



Internet Engineering Task Force (IETF)                    R. Gandhi, Ed.
Request for Comments: 9503                                   C. Filsfils
Category: Standards Track                            Cisco Systems, Inc.
ISSN: 2070-1721                                                  M. Chen
                                                                  Huawei
                                                             B. Janssens
                                                                    Colt
                                                                R. Foote
                                                                   Nokia
                                                            October 2023


   Simple Two-Way Active Measurement Protocol (STAMP) Extensions for
                        Segment Routing Networks

Abstract

   Segment Routing (SR) leverages the source routing paradigm.  SR is
   applicable to both Multiprotocol Label Switching (SR-MPLS) and IPv6
   (SRv6) forwarding planes.  This document specifies Simple Two-Way
   Active Measurement Protocol (STAMP) extensions (as described in RFC
   8762) for SR networks, for both the SR-MPLS and SRv6 forwarding
   planes, by augmenting the optional extensions defined in RFC 8972.

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/rfc9503.

Copyright Notice

   Copyright (c) 2023 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
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   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 Revised BSD License text as described in Section 4.e of the
   Trust Legal Provisions and are provided without warranty as described
   in the Revised BSD License.

Table of Contents

   1.  Introduction
   2.  Conventions Used in This Document
     2.1.  Requirements Language
     2.2.  Abbreviations
     2.3.  Reference Topology
   3.  Destination Node Address TLV
   4.  Return Path TLV
     4.1.  Return Path Sub-TLVs
       4.1.1.  Return Path Control Code Sub-TLV
       4.1.2.  Return Address Sub-TLVs
       4.1.3.  Return Path Segment List Sub-TLVs
   5.  Interoperability with TWAMP Light
   6.  Security Considerations
   7.  IANA Considerations
   8.  References
     8.1.  Normative References
     8.2.  Informative References
   Appendix A.  Destination Node Address TLV Use-Case Example
   Acknowledgments
   Contributors
   Authors' Addresses

1.  Introduction

   Segment Routing (SR) leverages the source routing paradigm for
   Software-Defined Networks (SDNs).  SR is applicable to both
   Multiprotocol Label Switching (SR-MPLS) and IPv6 (SRv6) forwarding
   planes [RFC8402].  SR Policies as defined in [RFC9256] are used to
   steer traffic through specific, user-defined paths using a stack of
   Segments.  A comprehensive SR Performance Measurement (PM) toolset is
   one of the essential requirements to measure network performance to
   provide Service Level Agreements (SLAs).

   The Simple Two-Way Active Measurement Protocol (STAMP) provides
   capabilities for the measurement of various performance metrics in IP
   networks [RFC8762] without the use of a control channel to pre-signal
   session parameters.  [RFC8972] defines optional extensions, in the
   form of TLVs, for STAMP.  Note that the YANG data model defined in
   [IPPM-STAMP-YANG] can be used to provision the STAMP Session-Sender
   and STAMP Session-Reflector.

   STAMP test packets are transmitted along an IP path between a
   Session-Sender and a Session-Reflector to measure performance delay
   and packet loss along that IP path.  In SR networks, it may be
   desired that the same path (same set of links and nodes) between the
   Session-Sender and Session-Reflector be used for the STAMP test
   packets in both directions.  This is achieved by using the STAMP
   [RFC8762] extensions for SR-MPLS and SRv6 networks as specified in
   this document by augmenting the optional extensions defined in
   [RFC8972].

2.  Conventions Used in This Document

2.1.  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.

2.2.  Abbreviations

   MPLS:  Multiprotocol Label Switching

   SID:  Segment Identifier

   SR:  Segment Routing

   SR-MPLS:  Segment Routing over MPLS

   SRv6:  Segment Routing over IPv6

   SSID:  STAMP Session Identifier

   STAMP:  Simple Two-Way Active Measurement Protocol

2.3.  Reference Topology

   In the reference topology shown below, the STAMP Session-Sender S1
   initiates a STAMP test packet and the STAMP Session-Reflector R1
   transmits a reply STAMP test packet.  The reply test packet may be
   transmitted to the Session-Sender S1 on the same path (same set of
   links and nodes) or a different path in the reverse direction from
   the path taken towards the Session-Reflector R1.

