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Versions: 00

Network Working Group                                      L. Ciavattone
Internet-Draft                                                 A. Morton
Intended status: Standards Track                               AT&T Labs
Expires: September 9, 2021                                 March 8, 2021


           Test Protocol for One-way IP Capacity Measurement
             draft-morton-ippm-capacity-metric-protocol-00

Abstract

   This memo addresses the problem of protocol support for measuring
   Network Capacity metrics in RFC xxxx: draft-ietf-ippm-capacity-
   metric-method, where the method deploys a feedback channel from the
   receiver to control the sender's transmission rate in near-real-time.
   It supplies a simple protocol to perform the measurements.

   The authors seek feedback to determine what additional features will
   be necessary for an IETF Standards Track Protocol, beyond what is
   present in the running code available now.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 9, 2021.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect



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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Scope, Goals, and Applicability . . . . . . . . . . . . . . .   3
   3.  Protocol Overview . . . . . . . . . . . . . . . . . . . . . .   3
   4.  General Parameters and Definitions  . . . . . . . . . . . . .   4
   5.  Setup Request and Response Exchange . . . . . . . . . . . . .   6
     5.1.  Setup Response Processing at the Client . . . . . . . . .   9
   6.  Test Activation Request and Response  . . . . . . . . . . . .   9
     6.1.  nTest Activation Request at the client  . . . . . . . . .  10
     6.2.  Test Activation Request - server response . . . . . . . .  11
     6.3.  Test Activation Response action at the client . . . . . .  13
   7.  Test Stream Transmission and Measurement Feedback Messages  .  13
     7.1.  Test Packet PDU and Roles . . . . . . . . . . . . . . . .  13
     7.2.  Status PDU  . . . . . . . . . . . . . . . . . . . . . . .  16
   8.  Stopping the Test . . . . . . . . . . . . . . . . . . . . . .  21
   9.  Method of Measurement . . . . . . . . . . . . . . . . . . . .  21
     9.1.  Running Code  . . . . . . . . . . . . . . . . . . . . . .  22
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  22
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  23
   12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  23
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  24
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  24
     13.2.  Informative References . . . . . . . . . . . . . . . . .  25
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  27

1.  Introduction

   The IETF's efforts to define Network and Bulk Transport Capacity have
   been chartered and finally progressed after over twenty years.

   Over that time, the performance community has seen development of
   Informative definitions in [RFC3148] for Framework for Bulk Transport
   Capacity (BTC), RFC 5136 for Network Capacity and Maximum IP-layer
   Capacity, and the Experimental metric definitions and methods in
   [RFC8337], Model-Based Metrics for BTC.

   This memo looks at the problem of measuring Network Capacity metrics
   defined in [I-D.ietf-ippm-capacity-metric-method] where the method
   deploys a feedback channel from the receiver to control the sender's
   transmission rate in near-real-time.




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1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14[RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Scope, Goals, and Applicability

   The scope of this memo is to define a protocol to measure the Maximum
   IP-Layer Capacity metric and according to the standardized method.

   The continued goal is to harmonize the specified metric and method
   across the industry, and this protocol supports the specifications of
   IETF and other Standards Development Organizations.

   All active testing protocols currently defined by the IPPM WG are
   UDP-based, and this method is the same.

   The primary application of the protocol described here is the same as
   in Section 2 of [RFC7479] where:

   o  The access portion of the network is the focus of this problem
      statement.  The user typically subscribes to a service with
      bidirectional access partly described by rates in bits per second.

3.  Protocol Overview

   The test protocol memo describes the communication between two test
   end-points.  One end-point takes the role of server, awaiting
   connection requests on a well-known port from the other end-point,
   the client.

   The client, requires specification of a test direction parameter
   (upstream or downstream test) as well as the hostname or IP address
   of the server in order to begin the setup and configuration
   exchanges.

   The protocol uses UDP transport and has four phases:

   1.  Setup Request and Response Exchange: client and server confirm
       matching protocol versions, authentication mode, and jumbo
       datagram support, or reject the connection.  The server also
       communicates the ephemeral port for further communication when
       accepting the request.





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   2.  Test Activation Request and Response: the client composes a
       request conveying parameters such as the testing direction, the
       duration of the test interval and test sub-intervals, and various
       thresholds.  The server then chooses to accept, ignore or modify
       any of the test parameters, and communicates the set that will be
       used unless the client rejects the modifications.  Note that the
       Test Activiation echange has opened any firewalls and network
       address/port translators for the test connection and the traffic
       that follows.

   3.  Test Stream Transmission and Measurement Feedback Messages:
       Testing proceeds with one end-point sending load PDUs and the
       other end-point receiving the load PDUs and sending frequent
       status messages to communicate status and transmission conditions
       there.  The feedback messsages are input to a load-control
       algorithm at the server, which controls future sending rates at
       either end-point as needed.  The choice to locate the load-
       control algorithm at the server, regardlesss of transmiision
       direction, means that the algorithm can be updated more easily at
       a host within the network, and at a fewer number of hosts than
       the number of clients.

