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Versions: (draft-ali-spring-srv6-pm) 00 01 02 draft-gandhi-spring-rfc6374-srpm-udp

SPRING Working Group                                      R. Gandhi, Ed.
Internet-Draft                                               C. Filsfils
Intended Status: Standards Track                     Cisco Systems, Inc.
Expires: March 18, 2019                                         D. Voyer
                                                             Bell Canada
                                                              S. Salsano
                                        Universita di Roma "Tor Vergata"
                                                            P. L. Ventre
                                                                    CNIT
                                                                 M. Chen
                                                                  Huawei
                                                      September 14, 2018


                          UDP Path for In-band
          Performance Measurement for Segment Routing Networks
                     draft-gandhi-spring-udp-pm-02

Abstract

   Segment Routing (SR) is applicable to both Multiprotocol Label
   Switching (SR-MPLS) and IPv6 (SRv6) data planes.  This document
   specifies procedures for using UDP path for sending and processing
   in-band probe query and response messages for Performance
   Measurement.  The procedure uses the RFC 6374 defined mechanisms for
   Delay and Loss performance measurement.  The procedure specified is
   applicable to SR-MPLS and SRv6 data planes for both links and
   end-to-end measurement for SR Policies.  This document also defines
   mechanisms for handling Equal Cost Multipaths (ECMPs) for SR
   Policies.  In addition, this document defines Return Path Segment
   List TLV for two-way performance measurement and Block Number TLV for
   loss measurement.


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 http://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."



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Copyright Notice

   Copyright (c) 2018 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
   (http://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  . . . . . . . . . . . . . .  4
     2.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  4
     2.2.  Abbreviations  . . . . . . . . . . . . . . . . . . . . . .  4
     2.3.  Reference Topology . . . . . . . . . . . . . . . . . . . .  5
   3.  Probe Messages . . . . . . . . . . . . . . . . . . . . . . . .  6
     3.1.  Probe Query Message  . . . . . . . . . . . . . . . . . . .  6
       3.1.1.  Delay Measurement Probe Query Message  . . . . . . . .  6
       3.1.2.  Loss Measurement Probe Query Message . . . . . . . . .  7
         3.1.2.1.  Block Number TLV . . . . . . . . . . . . . . . . .  8
       3.1.3.  In-band Probe Query for SR Links . . . . . . . . . . .  8
       3.1.4.  In-band Probe Query for End-to-end Measurement of SR
               Policy . . . . . . . . . . . . . . . . . . . . . . . .  8
         3.1.4.1.  In-band Probe Query Message for SR-MPLS Policy . .  8
         3.1.4.2.  In-band Probe Query Message for SRv6 Policy  . . .  9
     3.2.  Probe Response Message . . . . . . . . . . . . . . . . . .  9
       3.2.1.  One-way Measurement for SR Link and end-to-end SR
               Policy . . . . . . . . . . . . . . . . . . . . . . . . 10
         3.2.1.1.  Probe Response Message to Controller . . . . . . . 11
       3.2.2.  Two-way Measurement for SR Links . . . . . . . . . . . 11
       3.2.3.  Two-way End-to-end Measurement of SR Policy  . . . . . 11
         3.2.3.1.  Return Path Segment List TLV . . . . . . . . . . . 11
         3.2.3.2.  In-band Probe Response Message for SR-MPLS
                   Policy . . . . . . . . . . . . . . . . . . . . . . 13
         3.2.3.3.  In-band Probe Response Message for SRv6 Policy . . 13
   4.  Performance Measurement for P2MP SR Policies . . . . . . . . . 14
   5.  ECMP Support . . . . . . . . . . . . . . . . . . . . . . . . . 14
   6.  Sequence Number TLV  . . . . . . . . . . . . . . . . . . . . . 14
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 15
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15



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   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 16
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 16
   Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . . . 19
   Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19



1.  Introduction

   Segment Routing (SR) technology greatly simplifies network operations
   for Software Defined Networks (SDNs).  SR is applicable to both
   Multiprotocol Label Switching (SR-MPLS) and IPv6 (SRv6) data planes.
   SR takes advantage of the Equal-Cost Multipaths (ECMPs) between
   source, transit and destination nodes.  SR Policies as defined in
   [I-D.spring-segment-routing-policy] are used to steer traffic through
   a specific, user-defined path using a stack of Segments.  Built-in SR
   Performance Measurement (PM) is one of the essential requirements to
   provide Service Level Agreements (SLAs).