   T1 is a transmit timestamp, and T4 is a receive timestamp added by
   node S1.  T2 is a receive timestamp, and T3 is a transmit timestamp
   added by node R1.

   The nodes S1 and R1 may be connected via a link or an SR path
   [RFC8402].  The link may be a physical interface, virtual link, Link
   Aggregation Group (LAG) [IEEE802.1AX], or LAG member.  The SR path
   may be an SR Policy [RFC9256] on node S1 (called "head-end") with a
   destination to node R1 (called "tail-end").

                          T1                T2
                         /                   \
                +-------+     Test Packet     +-------+
                |       | - - - - - - - - - ->|       |
                |   S1  |=====================|   R1  |
                |       |<- - - - - - - - - - |       |
                +-------+  Reply Test Packet  +-------+
                         \                   /
                          T4                T3

            STAMP Session-Sender        STAMP Session-Reflector

                        Figure 1: Reference Topology

3.  Destination Node Address TLV

   The Session-Sender may need to transmit test packets to the Session-
   Reflector with a Destination Address that is not a routable address
   (i.e., not suitable for use as the Source Address of the reply test
   packet) of the Session-Reflector.  This can be facilitated, for
   example, by encapsulating the STAMP packet by a tunneling protocol;
   see Appendix A for an example.

   [RFC8972] defines STAMP Session-Sender and Session-Reflector test
   packets that can include one or more optional TLVs.  In this
   document, the TLV Type (value 9 for IPv4 and IPv6) is defined for the
   Destination Node Address TLV for the STAMP test packet [RFC8972].
   The formats of the Destination Node Address TLVs are shown in
   Figure 2:

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |STAMP TLV Flags|    Type=9     |         Length=4              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         IPv4 Address                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |STAMP TLV Flags|    Type=9     |         Length=16             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |                         IPv6 Address                          |
    |                                                               |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 2: Destination Node Address TLV Formats

   The TLV fields are defined as follows:

   STAMP TLV Flags:  The STAMP TLV Flags follow the procedures described
      in [RFC8972] and this document.

   Type:  Type (value 9) for the IPv4 Destination Node Address TLV or
      IPv6 Destination Node Address TLV.

   Length:  A 2-octet field equal to the length of the Address field in
      octets.  The length is 4 octets for an IPv4 address and 16 octets
      for an IPv6 address.

   The Destination Node Address TLV indicates an address of the intended
   Session-Reflector node of the test packet.  If the received
   Destination Node Address is one of the addresses of the Session-
   Reflector, it SHOULD be used as the Source Address in the IP header
   of the reply test packet.  If the Destination Node Address TLV is
   sent, the SSID MUST also be sent.

   A Session-Reflector that recognizes this TLV MUST set the U flag
   [RFC8972] in the reply test packet to 1 if the Session-Reflector
   determined that it is not the intended destination as identified in
   the Destination Node Address TLV.  In this case, the Session-
   Reflector does not use the received Destination Node Address as the
   Source Address in the IP header of the reply test packet.  Otherwise,
   the Session-Reflector MUST set the U flag in the Destination Node
   Address TLV in the reply test packet to 0.

4.  Return Path TLV

   For end-to-end SR paths, the Session-Reflector may need to transmit
   the reply test packet on a specific Return Path.  The Session-Sender
   can request this in the test packet to the Session-Reflector using a
   Return Path TLV.  With this TLV carried in the Session-Sender test
   packet, signaling and maintaining dynamic SR network state for the
   STAMP sessions on the Session-Reflector are avoided.

   There are two modes defined for the behaviors on the Session-
   Reflector in Section 4 of [RFC8762]: Stateless and Stateful.  A
   Stateful Session-Reflector requires configuration that must match all
   Session-Sender parameters, including the Source Address, Destination
   Address, Source UDP Port, Destination UDP Port, and possibly SSID
   (assuming the SSID is configurable and not auto-generated).  In this
   case, a local policy can be used to direct the test packet by
   creating additional states for the STAMP sessions on the Session-
   Reflector.  In the case of promiscuous operation, the Stateless
   Session-Reflector will require an indication of how to return the
   test packet on a specific path, for example, for measurement in an
   ECMP environment.