   4.  Stopping the Test: The server initiates the phase to stop the
       test by setting the STOP1 indication in load PDUs or sstatus
       feedback messages.  The client acknowledges by setting the STOP2
       in further load PDUs or messages, and a graceful connection
       termination at each end-point follows.

4.  General Parameters and Definitions

   This section lists the REQUIRED input factors to specify a Sender or
   Receiver metric.

   o  Src, the address of a host (such as the globally routable IP
      address).

   o  Dst, the address of a host (such as the globally routable IP
      address).

   o  MaxHops, the limit on the number of Hops a specific packet may
      visit as it traverses from the host at Src to the host at Dst
      (implemented in the TTL or Hop Limit).

   o  T0, the time at the start of measurement interval, when packets
      are first transmitted from the Source.

   o  I, the nominal duration of a measurement interval at the
      destination (default 10 sec)



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   o  dt, the nominal duration of m equal sub-intervals in I at the
      destination (default 1 sec)

   o  dtn, the beginning boundary of a specific sub-interval, n, one of
      m sub-intervals in I

   o  FT, the feedback time interval between status feedback messages
      communicating measurement results, sent from the receiver to
      control the sender.  The results are evaluated to determine how to
      adjust the current offered load rate at the sender (default 50ms)

   o  Tmax, a maximum waiting time for test packets to arrive at the
      destination, set sufficiently long to disambiguate packets with
      long delays from packets that are discarded (lost), such that the
      distribution of one-way delay is not truncated.

   o  F, the number of different flows synthesized by the method
      (default 1 flow)

   o  flow, the stream of packets with the same n-tuple of designated
      header fields that (when held constant) result in identical
      treatment in a multi-path decision (such as the decision taken in
      load balancing).  Note: The IPv6 flow label MAY be included in the
      flow definition when routers have complied with [RFC6438]
      guidelines.

   o  Type-P, the complete description of the test packets for which
      this assessment applies (including the flow-defining fields).
      Note that the UDP transport layer is one requirement for test
      packets specified below.  Type-P is a parallel concept to
      "population of interest" defined in clause 6.1.1 of[Y.1540].

   o  PM, a list of fundamental metrics, such as loss, delay, and
      reordering, and corresponding target performance threshold.  At
      least one fundamental metric and target performance threshold MUST
      be supplied (such as One-way IP Packet Loss [RFC7680] equal to
      zero).

   A non-Parameter which is required for several metrics is defined
   below:

   o  T, the host time of the *first* test packet's *arrival* as
      measured at the destination Measurement Point, or MP(Dst).  There
      may be other packets sent between source and destination hosts
      that are excluded, so this is the time of arrival of the first
      packet used for measurement of the metric.





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   Note that time stamp format and resolution, sequence numbers, etc.
   will be established by the chosen test protocol standard or
   implementation.

5.  Setup Request and Response Exchange

   The client SHALL begin the Control protocol connection by sending a
   Setup Request message to the server's control port.

   The client SHALL simultaneously start a test initiation timer so that
   if the control protocol fails to complete all exchanges in the
   allocated time, the client software SHALL exit (close the UDP socket
   and indicate an error message to the user).

   (Note: in version 8, the watchdog time is configured, in udpst.h, as
   #define WARNING_NOTRAFFIC 1 // Receive traffic stopped warning
   threshold (sec) #define TIMEOUT_NOTRAFFIC (WARNING_NOTRAFFIC + 4) or
   5 seconds)

   The Setup Request message PDU SHALL be organized as follows:

        uint16_t controlId;   // Control ID = 0xACE1
        uint16_t protocolVer; // Protocol version = 0x08
        uint8_t cmdRequest;   // Command request = 1 (request)
        uint8_t cmdResponse;  // Command response = 0
        uint16_t reserved1;   // Reserved (alignment)
        uint16_t testPort;    // Test port on server  (=0 for Request)
        uint8_t jumboStatus;  // Jumbo datagram support status (BOOL)
        uint8_t authMode;     // Authentication mode
        uint32_t authUnixTime;// Authentication time stamp
        unsigned char authDigest[AUTH_DIGEST_LENGTH] // SHA256_DIGEST_LENGTH = 32 oct


   The UDP PDU format layout SHALL be as follows (big-endian AB):

















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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          controlId            |          protocolVer          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  cmdRequest   | cmdResponse   |           reserved1           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           testPort            |  jumboStatus  |   authMode    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         authUnixTime                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                                                               |
      |                                                               |
      |                                                               |
      |          authDigest[AUTH_DIGEST_LENGTH](256 bits)             |
      |                                                               |
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   When the server receives the Setup Request it SHALL validate the
   request by checking the protocol version, the jumbo datagram support
   indicator, and the authentication data if utilized.  If the client
   has selected options for:

   o  Jumbo datagram support status (BOOL),

   o  Authentication mode, and

   o  Authentication time stamp

   that do not match the server configuration, the server MUST reject
   the Setup Request.

