



MPLS Working Group                                        R. Gandhi, Ed.
Internet-Draft                                              P. Brissette
Intended status: Standards Track                     Cisco Systems, Inc.
Expires: 31 May 2026                                           E. Leyton
                                                        Verizon Wireless
                                                                  X. Min
                                                               ZTE Corp.
                                                        27 November 2025


Encapsulation of Simple Two-Way Active Measurement Protocol for LSPs and
                      Pseudowires in MPLS Networks
                      draft-ietf-mpls-stamp-pw-02

Abstract

   This document describes the procedure for encapsulation of the Simple
   Two-Way Active Measurement Protocol (STAMP) defined in RFC 8762 and
   its optional extensions defined in RFC 8972 in MPLS networks.  Label
   Switched Paths (LSPs) and Pseudowires (PWs) are used in MPLS networks
   for various services including carrying Layer 2 and Layer 3 data
   packets and may optionally carry Control Word (CW).  The procedure
   described uses the Generic Associated Channel (G-ACh) to encapsulate
   the STAMP test packets with or without an IP/UDP header for the LSPs
   and PWs that carry CW.

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
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on 31 May 2026.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




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   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 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
     1.1.  Requirements  . . . . . . . . . . . . . . . . . . . . . .   4
     1.2.  Examples of MPLS Data Traffic Use Cases . . . . . . . . .   5
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   6
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   6
     2.2.  Abbreviations . . . . . . . . . . . . . . . . . . . . . .   6
     2.3.  STAMP Reference Topology  . . . . . . . . . . . . . . . .   6
   3.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  G-ACh Types for STAMP . . . . . . . . . . . . . . . . . .   7
     3.2.  Using STAMP for LSPs and PWs  . . . . . . . . . . . . . .   8
     3.3.  Forwarding STAMP Packets on a Broken LSP  . . . . . . . .   9
     3.4.  Applicability of Control Channel Types to STAMP for LSPs
           and PWs . . . . . . . . . . . . . . . . . . . . . . . . .   9
   4.  Session-Sender Test Packet  . . . . . . . . . . . . . . . . .  10
     4.1.  Session-Sender Test Packet with IP/UDP Header . . . . . .  10
     4.2.  Session-Sender Test Packet without IP/UDP Header  . . . .  12
   5.  Session-Reflector Test Packet . . . . . . . . . . . . . . . .  13
     5.1.  Session-Reflector Test Packet with IP/UDP Header  . . . .  13
     5.2.  Session-Reflector Test Packet without IP/UDP Header . . .  15
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  17
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  18
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

1.  Introduction

   The Simple Two-Way Active Measurement Protocol (STAMP) provides
   capabilities for the measurement of various metrics in IP networks
   [RFC8762] without the use of a control channel to pre-signal session
   parameters.  [RFC8972] defines optional extensions for STAMP.







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   Label Switched Paths (LSPs) are used in MPLS networks for various
   services including carrying Layer 2 and Layer 3 data packets.  The
   MPLS LSPs may use an optional CW as defined in Section 3, "Generic PW
   MPLS Control Word" of [RFC4385].

   Pseudowires (PWs) are used in MPLS networks for various services
   including carrying Layer 2 and Layer 3 data packets [RFC6658].  PWs
   are bidirectional in nature.  They can be point-to-point or point-to-
   multipoint.  PWs may use an optional Control Word (CW) as defined in
   Section 3, "Generic PW MPLS Control Word" of [RFC4385].

   MPLS Transport Profile (MPLS-TP) [RFC5960] was designed to use the
   MPLS data plane without any changes.  Therefore, when STAMP is
   specified over an MPLS data plane, it is equally applicable to MPLS-
   TP networks.  As specified in Section 2 of [RFC5921], "OAM and
   protection mechanisms, and forwarding of data packets, must be able
   to operate without IP forwarding support".

   When using STAMP for MPLS and MPLS-TP for both LSPs and PWs, there
   are unique aspects that need to be considered concerning the CW; and
   these aspects are addressed in this document.

   A Generic Associated Channel (G-ACh) [RFC5586] provides a mechanism
   to transport Operations, Administration, and Maintenance (OAM) and
   other control messages over the MPLS data plane.  The G-ACh types
   identify the various OAM messages being transported over the channel.