   The One-Way Active Measurement Protocol (OWAMP) defined in [RFC4656]
   and Two-Way Active Measurement Protocol (TWAMP) defined in [RFC5357]
   provide capabilities for the measurement of various performance
   metrics in IP networks.  These protocols rely on control channel
   signaling to establish a test channel over an UDP path.  These
   protocols lack support for IEEE 1588 timestamp [IEEE1588] format and
   direct-mode Loss Measurement (LM), which are required in SR networks
   [RFC6374].  The Simple Two-way Active Measurement Protocol (STAMP)
   [I-D.ippm-stamp] alleviates the control channel signaling by using
   configuration data model to provision test channels.  In addition,
   the STAMP supports IEEE 1588 timestamp format for Delay Measurement
   (DM).  The TWAMP Light from broadband forum [BBF.TR-390] provides
   simplified mechanisms for active performance measurement in Customer
   Edge IP networks.

   [RFC6374] specifies protocol mechanisms to enable the efficient and
   accurate measurement of performance metrics and can be used in SR
   networks with MPLS data plane [I-D.spring-sr-mpls-pm].  [RFC6374]
   addresses the limitations of the IP based performance measurement
   protocols as specified in Section 1 of [RFC6374].  The [RFC6374]
   requires data plane to support MPLS Generic Associated Channel Label
   (GAL) and Generic Associated Channel (G-Ach), which may not be
   supported on all nodes in the network.

   [RFC7876] specifies the procedures to be used when sending and
   processing out-of-band performance measurement probe response
   messages over an UDP return path for RFC 6374 based probe queries.



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   [RFC7876] can be used to send out-of-band PM probe responses in both
   SR-MPLS and SRv6 networks for one-way performance measurement.

   For SR Policies, there are ECMPs between the source and transit
   nodes, between transit nodes and between transit and destination
   nodes.  Existing PM protocols (e.g. RFC 6374) do not define handling
   for ECMP forwarding paths in SR networks.

   For two-way measurements for SR Policies, there is a need to specify
   a return path in the form of a Segment List in PM probe query
   messages without requiring any SR Policy state on the destination
   node.  Exiting protocols do not have such mechanisms to specify
   return path in the PM probe query messages.

   This document specifies a procedure for using UDP path for sending
   and processing in-band probe query and response messages for
   Performance Measurement that does not require to bootstrap PM
   sessions.  The procedure uses RFC 6374 defined mechanisms for Delay
   and Loss PM and unless otherwise specified, the procedures from RFC
   6374 are not modified.  The procedure specified is applicable to both
   SR-MPLS and SRv6 data planes.  The procedure does not require to
   bootstrap PM sessions and can be used for both SR links and
   end-to-end performance  measurement for SR Policies.  This document
   also defines mechanisms for handling Equal Cost Multipaths (ECMPs)
   for SR Policies.  In addition, this document defines Return Path
   Segment List (RPSL) TLV for two-way performance measurement and Block
   Number TLV for loss measurement.


2.  Conventions Used in This Document

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

   ACH: Associated Channel Header.

   BSID: Binding Segment ID.

   DFLag: Data Format Flag.

   DM: Delay Measurement.




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   ECMP: Equal Cost Multi-Path.

   G-ACh: Generic Associated Channel (G-ACh).

   GAL: Generic Associated Channel (G-ACh) Label.

   LM: Loss Measurement.

   MPLS: Multiprotocol Label Switching.

   NTP: Network Time Protocol.

   OWAMP: One-Way Active Measurement Protocol.

   PM: Performance Measurement.

   PTP: Precision Time Protocol.

   RPSL: Return Path Segment List.

   SID: Segment ID.

   SL: Segment List.

   SR: Segment Routing.

   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.

   TWAMP: Two-Way Active Measurement Protocol.

   URO: UDP Return Object.


2.3.  Reference Topology

   In the reference topology, the querier node R1 initiates a probe
   query for performance measurement and the responder node R5 sends a
   probe response for the query message received.  The probe response
   may be sent to the querier node R1 or to a controller node R100.  The
   nodes R1 and R5 may be directly connected via a link enabled with
   Segment Routing or there exists a Point-to-Point (P2P) SR Policy
   [I-D.spring-segment-routing-policy] on node R1 with destination to



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   node R5.  In case of Point-to-Multipoint (P2MP), SR Policy
   originating from source node R1 may terminate on multiple destination
   leaf nodes [I-D.spring-sr-p2mp-policy].