   (Note: in version 8, the watchdog time is configured, in udpst.h, as
   #define WARNING_NOTRAFFIC 1 // Receive traffic stopped warning
   threshold (sec) #define TIMEOUT_NOTRAFFIC (WARNING_NOTRAFFIC + 4) or
   5 seconds)

   If the Setup Request must be rejected (due to any of the reasons in
   the Command response codes listed below), a Setup Response SHALL be
   sent back to the client with a corresponding command response value
   indicating the reason for the rejection.







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        uint16_t controlId;   // Control ID = 0xACE1
        uint16_t protocolVer; // Protocol version = 0x08
        uint8_t cmdRequest;   // Command request = 2 (reply)
        uint8_t cmdResponse;  // Command response = <see table below>
        uint16_t reserved1;   // Reserved (alignment)
        uint16_t testPort;    // Test port on server  (available port in Response)
        uint8_t jumboStatus;  // Jumbo datagram support status (BOOL)
        uint8_t authMode;     // Authentication mode
        uint32_t authUnixTime;// Authentication time stamp
        unsigned char authDigest[AUTH_DIGEST_LENGTH] // 32 octets, MBZ

Command Response Codes
Control Header Setup Request Code CHSR_CRSP_NONE     0 = None
Control Header Setup Request Code CHSR_CRSP_ACKOK    1 = Acknowledgement
Control Header Setup Request Code CHSR_CRSP_BADVER   2 = Bad Protocol Version
Control Header Setup Request Code CHSR_CRSP_BADJS    3 = Invalid Jumbo datagram option
Control Header Setup Request Code CHSR_CRSP_AUTHNC   4 = Unexpected Authentication in Setup Request
Control Header Setup Request Code CHSR_CRSP_AUTHREQ  5 = Authentication missing in Setup Request
Control Header Setup Request Code CHSR_CRSP_AUTHINV  6 = Invalid authentication method
Control Header Setup Request Code CHSR_CRSP_AUTHFAIL 7 = Authentication failure
Control Header Setup Request Code CHSR_CRSP_AUTHTIME 8 = Authentication time is invalid in Setup Request

   If the server finds that the Setup Request matches its configuration
   and is otherwise acceptable, the server SHALL initiate a new
   connection for the client, using a new UDP socket allocated from the
   UDP ephemeral port range.  Then, the server SHALL start a watchdog
   timer (to terminate the connection in case the client goes silent),
   and sends the Setup Response back to the client (see below for
   composition).

   If the Setup Request is accepted by the server, a Setup Response
   SHALL be sent back to the client with a corresponding command
   response value indicating 1 = Acknowledgement.

        uint16_t controlId;   // Control ID = 0xACE1
        uint16_t protocolVer; // Protocol version = 0x08
        uint8_t cmdRequest;   // Command request = 2 (reply)
        uint8_t cmdResponse;  // Command response = 1 (Acknowledgement)
        uint16_t reserved1;   // Reserved (alignment)
        uint16_t testPort;    // Test port on server  (available port in Response)
        uint8_t jumboStatus;  // Jumbo datagram support status (BOOL)
        uint8_t authMode;     // Authentication mode
        uint32_t authUnixTime;// Authentication time stamp
        unsigned char authDigest[AUTH_DIGEST_LENGTH] // 32 octets, MBZ
        ...

   The new connection is associated with a new UDP socket allocated from
   the UDP ephemeral port range at the server.  The server SHALL set a



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   timer for the new connection as a watchdog (in case the client goes
   quiet) and send the Setup response back to the client.

   (Note: in version 8, the watchdog time-out is configured at 5
   seconds)

   The Setup Response SHALL include the port number at the server for
   the new socket, and this UDP port-pair SHALL be used for all
   subsequent communication.  The server SHALL also include the values
   of:

   o  Jumbo datagram support status (BOOL),

   o  Authentication mode, and

   o  Authentication time stamp

   for the client's use on the new connection in its Setup Response, and
   the remaining 32 octets MUST Be Zero (MBZ).

   Finally, the new UDP connection associated with the new socket and
   port number is opened, and the server awaits communication there.

   If a Test Activation request is not subsequently received from the
   client on this new port number before the watchdog timer expires, the
   server SHALL close the socket and deallocate the port.

5.1.  Setup Response Processing at the Client

   When the client receives the Setup response from the server it first
   checks the cmdResponse value.  If this value indicates an error the
   client SHALL display/report a relevant message to the user or
   management process and exit.  If the client receives a Command
   Response code (CRSP) that is not equal to one of the codes defined
   above, then the client MUST terminate the connection and terminate
   operation of the current Setup Request.  If the Command Response code
   (CRSP) value indicates success the client SHALL compose a Test
   Activation Request with all the test parameters it desires such as
   the test direction, the test duration, etc.

6.  Test Activation Request and Response

   This section is divided accrding to the sending and processing of the
   client, server, and again at the client.







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6.1.  nTest Activation Request at the client

   Upon a successful setup, the client SHALL then send the Test
   Activation Request to the UDP port number the server communicated in
   the Setup Response.

