RTDelay_Active_IP-ICMP-SendOnRcv_RFC8912sec9_Seconds_Min All section numbers below refer to RFC 8912  9.1. Summary This category includes multiple indexes to the Registry Entries: the element ID and Metric Name. 9.1.1. ID (Identifier) 19 9.1.2. Name RTDelay_Active_IP-ICMP-SendOnRcv_RFC8912sec9_Seconds_Min 9.1.3. URI URL: https://www.iana.org/assignments/performance-metrics/RTDelay_Active_IP-ICMP-SendOnRcv_RFC8912sec9_Seconds_Min 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 minimum of their conditional delay distribution. 9.1.5. Change Controller IETF 9.1.6. Version (of Registry Format) 1.0 9.2. Metric Definition This category includes columns to prompt the entry of all necessary details related to the metric definition, including the RFC reference and values of input factors, called "Fixed Parameters". 9.2.1. Reference Definition Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip Delay Metric for IPPM", RFC 2681, DOI 10.17487/RFC2681, September 1999, . [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. Morton, A., "Round-Trip Packet Loss Metrics", RFC 6673, DOI 10.17487/RFC6673, August 2012, . [RFC6673] Both Delay and Loss metrics employ a maximum waiting time for received packets, so the count of lost packets to total packets sent is the basis for the loss ratio calculation as per Section 6.1 of [RFC6673]. 9.2.2. Fixed Parameters Type-P as defined in Section 13 of [RFC2330]:   IPv4 header values:       DSCP:  Set to 0       TTL:  Set to 255        Protocol:  Set to 01 (ICMP)     IPv6 header values:        DSCP:  Set to 0        Hop Count:  Set to 255        Next Header:  Set to 128 decimal (ICMP)        Flow Label:  Set to 0        Extension Headers:  None    ICMP header values:        Type:  8 (Echo Request)        Code:  0        Checksum:  The checksum MUST be calculated and the non-zero checksum         included in the header        (Identifier and sequence number set at runtime)        ICMP Payload:           Total of 32 bytes of random information, constant per test Other measurement Parameters: Tmax:  A loss threshold waiting time with value 3.0, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms), with lossless conversion to/from the 32-bit NTP timestamp as per Section 6 of [RFC5905]. 9.3. Method of Measurement This category includes columns for references to relevant sections of the RFC(s) and any supplemental information needed to ensure an unambiguous method for implementations. 9.3.1. Reference Methods The methodology for this metric (equivalent to Type-P-Round-trip-Delay-Poisson-Stream) is defined as in Section 2.6 of [RFC2681] (for singletons) and Section 3.6 of [RFC2681] (for samples) using the Type-P and Tmax defined in the Fixed Parameters column. The reference method distinguishes between long-delayed packets and lost packets by implementing a maximum waiting time for packet arrival. Tmax is the waiting time used as the threshold to declare a packet lost. Lost packets SHALL be designated as having undefined delay and counted for the RTLoss metric. The calculations on the delay (RTD) SHALL be performed on the conditional distribution, conditioned on successful packet arrival within Tmax. Also, when all packet delays are stored, the process that calculates the RTD value MUST enforce the Tmax threshold on stored values before calculations. See Section 4.1 of [RFC3393] for details on the conditional distribution to exclude undefined values of delay, and see Section 5 of [RFC6703] for background on this analysis choice. The reference method requires some way to distinguish between different packets in a stream to establish correspondence between sending times and receiving times for each successfully arriving packet. Sequence numbers or other send-order identification MUST be retained at the Src or included with each packet to disambiguate packet reordering if it occurs. The measurement process will determine the sequence numbers applied to test packets after the Fixed and Runtime Parameters are passed to that process. The ICMP measurement process and protocol will dictate the format of sequence numbers and other Identifiers. Refer to Section 4.4 of [RFC6673] for an expanded discussion of the instruction to "send a Type-P packet back to the Src as quickly as possible" in Section 2.6 of [RFC2681]. Section 8 of [RFC6673] presents additional requirements that MUST be included in the Method of Measurement for this metric. 