   For links, the Session-Reflector may need to transmit the reply test
   packet on the same incoming link in the reverse direction.  The
   Session-Sender can request this in the test packet to the Session-
   Reflector using a Return Path TLV.

   [RFC8972] defines STAMP test packets that can include one or more
   optional TLVs.  In this document, the TLV Type (value 10) is defined
   for the Return Path TLV that carries the Return Path for the Session-
   Sender test packet.  The format of the Return Path TLV is shown in
   Figure 3:

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |STAMP TLV Flags|    Type=10    |         Length                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                   Return Path Sub-TLVs                        |
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 3: Return Path TLV Format

   The TLV fields are defined as follows:

   STAMP TLV Flags:  The STAMP TLV Flags follow the procedures described
      in [RFC8972] and this document.

   Type:  Type (value 10) for the Return Path TLV.

   Length:  A 2-octet field equal to the length of the Return Path Sub-
      TLVs field in octets.

   Return Path Sub-TLVs:  As defined in Section 4.1.

   A Session-Sender MUST NOT insert more than one Return Path TLV in the
   STAMP test packet.  A Session-Reflector that supports this TLV MUST
   only process the first Return Path TLV in the test packet and ignore
   other Return Path TLVs if present.  A Session-Reflector that supports
   this TLV MUST reply using the Return Path received in the Session-
   Sender test packet, if no error was encountered while processing the
   TLV.

   A Session-Reflector that recognizes this TLV MUST set the U flag
   [RFC8972] in the reply test packet to 1 if the Session-Reflector
   determined that it cannot use the Return Path in the test packet to
   transmit the reply test packet.  Otherwise, the Session-Reflector
   MUST set the U flag in the reply test packet to 0.

4.1.  Return Path Sub-TLVs

   The Return Path TLV contains one or more Sub-TLVs to carry the
   information for the requested Return Path.  A Return Path Sub-TLV can
   carry a Return Path Control Code, Return Path IP Address, or Return
   Path Segment List.

   The STAMP Sub-TLV Flags are set using the procedures described in
   [RFC8972].

   A Return Path TLV MUST NOT contain more than one Control Code Sub-
   TLV, Return Address Sub-TLV, or Return Path Segment List Sub-TLV in a
   Session-Sender test packet.

   A Return Path TLV MUST NOT contain both a Control Code Sub-TLV and a
   Return Address or Return Path Segment List Sub-TLV in a Session-
   Sender test packet.

   A Return Path TLV MAY contain both a Return Address and a Return Path
   Segment List Sub-TLV in a Session-Sender test packet.

4.1.1.  Return Path Control Code Sub-TLV

   The format of the Control Code Sub-TLV in the Return Path TLV is
   shown in Figure 4.

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |STAMP TLV Flags|   Type=1      |         Length=4              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                   Control Code Flags                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    Figure 4: Format of the Control Code Sub-TLV in the Return Path TLV

   The TLV fields are defined as follows:

   Type:  Type (value 1) for the Return Path Control Code.  The Session-
      Sender can request the Session-Reflector to transmit the reply
      test packet based on the flags defined in the Control Code Flags
      field.

   STAMP TLV Flags:  The STAMP TLV Flags follow the procedures described
      in [RFC8972] and this document.

   Length:  A 2-octet field equal to the length of the Control Code
      flags, which is 4 octets.

   Control Code Flags (32 bits):  Reply Request Flag at bit 31 (least
      significant bit) is defined as follows.

      0x0:  No Reply Requested

      0x1:  Reply Requested on the Same Link

   All other bits are reserved and must be transmitted as 0 and ignored
   by the receiver.

   When Control Code flag for Reply Request is set to 0x0 in the
   Session-Sender test packet, the Session-Reflector does not transmit a
   reply test packet to the Session-Sender and terminates the STAMP test
   packet.  Only the one-way measurement is applicable in this case.
   Optionally, the Session-Reflector may locally stream performance
   metrics via telemetry using the information from the received test
   packet.  All other Return Path Sub-TLVs MUST be ignored in this case.