   The client SHALL compose Test Activation Request as follows:

        uint16_t controlId;   // Control ID
        uint16_t protocolVer; // Protocol version
        uint8_t cmdRequest; // Command request, 1 = upstream, 2 = downstream
        uint8_t cmdResponse;         // Command response (set to 0)
        uint16_t lowThresh;          // Low delay variation threshold
        uint16_t upperThresh;        // Upper delay variation threshold
        uint16_t trialInt;           // Status feedback/trial interval (ms)
        uint16_t testIntTime;        // Test interval time (sec)
        uint8_t subIntPeriod;        // Sub-interval period (sec)
        uint8_t ipTosByte;           // IP ToS byte for testing
        uint16_t srIndexConf;        // Configured sending rate index (see Note below)
        uint8_t useOwDelVar;         // Use one-way delay instead of RTT
        uint8_t highSpeedDelta;      // High-speed row adjustment delta
        uint16_t slowAdjThresh;      // Slow rate adjustment threshold
        uint16_t seqErrThresh;       // Sequence error threshold
        uint8_t ignoreOooDup;        // Ignore Out-of-Order/Duplicate datagrams
        uint8_t reserved1;           // (Alignment)
        uint16_t reserved2;          // (Alignment)

Control Header Test Activation Command Request Values:
CHTA_CREQ_NONE      0 = No Request
CHTA_CREQ_TESTACTUS 1 = Request test in Upstream direction (client to server, client takes the role of sending test packets)
CHTA_CREQ_TESTACTDS 2 = Request test in Downstream direction (server to client, client takes the role of receiving test packets)

Control Header Test Activation Command Response Values:
CHTA_CRSP_NONE     0 = Used by client when making a Request
CHTA_CRSP_ACKOK    1 = Used by Server in affirmative Response
CHTA_CRSP_BADPARAM 2 = Used by Server to indicate an error; bad parameter; reject;

   Note: uint16_t srIndexConf is the table index of the configured
   *fixed* sending rate index to use.  The client can request the
   specified rate, or the server can use this field to coerce a maximum
   rate in its response.  If the server sets to 0 in its response,
   client SHALL not use fixed rate.

   The UDP PDU format of the Test Activation Request is as follows (big-
   endian AB):






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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |          controlId            |          protocolVer          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  cmdRequest   | cmdResponse   |           lowThresh           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         upperThresh           |           trialInt            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         testIntTime           | subIntPeriod  |  ipTosByte    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         srIndexConf           |  useOwDelVar  |highSpeedDelta |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         slowAdjThresh         |         seqErrThresh          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | ignoreOooDup  | reserved1     |           reserved2           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Note: This is only 28 octets of the 56 octet PDU sent, the rest are MBZ
 for a Test Activation Request.

   The client SHALL use the configuration for

   o  Jumbo datagram support status (BOOL),

   o  Authentication mode, and

   o  Authentication time stamp

   requested and confirmed by the server.

6.2.  Test Activation Request - server response

   After the server receives the Test Activation request on the new
   connection, it MUST choose to accept, ignore or modify any of the
   test parameters.

   When the server sends the Test Activation response back, it SHALL set
   the cmd Response field to:

   uint8_t cmdResponse;// Command response (set to 1, ACK, or 2 error)

   The server SHALL include all the test parameters again to make the
   client aware of any changes.

   If the client has requested an upstream test, the server SHALL
   include the transmission parameters from the first row of the sending
   rate table.




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   The remaining 28 octets of the Test Activation Request (normally read
   from the first row of the sending rate table) are called the Sending
   Rate Structure, and SHALL be organized as follows:

           uint32_t txInterval1; // Transmit interval (us)
           uint32_t udpPayload1; // UDP payload (bytes)
           uint32_t burstSize1;  // UDP burst size per interval
           uint32_t txInterval2; // Transmit interval (us)
           uint32_t udpPayload2; // UDP payload (bytes)
           uint32_t burstSize2;  // UDP burst size per interval
           uint32_t udpAddon2;   // UDP add-on (bytes)

   with

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          txInterval1                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          udpPayload1                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          burstSize1                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          txInterval2                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          udpPayload2                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          burstSize2                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          udpAdddon2                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Note that the server additionally has the option of completely
   rejecting the request and sending back an appropriate command
   response value:

   uint8_t cmdResponse; // Command response (set to 2, error)

   If activation continues, the new connection is prepared for an
   upstream OR downstream test.

   In the case of a downstream test, the server prepares to send with
   either a single timer to send status PDUs at the specified interval
   OR dual timers to send load PDUs based on the first row of the
   sending rate table.

   The server SHALL then send a Test Activation response back to the
   client, update the watchdog timer with a new time-out value, and set
   a test duration timer to eventually stop the test.




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   The new connection is now ready for testing.

6.3.  Test Activation Response action at the client

   When the client receives the Test Activation response, it first
   checks the command response value.

   If the client receives a Test Activation command response value that
   indicates an error, the client SHALL display/report a relevant
   message to the user or management process and exit.