                                             ------
                                             |R100|
                                             ------
                                               ^
                                               | Response
                                               |
             +-------+        Query        +-------+
             |       | - - - - - - - - - ->|       |
             |   R1  |---------------------|   R5  |
             |       |<- - - - - - - - - - |       |
             +-------+       Response      +-------+

                        Reference Topology

   Both Delay and Loss performance measurement is performed in-band for
   the traffic traversing between node R1 and node R5.  One-way delay
   and two-way delay measurements are defined in Section 2.4 of
   [RFC6374].  Transmit and Receive packet loss measurements are defined
   in Section 2.2 and Section 2.6 of [RFC6374].  One-way loss
   measurement provides receive packet loss whereas two-way loss
   measurement provides both transmit and receive packet loss.


3.  Probe Messages

3.1.  Probe Query Message

   In this document, UDP path is defined for sending and processing PM
   probe query messages for Delay and Loss measurements for SR links and
   end-to-end SR Policies as described in the following Sections.  As
   well-known UDP port is used for identifying PM probe packets,
   bootstrapping of the PM session [RFC5357] is not required.  The TTL /
   Hop Limit field of the IP header MUST be set to 1.

3.1.1.  Delay Measurement Probe Query Message

   The message content for Delay Measurement probe query message using
   UDP header [RFC768] is shown in Figure 1.  As shown, the DM probe
   query message is sent with Destination UDP port number TBA1 defined
   in this document.  The Source UDP port may optionally be set to TBA1
   for two-way delay measurement.  The DM probe query message contains
   the payload for delay measurement defined in Section 3.2 of
   [RFC6374].




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    +---------------------------------------------------------------+
    | IP Header                                                     |
    .   Source IP Address = Querier IPv4 or IPv6 Address            .
    .   Destination IP Address = Responder IPv4 or IPv6 Address     .
    .   Protocol = UDP                                              .
    .   IP TTL = 1                                                  .
    .   Router Alert Option Not Set                                 .
    .                                                               .
    +---------------------------------------------------------------+
    | UDP Header                                                    |
    .   Source Port = As chosen by Querier                          .
    .   Destination Port = TBA1 by IANA for Delay Measurement       .
    .                                                               .
    +---------------------------------------------------------------+
    | Payload = Message as specified in Section 3.2 of RFC 6374     |
    .                                                               .
    +---------------------------------------------------------------+

                  Figure 1: DM Probe Query Message

3.1.2.  Loss Measurement Probe Query Message

   The message content for Loss measurement probe query message using
   UDP header [RFC768] is shown in Figure 2.  As shown, the LM probe
   query message is sent with Destination UDP port number TBA2 defined
   in this document.  The Source UDP port may optionally be set to TBA2
   for two-way loss measurement.  The LM probe query message contains
   the payload for loss measurement defined in Section 3.1 of [RFC6374].


    +---------------------------------------------------------------+
    | IP Header                                                     |
    .   Source IP Address = Querier IPv4 or IPv6 Address            .
    .   Destination IP Address = Responder IPv4 or IPv6 Address     .
    .   Protocol = UDP                                              .
    .   IP TTL = 1                                                  .
    .   Router Alert Option Not Set                                 .
    .                                                               .
    +---------------------------------------------------------------+
    | UDP Header                                                    |
    .   Source Port = As chosen by Querier                          .
    .   Destination Port = TBA2 by IANA for Loss Measurement        .
    .                                                               .
    +---------------------------------------------------------------+
    | Payload = Message as specified in Section 3.1 of RFC 6374     |
    .                                                               .
    +---------------------------------------------------------------+




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                  Figure 2: LM Probe Query Message

   The path segment identifier [I-D.spring-mpls-path-segment]
   [I-D.pce-sr-path-segment] of the SR Policy is required for accounting
   received traffic on the egress node for loss measurement.

3.1.2.1.  Block Number TLV

   The Loss Measurement using Alternate-Marking method defined in
   [RFC8321] requires to identify the Block Number (color) of the
   traffic counters carried by the probe query and response messages.
   Probe query and response messages specified in [RFC6374] for Loss
   Measurement do not define any means to carry the Block Number.

