RFC8762

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Internet Engineering Task Force (IETF) G. Mirsky Request for Comments: 8762 G. Jun Category: Standards Track ZTE Corp. ISSN: 2070-1721 H. Nydell

                                                      Accedian Networks
                                                               R. Foote
                                                                  Nokia
                                                             March 2020


              Simple Two-Way Active Measurement Protocol

Abstract

  This document describes the Simple Two-way Active Measurement
  Protocol (STAMP), which enables the measurement of both one-way and
  round-trip performance metrics, like delay, delay variation, and
  packet loss.

Status of This Memo

  This is an Internet Standards Track document.
  This document is a product of the Internet Engineering Task Force
  (IETF).  It represents the consensus of the IETF community.  It has
  received public review and has been approved for publication by the
  Internet Engineering Steering Group (IESG).  Further information on
  Internet Standards is available in Section 2 of RFC 7841.
  Information about the current status of this document, any errata,
  and how to provide feedback on it may be obtained at
  https://www.rfc-editor.org/info/rfc8762.

Copyright Notice

  Copyright (c) 2020 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
  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.  Conventions Used in This Document
    2.1.  Terminology
    2.2.  Requirements Language
  3.  Operation and Management of Performance Measurement Based on
          STAMP
  4.  Theory of Operation
    4.1.  UDP Port Numbers in STAMP Testing
    4.2.  Session-Sender Behavior and Packet Format
      4.2.1.  Session-Sender Packet Format in Unauthenticated Mode
      4.2.2.  Session-Sender Packet Format in Authenticated Mode
    4.3.  Session-Reflector Behavior and Packet Format
      4.3.1.  Session-Reflector Packet Format in Unauthenticated Mode
      4.3.2.  Session-Reflector Packet Format in Authenticated Mode
    4.4.  Integrity Protection in STAMP
    4.5.  Confidentiality Protection in STAMP
    4.6.  Interoperability with TWAMP Light
  5.  Operational Considerations
  6.  IANA Considerations
  7.  Security Considerations
  8.  References
    8.1.  Normative References
    8.2.  Informative References
  Acknowledgments
  Authors' Addresses

1. Introduction

  Development and deployment of the Two-Way Active Measurement Protocol
  (TWAMP) [RFC5357] and its extensions (e.g., [RFC6038], which defines
  Symmetrical Size for TWAMP) provided invaluable experience.  Several
  independent implementations of both TWAMP and TWAMP Light exist, have
  been deployed, and provide important operational performance
  measurements.
  At the same time, there has been noticeable interest in using a more
  straightforward mechanism for active performance monitoring that can
  provide deterministic behavior and inherent separation of control
  (vendor-specific configuration or orchestration) and test functions.
  Recent work on "Performance Measurement from IP Edge to Customer
  Equipment using TWAMP Light" [BBF.TR-390] by the Broadband Forum
  demonstrates that interoperability among implementations of TWAMP
  Light is difficult because the composition and operation of TWAMP
  Light were not sufficiently specified in [RFC5357].  According to
  [RFC8545], TWAMP Light includes a subset of TWAMP-Test functions.
  Thus, to have a comprehensive tool to measure packet loss and delay
  requires support by other applications that provide, for example,
  control and security.
  This document defines an active performance measurement test
  protocol, Simple Two-way Active Measurement Protocol (STAMP), that
  enables measurement of both one-way and round-trip performance
  metrics, like delay, delay variation, and packet loss.  Support of
  some optional TWAMP extensions, e.g., [RFC7750], is discussed in
  [STAMP-OPTION].

2. Conventions Used in This Document

2.1. Terminology

  STAMP:      Simple Two-way Active Measurement Protocol
  NTP:        Network Time Protocol
  PTP:        Precision Time Protocol
  HMAC:       Hashed Message Authentication Code
  OWAMP:      One-Way Active Measurement Protocol
  TWAMP:      Two-Way Active Measurement Protocol
  MBZ:        Must be Zero
  PDU:        Protocol Data Unit

2.2. 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.

