.org/performance-metrics/RTDelay_Active_IP-ICMP-SendOnRcv_RFC8912sec9_Seconds_Max¶

URL: https://www.iana.org/performance-metrics/RTLoss_Active_IP-ICMP-SendOnRcv_RFC8912sec9_Percent_LossRatio¶

9.1.4. Description

RTDelay:

This metric assesses the delay of a stream of ICMP packets exchanged between two hosts (which are the two measurement points). The output is the round-trip delay for all successfully exchanged packets expressed as the <statistic> of their conditional delay distribution, where <statistic> is one of:¶

• Mean¶
• Min¶
• Max¶

RTLoss:

This metric assesses the loss ratio of a stream of ICMP packets exchanged between two hosts (which are the two measurement points). The output is the round-trip loss ratio for all transmitted packets expressed as a percentage.¶

9.1.5. Change Controller

IETF¶

9.1.6. Version (of Registry Format)

1.0¶

9.2.1. Reference Definition

For delay:¶

Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip Delay Metric for IPPM", RFC 2681, DOI 10.17487/RFC2681, September 1999, <https://www.rfc-editor.org/info/rfc2681>. [RFC2681]¶

Section 2.4 of [RFC2681] provides the reference definition of the singleton (single value) round-trip delay metric. Section 3.4 of [RFC2681] provides the reference definition expanded to cover a multi-singleton sample. Note that terms such as "singleton" and "sample" are defined in Section 11 of [RFC2330].¶

Note that although the definition of round-trip delay between the Source (Src) and the Destination (Dst) as provided in Section 2.4 of [RFC2681] is directionally ambiguous in the text, this metric tightens the definition further to recognize that the host in the Src Role will send the first packet to the host in the Dst Role and will ultimately receive the corresponding return packet from the Dst (when neither is lost).¶

Finally, note that the variable "dT" is used in [RFC2681] to refer to the value of round-trip delay in metric definitions and methods. The variable "dT" has been reused in other IPPM literature to refer to different quantities and cannot be used as a global variable name.¶

For loss:¶

Morton, A., "Round-Trip Packet Loss Metrics", RFC 6673, DOI 10.17487/RFC6673, August 2012, <https://www.rfc-editor.org/info/rfc6673>. [RFC6673]¶

Both Delay and Loss metrics employ a maximum waiting time for received packets, so the count of lost packets to total packets sent is the basis for the loss ratio calculation as per Section 6.1 of [RFC6673].¶

9.2.2. Fixed Parameters

Type-P as defined in Section 13 of [RFC2330]:

IPv4 header values:

DSCP:

Set to 0¶

TTL:

Set to 255¶

Protocol:

Set to 01 (ICMP)¶

IPv6 header values:

DSCP:

Set to 0¶

Hop Count:

Set to 255¶

Next Header:

Set to 128 decimal (ICMP)¶

Flow Label:

Set to 0¶

Extension Headers:

None¶

ICMP header values:

Type:

8 (Echo Request)¶

Code:

0¶

Checksum:

The checksum MUST be calculated and the non-zero checksum included in the header¶

(Identifier and sequence number set at runtime)

ICMP Payload:

Total of 32 bytes of random information, constant per test¶

Other measurement Parameters:

Tmax:

A loss threshold waiting time with value 3.0, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms), with lossless conversion to/from the 32-bit NTP timestamp as per Section 6 of [RFC5905].¶

9.3.1. Reference Methods

The methodology for this metric (equivalent to Type-P-Round-trip-Delay-Poisson-Stream) is defined as in Section 2.6 of [RFC2681] (for singletons) and Section 3.6 of [RFC2681] (for samples) using the Type-P and Tmax defined in the Fixed Parameters column.¶

The reference method distinguishes between long-delayed packets and lost packets by implementing a maximum waiting time for packet arrival. Tmax is the waiting time used as the threshold to declare a packet lost. Lost packets SHALL be designated as having undefined delay and counted for the RTLoss metric.¶

The calculations on the delay (RTD) SHALL be performed on the conditional distribution, conditioned on successful packet arrival within Tmax. Also, when all packet delays are stored, the process that calculates the RTD value MUST enforce the Tmax threshold on stored values before calculations. See Section 4.1 of [RFC3393] for details on the conditional distribution to exclude undefined values of delay, and see Section 5 of [RFC6703] for background on this analysis choice.¶

The reference method requires some way to distinguish between different packets in a stream to establish correspondence between sending times and receiving times for each successfully arriving packet. Sequence numbers or other send-order identification MUST be retained at the Src or included with each packet to disambiguate packet reordering if it occurs.¶

The measurement process will determine the sequence numbers applied to test packets after the Fixed and Runtime Parameters are passed to that process. The ICMP measurement process and protocol will dictate the format of sequence numbers and other Identifiers.¶