   Virtual Circuit Connectivity Verification (VCCV) is used as a Control
   Channel for PWs as described in [RFC5085].  A G-ACh can be used as a
   VCCV Control Channel as described in [RFC7708].

   This document describes the procedure for the encapsulation of STAMP
   defined in [RFC8762] and its optional extensions defined in
   [RFC8972], for point-to-point LSPs and PWs in MPLS networks.  The
   procedure uses G-ACh to encapsulate STAMP test packets with or
   without an IP/UDP header for LSPs and PWs that carry Control Word.

   This document defines two new G-ACh types when using STAMP without an
   IP/UDP header.  These types are PW demultiplexer agnostic and hence
   applicable to both PWs and Layer 2 Tunneling Protocol version 3
   (L2TPv3) PW demultiplexers.  This document uses the existing G-ACh
   types for IPv4 and IPv6 when using the STAMP packets with an IP/UDP
   header for LSPs and PWs that carry Control Word.








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1.1.  Requirements

   The STAMP test packets need to be transmitted with the same label
   stack as that used by the LSP and PW to ensure proper validation of
   the underlay path taken by the actual data traffic.  Also, the test
   packets need to follow the same ECMP underlay path taken by the LSP
   and PW data traffic in the network.  PW data traffic may be
   encapsulated using CW [RFC4385] and an IP header.  As such, the STAMP
   test packets need to be transmitted over the PW using G-ACh and an
   IP/UDP header.

   When a STAMP packet is transmitted to a target IP address of a STAMP
   Reflector, it may be encapsulated over an MPLS LSP by the data plane
   based on the reachability of the IP address over the LSP.  Hence, the
   STAMP packets would be treated the same way as the data traffic
   forwarded over the LSP by the transit nodes along the path.

   Data traffic over L2-Specific Sublayer (L2SS) as used in L2TP PW
   carries CW but does not carry an IP/UDP header.  As such, the STAMP
   packets need to be transmitted over L2SS as used in L2TP PW using
   G-ACh without any IP/UDP header (as raw STAMP payload).

   Private Line Emulation (PLE) [RFC9801] traffic is sent over a Packet
   Switched Network (PSN) as Virtual Private Wire Services (VPWS) using
   PWs.  The data packets are encapsulated with PLE CW, but they do not
   carry any IP header.  As such, the STAMP test packets need to be
   transmitted using the same label stack including the VPWS PW Label as
   the PLE traffic [RFC9801], and encapsulated using G-ACh but without
   an IP/UDP header.  This allows the STAMP test packets to experience
   the same forwarding behaviour, follow the same underlay path as the
   PLE traffic, and avoid different ECMP behavior on intermediate nodes.

   The G-ACh type allows for the demultiplexing of the VCCV Control
   Channel for PWs [RFC7708].  The G-ACh types for STAMP packets with or
   without IP/UDP headers are also used to demultiplex the VCCV Control
   Channel for PWs.  Signaling extensions for the VCCV Control Channel
   for PW for STAMP are outside the scope of this document.

   The G-ACh provides support for the OAM Control Channel associated
   with the MPLS Transport Profile (MPLS-TP) [RFC5960] LSPs and PWs.
   The OAM Control Channel for MPLS-TP needs to be extended to
   encapsulate STAMP test packets (just like the delay and loss
   measurement packets defined in [RFC6374]).  The G-ACh types for STAMP
   also allow for the demultiplexing of the OAM Control Channel for
   MPLS-TP.

   The requirements for the encapsulation of the STAMP test packets for
   the LSPs and PWs in MPLS networks can be summarized as follows:



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   o The G-ACh MUST support STAMP test packets with an IP/UDP header.

   o The G-ACh MUST support STAMP test packets without an IP/UDP header.

   o The G-ACh MUST support STAMP to demultiplex the Control Channel.

   o Session-Sender test packets MUST follow the underlay path taken by
   the data traffic that is using CW.

   o Session-Sender test packets MUST follow the same ECMP underlay path
   taken by the data traffic that is using CW and an Entropy Label
   defined in [RFC6790].

   o Session-Sender test packets MUST follow the same ECMP underlay path
   taken by the data traffic that is using CW but not using an Entropy
   Label defined in [RFC6790].

   o Session-Reflector test packets MAY follow the reverse underlay path
   taken by Session-Sender test packets.

   o Session-Reflector test packets MAY follow the same reverse ECMP
   underlay path taken by Session-Sender test packets.