   [RFC6374] defines probe query and response messages that can include
   one or more optional TLVs.  New TLV Type (value TBA8) is defined in
   this document to carry Block Number (32-bit) for the traffic counters
   in the probe query and response messages for loss measurement.  The
   format of the Block Number TLV is shown in Figure 11:

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Type TBA8   |    Length     |      Reserved                 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       Block Number                            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 11: Block Number TLV

   The Block Number TLV is optional.  The PM querier node SHOULD only
   insert one Block Number TLV in the probe query message and the
   responder node in the probe response message SHOULD return the first
   Block Number TLV from the probe query messages and ignore other Block
   Number TLVs if present.  In both probe query and response messages,
   the counters MUST belong to the same Block Number.

3.1.3.  In-band Probe Query for SR Links

   The probe query message as defined in Figure 1 is sent in-band for
   Delay measurement.  The probe query message as defined in Figure 2 is
   sent in-band for Loss measurement.

3.1.4.  In-band Probe Query for End-to-end Measurement of SR Policy

3.1.4.1.  In-band Probe Query Message for SR-MPLS Policy

   The message content for in-band probe query message using UDP header



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   for end-to-end performance measurement of SR-MPLS Policy 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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Segment List(0)        | EXP |S|      TTL      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                                                               .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Segment List(n)        | EXP |S|      TTL      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Message as shown in Figure 1 for DM or Figure 2 for LM        |
    .                                                               .
    +---------------------------------------------------------------+

         Figure 3: In-band Probe Query Message for SR-MPLS Policy

   The Segment List (SL) can be empty to indicate Implicit NULL label
   case.

3.1.4.2.  In-band Probe Query Message for SRv6 Policy

   The in-band probe query messages using UDP header for end-to-end
   performance measurement of an SRv6 Policy is sent using SRv6 Segment
   Routing Header (SRH) and Segment List of the SRv6 Policy as defined
   in [I-D.6man-segment-routing-header] and 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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           SRH                                 |
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Message as shown in Figure 1 for DM or Figure 2 for LM        |
    .                                                               .
    +---------------------------------------------------------------+

          Figure 4: In-band Probe Query Message for SRv6 Policy


3.2.  Probe Response Message

   When the received probe query message does not contain any UDP Return
   Object (URO) TLV [RFC7876], the probe response message is sent using
   the IP/UDP information from the probe query message.  The content of



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   the probe response message is shown in Figure 5.

    +---------------------------------------------------------------+
    | IP Header                                                     |
    .   Source IP Address = Responder IPv4 or IPv6 Address          .
    .   Destination IP Address = Source IP Address from Query       .
    .   Protocol = UDP                                              .
    .   Router Alert Option Not Set                                 .
    .                                                               .
    +---------------------------------------------------------------+
    | UDP Header                                                    |
    .   Source Port = As chosen by Responder                        .
    .   Destination Port = Source Port from Query                   .
    .                                                               .
    +---------------------------------------------------------------+
    | Message as specified in Section 3.2 of RFC 6374 for DM, or    |
    . Message as specified in Section 3.1 of RFC 6374 for LM        .
    .                                                               .
    +---------------------------------------------------------------+

                    Figure 5: Probe Response Message

   When the received probe query message contains UDP Return Object
   (URO) TLV [RFC7876], the probe response message the message uses the
   IP/UDP information from the URO in the probe query message.  The
   content of the probe response message is shown in Figure 6.

    +---------------------------------------------------------------+
    | IP Header                                                     |
    .   Source IP Address = Responder IPv4 or IPv6 Address          .
    .   Destination IP Address = URO.Address                        .
    .   Protocol = UDP                                              .
    .   Router Alert Option Not Set                                 .
    .                                                               .
    +---------------------------------------------------------------+
    | UDP Header                                                    |
    .   Source Port = As chosen by Responder                        .
    .   Destination Port = URO.UDP-Destination-Port                 .
    .                                                               .
    +---------------------------------------------------------------+
    | Message as specified in Section 3.2 of RFC 6374 for DM, or    |
    . Message as specified in Section 3.1 of RFC 6374 for LM        .
    .                                                               .
    +---------------------------------------------------------------+

   Figure 6: Probe Response Message Using URO from Probe Query Message

3.2.1.  One-way Measurement for SR Link and end-to-end SR Policy



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   For one-way performance measurement, the probe response message as
   defined in Figure 5 or Figure 6 is sent out-of-band for both SR links
   and SR Policies.