   If the client receives a Test Activation command response value that
   is not equal to one of the codes defined above, then the client MUST
   terminate the connection and terminate operation of the current Setup
   Request.

   If the client receives a Test Activation command response value that
   indicates success (CHTA_CRSP_ACKOK) the client SHALL update its
   configuration to use any test parameters modified by the server.

   Next, the client SHALL prepare its connection for either an upstream
   test with dual timers set to send load PDUs (based on the starting
   transmission parameters sent by the server), OR a downstream test
   with a single timer to send status PDUs at the specified interval.

   Then, the client SHALL stop the test initiation timer, set a new
   time-out value for the watchdog timer, and start the timer (in case
   the server goes quiet).

   The connection is now ready for testing.

7.  Test Stream Transmission and Measurement Feedback Messages

   This section describes the testing phase of the protocol.  The roles
   of sender and receiver vary depending whether the direction of
   testing is from server to client, or the reverse.

7.1.  Test Packet PDU and Roles

   Testing proceeds with one end point sending load PDUs, based on
   transmission parameters from the sending rate table, and the other
   end point receiving the load PDUs and sending status messages to
   communicate the traffic conditions at the receiver.

   The watchdog timer at the receiver SHALL be reset each time a test
   PDU is received.





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   When the server is sending Load PDUs in the role of sender, it SHALL
   use the transmission parameters directly from the sending rate table
   via the index that is currently selected (which was based on the
   feedback in its received status messages).

   However, when the client is sending load PDUs in the role of sender,
   it SHALL use the discreet transmission parameters that were
   communicated by the server in its periodic status messages (and not
   referencing a sending rate table).  This approach allows the server
   to control the individual sending rates as well as the algorithm used
   to decide when and how to adjust the rate.

   The server uses a load adjustment algorithm which evaluates
   measurements, either it's own or the contents of received feedback
   messages.  This algorithm is unique to udpst; it provides the ability
   to search for the Maximum IP Capacity that is absent from other
   testing tools.  Although the algorithm depends on the protocol, it is
   not part of the protocol per se.

   The current algorithm has three paths to its decision on the next
   sending rate:

   1.  When there are no impairments present (no sequence errors, low
       delay variation), resulting in sending rate increase.

   2.  When there are low impairments present (no sequence errors but
       higher levels of delay variation), so the same sending rate is
       retained.

   3.  When the impairment levels are above the thresholds set for this
       purpose and "congestion" is inferred, resulting in sending rate
       decrease.

   The algorithm also has two modes for increasing/decreasing the
   sending rate:

   o  A high-speed mode to achieve high sending rates quickly, but also
      back-off quickly when "congestion" is inferred from the
      measurements.  Any two consecutive feedback intervals that have a
      sequence number anomaly and/or contain an upper delay variation
      threshold exception in both of the two consecutive intervals,
      count as the two consecutive feedback measurements required to
      declare "congestion" within a test.

   o  A single-step mode where all rate adjustments use the minimum
      increase or decrease of one step in the sending rate table.  The
      single step mode continues after the first inference of
      "congestion" from measured impairments.



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   On the other hand, the test configuration MAY use a fixed sending
   rate requested by the client, using the field below:

   uint16_t srIndexConf; // Configured sending rate index

   The client MAY communicate the desired fixed rate in it's activation
   request.

   The Load PDU SHALL have the following format and field definitions:

        uint16_t loadId; // Load ID (=0xBEEF for the LOad PDU)
        uint8_t testAction;  // Test action (= 0x00 normally, until test stop)
        uint8_t rxStopped;   // Receive traffic stopped indicator (BOOL)
        uint32_t lpduSeqNo;  // Load PDU sequence number (starts at 1)
        uint16_t udpPayload; // UDP payload LENGTH(bytes)
        uint16_t spduSeqErr; // Status PDU sequence error count
        //
        uint32_t spduTime_sec;  // Send time in last received status PDU
        uint32_t spduTime_nsec; // Send time in last received status PDU
        uint32_t lpduTime_sec;  // Send time of this load PDU
        uint32_t lpduTime_nsec; // Send time of this load PDU

Test Action Codes
TEST_ACT_TEST  0  // normal
TEST_ACT_STOP1 1  // normal stop at end of test: server sends in STATUS or Test PDU
TEST_ACT_STOP2 2  // ACK of STOP1: sent by client in STATUS or Test PDU

   The Test Load UDP PDU format is as follows (big-endian AB):























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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           loadId              |   testAction  | rxStopped     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           lpduSeqNo                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           udpPayload          |           spduSeqErr          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          spduTime_sec                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         spduTime_nsec                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          lpduTime_sec                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         lpduTime_nsec                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .                    MBZ = udpPayload - 28 octets               .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .                                                               .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .                                                               .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .                                                               .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .                                                               .

7.2.  Status PDU

   The receiver SHALL send a Status PDU to the sender during a test at
   the configured feedback interval.