   This document is concerned with the STAMP operation for the P2P
   Single-Segment PWs (SS-PWs).  The procedure for STAMP operation for
   point-to-multipoint (P2MP) PWs is outside the scope of this document.

1.2.  Examples of MPLS Data Traffic Use Cases

   Examples of MPLS data traffic use cases for STAMP test packets with
   IP/UDP headers:

      1.  MPLS PW Data Traffic (with CW and IP header)

      2.  MPLS-TP PW Data Traffic (with CW and IP header)

      3.  MPLS LSP Data Traffic (with IP header)

   Examples of MPLS data traffic use cases for STAMP test packets
   without IP/UDP headers:

      1.  MPLS Ethernet PW Data Traffic [RFC4448]

      2.  L2-Specific Sublayer (L2SS) used in L2TPv3 PW Data Traffic
      [RFC3931]

      3.  Private Line Emulation [RFC9801] PW Data Traffic




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      4.  TDM over IP [RFC5087] PW Data Traffic (with no IP header)

      5.  MPLS-TP LSP Data Traffic

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

   ECMP: Equal Cost Multi-Path.

   G-ACh: Generic Associated Channel.

   GAL: G-ACh Label.

   HMAC: Hashed Message Authentication Code.

   MPLS: Multiprotocol Label Switching.

   OAM: Operations, Administration, and Maintenance.

   PLE: Private Line Emulation.

   PW: Pseudowire.

   SHA: Secure Hash Algorithm.

   STAMP: Simple Two-Way Active Measurement Protocol.

   TC: Traffic Class.

   TTL: Time-To-Live.

2.3.  STAMP Reference Topology

   In the STAMP reference topology shown in Figure 1, there exists an
   LSP or a PW to transport data between Provider Edge (PE) Endpoints S1
   and R1.  The STAMP Session-Sender on PE node S1 initiates a Session-
   Sender test packet, and the STAMP Session-Reflector on PE node R1
   transmits a reply test packet.  The Session-Reflector reply test
   packet may be transmitted to the STAMP Session-Sender node S1 on the



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   same path (same set of links and nodes) in the reverse direction of
   the path taken towards the Session-Reflector node 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.

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

            STAMP Session-Sender        STAMP Session-Reflector
            Provider Edge Endpoint      Provider Edge Endpoint

            Figure 1: STAMP Reference Topology using LSP and PW

3.  Overview

   The STAMP Session-Sender and Session-Reflector test packets defined
   in [RFC8972] are encapsulated and transmitted over the PWs in MPLS
   networks.  The base STAMP test packets can be encapsulated using an
   IP/UDP header and may use destination UDP port 862 [RFC8762].  The
   source UDP port is chosen by the Session-Sender.

3.1.  G-ACh Types for STAMP

   There are two ways in which STAMP test packets may be encapsulated
   over a G-ACh: either using an IP/UDP header, referred to as Format1,
   or without using an IP/UDP header, referred to as Format2.

   For encapsulating the STAMP test packets over a G-ACh with IP/UDP
   headers (in Format1), IPv4 and IPv6 channel types [RFC4385] are used
   for both Session-Sender and Session-Reflector test packets.  The
   destination UDP port number in the Session-Sender and Session-
   Reflector test packets discriminates the test packets.  The IP
   version (IPv4 or IPv6) MUST match the IP version used for the LSPs
   and PWs being measured.





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   For encapsulating the STAMP test packets over a G-ACh without adding
   IP/UDP headers (in Format2), two new channel types are defined in
   this document: one for the Session-Sender test packets and one for
   the Session-Reflector test packets.  The different channel types are
   required for the Session-Sender and Session-Reflector test packets as
   the STAMP test packets do not have a way to discriminate between
   them.

