SPRING Working Group                                      R. Gandhi, Ed.
Internet-Draft                                               C. Filsfils
Intended status: Standards Track                     Cisco Systems, Inc.
Expires: 25 February 2022                                   N. Vaghamshi
                                                                Reliance
                                                            M. Nagarajah
                                                                 Telstra
                                                                R. Foote
                                                                   Nokia
                                                                 M. Chen
                                                                  Huawei
                                                          24 August 2021


 Enhanced Performance Measurement Using Simple TWAMP in Segment Routing
                                Networks
                  draft-gandhi-spring-enhanced-srpm-00

Abstract

   Segment Routing (SR) leverages the source routing paradigm.  SR is
   applicable to both Multiprotocol Label Switching (SR-MPLS) and IPv6
   (SRv6) data planes.  This document defines procedure for Enhanced
   Performance Measurement of end-to-end SR paths including SR Policies
   for both SR-MPLS and SRv6 data planes using Simple Two-Way Active
   Measurement Protocol (STAMP) defined in RFC 8762.  The procedure
   reduces the deployment and operational complexities in a network.

Status of This Memo

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

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

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

   This Internet-Draft will expire on 25 February 2022.







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Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect 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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   3
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   4
     2.2.  Abbreviations . . . . . . . . . . . . . . . . . . . . . .   4
     2.3.  Reference Topology  . . . . . . . . . . . . . . . . . . .   5
   3.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Enhanced Loopback Mode Enabled with Network Programming
           Function  . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Example Provisioning Model  . . . . . . . . . . . . . . .   6
   4.  Enhanced Performance Measurement Procedure  . . . . . . . . .   7
     4.1.  Enhanced Performance Measurement Procedure for SR-MPLS
           Policies  . . . . . . . . . . . . . . . . . . . . . . . .   7
       4.1.1.  Timestamp Label Allocation  . . . . . . . . . . . . .   9
       4.1.2.  Node Capability for Timestamp Label . . . . . . . . .   9
     4.2.  Enhanced Performance Measurement Procedure for SRv6
           Policies  . . . . . . . . . . . . . . . . . . . . . . . .   9
       4.2.1.  Timestamp Endpoint Function Assignment  . . . . . . .  11
       4.2.2.  Node Capability for Timestamp Endpoint Function . . .  12
   5.  Example Failure Notifications . . . . . . . . . . . . . . . .  12
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  15
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16









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1.  Introduction

   Segment Routing (SR) leverages the source routing paradigm and
   greatly simplifies network operations for Software Defined Networks
   (SDNs).  SR is applicable to both Multiprotocol Label Switching (SR-
   MPLS) and IPv6 (SRv6) data planes [RFC8402].  SR Policies as defined
   in [I-D.ietf-spring-segment-routing-policy] are used to steer traffic
   through a specific, user-defined paths using a stack of Segments.
   Built-in Performance Measurement (PM) for delay and packet loss as
   well as Connectivity Verification (CV) are essential requirements to
   provide Service Level Agreements (SLAs) in SR networks.

   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.  As described in [I-D.ietf-spring-stamp-srpm],
   the STAMP can be used for performance measurement for delay and
   packet loss of end-to-end SR paths.

   Seamless Bidirectional Forwarding Detection (S-BFD) [RFC7880]
   provides a simplified mechanism for using BFD for path monitoring
   with a large proportion of negotiation aspects eliminated.  The S-BFD
   can be used for connectivity verification of end-to-end SR paths.

   Both STAMP and S-BFD require protocol support on the far-end
   Reflector node to process the received packets, and hence the
   received packets need to be punted from the forwarding fast path and
   return packets need to be generated.  This limits the scale for
   number sessions and the ability to provide faster detection interval.

   Enabling multiple protocols, S-BFD for connectivity verification and
   STAMP for performance measurement increases the deployment and
   operational complexities in a network.  Also, implementing multiple
   protocols in a hardware significantly increases the development cost.

   This document defines procedure for Enhanced Performance Measurement
   of end-to-end SR paths including SR Policies for both SR-MPLS and
   SRv6 data planes, using Simple Two-Way Active Measurement Protocol
   (STAMP) defined in [RFC8762].  The procedure reduces the deployment
   and operational complexities in a network.

2.  Conventions Used in This Document









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2.1.  Requirements Language

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

2.2.  Abbreviations

   S-BFD: Seamless Bidirectional Forwarding Detection.

   BSID: Binding Segment ID.