Refer to Section 4.4 of [RFC6673] for an expanded discussion of the instruction to "send a Type-P packet back to the Src as quickly as possible" in Section 2.6 of [RFC2681]. Section 8 of [RFC6673] presents additional requirements that MUST be included in the Method of Measurement for this metric.¶

9.3.2. Packet Stream Generation

This section provides details regarding packet traffic, which is used as the basis for measurement. In IPPM Metrics, this is called the "stream"; this stream can easily be described by providing the list of stream Parameters.¶

The ICMP metrics use a sending discipline called "SendOnRcv" or Send On Receive. This is a modification of Section 3 of [RFC3432], which prescribes the method for generating Periodic streams using associated Parameters as defined below for this description:¶

incT:

The nominal duration of the inter-packet interval, first bit to first bit.¶

dT:

The duration of the interval for allowed sample start times.¶

The incT stream Parameter will be specified as a Runtime Parameter, and dT is not used in SendOnRcv.¶

A SendOnRcv sender behaves exactly like a Periodic stream generator while all reply packets arrive with RTD < incT, and the inter-packet interval will be constant.¶

If a reply packet arrives with RTD >= incT, then the inter-packet interval for the next sending time is nominally RTD.¶

If a reply packet fails to arrive within Tmax, then the inter-packet interval for the next sending time is nominally Tmax.¶

If an immediate Send On Reply arrival is desired, then set incT = 0.¶

9.3.3. Traffic Filtering (Observation) Details

N/A¶

9.3.4. Sampling Distribution

N/A¶

9.3.5. Runtime Parameters and Data Format

Runtime Parameters are input factors that must be determined, configured into the measurement system, and reported with the results for the context to be complete.¶

Src:

The IP address of the host in the Src Role (format ipv4‑address-no-zone value for IPv4 or ipv6-address-no-zone value for IPv6; see Section 4 of [RFC6991]).¶

Dst:

The IP address of the host in the Dst Role (format ipv4‑address-no-zone value for IPv4 or ipv6-address-no-zone value for IPv6; see Section 4 of [RFC6991]).¶

incT:

The nominal duration of the inter-packet interval, first bit to first bit, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms).¶

T0:

A time, the start of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330]. When T0 is "all-zeros", a start time is unspecified and Tf is to be interpreted as the duration of the measurement interval. The start time is controlled through other means.¶

Count:

The total count of ICMP Echo Requests to send, formatted as a uint16, as per Section 9.2 of [RFC6020].¶

See the Packet Stream Generation section for additional Runtime Parameters.¶

9.3.6. Roles

Src:

Launches each packet and waits for return transmissions from the Dst.¶

Dst:

Waits for each packet from the Src and sends a return packet to the Src (ICMP Echo Reply, Type 0).¶

9.4.1. Type

Latency and Loss Types are discussed in the subsections below.¶

9.4.2. Reference Definition

For all output types:¶

T0:

The start of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330].¶

Tf:

The end of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330].¶

TotalCount:

The count of packets actually sent by the Src to the Dst during the measurement interval.¶

For each <statistic> or Percent_LossRatio, one of the following subsections applies.¶

   Max = (FiniteDelay[j])

9.4.3. Metric Units

The <statistic> of round-trip delay is expressed in seconds, where <statistic> is one of:¶

• Mean¶
• Min¶
• Max¶

The round-trip loss ratio is expressed as a percentage of lost packets to total packets sent.¶

9.4.4. Calibration

Section 3.7.3 of [RFC7679] provides a means to quantify the systematic and random errors of a time measurement. Calibration in-situ could be enabled with an internal loopback at the Source host that includes as much of the measurement system as possible, performs address manipulation as needed, and provides some form of isolation (e.g., deterministic delay) to avoid send-receive interface contention. Some portion of the random and systematic error can be characterized in this way.¶

When a measurement controller requests a calibration measurement, the loopback is applied and the result is output in the same format as a normal measurement, with an additional indication that it is a calibration result.¶

Both internal loopback calibration and clock synchronization can be used to estimate the available accuracy of the Output Metric Units. For example, repeated loopback delay measurements will reveal the portion of the output result resolution that is the result of system noise and is thus inaccurate.¶

9.5.1. Status

Current¶

9.5.2. Requester

RFC 8912¶

9.5.3. Revision

1.0¶

9.5.4. Revision Date

YYYY-MM-DD¶

10.1.1. ID (Identifier)

IANA has allocated the numeric Identifiers 22-26 for the five Named Metric Entries in Section 10. See Section 10.1.2 for mapping to Names.¶

10.1.3. URI

URL: https://www.iana.org/performance-metrics/RTDelay_Passive_IP-TCP_RFC8912sec10_Seconds_Mean¶

URL: https://www.iana.org/performance-metrics/RTDelay_Passive_IP-TCP_RFC8912sec10_Seconds_Min¶