3.2.  Using STAMP for LSPs and PWs

   The STAMP test packets are encapsulated with an MPLS header using the
   same label stack as the PW data traffic (including the PW label) and
   a G-ACh header (instead of the CW used by the data traffic).  The
   encapsulation allows the STAMP test packets to follow the same path
   as the PW data traffic, and provide the same ECMP behaviour on the
   intermediate nodes.

   Similarly, the STAMP test packets are encapsulated in Format1, but
   without a G-ACh header, and with an MPLS header using the same label
   stack as the MPLS LSP and MPLS-TP LSP data traffic that contains an
   IP header, without CW.  The encapsulation provides the STAMP test
   packets with the same ECMP behaviour on the intermediate nodes.

   The IPv4 Time to Live (TTL), IPv6 Hop Limit, and Generalized TTL
   Security Mechanism (GTSM) procedures from [RFC5082] also apply to the
   encapsulation of STAMP test packets, and hence the IPv4 and MPLS TTL
   and IPv6 Hop Limit MUST be set to 255.

   The OAM Control Channel traffic between two Provider Edge (PE)
   endpoints is not forwarded past the PE endpoints towards Customer
   Edge (CE) devices; instead, the OAM messages are intercepted at the
   PE endpoints for exception processing in the control plane.
   [RFC5085] defines mechanisms for the VCCV Control Channel to carry
   OAM messages for PWs.

   The "In-band VCCV for Control Word with 0001b as first nibble (Type
   1)" defined in Section 5.1.1 of [RFC5085] MUST be added when
   measuring PWs with CW to avoid the different ECMP hashing behaviour.

   The method for "TTL Expiry VCCV (Type 3)" defined in Section 5.1.3 of
   [RFC5085] allows the termination of OAM messages on the remote PE
   endpoint nodes.  This method is applied to the STAMP test packets to
   force test packets to be processed on Session-Sender and Session-
   Reflector control planes by adding the PW label with a TTL value of
   1.






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   VCCC Type 2 is also referred to as 'MPLS Router Alert Label"
   [RFC5085].  This method could result in a different Equal Cost Multi-
   Path (ECMP) hashing behavior, and thus result in the STAMP packets
   taking a path that differs from that of the actual data traffic under
   test [RFC5085].  Hence, the VCCV Type 2 is not supported for STAMP
   for measuring the PW traffic.

   The procedure to encapsulate STAMP packets for PWs, is also
   applicable to MPLS LSPs and MPLS-TP LSPs when using CW.  For
   measuring the data traffic over MPLS LSPs using an IP header, STAMP
   test packets in Format1 are transmitted.  For measuring the data
   traffic over MPLS-TP LSPs, not using an IP header, STAMP test packets
   in Format2 are transmitted with a TTL value of 1 in the ultimate LSP
   label in the MPLS header.

   The G-ACh label (GAL) [RFC5586], along with Generic Associated
   Channel (G-ACh) types defined in this document, can be used with
   STAMP test packets without an IP/UDP header (in Format2), similar to
   the case of MPLS-TP LSP performance measurement defined in [RFC6374].

3.3.  Forwarding STAMP Packets on a Broken LSP

   Setting the destination address to the egress node (STAMP Reflector)
   address of the LSP and forwarding STAMP packets on a broken LSP,
   would lead to the STAMP session being down if all data traffic on the
   LSP is dropped.

   Otherwise, if the data traffic is not dropped but is incorrectly MPLS
   or IP forwarded to the egress node, it could lead to an invalid
   measurement to the egress node (STAMP Reflector) of the LSP if the
   STAMP packets follow a different path.  In this case, invalid
   measurements for a broken LSP by STAMP would be detected by network
   analytics.