   ECMP: Equal Cost Multi-Path.

   EB: Endpoint Behaviour.

   HMAC: Hashed Message Authentication Code.

   MBZ: Must be Zero.

   MPLS: Multiprotocol Label Switching.

   PM: Performance Measurement.

   PTP: Precision Time Protocol.

   SID: Segment ID.

   SL: Segment List.

   SR: Segment Routing.

   SRH: Segment Routing Header.

   SR-MPLS: Segment Routing with MPLS data plane.

   SRv6: Segment Routing with IPv6 data plane.

   STAMP: Simple Two-way Active Measurement Protocol.

   TC: Traffic Class.

   TTL: Time To Live.







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2.3.  Reference Topology

   In the reference topology shown in Figure 1, the STAMP Session-Sender
   [RFC8762] S1 initiates a Session-Sender test packet and the Session-
   Reflector R1 returns the test packet.  The return test packet is
   transmitted back 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.

   The Session-Sender S1 and Session-Reflector R1 are connected via an
   SR path [RFC8402].  The SR path can be an SR Policy
   [I-D.ietf-spring-segment-routing-policy] on node S1 (called head-end)
   with destination to node R1 (called tail-end).

                            T1                  T2
                           /                     \
                  +-------+   STAMP Test Packet   +-------+
                  |       | - - - - - - - - - - - |       |
                  |   S1  |======================||  R1   |
                  |       |<- - - - - - - - - - - |       |
                  +-------+   Return Test Packet  +-------+
                           \
                            T4

                Session-Sender                 Session-Reflector
                                                (Timestamp,
                                                 Pop and Forward)

     Figure 1: Loopback Mode Enabled with Network Programming Function

3.  Overview

3.1.  Enhanced Loopback Mode Enabled with Network Programming Function

   As described in [I-D.ietf-spring-stamp-srpm], in loopback mode, the
   STAMP Session-Sender S1 initiates Session-Sender test packets and the
   Session-Reflector R1 forwards them back to the Session-Sender S1.
   The received STAMP test packets are not punted out of the fast path
   in forwarding at the Session-Reflector.  At the Session-Reflector,
   the loopback function simply makes the necessary changes to the
   encapsulation including IP and UDP headers to return the STAMP test
   packet to the Session-Sender S1.  No STAMP test session is created on
   the Session-Reflector R1.

   This document defines a new STAMP measurement mode, enhanced loopback
   mode, that is loopback mode enabled with network programming
   function.  In this mode, both transmit (T1) and receive (T2)
   timestamps in data plane are collected by the Session-Sender test



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   packets as shown in Figure 1.  The network programming function
   optimizes the "operations of punt test packet and generate return
   test packet" on the Session-Reflector as timestamping is implemented
   in forwarding fast path in hardware.  This helps to achieve higher
   STAMP test session scale and faster detection interval.

   The Session-Sender adds transmit timestamp (T1) in the payload of the
   Session-Sender test packet.  The Session-Reflector adds the receive
   timestamp (T2) in the payload of the received test packet in
   forwarding fast path in hardware without punting the test packet
   (e.g. to slow path or control-plane).  The network programming
   function enables Session-Reflector to add the receive timestamp (T2)
   at a specific offset in the payload which is locally provisioned,
   consistently in the network.

   The Session-Reflector only adds the receive timestamp if the source
   IP address (in case of SR-MPLS) or outer IPv6 header destination IP
   address (in case of SRv6) in the test packet matches the local node
   address to ensure that the test packet reaches the intended Session-
   Reflector and the receive timestamp is returned by the intended
   Session-Reflector.

3.2.  Example Provisioning Model

   An example provisioning model and typical measurement parameters are
   shown in Figure 2:

                                  +------------+
                                  | Controller |
                                  +------------+
    STAMP Mode                        /    \     Timestamp Label/SRv6 EB
      Enhanced Loopback Mode         /      \      Timestamp Offset
    Timestamp Label/SRv6 EB         /        \     Timestamp Format
      Timestamp Format             /          \
    Missed Packet Count (N)       /            \
    Delay Threshold/Count(TH/M)  /              \
    Packet Loss Threshold(XofY) /                \
                               v                  v
                           +-------+          +-------+
                           |       |          |       |
                           |   S1  |==========|   R1  |
                           |       |          |       |
                           +-------+          +-------+

                        Session-Sender     Session-Reflector

                    Figure 2: Example Provisioning Model




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   Example of a STAMP mode is enhanced loopback mode defined in this
   document.  The values for Timestamp Label and SRv6 Endpoint Behaviour
   may be provisioned as described in this document.  Example of
   Timestamp Format is 64-bit PTPv2 [IEEE1588].  Example of Timestamp
   Offset is 16 and 32 bytes for the unauthenticated and authenticated
   STAMP Session-Sender test packets, respectively.  Example of
   threshold values configured for generating notifications are: Missed
   Packet Count (N), Delay Exceeded Threshold and Packet Count (TH/M)
   and Packet Loss Threshold (XofY), as described in this document.