URL: https://www.iana.org/performance-metrics/RTDelay_Passive_IP-TCP_RFC8912sec10_Seconds_Max¶

URL: https://www.iana.org/performance-metrics/RTDelay_Passive_IP-TCP-HS_RFC8912sec10_Seconds_Singleton¶

URL: https://www.iana.org/performance-metrics/RTLoss_Passive_IP-TCP_RFC8912sec10_Packet_Count¶

10.1.4. Description

RTDelay:

This metric assesses the round-trip delay of TCP packets constituting a single connection, exchanged between two hosts. We consider the measurement of round-trip delay based on a single Observation Point (OP) [RFC7011] somewhere in the network. The output is the round-trip delay for all successfully exchanged packets expressed as the <statistic> of their conditional delay distribution, where <statistic> is one of:¶

• Mean¶
• Min¶
• Max¶

RTDelay Singleton:

This metric assesses the round-trip delay of TCP packets initiating a single connection (or 3-way handshake), exchanged between two hosts. We consider the measurement of round-trip delay based on a single Observation Point (OP) [RFC7011] somewhere in the network. The output is the single measurement of Round-trip delay, or Singleton.¶

RTLoss:

This metric assesses the estimated loss count for TCP packets constituting a single connection, exchanged between two hosts. We consider the measurement of round-trip delay based on a single OP [RFC7011] somewhere in the network. The output is the estimated loss count for the measurement interval.¶

10.1.5. Change Controller

IETF¶

10.1.6. Version (of Registry Format)

1.0¶

10.2.1. Reference Definition

Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip Delay Metric for IPPM", RFC 2681, DOI 10.17487/RFC2681, September 1999, <https://www.rfc-editor.org/info/rfc2681>. [RFC2681]¶

Although there is no RFC that describes Passive Measurement of round-trip delay, the parallel definition for Active Measurement is provided in [RFC2681].¶

This metric definition uses the terms "singleton" and "sample" as defined in Section 11 of [RFC2330]. (Section 2.4 of [RFC2681] provides the reference definition of the singleton (single value) round-trip delay metric. Section 3.4 of [RFC2681] provides the reference definition expanded to cover a multi-singleton sample.)¶

With the OP [RFC7011] typically located between the hosts participating in the TCP connection, the round-trip delay metric requires two individual measurements between the OP and each host, such that the Spatial Composition [RFC6049] of the measurements yields a round-trip delay singleton (we are extending the composition of one-way subpath delays to subpath round-trip delay).¶

Using the direction of TCP SYN transmission to anchor the nomenclature, host A sends the SYN, and host B replies with SYN-ACK during connection establishment. The direction of SYN transfer is considered the Forward direction of transmission, from A through the OP to B (the Reverse direction is B through the OP to A).¶

Traffic Filters reduce the packet stream at the OP to a Qualified bidirectional flow of packets.¶

In the definitions below, Corresponding Packets are transferred in different directions and convey a common value in a TCP header field that establishes correspondence (to the extent possible). Examples may be found in the TCP timestamp fields.¶

For a real number, RTD_fwd, >> the round-trip delay in the Forward direction from the OP to host B at time T' is RTD_fwd << it is REQUIRED that the OP observed a Qualified Packet to host B at wire‑time T', that host B received that packet and sent a Corresponding Packet back to host A, and the OP observed the Corresponding Packet at wire‑time T' + RTD_fwd.¶

For a real number, RTD_rev, >> the round-trip delay in the Reverse direction from the OP to host A at time T'' is RTD_rev << it is REQUIRED that the OP observed a Qualified Packet to host A at wire‑time T'', that host A received that packet and sent a Corresponding Packet back to host B, and that the OP observed the Corresponding Packet at wire‑time T'' + RTD_rev.¶

Ideally, the packet sent from host B to host A in both definitions above SHOULD be the same packet (or, when measuring RTD_rev first, the packet from host A to host B in both definitions should be the same).¶

The REQUIRED Composition Function for a singleton of round-trip delay at time T (where T is the earliest of T' and T'' above) is:¶

RTDelay = RTD_fwd + RTD_rev¶

Note that when the OP is located at host A or host B, one of the terms composing RTDelay will be zero or negligible.¶

When the Qualified and Corresponding Packets are a TCP-SYN and a TCP‑SYN-ACK, RTD_fwd == RTD_HS_fwd.¶

When the Qualified and Corresponding Packets are a TCP-SYN-ACK and a TCP-ACK, RTD_rev == RTD_HS_rev.¶

The REQUIRED Composition Function for a singleton of round-trip delay for the connection handshake is:¶

RTDelay_HS = RTD_HS_fwd + RTD_HS_rev¶

The definition of round-trip loss count uses the nomenclature developed above, based on observation of the TCP header sequence numbers and storing the sequence number gaps observed. Packet losses can be inferred from:¶