3.4.  Applicability of Control Channel Types to STAMP for LSPs and PWs

   Control Channel Types defined in [RFC5085] are applicable to STAMP
   Test Packets for LSPs and PWs as follows:













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   +==============+==================+==============+=================+
   | Control      | Control Channel  | STAMP Header | G-ACh Type      |
   | Channel Type | Name             | Format       |                 |
   +==============+==================+==============+=================+
   | Type 1       | In-band: Control | Format1 (IP/ | IPv4 G-ACH      |
   |              | Word with 0001b  | UDP Headers) | (0x21) and IPv6 |
   |              | as first nibble  |              | G-ACH (0x57)    |
   +--------------+------------------+--------------+-----------------+
   | Type 1       | In-band: Control | Format2 (No  | G-ACH Type      |
   |              | Word with 0001b  | IP/UDP       | STAMP G-ACH     |
   |              | as first nibble  | Headers)     | (TBD1/TBD2)     |
   +--------------+------------------+--------------+-----------------+
   | Type 2       | Out-of-band:     | Not          | Not supported   |
   |              | MPLS Router      | supported    |                 |
   |              | Alert Label      |              |                 |
   +--------------+------------------+--------------+-----------------+
   | Type 3       | TTL Expiry:      | Format 1     | IPv4 G-ACH      |
   |              | Label with TTL   | (IP/UDP      | (0x21) and IPv6 |
   |              | as 1             | Headers)     | G-ACH (0x57)    |
   +--------------+------------------+--------------+-----------------+
   | Type 3       | TTL Expiry:      | Format2 (No  | G-ACH Type      |
   |              | Label with TTL   | IP/UDP       | STAMP G-ACH     |
   |              | as 1             | Headers)     | (TBD1/TBD2)     |
   +--------------+------------------+--------------+-----------------+

             Table 1: Control Channel Types for LSPs and PWs

4.  Session-Sender Test Packet

   STAMP Session-Sender test packets are transmitted for an LSP or a PW
   using an MPLS header with or without an IP/UDP header.  Session-
   Sender STAMP test packets are transmitted using the label stack of
   the PW, including the PW label and the G-ACh.  Session-Sender STAMP
   test packets are transmitted using the label stack of the LSP as well
   as the G-ACh.

4.1.  Session-Sender Test Packet with IP/UDP Header

   The content of an example STAMP Session-Sender test packet for an LSP
   or a PW encapsulated using a G-ACh and an IP/UDP header is shown in
   Figure 2.










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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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Label(1)               | TC  |S|      TTL      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                                                               .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    PW Label or Ultimate LSP Label     | TC  |1|      1        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |0 0 0 1|Version|    Reserved   | IPv4 (0x0021) or IPv6 (0x0057)|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | IP Header                                                     |
    .  Source IP Address = Session-Sender IPv4 or IPv6 Address      .
    .  Destination IP Address=Session-Reflector IPv4 or IPv6 Address.
    .  IPv4 Protocol or IPv6 Next Header = UDP (17)                 .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | UDP Header                                                    |
    .  Source Port = As chosen by Session-Sender                    .
    .  Destination Port = User-configured Destination Port | 862    .
    .                                                               .
    +---------------------------------------------------------------+
    | Payload = Test Packet as specified in Section 3 of RFC 8972   |
    .           in Figure 1 and Figure 3                            .
    .                                                               .
    +---------------------------------------------------------------+
    | Optional STAMP Extension TLVs                                 |
    .                                                               .
    +---------------------------------------------------------------+

      Figure 2: Example Session-Sender Test Packet with IP/UDP Header

   The G-ACh header [RFC5586] with the channel type for IPv4 or IPv6
   MUST immediately follow the bottom of the label stack.  The payload
   contains the STAMP Session-Sender test packet defined in [RFC8972].

   The STAMP Session-Sender test packet G-ACh header contains the
   following fields:

   Version:  The Version field is set to 0, as defined in [RFC4385].

   Reserved:  Reserved bits MUST be set to zero upon transmission and
     ignored upon receipt.

   Channel Type:  G-ACh type for IPv4 header (0x0021) or IPv6 header
     (0x0057) [RFC4385].



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4.2.  Session-Sender Test Packet without IP/UDP Header

   The content of an example STAMP Session-Sender test packet for an LSP
   or a PW encapsulated using a G-ACh without an IP/UDP header 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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Label(1)               | TC  |S|      TTL      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                                                               .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    PW Label or Ultimate LSP Label     | TC  |1|      1        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |0 0 0 1|Version|    Reserved   | STAMP Sender G-ACh (TBD1)     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Payload = Test Packet as specified in Section 3 of RFC 8972   |
    .           in Figure 1 and Figure 3                            .
    .                                                               .
    +---------------------------------------------------------------+
    | Optional STAMP Extension TLVs                                 |
    .                                                               .
    +---------------------------------------------------------------+

     Figure 3: Example Session-Sender Test Packet without IP/UDP Header

   The G-ACh header [RFC5586] with the new STAMP Session-Sender channel
   type (value TBD1) MUST immediately follow the bottom of the label
   stack.  The payload contains the STAMP Session-Sender test packet
   defined in [RFC8972].