   The mechanisms to provision the Session-Sender and Session-Reflector
   are outside the scope of this document.

4.  Enhanced Performance Measurement Procedure

   For enhanced performance monitoring of an end-to-end SR path
   including SR Policy, STAMP Session-Sender test packets are
   transmitted in loopback mode enabled with network programming
   function to timestamp and forward the packet.

   For SR Policy, the Session-Sender test packets are transmitted using
   the Segment List (SL) of the Candidate-Path
   [I-D.ietf-spring-segment-routing-policy].  When a Candidate-Path has
   more than one Segment Lists, multiple Session-Sender test packets
   MUST be transmitted, one using each Segment List.

4.1.  Enhanced Performance Measurement Procedure for SR-MPLS Policies

   The STAMP Session-Sender test packets is transmitted using an MPLS
   header for each Label Stack of the SR-MPLS Policy Candidate-Path(s)
   as shown in Figure 3.

   The SR-MPLS header can contain the MPLS label stack of the forward
   path or both forward and the reverse direction paths.  In the former
   case, the return test packets are received by the Session-Sender via
   IP/UDP [RFC0768] return path and the MPLS header is removed by the
   Session-Reflector.

   In the latter case, the Segment List of the reverse direction SR path
   is added in the Session-Sender test packet header to receive the
   return test packet on a specific path, either using the Binding SID
   [I-D.ietf-pce-binding-label-sid] or Segment List of the Reverse SR
   Policy [I-D.ietf-pce-sr-bidir-path].  In this case, the MPLS header
   is not removed by the Session-Reflector.

   In both cases, the Session-Sender MUST set the Destination Address
   equal to the Session-Sender address and the Source Address equal to
   the Session-Reflector address in the IP header of the test packets.



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   In this document, two new Timestamp Labels are defined for SR-MPLS
   data plane to enable network programming function for "timestamp, pop
   and forward" the received test packet, one for unauthenticated mode
   and one for authenticated mode.

   In the Session-Sender test packets for SR-MPLS Policies, a Timestamp
   Label is added in the MPLS header as shown in Figure 3, to collect
   "Receive Timestamp" field in the payload of the test packet.  The
   Label Stack for the reverse direction SR-MPLS path can be added after
   the Timestamp Label (not shown in the Figure) to receive the return
   test packet on a specific path.  When a Session-Reflector receives a
   packet with Timestamp Label, after timestamping the packet at a
   specific offset, the Session-Reflector pops the Timestamp Label and
   forwards the packet using the next label or IP header in the packet
   (just like the data packets for the normal traffic).

     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      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .                                                               .
     .                                                               .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            Label(n)                   | TC  |S|      TTL      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            Extension Label (15)       | TC  |S|      TTL      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       Timestamp Label (TBA1 or TBA2)  | TC  |S|      TTL      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | IP Header                                                     |
     .  Source IP Address = Session-Reflector IPv4 or IPv6 Address   .
     .  Destination IP Address = Session-Sender IPv4 or IPv6 Address .
     .  Protocol = UDP                                               .
     .                                                               .
     +---------------------------------------------------------------+
     | UDP Header                                                    |
     .  Source Port = As chosen by Session-Sender                    .
     .  Destination Port = As chosen by Session-Sender               .
     .                                                               .
     +---------------------------------------------------------------+
     | Payload = Test Packet as specified in Section 3 of RFC 8972   |
     .           in Figure 1 and Figure 3                            .
     .                                                               .
     +---------------------------------------------------------------+

    Figure 3: Example STAMP Test Packet with Timestamp Label for SR-MPLS



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4.1.1.  Timestamp Label Allocation

   The timestamp Labels for STAMP test packets in unauthenticated and
   authenticated modes can be allocated using one of the following
   methods:

   *  Labels (values TBA1 and TBA2) assigned by IANA from the "Extended
      Special-Purpose MPLS Values" [RFC9017].  For Label (value TBA1),
      the timestamp offset is fixed at byte-offset 16 from the start of
      the payload for the STAMP test packets in unauthenticated mode,
      and Label (value TBA2) at byte-offset 32 from the start of the
      payload for the STAMP test packets in authenticated mode, both
      using the timestamp format 64-bit PTPv2.