3. Operation and Management of Performance Measurement Based on STAMP

  Figure 1 presents the Simple Two-way Active Measurement Protocol
  (STAMP) Session-Sender and Session-Reflector with a measurement
  session.  In this document, a measurement session, also referred to
  as a "STAMP session", is the bidirectional packet flow between one
  specific Session-Sender and one particular Session-Reflector for a
  time duration.  The configuration and management of the STAMP
  Session-Sender, Session-Reflector, and sessions are outside the scope
  of this document and can be achieved through various means.  A few
  examples are Command Line Interface, telecommunication services'
  Operational Support System (OSS) / Business Support System (BSS),
  SNMP, and NETCONF/YANG-based Software-Defined Networking (SDN)
  controllers.
        o----------------------------------------------------------o
        |                      Configuration and                   |
        |                         Management                       |
        o----------------------------------------------------------o
               ||                                          ||
               ||                                          ||
               ||                                          ||
    +----------------------+                +-------------------------+
    | STAMP Session-Sender | <--- STAMP---> | STAMP Session-Reflector |
    +----------------------+                +-------------------------+
                     Figure 1: STAMP Reference Model

4. Theory of Operation

  The STAMP Session-Sender transmits test packets over UDP transport
  toward the STAMP Session-Reflector.  The STAMP Session-Reflector
  receives the Session-Sender's packet and acts according to the
  configuration.  Two modes of the STAMP Session-Reflector characterize
  the expected behavior and, consequently, performance metrics that can
  be measured:
  Stateless:
     The STAMP Session-Reflector does not maintain test state and will
     use the value in the Sequence Number field in the received packet
     as the value for the Sequence Number field in the reflected
     packet.  As a result, values in the Sequence Number and Session-
     Sender Sequence Number fields are the same, and only round-trip
     packet loss can be calculated while the reflector is operating in
     stateless mode.
  Stateful:
     STAMP Session-Reflector maintains the test state, thus allowing
     the Session-Sender to determine directionality of loss using the
     combination of gaps recognized in the Session Sender Sequence
     Number and Sequence Number fields, respectively.  As a result,
     both near-end (forward) and far-end (backward) packet loss can be
     computed.  That implies that the STAMP Session-Reflector MUST
     maintain a state for each configured STAMP-Test session, thereby
     uniquely associating STAMP-Test packets with one such session
     instance and, thus, enabling the addition of a sequence number in
     the test reply that is individually incremented by one on a per-
     session basis.
  STAMP supports two authentication modes: unauthenticated and
  authenticated.  Unauthenticated STAMP-Test packets, defined in
  Sections 4.2.1 and 4.3.1, ensure interworking between STAMP and TWAMP
  Light, as described in Section 4.6 regarding packet formats.
  By default, STAMP uses symmetrical packets, i.e., the size of the
  packet transmitted by the Session-Reflector equals the size of the
  packet received by the Session-Reflector.

4.1. UDP Port Numbers in STAMP Testing

  A STAMP Session-Sender MUST use UDP port 862 (TWAMP-Test Receiver
  Port) as the default destination UDP port number.  A STAMP
  implementation of the Session-Sender MUST be able to be used as the
  destination UDP port numbers from the User Ports (aka Registered
  Ports) and Dynamic Ports (aka Private or Ephemeral Ports) ranges
  defined in [RFC6335].  Before using numbers from the User Ports
  range, the possible impact on the network MUST be carefully studied
  and agreed on by all users of the network domain where the test has
  been planned.
  By default, an implementation of the STAMP Session-Reflector MUST
  receive STAMP-Test packets on UDP port 862.  An implementation of the
  Session-Reflector that supports this specification MUST be able to
  define the port number to receive STAMP-Test packets from User Ports
  and Dynamic Ports ranges, which are defined in [RFC6335].  STAMP
  defines two different test packet formats: one for packets
  transmitted by the STAMP Session-Sender and one for packets
  transmitted by the STAMP Session-Reflector.

4.2. Session-Sender Behavior and Packet Format

  A STAMP Session-Reflector supports the symmetrical size of test
  packets, as defined in Section 3 of [RFC6038], as the default
  behavior.  A reflected base test packet includes information from the
  Session-Reflector and, thus, is larger.  To maintain the symmetry
  between base STAMP packets, the base STAMP Session-Sender packet
  includes the Must-Be-Zero (MBZ) field to match to the size of a base
  reflected STAMP test packet.  Hence, the base STAMP Session-Sender
  packet has a minimum size of 44 octets in unauthenticated mode (see
  Figure 2) and 112 octets in the authenticated mode (see Figure 4).
  Generating variable length of a test packet in STAMP is defined in
  [STAMP-OPTION].