   When Control Code flag for Reply Request is set to 0x1 in the
   Session-Sender test packet, the Session-Reflector transmits the reply
   test packet over the same incoming link where the test packet is
   received in the reverse direction towards the Session-Sender.  The
   link may be a physical interface, virtual link, LAG [IEEE802.1AX], or
   LAG member.  All other Return Path Sub-TLVs MUST be ignored in this
   case.  When using LAG member links, the STAMP extension for the
   Micro-Session ID TLV defined in [STAMP-ON-LAG] can be used to
   identify the link.

4.1.2.  Return Address Sub-TLVs

   The STAMP reply test packet may be transmitted to the Session-Sender
   to the specified Return Address in the Return Address Sub-TLV instead
   of transmitting to the Source Address in the Session-Sender test
   packet.

   The formats of the IPv4 and IPv6 Return Address Sub-TLVs in the
   Return Path TLV are shown in Figure 5.

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |STAMP TLV Flags|     Type=2    |         Length=4              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                    Return IPv4 Address                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |STAMP TLV Flags|     Type=2    |         Length=16             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |                    Return IPv6 Address                        |
    |                                                               |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Figure 5: Formats of the Return Address Sub-TLVs in the Return
                                  Path TLV

   The TLV fields are defined as follows:

   Type:  Type (value 2) for the Return IPv4 Address or Return IPv6
      Address.

   The Return Address requests that the Session-Reflector reply test
   packet be sent to the specified address rather than to the Source
   Address in the Session-Sender test packet.

   STAMP TLV Flags:  The STAMP TLV Flags follow the procedures described
      in [RFC8972] and this document.

   Length:  A 2-octet field equal to the length of the Return Address
      field in octets.  The length is 4 octets for an IPv4 address and
      16 octets for an IPv6 address.

4.1.3.  Return Path Segment List Sub-TLVs

   The format of the Segment List Sub-TLVs in the Return Path TLV is
   shown in Figures 6 and 7.  The Segments carried in Segment List Sub-
   TLVs are described in [RFC8402].  The segment entries MUST be in
   network order.

   The Session-Sender MUST only insert one Return Path Segment List Sub-
   TLV in the test packet, and the Segment List MUST contain at least
   one Segment.  The Session-Reflector MUST only process the first
   Return Path Segment List Sub-TLV in the test packet and ignore other
   Return Path Segment List Sub-TLVs if present.

   The TLV fields are defined as follows:

   The Return Path Segment List Sub-TLV can be one of the following
   Types:

      Type (value 3):  SR-MPLS Label Stack of the Return Path

      Type (value 4):  SRv6 Segment List of the Return Path

   STAMP TLV Flags:  The STAMP TLV Flags follow the procedures described
      in [RFC8972] and this document.

   Length:  A 2-octet field equal to the length of the Segment List
      field in octets.  The length MUST NOT be 0.

4.1.3.1.  Return Path SR-MPLS Label Stack Sub-TLV

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |STAMP TLV Flags|     Type=3    |         Length                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |      Segment(1)                       | TC  |S|      TTL      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                                                               .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |      Segment(n) (bottom of stack)     | TC  |S|      TTL      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Figure 6: Format of the SR-MPLS Label Stack Sub-TLV in the Return
                                  Path TLV

   The SR-MPLS Label Stack contains a list of 32-bit Label Stack Entries
   (LSEs) that includes a 20-bit label value, an 8-bit Time-To-Live
   (TTL) value, a 3-bit Traffic Class (TC) value, and a 1-bit End-of-
   Stack (S) field.  The length of the Sub-TLV modulo 4 MUST be 0.

   As an example, an SR-MPLS Label Stack Sub-TLV could carry only the
   Binding SID Label [PCE-BINDING-LABEL-SID] of the Return SR-MPLS
   Policy.  The Binding SID Label of the Return SR-MPLS Policy is local
   to the Session-Reflector.  The mechanism to signal the Binding SID
   Label to the Session-Sender is outside the scope of this document.

   As another example, an SR-MPLS Label Stack Sub-TLV could include the
   Path Segment Identifier Label of the Return SR-MPLS Policy in the
   Segment List of the SR-MPLS Policy.