   The Status Header PDU SHALL have the following format and field
   definitions:

















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// Status feedback header for UDP payload of status PDUs
//

        uint16_t statusId;  // Status ID = 0xFEED
        uint8_t testAction; // Test action
        uint8_t rxStopped;  // Receive traffic stopped indicator (BOOL)
        uint32_t spduSeqNo; // Status PDU sequence number (starts at 1)
        //
        struct sendingRate srStruct; // Sending Rate Structure (28 octets)
        //
        uint32_t subIntSeqNo;      // Sub-interval sequence number
        struct subIntStats sisSav; // Sub-interval Saved Stats Structure  (52 octets)
        //
        uint32_t seqErrLoss; // Loss sum
        uint32_t seqErrOoo;  // Out-of-Order sum
        uint32_t seqErrDup;  // Duplicate sum
        //
        uint32_t clockDeltaMin; // Clock delta minimum (either RTT or 1-way delay)
        uint32_t delayVarMin;   // Delay variation minimum
        uint32_t delayVarMax;   // Delay variation maximum
        uint32_t delayVarSum;   // Delay variation sum
        uint32_t delayVarCnt;   // Delay variation count
        uint32_t rttMinimum;    // Minimum round-trip time sampled
        uint32_t rttSample;     // Last round-trip time sample
        uint8_t delayMinUpd;    // Delay minimum(s) updated observed, communicated in both directions.
        uint8_t reserved2;      // (alignment)
        uint16_t reserved3;     // (alignment)
        //
        uint32_t tiDeltaTime;   // Trial interval delta time
        uint32_t tiRxDatagrams; // Trial interval receive datagrams
        uint32_t tiRxBytes;     // Trial interval receive bytes
        //
        uint32_t spduTime_sec;  // Send time of this status PDU
        uint32_t spduTime_nsec; // Send time of this status PDU

   The Status feedback UDP payload PDUs format is as follows (big-endian
   AB):














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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          statusId             |   testAction  | rxStopped     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           spduSeqNo                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .               Sending Rate Structure (28 octets)              .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          subIntSeqNo                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .        Sub-interval Saved Stats Structure  (52 octets)        .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           seqErrLoss                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           seqErrOoo                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           seqErrDup                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         clockDeltaMin                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          delayVarMin                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          delayVarMax                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          delayVarSum                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          delayVarCnt                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          rttMinimum                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           rttSample                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  delayMinUpd  |   reserved2   |           reserved3           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          tiDeltaTime                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         tiRxDatagrams                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           tiRxBytes                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         spduTime_sec                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         spduTime_nsec                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Note that the Sending Rate Structure (28 octets) is defined in the
   Test Activation section.



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   Also note that the Sub-interval Saved Stats Structure (52 octets)
   SHALL be included (and populated as required when the server is in
   the receiver role) as defined below.

   The Sub-interval saved statistics structure for received traffic
   measurements SHALL be organized and formatted as follows:













































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        uint32_t rxDatagrams; // Received datagrams
        uint32_t rxBytes;     // Received bytes
        uint32_t deltaTime;   // Time delta
        uint32_t seqErrLoss;  // Loss sum
        uint32_t seqErrOoo;   // Out-of-Order sum
        uint32_t seqErrDup;   // Duplicate sum
        uint32_t delayVarMin; // Delay variation minimum
        uint32_t delayVarMax; // Delay variation maximum
        uint32_t delayVarSum; // Delay variation sum
        uint32_t delayVarCnt; // Delay variation count
        uint32_t rttMinimum;  // Minimum round-trip time
        uint32_t rttMaximum;  // Maximum round-trip time
        uint32_t accumTime;   // Accumulated time
----------------------------------------------------------------------------

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          rxDatagrams                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            rxBytes                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           deltaTime                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           seqErrLoss                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           seqErrOoo                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           seqErrDup                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          delayVarMin                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          delayVarMax                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          delayVarSum                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          delayVarCnt                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          rttMinimum                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          rttMaximum                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           accumTime                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Note that the 52 octet saved statistics structure above has slight
   differences from the 40 octets that follow in the status feedback
   PDU, particularly the time-related fields.



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   Upon receiving the Status Feedback PDU or expiration of the feedback
   interval, the server SHALL perform calculations required by the Load
   adjustment algorithm and adjust its sending rate, or signal that the
   client do so in its role as as sender.

8.  Stopping the Test

   When the test duration timer on the server expires, it SHALL set the
   connection test action to STOP and also starts marking all outgoing
   load or status PDUs with a test action of STOP1.

   uint8_t testAction; // Test action (server sets STOP1)

   This is simply a non-reversible state for all future messages sent
   from the server.

   When the client receives a load or status PDU with the STOP1
   indication, it SHALL finalize testing, display the test results, and
   also mark its connection with a test action of STOP (so that any PDUs
   received subsequent to the STOP1 are ignored).

   With the test action of the client's connection set to STOP, the very
   next expiry of a send timer for either a load or status PDU SHALL
   cause the client to schedule an immediate end time to exit.