Out-of-order segments:

TCP segments are transmitted with monotonically increasing sequence numbers, but these segments may be received out of order. Section 3 of [RFC4737] describes the notion of "next expected" sequence numbers, which can be adapted to TCP segments (for the purpose of detecting reordered packets). Observation of out-of-order segments indicates loss on the path prior to the OP and creates a gap.¶

Duplicate segments:

Section 2 of [RFC5560] defines identical packets and is suitable for evaluation of TCP packets to detect duplication. Observation of duplicate segments *without a corresponding gap* indicates loss on the path following the OP (because they overlap part of the delivered sequence numbers already observed at the OP).¶

Each observation of an out-of-order or duplicate segment infers a singleton of loss, but the composition of round-trip loss counts will be conducted over a measurement interval that is synonymous with a single TCP connection.¶

With the above observations in the Forward direction over a measurement interval, the count of out-of-order and duplicate segments is defined as RTL_fwd. Comparable observations in the Reverse direction are defined as RTL_rev.¶

For a measurement interval (corresponding to a single TCP connection) T0 to Tf, the REQUIRED Composition Function for the two single-direction counts of inferred loss is:¶

RTLoss = RTL_fwd + RTL_rev¶

10.2.2. Fixed Parameters

Traffic Filters:

IPv4 header values:

DSCP:

Set to 0¶

Protocol:

Set to 06 (TCP)¶

IPv6 header values:

DSCP:

Set to 0¶

Hop Count:

Set to 255¶

Next Header:

Set to 6 (TCP)¶

Flow Label:

Set to 0¶

Extension Headers:

None¶

TCP header values:

Flags:

ACK, SYN, FIN, set as required¶

Timestamps Option (TSopt):

Set.  See Section 3.2 of [RFC7323]¶

10.3.2. Packet Stream Generation

N/A¶

10.3.3. Traffic Filtering (Observation) Details

The Fixed Parameters above give a portion of the Traffic Filter. Other aspects will be supplied as Runtime Parameters (below).¶

10.3.4. Sampling Distribution

This metric requires a complete sample of all packets that qualify according to the Traffic Filter criteria.¶

10.3.5. Runtime Parameters and Data Format

Runtime Parameters are input factors that must be determined, configured into the measurement system, and reported with the results for the context to be complete.¶

Src:

The IP address of the host in the host A Role (format ipv4‑address-no-zone value for IPv4 or ipv6-address-no-zone value for IPv6; see Section 4 of [RFC6991]).¶

Dst:

The IP address of the host in the host B Role (format ipv4‑address-no-zone value for IPv4 or ipv6-address-no-zone value for IPv6; see Section 4 of [RFC6991]).¶

T0:

A time, the start of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330]. When T0 is "all-zeros", a start time is unspecified and Tf is to be interpreted as the duration of the measurement interval. The start time is controlled through other means.¶

Tf:

Optionally, the end of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]), or the duration (see T0). The UTC Time Zone is required by Section 6.1 of [RFC2330]. Alternatively, the end of the measurement interval MAY be controlled by the measured connection, where the second pair of FIN and ACK packets exchanged between host A and host B effectively ends the interval.¶

TTL or Hop Limit:

Set at desired value.¶

10.3.6. Roles

host A:

Launches the SYN packet to open the connection. The Role of "host A" is synonymous with the IP address used at host A.¶

host B:

Replies with the SYN-ACK packet to open the connection. The Role of "host B" is synonymous with the IP address used at host B.¶

10.4.1. Type

RTDelay Types are discussed in the subsections below.¶

For RTLoss: The count of lost packets.¶

10.4.2. Reference Definition

For all output types:¶

T0:

The start of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330].¶

Tf:

The end of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330]. The end of the measurement interval MAY be controlled by the measured connection, where the second pair of FIN and ACK packets exchanged between host A and host B effectively ends the interval.¶

RTDelay_Passive_IP-TCP-HS:

The round-trip delay of the handshake is a Singleton.¶

RTLoss:

The count of lost packets.¶

For each <statistic>, Singleton, or Loss Count, one of the following subsections applies.¶

   Max = (FiniteDelay[j])

10.4.3. Metric Units

The <statistic> of round-trip delay is expressed in seconds, where <statistic> is one of:¶

• Mean¶
• Min¶
• Max¶

The round-trip delay of the TCP handshake singleton is expressed in seconds.¶

The round-trip loss count is expressed as a number of packets.¶

10.4.4. Calibration

Passive Measurements at an OP could be calibrated against an Active Measurement (with loss emulation) at host A or host B, where the Active Measurement represents the ground truth.¶

10.5.1. Status

Current¶

10.5.2. Requester

RFC 8912¶

10.5.3. Revision

1.0¶

10.5.4. Revision Date

YYYY-MM-DD¶