4.1.3.2.  Return Path SRv6 Segment List Sub-TLV

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |STAMP TLV Flags|     Type=4    |         Length                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |      Segment(1) (128-bit IPv6 Address)                        |
    |                                                               |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                                                               .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |      Segment(n) (128-bit IPv6 Address) (bottom of stack)      |
    |                                                               |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Figure 7: Format of the SRv6 Segment List Sub-TLV in the Return
                                  Path TLV

   The SRv6 Segment List contains a list of 128-bit IPv6 addresses
   representing the SRv6 SIDs.  The length of the Sub-TLV modulo 16 MUST
   be 0.

   As an example, a Return Path SRv6 Segment List Sub-TLV could carry
   only the SRv6 Binding SID [PCE-BINDING-LABEL-SID] of the Return SRv6
   Policy.  The SRv6 Binding SID of the Return SRv6 Policy is local to
   the Session-Reflector.  The mechanism to signal the SRv6 Binding SID
   to the Session-Sender is outside the scope of this document.

   As another example, a Return Path SRv6 Segment List Sub-TLV could
   include the SRv6 Path Segment Identifier of the Return SRv6 Policy in
   the Segment List of the SRv6 Policy.

5.  Interoperability with TWAMP Light

   This document does not introduce any additional considerations for
   interoperability with the Two-Way Active Measurement Protocol (TWAMP)
   Light than those described in Section 4.6 of [RFC8762].

   As described in [RFC8762], there are two possible combinations for
   such an interoperability use case:

   *  STAMP Session-Sender with TWAMP Light Session-Reflector

   *  TWAMP Light Session-Sender with STAMP Session-Reflector

   If any of the STAMP extensions defined in this document are used by
   STAMP Session-Sender, the TWAMP Light Session-Reflector will view
   them as the Packet Padding field.

6.  Security Considerations

   The security considerations specified in [RFC8762] and [RFC8972] also
   apply to the extensions defined in this document.  Specifically, the
   authenticated mode and the message integrity protection using Hashed
   Message Authentication Code (HMAC), as defined in Section 4.4 of
   [RFC8762], also apply to the procedures described in this document.

   STAMP uses the well-known UDP port number that could become a target
   of denial of service (DoS) or could be used to aid on-path attacks.
   Thus, the security considerations and measures to mitigate the risk
   of the attack documented in Section 6 of [RFC8545] equally apply to
   the STAMP extensions in this document.

   If desired, attacks can be mitigated by performing basic validation
   checks of the timestamp fields (such as T2 is later than T1 in the
   reference topology in Section 2.3) in received reply test packets at
   the Session-Sender.  The minimal state associated with these
   protocols also limit the extent of measurement disruption that can be
   caused by a corrupt or invalid test packet to a single test cycle.

   The usage of STAMP extensions defined in this document is intended
   for deployment in a single network administrative domain.  As such,
   the Session-Sender address, Session-Reflector address, and Return
   Path are provisioned by the operator for the STAMP session.  It is
   assumed that the operator has verified the integrity of the Return
   Path and identity of the far-end Session-Reflector.

   The STAMP extensions defined in this document may be used for
   potential address spoofing.  For example, a Session-Sender may
   specify a Return Path IP Address that is different from the Session-
   Sender address.  The Session-Reflector MAY drop the Session-Sender
   test packet when it cannot determine whether the Return Path IP
   Address is local on the Session-Sender.  To help the Session-
   Reflector to make that determination, the Return Path IP Address may
   also be provisioned by the operator, for example, in an access
   control list.

7.  IANA Considerations

   IANA has allocated a value for the Destination Address TLV Type and a
   value for the Return Path TLV Type from the IETF Review TLV range in
   the "STAMP TLV Types" registry [RFC8972] as follows.