   The STAMP channel type allows the identification of the encapsulated
   STAMP payload when demultiplexing G-ACh.

   The STAMP Session-Sender test packet G-ACh header contains the
   following fields:

   Version:  The Version field is set to 0, as defined in [RFC4385].

   Reserved:  Reserved bits MUST be set to zero upon transmission and
     ignored upon receipt.

   Channel Type:  G-ACh type for STAMP Session-Sender packet (TBD1).





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5.  Session-Reflector Test Packet

   The STAMP Session-Reflector reflects the test packet back to the
   Session-Sender using the same channel in the reverse direction of the
   LSP or PW on which it was received.  The Session-Reflector has enough
   information to reflect the test packet received by it to the Session-
   Sender using the LSP or PW context.

   The STAMP Session-Reflector reply test packet is transmitted on the
   same path in the reverse direction of the LSP or the PW.  The STAMP
   test packet can be transmitted using an MPLS header with or without
   an IP/UDP header.  The Session-Reflector test packet is sent with an
   IP/UDP header if the Session-Sender test packet is received with an
   IP/UDP header; otherwise, it is sent without an IP/UDP header.

   The Session-Reflector can use the PW label or the ultimate LSP label
   in the received packet to find the LSP or the PW in the reverse
   direction.  The Session-Reflector uses the label stack of that LSP or
   PW as well as the G-ACh, to transmit the Session-Reflector test
   packet.  The Session-Reflector test packet uses the same G-ACh as
   that received in the Session-Sender test packet.

5.1.  Session-Reflector Test Packet with IP/UDP Header

   The content of an example STAMP Session-Reflector test packet for an
   LSP or a PW encapsulated using a G-ACh and an IP/UDP header is shown
   in Figure 4.
























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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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Label(1)               | TC  |S|      TTL      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                                                               .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    PW Label or Ultimate LSP Label     | TC  |1|      1        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |0 0 0 1|Version|    Reserved   | IPv4 (0x0021) or IPv6 (0x0057)|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | IP Header                                                     |
    .  Source IP Address                                            .
    .     = As chosen by Session-Reflector                          .
    .  Destination IP Address                                       .
    .     = Source IP Address from Session-Sender Test Packet       .
    .  IPv4 Protocol or IPv6 Next Header = UDP (17)                 .
    .                                                               .
    +---------------------------------------------------------------+
    | UDP Header                                                    |
    .  Source Port = As chosen by Session-Reflector                 .
    .  Destination Port                                             .
    .     = Source Port from Session-Sender Test Packet             .
    .                                                               .
    +---------------------------------------------------------------+
    | Payload = Test Packet as specified in Section 3 of RFC 8972   |
    .           in Figure 2 and Figure 4                            .
    .                                                               .
    +---------------------------------------------------------------+
    | STAMP TLVs from Session-Sender Test Packet                    |
    .                                                               .
    +---------------------------------------------------------------+

     Figure 4: Example Session-Reflector Test Packet with IP/UDP Header

   The G-ACh header [RFC5586] with the channel type IPv4 or IPv6 MUST
   immediately follow the bottom of the label stack.  The payload
   contains the STAMP Session-Reflector test packet defined in
   [RFC8972].

   The STAMP Session-Reflector reply test packet MUST use the IP/UDP
   information from the received test packet when an IP/UDP header is
   present in the received test packet.

   The STAMP Session-Reflector test packet G-ACh header contains the
   following fields:



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   Version:  The Version field is set to 0, as defined in [RFC4385].

   Reserved:  Reserved bits MUST be set to zero upon transmission and
     ignored upon receipt.

   Channel Type:  G-ACh type for IPv4 header (0x0021) or IPv6 header
     (0x0057) [RFC4385].