4.2.1. Session-Sender Packet Format in Unauthenticated Mode


      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                        Sequence Number                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          Timestamp                            |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Error Estimate        |                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
     |                                                               |
     |                                                               |
     |                        MBZ  (30 octets)                       |
     |                                                               |
     |                                                               |
     |                                                               |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           Figure 2: STAMP Session-Sender Test Packet Format in
                           Unauthenticated Mode
  The fields are defined as following:
  *  The Sequence Number field is four octets long.  For each new
     session, its value starts at zero and is incremented by one with
     each transmitted packet.
  *  The Timestamp field is eight octets long.  The STAMP node MUST
     support the Network Time Protocol (NTP) version 4 64-bit timestamp
     format [RFC5905], the format used in [RFC5357].  The STAMP node
     MAY support the IEEE 1588v2 Precision Time Protocol (PTP)
     truncated 64-bit timestamp format [IEEE.1588.2008], the format
     used in [RFC8186].  The use of the specific format, NTP or PTP, is
     part of configuration of the Session-Sender or the particular test
     session.
  *  The Error Estimate field is two octets long with the format
     displayed in Figure 3:
              0                   1
              0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             |S|Z|   Scale   |   Multiplier  |
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                      Figure 3: Error Estimate Format
     The S, Scale, and Multiplier fields are interpreted as they are
     defined in Section 4.1.2 of [RFC4656].  The Z field is interpreted
     as it is defined in Section 2.3 of [RFC8186]:
     0:  NTP 64-bit format of a timestamp
     1:  PTPv2 truncated format of a timestamp
     The default behavior of the STAMP Session-Sender and Session-
     Reflector is to use the NTP 64-bit timestamp format (Z field value
     of 0).  An operator using configuration/management function MAY
     configure the STAMP Session-Sender and Session-Reflector to use
     the PTPv2 truncated format of a timestamp (Z field value of 1).
     Note that an implementation of a Session-Sender that supports this
     specification MAY be configured to use the PTPv2 format of a
     timestamp even though the Session-Reflector is configured to use
     NTP format.
  *  The MBZ field in the Session-Sender unauthenticated packet is 30
     octets long.  It MUST be all zeroed on the transmission and MUST
     be ignored on receipt.

4.2.2. Session-Sender Packet Format in Authenticated Mode


    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Sequence Number                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                      MBZ (12 octets)                          |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Timestamp                              |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Error Estimate         |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   ~                                                               ~
   |                         MBZ (70 octets)                       |
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                       HMAC (16 octets)                        |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           Figure 4: STAMP Session-Sender Test Packet Format in
                            Authenticated Mode
  The field definitions are the same as the unauthenticated mode,
  listed in Section 4.2.1.  Also, MBZ fields are used to make the
  packet length a multiple of 16 octets.  The value of the field MUST
  be zeroed on transmission and MUST be ignored on receipt.  Note, that
  both MBZ fields are used to calculate a key hashed message
  authentication code (HMAC) [RFC2104] hash.  Also, the packet includes
  an HMAC hash at the end of the PDU.  The detailed use of the HMAC
  field is described in Section 4.4.

4.3. Session-Reflector Behavior and Packet Format

  The Session-Reflector receives the STAMP-Test packet and verifies it.
  If the base STAMP-Test packet is validated, the Session-Reflector
  that supports this specification prepares and transmits the reflected
  test packet symmetric to the packet received from the Session-Sender
  copying the content beyond the size of the base STAMP packet (see
  Section 4.2).