   *  Labels allocated by a Controller from the global table of the
      Session-Reflector.  The Controller provisions the labels on both
      Session-Sender and Session-Reflector, as well as timestamp offsets
      and timestamp formats.

   *  Labels allocated by the Session-Reflector.  The signaling and IGP
      flooding extension for the labels (including timestamp offsets and
      timestamp formats) are outside the scope of this document.

4.1.2.  Node Capability for Timestamp Label

   The STAMP Session-Sender needs to know if the Session-Reflector can
   process the Timestamp Label to avoid dropping test packets.  The
   signaling extension for this capability exchange is outside the scope
   of this document.

4.2.  Enhanced Performance Measurement Procedure for SRv6 Policies

   The STAMP Session-Sender test packets for SRv6 data plane is
   transmitted using a Segment Routing Header (SRH) [RFC8754] for each
   Segment List of the SRv6 Policy Candidate-Path(s) as shown in
   Figure 4.

   The SRH can contain the Segment List of the forward path or both
   forward and the reverse direction paths.  In the former case, an
   inner IPv6 header (after SRH and before UDP header) MUST be added
   that contains the Destination Address equal to the Session-Sender
   address and the Source Address equal to the Session-Reflector address
   as shown in Figure 4.  In this case, the SRH is removed by the
   Session-Reflector and IP/UDP return path is used.

   In the latter case, the Segment List of the reverse direction SR path
   is added in the SRH to receive the return test packet on a specific
   path, either using the Binding SID [I-D.ietf-pce-binding-label-sid]



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   or Segment List of the Reverse SR Policy
   [I-D.ietf-pce-sr-bidir-path].  In this case, the SRH is not removed
   by the Session-Reflector and an inner IPv6 header is not required.
   When the return test packet contains an SRH at the Session-Sender,
   the procedure defined for upper-layer header processing for SRv6 SIDs
   in [RFC8986] MUST be used to process the UDP header in the received
   test packets.

   The [RFC8986] defines SRv6 Endpoint Behaviours (EB) for SRv6 nodes.
   In this document, two new Timestamp Endpoint Behaviours are defined
   for Segment Routing Header (SRH) [RFC8754] to enable "Timestamp and
   Forward (TSF)" function for the received test packets, one for
   unauthenticated mode and one for authenticated mode.

   In the Session-Sender test packets for SRv6 Policies, Timestamp
   Endpoint Function (End.TSF) is carried with the target Segment
   Identifier (SID) in SRH [RFC8754] as shown in Figure 4, to collect
   "Receive Timestamp" field in the payload of the test packet.  The
   Segment List for the reverse direction path can be added after the
   target SID to receive the return test packet on a specific path.
   When a Session-Reflector receives a packet with Timestamp Endpoint
   (End.TSF) for the target SID which is local, after timestamping the
   packet at a specific offset, the Session-Reflector forwards the
   packet using the next SID in the SRH or inner IPv6 header in the
   packet (just like the data packets for the normal traffic).


























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     +---------------------------------------------------------------+
     | IP Header                                                     |
     .  Source IP Address = Session-Sender IPv6 Address              .
     .  Destination IP Address = Destination IPv6 Address            .
     .                                                               .
     +---------------------------------------------------------------+
     | SRH as specified in RFC 8754                                  |
     .     <Segment List>                                            .
     .     SRv6 Endpoint End.TSF (value TBA3 or TBA4)                .
     .                                                               .
     +---------------------------------------------------------------+
     | IP Header                                                     |
     .  Source IP Address = Session-Reflector IPv6 Address           .
     .  Destination IP Address = Session-Sender IPv6 Address         .
     .                                                               .
     +---------------------------------------------------------------+
     | UDP Header                                                    |
     .  Source Port = As chosen by Session-Sender                    .
     .  Destination Port = As chosen by Session-Sender               .
     .                                                               .
     +---------------------------------------------------------------+
     | Payload = Test Packet as specified in Section 3 of RFC 8972   |
     .           in Figure 1 and Figure 3                            .
     .                                                               .
     +---------------------------------------------------------------+