5.2.  Session-Reflector Test Packet without IP/UDP Header

   The content of an example STAMP Session-Reflector test packet for an
   LSP or a PW encapsulated using a G-ACh without an IP/UDP header is
   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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Label(1)               | TC  |S|      TTL      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                                                               .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    PW Label or Ultimate LSP Label     | TC  |1|      1        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |0 0 0 1|Version|    Reserved   | STAMP Reflector G-ACh (TBD2)  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Payload = Test Packet as specified in Section 3 of RFC 8972   |
    .           in Figure 2 and Figure 4                            .
    .                                                               .
    +---------------------------------------------------------------+
    | STAMP TLVs from Session-Sender Test Packet                    |
    .                                                               .
    +---------------------------------------------------------------+

   Figure 5: Example Session-Reflector Test Packet without IP/UDP Header

   The G-ACh header [RFC5586] with the new STAMP Session-Reflector
   channel type (value TBD2) MUST immediately follow the bottom of the
   label stack.  The payload contains the STAMP Session-Reflector test
   packet defined in [RFC8972].

   The STAMP channel type allows the identification of the encapsulated
   STAMP payload when demultiplexing G-ACh.

   The STAMP Session-Reflector test packet G-ACh header contains the
   following fields:




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   Version:  The Version field is set to 0, as defined in [RFC4385].

   Reserved:  Reserved bits MUST be set to zero upon transmission and
     ignored upon receipt.

   Channel Type:  G-ACh type for STAMP Session-Reflector packet (TBD2).

6.  Security Considerations

   The procedures defined in this document are intended for deployment
   in a single network administrative domain.  As such, the Session-
   Sender address, Session-Reflector address, and IP and MPLS forward
   and return paths are provisioned by the operator for the STAMP
   session.  It is assumed that the operator has verified the integrity
   of the IP and MPLS forward and return paths used to transmit STAMP
   test packets.

   The security considerations specified in [RFC8762] and [RFC8972] also
   apply to the procedure described in this document.  Specifically, the
   message integrity protection using HMAC, as defined in Section 4.4 of
   [RFC8762], also applies to the procedure described in this document.

   Routers that support G-ACh are subject to the same security
   considerations as defined in [RFC4385] and [RFC5586].

   The message throttling mechanisms described in the 'Security
   Considerations' Section of [RFC5085] also apply to the procedure
   described in this document.

   STAMP uses a 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
   STAMP Reference Topology shown in Figure 1 in received reply test
   packets at the Session-Sender.  The minimal state associated with
   these protocols also limits the extent of measurement disruption that
   can be caused by a corrupt or invalid test packet to a single test
   cycle.

   The destination IP address-based filtering in the data plane is
   provisioned on the nodes in an MPLS administrative domain to prevent
   the packets with an IP destination address set to the egress node
   address within the network from leaking to outside of the domain.
   This will also ensure that the STAMP packets with an IP destination



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   address set to the egress node address (STAMP Reflector) of an LSP
   will not be leaked outside of the domain (for example, in the case of
   a broken LSP).

7.  IANA Considerations

   IANA maintains the G-ACh Type Registry (see
   https://www.iana.org/assignments/g-ach-parameters/g-ach-
   parameters.xhtml).  IANA is requested to allocate values for the
   G-ACh Types for STAMP from the "MPLS Generalized Associated Channel
   (G-ACh) Types (including Pseudowire Associated Channel Types)"
   registry.

      +=======+====================================+===============+
      | Value | Description                        | Reference     |
      +=======+====================================+===============+
      | TBD1  | STAMP Session-Sender G-ACh Type    | This document |
      +-------+------------------------------------+---------------+
      | TBD2  | STAMP Session-Reflector G-ACh Type | This document |
      +-------+------------------------------------+---------------+

                        Table 2: STAMP G-ACh Type

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>.

   [RFC4385]  Bryant, S., Swallow, G., Martini, L., and D. McPherson,
              "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
              Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385,
              February 2006, <https://www.rfc-editor.org/info/rfc4385>.

   [RFC5085]  Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual
              Circuit Connectivity Verification (VCCV): A Control
              Channel for Pseudowires", RFC 5085, DOI 10.17487/RFC5085,
              December 2007, <https://www.rfc-editor.org/info/rfc5085>.