   The PM querier node can receive probe response message back by
   properly setting its own IP address as Source Address of the header
   or by adding URO TLV in the probe query message and setting its own
   IP address in the IP Address in the URO TLV (Type=131) [RFC7876].  In
   addition, the "control code" in the probe query message is set to
   "out-of-band response requested".  The "Source Address" TLV (Type
   130), and "Return Address" TLV (Type 1), if present in the probe
   query message, are not used to send probe response message.

3.2.1.1.  Probe Response Message to Controller

   As shown in the Reference Topology, if the querier node requires the
   probe response message to be sent to the controller R100, it adds URO
   TLV in the probe query message and sets the IP address of R100 in the
   IP Address field and UDP port TBA1 for DM and TBA2 for LM in the
   UDP-Destination-Port field of the URO TLV (Type=131) [RFC7876].

3.2.2.  Two-way Measurement for SR Links

   For two-way performance measurement, when using a bidirectional
   channel, the probe response message as defined in Figure 5 or Figure
   6 is sent back in-band to the querier node for SR links.  In this
   case, the "control code" in the probe query message is set to
   "in-band response requested" [RFC6374].

3.2.3.  Two-way End-to-end Measurement of SR Policy

   For two-way performance measurement, when using a bidirectional
   channel, the probe response message is sent back in-band to the
   querier node for end-to-end measurement of SR Policies.  In this
   case, the "control code" in the probe query message is set to
   "in-band response requested" [RFC6374].

   The path segment identifier [I-D.spring-mpls-path-segment]
   [I-D.pce-sr-path-segment] of the forward SR Policy can be used to
   find the reverse SR Policy to send the probe response message in the
   absence of RPSL TLV defined in the following Section.

3.2.3.1.  Return Path Segment List TLV

   For two-way performance measurement, the responder node needs to send
   the probe response message in-band on a specific reverse SR path.
   This way the destination node does not require any additional SR
   Policy state.  The querier node can request in the probe query



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   message to the responder node to send a response back on a given
   reverse path (typically co-routed path for two-way measurement).

   [RFC6374] defines DM and LM probe query messages that can include one
   or more optional TLVs.  New TLV Types are defined in this document
   for Return Path Segment List (RPSL) to carry reverse SR path for
   probe response messages.  The format of the RPSL TLV is shown in
   Figure 7:

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   RPSL Type   |    Length     |      Reserved                 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     Segment List(0)                           |
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                                                               .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     Segment List(n)                           |
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Figure 7: Return Path Segment List TLV

   The RPSL can be one of following Types:

   o  RPSL Type (value TBA3): SR-MPLS Label Stack of the Reverse SR
      Policy

   o  RPSL Type (value TBA4): SRv6 Segment List of the Reverse SR Policy

   o  RPSL Type (value TBA5): SR-MPLS Binding SID
      [I-D.pce-binding-label-sid] of the Reverse SR Policy

   o  RPSL Type (value TBA6): SRv6 Binding SID
      [I-D.pce-binding-label-sid] of the Reverse SR Policy


   The Segment List(0) can be used by the responder node to compute the
   next-hop IP address and outgoing interface to send the probe response
   messages.

   The RPSL TLV is optional.  The PM querier node MUST only insert one
   RPSL TLV in the probe query message and the responder node MUST only
   process the first RPSL TLV in the probe query message and ignore



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   other RPSL TLVs if present.  The responder node MUST send probe
   response message back on the reverse path specified in the RPSL TLV
   and MUST NOT add RPSL TLV in the probe response message.

3.2.3.2.  In-band Probe Response Message for SR-MPLS Policy

   The message content for sending probe response message in-band using
   UDP header for two-way end-to-end performance measurement of an
   SR-MPLS Policy is shown in Figure 8.  The SR-MPLS label stack in the
   packet header is built using the Segment List received in the RPSL
   TLV in the probe query message.

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Segment List(0)        | EXP |S|      TTL      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    .                                                               .
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Segment List(n)        | EXP |S|      TTL      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Message as shown in Figure 5 or 6                             |
    . IP TTL = 1                                                    .
    .                                                               .
    +---------------------------------------------------------------+

       Figure 8: In-band Probe Response Message for SR-MPLS Policy

3.2.3.3.  In-band Probe Response Message for SRv6 Policy

   The message content for sending probe response message in-band using
   UDP header for two-way end-to-end performance measurement of an SRv6
   Policy is shown in Figure 9.  For SRv6 Policy, the SRv6 SID list in
   the SRH of the probe response message is built using the SRv6 Segment
   List received in the RPSL TLV in the probe query message.