4.3.1. Session-Reflector Packet Format in Unauthenticated Mode


    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Sequence Number                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Timestamp                            |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Error Estimate        |            MBZ                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Receive Timestamp                    |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Session-Sender Sequence Number                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Session-Sender Timestamp                     |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Session-Sender Error Estimate |            MBZ                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Ses-Sender TTL |                      MBZ                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         Figure 5: STAMP Session-Reflector Test Packet Format in
                           Unauthenticated Mode
  Fields are defined as the following:
  *  The Sequence Number field is four octets long.  The value of the
     Sequence Number field is set according to the mode of the STAMP
     Session-Reflector:
     -  In the stateless mode, the Session-Reflector copies the value
        from the received STAMP-Test packet's Sequence Number field.
     -  In the stateful mode, the Session-Reflector counts the
        transmitted STAMP-Test packets.  It starts with zero and is
        incremented by one for each subsequent packet for each test
        session.  The Session-Reflector uses that counter to set the
        value of the Sequence Number field.
  *  The Timestamp and Receive Timestamp fields are each eight octets
     long.  The format of these fields, NTP or PTPv2, is indicated by
     the Z field of the Error Estimate field, as described in
     Section 4.2.1.  Receive Timestamp is the time the test packet was
     received by the Session-Reflector.  Timestamp is the time taken by
     the Session-Reflector at the start of transmitting the test
     packet.
  *  The Error Estimate field has the same size and interpretation as
     described in Section 4.2.1.  It is applicable to both Timestamp
     and Receive Timestamp.
  *  The Session-Sender Sequence Number, Session-Sender Timestamp, and
     Session-Sender Error Estimate fields are copies of the
     corresponding fields in the STAMP-Test packet sent by the Session-
     Sender.
  *  The Session-Sender TTL field is one octet long, and its value is
     the copy of the TTL field in IPv4 (or Hop Limit in IPv6) from the
     received STAMP-Test packet.
  *  The MBZ fields are used to achieve alignment of fields within the
     packet on a four-octet boundary.  The value of each MBZ field MUST
     be zeroed on transmission and MUST be ignored on receipt.

4.3.2. Session-Reflector Packet Format in Authenticated Mode


     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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                        Sequence Number                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                        MBZ (12 octets)                        |
     |                                                               |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          Timestamp                            |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Error Estimate        |                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
     |                        MBZ (6 octets)                         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                        Receive Timestamp                      |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                        MBZ (8 octets)                         |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                 Session-Sender Sequence Number                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                        MBZ (12 octets)                        |
     |                                                               |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                 Session-Sender Timestamp                      |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Session-Sender Error Estimate |                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
     |                        MBZ (6 octets)                         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |Ses-Sender TTL |                                               |
     +-+-+-+-+-+-+-+-+                                               +
     |                                                               |
     |                        MBZ (15 octets)                        |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                        HMAC (16 octets)                       |
     |                                                               |
     |                                                               |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         Figure 6: STAMP Session-Reflector Test Packet Format in
                            Authenticated Mode
  The field definitions are the same as the unauthenticated mode,
  listed in Section 4.3.1.  Additionally, the MBZ field is used to make
  the packet length a multiple of 16 octets.  The value of the field
  MUST be zeroed on transmission and MUST be ignored on receipt.  Note
  that the MBZ field is used to calculate the HMAC hash value.  Also,
  the STAMP Session-Reflector test packet format in authenticated mode
  includes the HMAC [RFC2104] hash at the end of the PDU.  The detailed
  use of the HMAC field is in Section 4.4.

4.4. Integrity Protection in STAMP

  Authenticated mode provides integrity protection to each STAMP
  message by adding Hashed Message Authentication Code (HMAC).  STAMP
  uses HMAC-SHA-256 truncated to 128 bits (similarly to the use of it
  in IPsec defined in [RFC4868]); hence, the length of the HMAC field
  is 16 octets.  In the authenticated mode, HMAC covers the first six
  blocks (96 octets).  HMAC uses its own key, which may be unique for
  each STAMP-Test session; key management and the mechanisms to
  distribute the HMAC key are outside the scope of this specification.
  One example is to use an orchestrator to configure the HMAC key based
  on the STAMP YANG data model [STAMP-YANG].  HMAC MUST be verified as
  early as possible to avoid using or propagating corrupted data.
  Future specifications may define the use of other, more advanced
  cryptographic algorithms, possibly providing an update to the STAMP
  YANG data model [STAMP-YANG].