       +=======+=======================================+===========+
       | Value | Description                           | Reference |
       +=======+=======================================+===========+
       | 9     | Destination Node IPv4 or IPv6 Address | RFC 9503  |
       +-------+---------------------------------------+-----------+
       | 10    | Return Path                           | RFC 9503  |
       +-------+---------------------------------------+-----------+

                          Table 1: STAMP TLV Types

   IANA has created the "Return Path Sub-TLV Types" registry.  All code
   points in the range 1 through 175 in this registry shall be allocated
   according to the "IETF Review" procedure as specified in [RFC8126].
   Code points in the range 176 through 239 shall be allocated according
   to the "First Come First Served" procedure as specified in [RFC8126].
   Remaining code points shall be allocated according to Table 2:

                   +=========+=========================+
                   | Range   | Registration Procedures |
                   +=========+=========================+
                   | 1-175   | IETF Review             |
                   +---------+-------------------------+
                   | 176-239 | First Come First Served |
                   +---------+-------------------------+
                   | 240-251 | Experimental Use        |
                   +---------+-------------------------+
                   | 252-254 | Private Use             |
                   +---------+-------------------------+

                        Table 2: Return Path Sub-TLV
                               Types Registry

   IANA has allocated values for the following Sub-TLV Types in the
   "Return Path Sub-TLV Types" registry.

      +=======+========================================+===========+
      | Value | Description                            | Reference |
      +=======+========================================+===========+
      | 0     | Reserved                               | RFC 9503  |
      +-------+----------------------------------------+-----------+
      | 1     | Return Path Control Code               | RFC 9503  |
      +-------+----------------------------------------+-----------+
      | 2     | Return IPv4 or IPv6 Address            | RFC 9503  |
      +-------+----------------------------------------+-----------+
      | 3     | SR-MPLS Label Stack of the Return Path | RFC 9503  |
      +-------+----------------------------------------+-----------+
      | 4     | SRv6 Segment List of the Return Path   | RFC 9503  |
      +-------+----------------------------------------+-----------+
      | 255   | Reserved                               | RFC 9503  |
      +-------+----------------------------------------+-----------+

                    Table 3: Return Path Sub-TLV Types

   IANA has created the "Return Path Control Code Flags" registry for
   Return Path Control Code Sub-TLVs.  All code points in the bit
   position 31 (counting from bit 31 as the least significant bit)
   through 12 in this registry shall be allocated according to the "IETF
   Review" procedure as specified in [RFC8126].  Code points in the bit
   position 11 through 8 shall be allocated according to the "First Come
   First Served" procedure as specified in [RFC8126].  Remaining code
   points shall be allocated according to Table 4:

                    +=======+=========================+
                    | Range | Registration Procedures |
                    +=======+=========================+
                    | 31-12 | IETF Review             |
                    +-------+-------------------------+
                    | 11-8  | First Come First Served |
                    +-------+-------------------------+
                    | 7-4   | Experimental Use        |
                    +-------+-------------------------+
                    | 3-0   | Private Use             |
                    +-------+-------------------------+

                        Table 4: Return Path Control
                            Code Flags Registry

   IANA has allocated a value in the "Return Path Control Code Flags"
   registry as follows.

                   +=======+===============+===========+
                   | Value | Description   | Reference |
                   +=======+===============+===========+
                   | 31    | Reply Request | RFC 9503  |
                   +-------+---------------+-----------+

                     Table 5: Return Path Control Code
                                   Flags

8.  References

8.1.  Normative References

   [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>.

   [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>.

   [RFC8762]  Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple
              Two-Way Active Measurement Protocol", RFC 8762,
              DOI 10.17487/RFC8762, March 2020,
              <https://www.rfc-editor.org/info/rfc8762>.

   [RFC8972]  Mirsky, G., Min, X., Nydell, H., Foote, R., Masputra, A.,
              and E. Ruffini, "Simple Two-Way Active Measurement
              Protocol Optional Extensions", RFC 8972,
              DOI 10.17487/RFC8972, January 2021,
              <https://www.rfc-editor.org/info/rfc8972>.

8.2.  Informative References

   [IEEE802.1AX]
              IEEE, "IEEE Standard for Local and metropolitan area
              networks -- Link Aggregation", IEEE Std 802.1AX-2014,
              DOI 10.1109/IEEESTD.2014.7055197, December 2014,
              <https://doi.org/10.1109/IEEESTD.2014.7055197>.