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          SRH                                  |
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Message as shown in Figure 5 or 6                             |
    . IP TTL = 1                                                    .
    .                                                               .
    +---------------------------------------------------------------+



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        Figure 9: In-band Probe Response Message for SRv6 Policy

4.  Performance Measurement for P2MP SR Policies

   The procedures for delay and loss measurement described in this
   document for Point-to-Point (P2P) SR-MPLS Policies are also equally
   applicable to the Point-to-Multipoint (P2MP) SR Policies.


5.  ECMP Support

   An SR Policy can have ECMPs between the source and transit nodes,
   between transit nodes and between transit and destination nodes.  The
   PM probe messages can be sent to traverse different ECMP paths to
   measure performance of an SR Policy.

   Forwarding plane has various hashing functions available to forward
   packets on specific ECMP paths.  Following mechanisms can be used in
   PM probe messages to take advantage of the hashing function in
   forwarding plane to influence the path taken by them.

   o  The mechanisms described in [RFC8029] [RFC5884] for handling ECMPs
      are also applicable to the performance measurement.  In the IP/UDP
      header of the PM probe messages, Destination Addresses in 127/8
      range for IPv4 or 0:0:0:0:0:FFFF:7F00/104 range for IPv6 can be
      used to exercise a particular ECMP path.  In addition, different
      Source Addresses or different Source UDP ports can be used for
      this purpose.  As specified in [RFC6437], 3-tuple of Flow Label,
      Source Address and Destination Address fields in the IPv6 header
      can also be used.

   o  For SR-MPLS, entropy label [RFC6790] in the PM probe messages can
      be used.

   o  For SRv6, Flow Label in SRH [I-D.6man-segment-routing-header] of
      the PM probe messages can be used.


6.  Sequence Number TLV

   The message formats for DM and LM [RFC6374] do not contain sequence
   number for probe query packets.  Sequence numbers can be useful when
   some probe query messages are lost or they arrive out of order.

   [RFC6374] defines DM and LM probe query and response messages that
   can include one or more optional TLVs.  New TLV Type (value TBA7) is
   defined in this document to carry sequence number for probe query and
   response messages for delay and loss measurement.  The format of the



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   Sequence Number TLV is shown in Figure 10:

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Type TBA7   |    Length     |      Reserved                 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     Sequence Number                           |
    .                                                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 10: Sequence Number TLV

   The sequence numbers start with 0 and are incremented by one for each
   subsequent probe query packet.  The sequence number can be of any
   length determined by the querier node.  The Sequence Number TLV is
   optional.  The PM querier node SHOULD only insert one Sequence Number
   TLV in the probe query message and the responder node in the probe
   response message SHOULD return the first Sequence Number TLV from the
   probe query message and ignore other Sequence Number TLVs if present.


7.  Security Considerations

   The performance measurement is intended for deployment in
   well-managed private and service provider networks.  The security
   considerations described in Section 8 of [RFC6374] are applicable to
   this specification, and particular attention should be paid to the
   last two paragraphs.  Cryptographic measures may be enhanced by the
   correct configuration of access-control lists and firewalls.


8.  IANA Considerations

   IANA is requested to allocate following UDP ports for performance
   measurements:

      o  UDP Port TBA1: Delay Performance Measurement

      o  UDP Port TBA2: Loss Performance Measurement


   IANA is also requested to allocate values for the following Return
   Path Segment List TLV Types for RFC 6374 to be carried in PM probe
   query messages:

      o  Type TBA3: SR-MPLS Label Stack of the Reverse SR Policy




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      o  Type TBA4: SRv6 Segment List of the Reverse SR Policy

      o  Type TBA5: SR-MPLS Binding SID of the Reverse SR Policy

      o  Type TBA6: SRv6 Binding SID of the Reverse SR Policy


   IANA is also requested to allocate a value for the following Sequence
   Number TLV Type for RFC 6374 to be carried in the PM probe query and
   response messages for delay and loss measurement:

      o  Type TBA7: Sequence Number TLV


   IANA is also requested to allocate a value for the following Block
   Number TLV Type for RFC 6374 to be carried in the PM probe query and
   response messages for loss measurement:

      o  Type TBA8: Block Number TLV


9.  References

9.1.  Normative References

   [RFC768]   Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              August 1980.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", RFC 2119, March 1997.