    Figure 4: Example STAMP Test Packet with Endpoint Function for SRv6

4.2.1.  Timestamp Endpoint Function Assignment

   The Timestamp Endpoint Functions for "Timestamp and Forward" can be
   signaled using one of the following methods:

   *  Timestamp Endpoint Functions (values TBA3 and TBA4) assigned by
      IANA from the "SRv6 Endpoint Behaviors Registry".  For endpoint
      behaviour (value TBA3), the timestamp offset is fixed at byte-
      offset 16 from the start of the payload for the STAMP test packets
      in unauthenticated mode, and endpoint behaviour (value TBA4) at
      byte-offset 32 from the start of the payload for the STAMP test
      packets in authenticated mode, both using the timestamp format
      64-bit PTPv2.

   *  Timestamp Endpoint Functions assigned by a Controller.  The
      Controller provisions the values on both Session-Sender and
      Session-Reflector, as well as timestamp offsets and timestamp
      formats.





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   *  Timestamp Endpoint Functions assigned by the Session-Reflector.
      The signaling and IGP flooding extension for the endpoint
      functions (including timestamp offsets and timestamp formats) are
      outside the scope of this document.

4.2.2.  Node Capability for Timestamp Endpoint Function

   The STAMP Session-Sender needs to know if the Session-Reflector can
   process the Timestamp Endpoint Function to avoid dropping test
   packets.  The signaling extension for this capability exchange is
   outside the scope of this document.

5.  Example Failure Notifications

   The timestamps T1 and T2 are used to measure the one-way delay.  The
   delay metrics for an end-to-end SR path are notified, for example,
   when consecutive M number of test packets have measured delay values
   exceed the user-configured threshold TH, where M (Delay Exceeded
   Packet Count) and TH (Absolute and Percentage Delay Exceeded
   Threshold) are also locally provisioned values.

   The round-trip packet loss for an end-to-end SR path is calculated
   using the Sequence Number in the Session-Sender test packets.  The
   packet loss metric is notified when X number of Session-Sender test
   packets were lost out of last Y number of test packets transmitted by
   the Session-Sender, where Threshold XofY is locally provisioned
   value.

   STAMP session state as UP (i.e.  Connectivity verification success)
   for an end-to-end SR path is initially notified as soon as one or
   more return test packets are received at the Session-Sender.

   STAMP session state as DOWN (i.e.  Connectivity verification failure)
   for an end-to-end SR path is notified when consecutive N number of
   return test packets are not received at the Session-Sender, where N
   (Missed Packet Count) is a locally provisioned value.

   In the loopback mode, a connectivity verification failure on the
   reverse direction path can cause the return test packets to not reach
   the Session-Sender.  This is also true in the case where the return
   test packets are generated by the stateless Session-Reflector in two-
   way measurement.  The stateful Session-Reflector can solve this issue
   by maintaining the forwarding direction state and notifying a
   connectivity verification success and failure to the Session-Sender.







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6.  Security Considerations

   The STAMP protocol is intended for deployment in limited domains
   [RFC8799].  As such, it assumes that a node involved in the STAMP
   protocol operation has previously verified the integrity of the path
   and the identity of the far-end Session-Reflector.

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

7.  IANA Considerations

   IANA maintains the "Special-Purpose Multiprotocol Label Switching
   (MPLS) Label Values" registry (see <https://www.iana.org/assignments/
   mpls-label-values/mpls-label-values.xml>).  IANA is requested to
   allocate Timestamp Label value from the "Extended Special-Purpose
   MPLS Label Values" registry:

     +-------------+---------------------------------+---------------+
     | Value       | Description                     | Reference     |
     +-------------+---------------------------------+---------------+
     | TBA1        | Timestamp Label                 | This document |
     |             | for offset 16 for STAMP         |               |
     |             | in Unauthenticated Mode         |               |
     +-------------+---------------------------------+---------------+
     | TBA2        | Timestamp Label                 | This document |
     |             | for offset 32 for STAMP         |               |
     |             | in Authenticated Mode           |               |
     +-------------+---------------------------------+---------------+

   IANA is requested to allocate, within the "SRv6 Endpoint Behaviors
   Registry" sub-registry belonging to the top-level "Segment Routing
   Parameters" registry [RFC8986], the following allocation:
















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     +-------------+---------------------------------+---------------+
     | Value       | Endpoint Behavior               | Reference     |
     +-------------+---------------------------------+---------------+
     | TBA3        | End.TSF (Timestamp and Forward) | This document |
     |             | for offset 16 for STAMP         |               |
     |             | in Unauthenticated Mode         |               |
     +-------------+---------------------------------+---------------+
     | TBA4        | End.TSF (Timestamp and Forward) | This document |
     |             | for offset 32 for STAMP         |               |
     |             | in Authenticated Mode           |               |
     +-------------+---------------------------------+---------------+


8.  References

8.1.  Normative References

   [RFC0768]  Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              DOI 10.17487/RFC0768, August 1980,
              <https://www.rfc-editor.org/info/rfc768>.