   [RFC5586]  Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
              "MPLS Generic Associated Channel", RFC 5586,
              DOI 10.17487/RFC5586, June 2009,
              <https://www.rfc-editor.org/info/rfc5586>.





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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>.

   [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

   [RFC3931]  Lau, J., Ed., Townsley, M., Ed., and I. Goyret, Ed.,
              "Layer Two Tunneling Protocol - Version 3 (L2TPv3)",
              RFC 3931, DOI 10.17487/RFC3931, March 2005,
              <https://www.rfc-editor.org/info/rfc3931>.

   [RFC4448]  Martini, L., Ed., Rosen, E., El-Aawar, N., and G. Heron,
              "Encapsulation Methods for Transport of Ethernet over MPLS
              Networks", RFC 4448, DOI 10.17487/RFC4448, April 2006,
              <https://www.rfc-editor.org/info/rfc4448>.

   [RFC5082]  Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C.
              Pignataro, "The Generalized TTL Security Mechanism
              (GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007,
              <https://www.rfc-editor.org/info/rfc5082>.

   [RFC5087]  Stein, Y., Shashoua, R., Insler, R., and M. Anavi, "Time
              Division Multiplexing over IP (TDMoIP)", RFC 5087,
              DOI 10.17487/RFC5087, December 2007,
              <https://www.rfc-editor.org/info/rfc5087>.

   [RFC5921]  Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau,
              L., and L. Berger, "A Framework for MPLS in Transport
              Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010,
              <https://www.rfc-editor.org/info/rfc5921>.

   [RFC5960]  Frost, D., Ed., Bryant, S., Ed., and M. Bocci, Ed., "MPLS
              Transport Profile Data Plane Architecture", RFC 5960,
              DOI 10.17487/RFC5960, August 2010,
              <https://www.rfc-editor.org/info/rfc5960>.





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   [RFC6374]  Frost, D. and S. Bryant, "Packet Loss and Delay
              Measurement for MPLS Networks", RFC 6374,
              DOI 10.17487/RFC6374, September 2011,
              <https://www.rfc-editor.org/info/rfc6374>.

   [RFC6658]  Bryant, S., Ed., Martini, L., Swallow, G., and A. Malis,
              "Packet Pseudowire Encapsulation over an MPLS PSN",
              RFC 6658, DOI 10.17487/RFC6658, July 2012,
              <https://www.rfc-editor.org/info/rfc6658>.

   [RFC6790]  Kompella, K., Drake, J., Amante, S., Henderickx, W., and
              L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
              RFC 6790, DOI 10.17487/RFC6790, November 2012,
              <https://www.rfc-editor.org/info/rfc6790>.

   [RFC7708]  Nadeau, T., Martini, L., and S. Bryant, "Using a Generic
              Associated Channel Label as a Virtual Circuit Connectivity
              Verification Channel Indicator", RFC 7708,
              DOI 10.17487/RFC7708, November 2015,
              <https://www.rfc-editor.org/info/rfc7708>.

   [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>.

   [RFC9801]  Gringeri, S., Whittaker, J., Leymann, N., Schmutzer, C.,
              Ed., and C. Brown, "Private Line Emulation over Packet
              Switched Networks", RFC 9801, DOI 10.17487/RFC9801, July
              2025, <https://www.rfc-editor.org/info/rfc9801>.

Acknowledgments

   The authors would like to thank Bharath Vasudevan, Ali Sianati, and
   Parag Jain for the discussions on the method to punt STAMP test
   packets to the control plane for processing.  The authors would also
   like to thank Greg Mirsky, Loa Andersson, Li Zhang, Richard Foote
   (Footer), and Stewart Bryant for reviewing this document and
   providing useful comments and suggestions.

Authors' Addresses

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




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   Patrice Brissette
   Cisco Systems, Inc.
   Canada
   Email: pbrisset@cisco.com


   Edward Leyton
   Verizon Wireless
   Email: edward.leyton@verizonwireless.com


   Xiao Min
   ZTE Corp.
   Nanjing
   China
   Email: xiao.min2@zte.com.cn



































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