   [IPPM-STAMP-YANG]
              Mirsky, G., Min, X., and W. S. Luo, "Simple Two-way Active
              Measurement Protocol (STAMP) Data Model", Work in
              Progress, Internet-Draft, draft-ietf-ippm-stamp-yang-11,
              13 March 2023, <https://datatracker.ietf.org/doc/html/
              draft-ietf-ippm-stamp-yang-11>.

   [PCE-BINDING-LABEL-SID]
              Sivabalan, S., Filsfils, C., Tantsura, J., Previdi, S.,
              and C. Li, Ed., "Carrying Binding Label/Segment Identifier
              (SID) in PCE-based Networks.", Work in Progress, Internet-
              Draft, draft-ietf-pce-binding-label-sid-16, 27 March 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-pce-
              binding-label-sid-16>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

   [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>.

   [RFC9256]  Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
              A., and P. Mattes, "Segment Routing Policy Architecture",
              RFC 9256, DOI 10.17487/RFC9256, July 2022,
              <https://www.rfc-editor.org/info/rfc9256>.

   [STAMP-ON-LAG]
              Li, Z., Zhou, T., Guo, J., Mirsky, G., and R. Gandhi,
              "Simple Two-Way Active Measurement Protocol Extensions for
              Performance Measurement on LAG", Work in Progress,
              Internet-Draft, draft-ietf-ippm-stamp-on-lag-05, 17
              October 2023, <https://datatracker.ietf.org/doc/html/
              draft-ietf-ippm-stamp-on-lag-05>.

Appendix A.  Destination Node Address TLV Use-Case Example

   STAMP test packets can be encapsulated with 1) an SR-MPLS Label Stack
   and IPv4 header containing an IPv4 Destination Address from the 127/8
   range or 2) an outer IPv6 header and a Segment Routing Header (SRH)
   with an inner IPv6 header containing an IPv6 Destination Address from
   the ::1/128 range.

   In an ECMP environment, the hashing function in forwarding may decide
   the outgoing path using the Source Address, Destination Address, UDP
   ports, IPv6 flow-label, etc. from the packet.  Hence, for IPv4, for
   example, different values of an IPv4 Destination Address from the
   127/8 range may be used in the IPv4 header of the STAMP test packets
   to measure different ECMP paths.  For IPv6, for example, different
   values of flow-label may be used in the IPv6 header of the STAMP test
   packets to measure different ECMP paths.

   In those cases, the STAMP test packets may reach a node that is not
   the Session-Reflector for this STAMP session in an error condition,
   and this unintended node may transmit a reply test packet that can
   result in the reporting of invalid measurement metrics.  The intended
   Session-Reflector address can be carried in the Destination Node
   Address TLV to help detect this error.

Acknowledgments

   The authors would like to thank Thierry Couture for the discussions
   on the use cases for Performance Measurement in Segment Routing.  The
   authors would also like to thank Greg Mirsky, Mike Koldychev, Gyan
   Mishra, Tianran Zhou, Al Morton, Reshad Rahman, Zhenqiang Li, Frank
   Brockners, Henrik Nydell, and Cheng Li for providing comments and
   suggestions.  Thank you to Joel Halpern for the Gen-ART review,
   Martin Duke for the AD review, and Kathleen Moriarty for the Security
   review.  The authors would also like to thank Robert Wilton, Éric
   Vyncke, Paul Wouters, John Scudder, Roman Danyliw, Lars Eggert, Erik
   Kline, Warren Kumari, and Jim Guichard for the IESG review.

Contributors

   The following person has contributed substantially to this document:

   Daniel Voyer
   Bell Canada
   Email: daniel.voyer@bell.ca


Authors' Addresses

   Rakesh Gandhi (editor)
   Cisco Systems, Inc.
   Canada
   Email: rgandhi@cisco.com


   Clarence Filsfils
   Cisco Systems, Inc.
   Email: cfilsfil@cisco.com


   Mach(Guoyi) Chen
   Huawei
   Email: mach.chen@huawei.com


   Bart Janssens
   Colt
   Email: Bart.Janssens@colt.net


   Richard Foote
   Nokia
   Email: footer.foote@nokia.com
