OWLoss_Active_IP-UDP-Poisson-Payload250B_RFC8912sec7_Percent_LossRatio
All section numbers below refer to RFC 8912

7.1. Summary

This category includes multiple indexes to the Registry Entries: the element ID and Metric Name.

7.1.1. ID (Identifier)

7.1.2. Name

OWLoss_Active_IP-UDP-Poisson-Payload250B_RFC8912sec7_Percent_LossRatio

7.1.3. URI

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

7.1.4. Description

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

7.1.5. Change Controller

IETF

7.1.6. Version (of Registry Format)

1.0

7.2. Metric Definition

This category includes columns to prompt the entry of all necessary details related to the metric definition,
including the RFC reference and values of input factors, called "Fixed Parameters".

7.2.1. Reference Definition

For loss:

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

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

7.2.2. Fixed Parameters

Type-P:

IPv4 header values:

DSCP: Set to 0
TTL: Set to 255
Protocol: Set to 17 (UDP)

IPv6 header values:

DSCP: Set to 0
Hop Count: Set to 255
Next Header: Set to 17 (UDP)
Flow Label: Set to 0
Extension Headers: None

UDP header values:

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

UDP Payload: TWAMP-Test packet formats (Section 4.1.2 of [RFC5357])
Security features in use influence the number of Padding octets
250 octets total, including the TWAMP format type, which MUST be reported

Other measurement Parameters:

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

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

7.3. Method of Measurement

This category includes columns for references to relevant sections of the RFC(s) and any supplemental
information needed to ensure an unambiguous method for implementations.

7.3.1. Reference Methods

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

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

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

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

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

7.3.2. Packet Stream Generation

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

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

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

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

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

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

7.3.3. Traffic Filtering (Observation) Details

N/A

7.3.4. Sampling Distribution

N/A

7.3.5. Runtime Parameters and Data Format

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

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

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

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

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

7.3.6. Roles

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

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

7.4. Output

This category specifies all details of the output of measurements using the metric.

7.4.1. Type

Types are discussed in the subsections below.

7.4.2. Reference Definition

For all output types:

T0: The start of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see
also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330].

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

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

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
0.000000001.

7.4.3. Metric Units

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

7.4.4. Calibration

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

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

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

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

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

7.5. Administrative Items

7.5.1. Status

Current

7.5.2. Requester

RFC 8912

7.5.3. Revision

1.0

7.5.4. Revision Date

2021-11-17

7.6. Comments and Remarks

None