4.5. Confidentiality Protection in STAMP

  If confidentiality protection for STAMP is required, a STAMP-Test
  session MUST use a secured transport.  For example, STAMP packets
  could be transmitted in the dedicated IPsec tunnel or share the IPsec
  tunnel with the monitored flow.  Also, the Datagram Transport Layer
  Security protocol would provide the desired confidentiality
  protection.

4.6. Interoperability with TWAMP Light

  One of the essential requirements to STAMP is the ability to
  interwork with a TWAMP Light device.  Because STAMP and TWAMP use
  different algorithms in authenticated mode (HMAC-SHA-256 versus HMAC-
  SHA-1), interoperability is only considered for unauthenticated mode.
  There are two possible combinations for such a use case:
  *  STAMP Session-Sender with TWAMP Light Session-Reflector
  *  TWAMP Light Session-Sender with STAMP Session-Reflector
  In the former case, the Session-Sender might not be aware that its
  Session-Reflector does not support STAMP.  For example, a TWAMP Light
  Session-Reflector may not support the use of UDP port 862, as
  specified in [RFC8545].  Thus, Section 4 permits a STAMP Session-
  Sender to use alternative ports.  If any of STAMP extensions are
  used, the TWAMP Light Session-Reflector will view them as the Packet
  Padding field.
  In the latter scenario, if a TWAMP Light Session-Sender does not
  support the use of UDP port 862, the test management system MUST set
  the STAMP Session-Reflector to use UDP port number, as permitted by
  Section 4.  The Session-Reflector MUST be set to use the default
  format for its timestamps, NTP.
  A STAMP Session-Reflector that supports this specification will
  transmit the base packet (Figure 5) if it receives a packet smaller
  than the STAMP base packet.  If the packet received from the TWAMP
  Session-Sender is larger than the STAMP base packet, the STAMP
  Session-Reflector that supports this specification will copy the
  content of the remainder of the received packet to transmit a
  reflected packet of symmetrical size.

5. Operational Considerations

  STAMP is intended to be used on production networks to enable the
  operator to assess service level agreements based on packet delay,
  delay variation, and loss.  When using STAMP over the Internet,
  especially when STAMP-Test packets are transmitted with the
  destination UDP port number from the User Ports range, the possible
  impact of the STAMP-Test packets MUST be thoroughly analyzed.  The
  use of STAMP for each case MUST be agreed by users of nodes hosting
  the Session-Sender and Session-Reflector before starting the STAMP-
  Test session.
  Also, the use of the well-known port number as the destination UDP
  port number in STAMP-Test packets transmitted by a Session-Sender
  would not impede the ability to measure performance in an Equal-Cost
  Multipath environment, and analysis in Section 5.3 of [RFC8545] fully
  applies to STAMP.

6. IANA Considerations

  This document has no IANA actions.

7. Security Considerations

  [RFC5357] does not identify security considerations specific to
  TWAMP-Test but refers to security considerations identified for OWAMP
  in [RFC4656].  Since both OWAMP and TWAMP include control-plane and
  data-plane components, only security considerations related to OWAMP-
  Test discussed in Sections 6.2 and 6.3 of [RFC4656] apply to STAMP.
  STAMP uses the well-known UDP port number allocated for the OWAMP-
  Test/TWAMP-Test Receiver Port.  Thus, the security considerations and
  measures to mitigate the risk of the attack using the registered port
  number documented in Section 6 of [RFC8545] equally apply to STAMP.
  Because of the control and management of a STAMP-Test being outside
  the scope of this specification, only the more general requirement is
  set:
     To mitigate the possible attack vector, the control and management
     of a STAMP-Test session MUST use the secured transport.
     The load of the STAMP-Test packets offered to a network MUST be
     carefully estimated, and the possible impact on the existing
     services MUST be thoroughly analyzed before launching the test
     session.  Section 3.1.5 of [RFC8085] provides guidance on handling
     network load for UDP-based protocol.  While the characteristic of
     test traffic depends on the test objective, it is highly
     recommended to stay in the limits, as provided in [RFC8085].
  Use of HMAC-SHA-256 in the authenticated mode protects the data
  integrity of the STAMP-Test packets.