   The client SHALL then send all subsequent load or status PDUs with a
   test action of STOP2

   uint8_t testAction; // Test action (client sets STOP2)

   as confirmation to the server, and a graceful termination of the test
   can begin.

   When the server receives the STOP2 confirmation in the load or status
   PDU, the server SHALL schedule an immediate end time for the
   connection which closes the socket and deallocates it.

   In a non-graceful test stop, the watchdog/quiet timers at each end-
   point will expire, notifications SHALL be made and the test action of
   each end-point's connection SHALL be set to STOP.

9.  Method of Measurement

   The architecture of the method REQUIRES two cooperating hosts
   operating in the roles of Src (test packet sender) and Dst
   (receiver), with a measured path and return path between them.





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   The duration of a test duration, parameter I, MUST be constrained in
   a production network, since this is an active test method and it will
   likely cause congestion on the Src to Dst host path during a test.

9.1.  Running Code

   This section is for the benefit of the Document Shepherd's form, and
   will be deleted prior to final review.

   Much of the development of the method and comparisons with existing
   methods conducted at IETF Hackathons and elsewhere have been based on
   the example udpst Linux measurement tool (which is a working
   reference for further development) [udpst].  The current project:

   o  is a utility that can function as a client or server daemon

   o  requires a successful client-initiated setup handshake between
      cooperating hosts and allows firewalls to control inbound
      unsolicited UDP which either go to a control port [expected and w/
      authentication] or to ephemeral ports that are only created as
      needed.  Firewalls protecting each host can both continue to do
      their job normally.  This aspect is similar to many other test
      utilities available.

   o  is written in C, and built with gcc (release 9.3) and its standard
      run-time libraries

   o  allows configuration of most of the parameters described in
      Sections 4 and 7.

   o  supports IPv4 and IPv6 address families.

   o  supports IP-layer packet marking.

10.  Security Considerations

   Active metrics and measurements have a long history of security
   considerations.  The security considerations that apply to any active
   measurement of live paths are relevant here.  See [RFC4656] and
   [RFC5357].

   When considering privacy of those involved in measurement or those
   whose traffic is measured, the sensitive information available to
   potential observers is greatly reduced when using active techniques
   which are within this scope of work.  Passive observations of user
   traffic for measurement purposes raise many privacy issues.  We refer
   the reader to the privacy considerations described in the Large Scale




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   Measurement of Broadband Performance (LMAP) Framework [RFC7594],
   which covers active and passive techniques.

   There are some new considerations for Capacity measurement as
   described in this memo.

   1.  Cooperating source and destination hosts and agreements to test
       the path between the hosts are REQUIRED.  Hosts perform in either
       the Src or Dst roles.

   2.  It is REQUIRED to have a user client-initiated setup handshake
       between cooperating hosts that allows firewalls to control
       inbound unsolicited UDP traffic which either goes to a control
       port [expected and w/authentication] or to ephemeral ports that
       are only created as needed.  Firewalls protecting each host can
       both continue to do their job normally.

   3.  Client-server authentication and integrity protection for
       feedback messages conveying measurements is RECOMMENDED.

   4.  Hosts MUST limit the number of simultaneous tests to avoid
       resource exhaustion and inaccurate results.

   5.  Senders MUST be rate-limited.  This can be accomplished using a
       pre-built table defining all the offered load rates that will be
       supported (Section 8.1).  The recommended load-control search
       algorithm results in "ramp up" from the lowest rate in the table.

   6.  Service subscribers with limited data volumes who conduct
       extensive capacity testing might experience the effects of
       Service Provider controls on their service.  Testing with the
       Service Provider's measurement hosts SHOULD be limited in
       frequency and/or overall volume of test traffic (for example, the
       range of I duration values SHOULD be limited).

   The exact specification of these features was hopefully accomplished
   during this protocol development.

11.  IANA Considerations

   This memo requests IANA to assign a UDP port.

12.  Acknowledgments

   Thanks to <folks who review the memo>.






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13.  References

13.1.  Normative References

   [I-D.ietf-ippm-capacity-metric-method]
              Morton, A., Geib, R., and L. Ciavattone, "Metrics and
              Methods for One-way IP Capacity", draft-ietf-ippm-
              capacity-metric-method-04 (work in progress), September
              2020.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

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

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

   [RFC4656]  Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
              Zekauskas, "A One-way Active Measurement Protocol
              (OWAMP)", RFC 4656, DOI 10.17487/RFC4656, September 2006,
              <https://www.rfc-editor.org/info/rfc4656>.

   [RFC5357]  Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
              Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
              RFC 5357, DOI 10.17487/RFC5357, October 2008,
              <https://www.rfc-editor.org/info/rfc5357>.

   [RFC6438]  Carpenter, B. and S. Amante, "Using the IPv6 Flow Label
              for Equal Cost Multipath Routing and Link Aggregation in
              Tunnels", RFC 6438, DOI 10.17487/RFC6438, November 2011,
              <https://www.rfc-editor.org/info/rfc6438>.