   [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>.

   [RFC8986]  Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
              D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
              (SRv6) Network Programming", RFC 8986,
              DOI 10.17487/RFC8986, February 2021,
              <https://www.rfc-editor.org/info/rfc8986>.





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   [I-D.ietf-spring-stamp-srpm]
              Gandhi, R., Filsfils, C., Voyer, D., Chen, M., Janssens,
              B., and R. Foote, "Performance Measurement Using Simple
              TWAMP (STAMP) for Segment Routing Networks", Work in
              Progress, Internet-Draft, draft-ietf-spring-stamp-srpm-01,
              6 July 2021, <https://www.ietf.org/archive/id/draft-ietf-
              spring-stamp-srpm-01.txt>.

8.2.  Informative References

   [IEEE1588] IEEE, "1588-2008 IEEE Standard for a Precision Clock
              Synchronization Protocol for Networked Measurement and
              Control Systems", March 2008.

   [RFC7880]  Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S.
              Pallagatti, "Seamless Bidirectional Forwarding Detection
              (S-BFD)", RFC 7880, DOI 10.17487/RFC7880, July 2016,
              <https://www.rfc-editor.org/info/rfc7880>.

   [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>.

   [RFC8754]  Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
              Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
              (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
              <https://www.rfc-editor.org/info/rfc8754>.

   [RFC8799]  Carpenter, B. and B. Liu, "Limited Domains and Internet
              Protocols", RFC 8799, DOI 10.17487/RFC8799, July 2020,
              <https://www.rfc-editor.org/info/rfc8799>.

   [RFC9017]  Andersson, L., Kompella, K., and A. Farrel, "Special-
              Purpose Label Terminology", RFC 9017,
              DOI 10.17487/RFC9017, April 2021,
              <https://www.rfc-editor.org/info/rfc9017>.

   [I-D.ietf-spring-segment-routing-policy]
              Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
              P. Mattes, "Segment Routing Policy Architecture", Work in
              Progress, Internet-Draft, draft-ietf-spring-segment-
              routing-policy-13, 28 May 2021,
              <https://www.ietf.org/archive/id/draft-ietf-spring-
              segment-routing-policy-13.txt>.






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   [I-D.ietf-pce-binding-label-sid]
              Sivabalan, S., Filsfils, C., Tantsura, J., Previdi, S.,
              and C. L. (editor), "Carrying Binding Label/Segment
              Identifier in PCE-based Networks.", Work in Progress,
              Internet-Draft, draft-ietf-pce-binding-label-sid-10, 10
              July 2021, <https://www.ietf.org/archive/id/draft-ietf-
              pce-binding-label-sid-10.txt>.

   [I-D.ietf-pce-sr-bidir-path]
              Li, C., Chen, M., Cheng, W., Gandhi, R., and Q. Xiong,
              "Path Computation Element Communication Protocol (PCEP)
              Extensions for Associated Bidirectional Segment Routing
              (SR) Paths", Work in Progress, Internet-Draft, draft-ietf-
              pce-sr-bidir-path-07, 12 July 2021,
              <https://www.ietf.org/archive/id/draft-ietf-pce-sr-bidir-
              path-07.txt>.

Acknowledgments

   The authors would like to thank Greg Mirsky, Kireeti Kompella, and
   Adrian Farrel for providing useful comments.

Authors' Addresses

   Rakesh Gandhi (editor)
   Cisco Systems, Inc.
   Canada

   Email: rgandhi@cisco.com


   Clarence Filsfils
   Cisco Systems, Inc.

   Email: cfilsfil@cisco.com


   Navin Vaghamshi
   Reliance

   Email: Navin.Vaghamshi@ril.com


   Moses Nagarajah
   Telstra

   Email: Moses.Nagarajah@team.telstra.com




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   Richard Foote
   Nokia

   Email: footer.foote@nokia.com


   Mach(Guoyi) Chen
   Huawei

   Email: mach.chen@huawei.com









































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