9.3.2. Packet Stream Generation This section provides details regarding packet traffic, which is used as the basis for measurement. In IPPM Metrics, this is called the "stream"; this stream can easily be described by providing the list of stream Parameters. The ICMP metrics use a sending discipline called "SendOnRcv" or Send On Receive. This is a modification of Section 3 of [RFC3432], which prescribes the method for generating Periodic streams using associated Parameters as defined below for this description: incT:  The nominal duration of the inter-packet interval, first bit to first bit. dT:  The duration of the interval for allowed sample start times. The incT stream Parameter will be specified as a Runtime Parameter, and dT is not used in SendOnRcv. A SendOnRcv sender behaves exactly like a Periodic stream generator while all reply packets arrive with RTD < incT, and the inter-packet interval will be constant. If a reply packet arrives with RTD >= incT, then the inter-packet interval for the next sending time is nominally RTD. If a reply packet fails to arrive within Tmax, then the inter-packet interval for the next sending time is nominally Tmax. If an immediate Send On Reply arrival is desired, then set incT = 0. 9.3.3. Traffic Filtering (Observation) Details N/A 9.3.4. Sampling Distribution N/A 9.3.5. Runtime Parameters and Data Format Runtime Parameters are input factors that must be determined, configured into the measurement system, and reported with the results for the context to be complete. Src:  The IP address of the host in the Src Role (format ipv4‑address-no-zone value for IPv4 or ipv6-address-no-zone value for IPv6; see Section 4 of [RFC6991]). Dst:  The IP address of the host in the Dst Role (format ipv4‑address-no-zone value for IPv4 or ipv6-address-no-zone value for IPv6; see Section 4 of [RFC6991]). incT:  The nominal duration of the inter-packet interval, first bit to first bit, expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 4 (see Section 9.3 of [RFC6020]) and with a resolution of 0.0001 seconds (0.1 ms). T0:  A time, the start of a measurement interval (format "date‑time" as specified in Section 5.6 of [RFC3339]; see also "date‑and‑time" in Section 3 of [RFC6991]). The UTC Time Zone is required by Section 6.1 of [RFC2330]. When T0 is "all-zeros", a start time is unspecified and Tf is to be interpreted as the duration of the measurement interval. The start time is controlled through other means. Count:  The total count of ICMP Echo Requests to send, formatted as a uint16, as per Section 9.2 of [RFC6020]. See the Packet Stream Generation section for additional Runtime Parameters. 9.3.6. Roles Src:  Launches each packet and waits for return transmissions from the Dst. Dst:  Waits for each packet from the Src and sends a return packet to the Src (ICMP Echo Reply, Type 0). 9.4. Output This category specifies all details of the output of measurements using the metric. 9.4.1. Type Latency 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. The minimum SHALL be calculated using the conditional distribution of all packets with a finite value of round-trip delay (undefined delays are excluded) -- a single value, as follows: See Section 4.1 of [RFC3393] for details on the conditional distribution to exclude undefined values of delay, and see Section 5 of [RFC6703] for background on this analysis choice. See Section 4.3.2 of [RFC6049] for details on calculating this statistic; see also Section 4.3.3 of [RFC6049]. Min: The time value of the result is expressed in units of seconds, as a positive value of type decimal64 with fraction digits = 9 (see Section 9.3 of [RFC6020]) with a resolution of 0.000000001 seconds (1.0 ns), and with lossless conversion to/from the 64-bit NTP timestamp as per Section 6 of [RFC5905]. 9.4.3. Metric Units The minimum of round-trip delay is expressed in seconds. 9.4.4. Calibration Section 3.7.3 of [RFC7679] provides a means to quantify the systematic and random errors of a time measurement. Calibration in-situ could be enabled with an internal loopback at the Source host that includes as much of the measurement system as possible, performs address manipulation as needed, and provides some form of isolation (e.g., deterministic delay) to avoid send-receive interface contention. Some portion of the random and systematic error can be characterized in this way. When a measurement controller requests a calibration measurement, the loopback is applied and the result is output in the same format as a normal measurement, with an additional indication that it is a calibration result. Both internal loopback calibration and clock synchronization can be used to estimate the available accuracy of the Output Metric Units. For example, repeated loopback delay measurements will reveal the portion of the output result resolution that is the result of system noise and is thus inaccurate. 9.5. Administrative Items 9.5.1. Status Current 9.5.2. Requester RFC 8912 9.5.3. Revision 1.0 9.5.4. Revision Date 2021-11-17 9.6. Comments and Remarks None