   [RFC7479]  Moonesamy, S., "Using Ed25519 in SSHFP Resource Records",
              RFC 7479, DOI 10.17487/RFC7479, March 2015,
              <https://www.rfc-editor.org/info/rfc7479>.

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




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   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8468]  Morton, A., Fabini, J., Elkins, N., Ackermann, M., and V.
              Hegde, "IPv4, IPv6, and IPv4-IPv6 Coexistence: Updates for
              the IP Performance Metrics (IPPM) Framework", RFC 8468,
              DOI 10.17487/RFC8468, November 2018,
              <https://www.rfc-editor.org/info/rfc8468>.

13.2.  Informative References

   [copycat]  Edleine, K., Kuhlewind, K., Trammell, B., and B. Donnet,
              "copycat: Testing Differential Treatment of New Transport
              Protocols in the Wild (ANRW '17)", July 2017,
              <https://irtf.org/anrw/2017/anrw17-final5.pdf>.

   [LS-SG12-A]
              12, I. S., "LS - Harmonization of IP Capacity and Latency
              Parameters: Revision of Draft Rec. Y.1540 on IP packet
              transfer performance parameters and New Annex A with Lab
              Evaluation Plan", May 2019,
              <https://datatracker.ietf.org/liaison/1632/>.

   [LS-SG12-B]
              12, I. S., "LS on harmonization of IP Capacity and Latency
              Parameters: Consent of Draft Rec. Y.1540 on IP packet
              transfer performance parameters and New Annex A with Lab &
              Field Evaluation Plans", March 2019,
              <https://datatracker.ietf.org/liaison/1645/>.

   [RFC2544]  Bradner, S. and J. McQuaid, "Benchmarking Methodology for
              Network Interconnect Devices", RFC 2544,
              DOI 10.17487/RFC2544, March 1999,
              <https://www.rfc-editor.org/info/rfc2544>.

   [RFC3148]  Mathis, M. and M. Allman, "A Framework for Defining
              Empirical Bulk Transfer Capacity Metrics", RFC 3148,
              DOI 10.17487/RFC3148, July 2001,
              <https://www.rfc-editor.org/info/rfc3148>.

   [RFC5136]  Chimento, P. and J. Ishac, "Defining Network Capacity",
              RFC 5136, DOI 10.17487/RFC5136, February 2008,
              <https://www.rfc-editor.org/info/rfc5136>.







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   [RFC6815]  Bradner, S., Dubray, K., McQuaid, J., and A. Morton,
              "Applicability Statement for RFC 2544: Use on Production
              Networks Considered Harmful", RFC 6815,
              DOI 10.17487/RFC6815, November 2012,
              <https://www.rfc-editor.org/info/rfc6815>.

   [RFC7312]  Fabini, J. and A. Morton, "Advanced Stream and Sampling
              Framework for IP Performance Metrics (IPPM)", RFC 7312,
              DOI 10.17487/RFC7312, August 2014,
              <https://www.rfc-editor.org/info/rfc7312>.

   [RFC7594]  Eardley, P., Morton, A., Bagnulo, M., Burbridge, T.,
              Aitken, P., and A. Akhter, "A Framework for Large-Scale
              Measurement of Broadband Performance (LMAP)", RFC 7594,
              DOI 10.17487/RFC7594, September 2015,
              <https://www.rfc-editor.org/info/rfc7594>.

   [RFC7799]  Morton, A., "Active and Passive Metrics and Methods (with
              Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
              May 2016, <https://www.rfc-editor.org/info/rfc7799>.

   [RFC8337]  Mathis, M. and A. Morton, "Model-Based Metrics for Bulk
              Transport Capacity", RFC 8337, DOI 10.17487/RFC8337, March
              2018, <https://www.rfc-editor.org/info/rfc8337>.

   [TR-471]   Morton, A., "Broadband Forum TR-471: IP Layer Capacity
              Metrics and Measurement", July 2020,
              <https://www.broadband-forum.org/technical/download/TR-
              471.pdf>.

   [udpst]    udpst Project Collaborators, "UDP Speed Test Open
              Broadband project", December 2020,
              <https://github.com/BroadbandForum/obudpst>.

   [Y.1540]   Y.1540, I. R., "Internet protocol data communication
              service - IP packet transfer and availability performance
              parameters", December 2019,
              <https://www.itu.int/rec/T-REC-Y.1540-201912-I/en>.

   [Y.Sup60]  Morton, A., "Recommendation Y.Sup60, (09/20) Interpreting
              ITU-T Y.1540 maximum IP-layer capacity measurements",
              September 2020,
              <https://www.itu.int/rec/T-REC-Y.Sup60/en>.








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Authors' Addresses

   Len Ciavattone
   AT&T Labs
   200 Laurel Avenue South
   Middletown,, NJ  07748
   USA

   Email: lencia@att.com


   Al Morton
   AT&T Labs
   200 Laurel Avenue South
   Middletown,, NJ  07748
   USA

   Phone: +1 732 420 1571
   Fax:   +1 732 368 1192
   Email: acm@research.att.com































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