8. References

8.1. Normative References

  [IEEE.1588.2008]
             IEEE, "IEEE Standard for a Precision Clock Synchronization
             Protocol for Networked Measurement and Control Systems",
             IEEE Standard 1588, July 2008.
  [RFC2104]  Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
             Hashing for Message Authentication", RFC 2104,
             DOI 10.17487/RFC2104, February 1997,
             <https://www.rfc-editor.org/info/rfc2104>.
  [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>.
  [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>.
  [RFC5905]  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>.
  [RFC6038]  Morton, A. and L. Ciavattone, "Two-Way Active Measurement
             Protocol (TWAMP) Reflect Octets and Symmetrical Size
             Features", RFC 6038, DOI 10.17487/RFC6038, October 2010,
             <https://www.rfc-editor.org/info/rfc6038>.
  [RFC6335]  Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
             Cheshire, "Internet Assigned Numbers Authority (IANA)
             Procedures for the Management of the Service Name and
             Transport Protocol Port Number Registry", BCP 165,
             RFC 6335, DOI 10.17487/RFC6335, August 2011,
             <https://www.rfc-editor.org/info/rfc6335>.
  [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>.
  [RFC8186]  Mirsky, G. and I. Meilik, "Support of the IEEE 1588
             Timestamp Format in a Two-Way Active Measurement Protocol
             (TWAMP)", RFC 8186, DOI 10.17487/RFC8186, June 2017,
             <https://www.rfc-editor.org/info/rfc8186>.
  [RFC8545]  Morton, A., Ed. and G. Mirsky, Ed., "Well-Known Port
             Assignments for the One-Way Active Measurement Protocol
             (OWAMP) and the Two-Way Active Measurement Protocol
             (TWAMP)", RFC 8545, DOI 10.17487/RFC8545, March 2019,
             <https://www.rfc-editor.org/info/rfc8545>.

8.2. Informative References

  [BBF.TR-390]
             Broadband Forum, "Performance Measurement from IP Edge to
             Customer Equipment using TWAMP Light", TR-390 Issue 1, May
             2017.
  [RFC4868]  Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-
             384, and HMAC-SHA-512 with IPsec", RFC 4868,
             DOI 10.17487/RFC4868, May 2007,
             <https://www.rfc-editor.org/info/rfc4868>.
  [RFC7750]  Hedin, J., Mirsky, G., and S. Baillargeon, "Differentiated
             Service Code Point and Explicit Congestion Notification
             Monitoring in the Two-Way Active Measurement Protocol
             (TWAMP)", RFC 7750, DOI 10.17487/RFC7750, February 2016,
             <https://www.rfc-editor.org/info/rfc7750>.
  [RFC8085]  Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
             Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
             March 2017, <https://www.rfc-editor.org/info/rfc8085>.
  [STAMP-OPTION]
             Mirsky, G., Xiao, M., Nydell, H., Foote, R., Masputra, A.,
             and E. Ruffini, "Simple Two-way Active Measurement
             Protocol Optional Extensions", Work in Progress, Internet-
             Draft, draft-ietf-ippm-stamp-option-tlv-03, 21 February
             2020, <https://tools.ietf.org/html/draft-ietf-ippm-stamp-
             option-tlv-03>.
  [STAMP-YANG]
             Mirsky, G., Xiao, M., and W. Luo, "Simple Two-way Active
             Measurement Protocol (STAMP) Data Model", Work in
             Progress, Internet-Draft, draft-ietf-ippm-stamp-yang-05,
             25 October 2019, <https://tools.ietf.org/html/draft-ietf-
             ippm-stamp-yang-05>.

Acknowledgments

  The authors express their appreciation to Jose Ignacio Alvarez-
  Hamelin and Brian Weis for their great insights into the security and
  identity protection as well as the most helpful and practical
  suggestions.  Also, our sincere thanks to David Ball, Rakesh Gandhi,
  and Xiao Min for their thorough reviews and helpful comments.

Authors' Addresses

  Greg Mirsky
  ZTE Corp.
  Email: [email protected]


  Guo Jun
  ZTE Corp.
  68# Zijinghua Road
  Nanjing
  Jiangsu, 210012
  China
  Phone: +86 18105183663
  Email: [email protected]


  Henrik Nydell
  Accedian Networks
  Email: [email protected]


  Richard Foote
  Nokia
  Email: [email protected]