   [RFC6374]  Frost, D. and S. Bryant, "Packet Loss and Delay
              Measurement for MPLS networks', RFC 6374, September 2011.

   [RFC7876]  Bryant, S., Sivabalan, S., and Soni, S., "UDP Return Path
              for Packet Loss and Delay Measurement for MPLS Networks",
              RFC 7876, July 2016.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", RFC 8174, May 2017.


9.2.  Informative References

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




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   [RFC4656]  Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
              Zekauskas, "A One-way Active Measurement Protocol
              (OWAMP)", RFC 4656, September 2006.

   [RFC5357]  Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
              Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
              RFC 5357, October 2008.

   [RFC5884]  Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
              "Bidirectional Forwarding Detection (BFD) for MPLS Label
              Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884,
              June 2010.

   [RFC6437]  Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme,
              "IPv6 Flow Label Specification", RFC 6437, November 2011.

   [RFC6790]  Kompella, K., Drake, J., Amante, S., Henderickx, W., and
              L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
              RFC 6790, November 2012.

   [RFC8029]  Kompella, K., Swallow, G., Pignataro, C., Kumar, N.,
              Aldrin, S. and M. Chen, "Detecting Multiprotocol Label
              Switched (MPLS) Data-Plane Failures", RFC 8029, March
              2017.

   [RFC8321]  Fioccola, G. Ed., "Alternate-Marking Method for Passive
              and Hybrid Performance Monitoring", RFC 8321, January
              2018.

   [I-D.spring-segment-routing-policy]  Filsfils, C., et al., "Segment
              Routing Policy Architecture",
              draft-ietf-spring-segment-routing-policy, work in
              progress.

   [I-D.spring-sr-p2mp-policy]  Voyer, D. Ed., et al., "SR Replication
              Policy for P2MP Service Delivery",
              draft-voyer-spring-sr-p2mp-policy, work in progress.

   [I-D.6man-segment-routing-header]  Filsfils, C., et al., "IPv6
              Segment Routing Header (SRH)",
              draft-ietf-6man-segment-routing-header, work in progress.

   [I-D.spring-sr-mpls-pm]  Filsfils, C., Gandhi, R. Ed., et al.
              "Performance Measurement in Segment Routing Networks with
              MPLS Data Plane", draft-gandhi-spring-sr-mpls-pm, work in
              progress.

   [I-D.pce-binding-label-sid]  Filsfils, C., et al., "Carrying Binding



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              Label Segment-ID in PCE-based Networks",
              draft-sivabalan-pce-binding-label-sid, work in progress.

   [I-D.spring-mpls-path-segment]  Cheng, W., et al., "Path Segment in
              MPLS Based Segment Routing Network",
              draft-cheng-spring-mpls-path-segment, work in progress.

   [I-D.pce-sr-path-segment]  Li, C., et al., "Path Computation Element
              Communication Protocol (PCEP) Extension for Path
              Identification in Segment Routing (SR)",
              draft-li-pce-sr-path-segment, work in progress.

   [I-D.ippm-stamp]  Mirsky, G. et al. "Simple Two-way Active
              Measurement Protocol", draft-ietf-ippm-stamp, work in
              progress.

   [BBF.TR-390]  "Performance Measurement from IP Edge to Customer
              Equipment using TWAMP Light", BBF TR-390, May 2017.

































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Acknowledgments

   The authors would like to thank Nagendra Kumar and Carlos Pignataro
   for the discussion on SRv6 Performance Measurement.


Contributors

   Sagar Soni
   Cisco Systems, Inc.
   Email: sagsoni@cisco.com


   Patrick Khordoc
   Cisco Systems, Inc.
   Email: pkhordoc@cisco.com


   Zafar Ali
   Cisco Systems, Inc.
   Email: zali@cisco.com


   Daniel Bernier
   Bell Canada
   Email: daniel.bernier@bell.ca


   Dirk Steinberg
   Steinberg Consulting
   Germany
   Email: dws@dirksteinberg.de


Authors' Addresses

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


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


   Daniel Voyer



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   Bell Canada
   Email: daniel.voyer@bell.ca


   Stefano Salsano
   Universita di Roma "Tor Vergata"
   Italy
   Email: stefano.salsano@uniroma2.it


   Pier Luigi Ventre
   CNIT
   Italy
   Email: pierluigi.ventre@cnit.it


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
































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