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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                                 S. Soni
Expires: December 11, 2018                           Cisco Systems, Inc.
                                                                D. Voyer
                                                             Bell Canada
                                                              S. Salsano
                                        Universita di Roma "Tor Vergata"
                                                            P. L. Ventre
                                                                    CNIT
                                                            June 9, 2018


                          UDP Path for In-band
          Performance Measurement for Segment Routing Networks
                     draft-gandhi-spring-udp-pm-01

Abstract

   Segment Routing (SR) is applicable to both Multiprotocol Label
   Switching (SR-MPLS) and IPv6 (SRv6) data planes.  This document
   specifies a procedure for using UDP path for sending and processing
   in-band probe query and response messages for Performance Measurement
   (PM).  The procedure uses the RFC 6374 defined mechanisms for Delay
   and Loss performance measurement.  The procedure specified is
   applicable to IPv4, IPv6, 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 new Return Path Segment
   List TLV for two-way performance 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
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   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 . . . . . . . . .  6
         3.1.2.1.  Loss Measurement Flags . . . . . . . . . . . . . .  7
       3.1.3.  In-band Probe Query for SR Links . . . . . . . . . . .  7
       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  . . .  8
     3.2.  Probe Response Message . . . . . . . . . . . . . . . . . .  8
       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 . . . . . . . 10
       3.2.2.  Two-way Measurement for SR Links . . . . . . . . . . . 10
       3.2.3.  Two-way End-to-end Measurement of SR Policy  . . . . . 10
         3.2.3.1.  Return Path Segment List TLV . . . . . . . . . . . 10
         3.2.3.2.  In-band Probe Response Message for SR-MPLS
                   Policy . . . . . . . . . . . . . . . . . . . . . . 11
         3.2.3.3.  In-band Probe Response Message for SRv6 Policy . . 12
     3.3.  ECMP Support . . . . . . . . . . . . . . . . . . . . . . . 12
     3.4.  Sequence Number TLV  . . . . . . . . . . . . . . . . . . . 13
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 15



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     6.1.  Normative References . . . . . . . . . . . . . . . . . . . 15
     6.2.  Informative References . . . . . . . . . . . . . . . . . . 15
   Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . . . 17
   Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17



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 connection over an UDP path to bootstrap PM
   sessions, and they are not compatible with the mechanisms defined in
   [RFC6374].  These protocols lack support for IEEE 1588 timestamps
   [IEEE1588] and direct-mode LM, which are required in Segment Routing
   networks [RFC6374].

   [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.  However, [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.
   [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 is a need to measure the performance of all
   end-to-end forwarding paths due to presence of ECMPs between the
   source and transit nodes, between transit nodes and between transit
   and destination nodes.  Existing PM protocols (e.g. OWAMP, TWAMP, RFC



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   6374, etc.) 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
   IPv4, IPv6, 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 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.


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].

2.2.  Abbreviations

   ACH: Associated Channel Header.

   BSID: Binding Segment ID.

   DFLag: Data Format Flag.

   DM: Delay Measurement.

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

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

   LM: Loss Measurement.

   MPLS: Multiprotocol Label Switching.



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   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.

   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 an SR Policy
   [I-D.spring-segment-routing-policy] on node R1 with destination to
   node R5.


                                           ------
                                           |R100|
                                           ------
                                             ^
                                             | Response (optional)
                                             |
           +-------+        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



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   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 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.

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].

    +---------------------------------------------------------------+
    | 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



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   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     |
    .                                                               .
    +---------------------------------------------------------------+

                  Figure 2: LM Probe Query Message

3.1.2.1.  Loss Measurement Flags

   An LM message carries Data Format Flags (DFlags) as defined in
   [RFC6374].  New Flag is defined in this document for Color (C) in the
   DFlags field as follows.

                              +-+-+-+-+
                              |X|B|C|0|
                              +-+-+-+-+

                          Data Format Flags

   The Flag C indicates the Color of the counters in the LM probe
   message [RFC6374] when using Alternate-Marking method defined in
   [RFC8321].

3.1.3.  In-band Probe Query for SR Links

   The probe query message defined in Figure 1 is sent in-band for Delay
   measurement and defined in Figure 2 is used for Loss measurement for
   SR links.



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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
   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 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



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   When the received probe query message does not contain any UDP Return
   Object (URO) TLV [RFC7876], the probe response message uses the
   IP/UDP information from the probe query message.  The content of 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 RFC 6374 Section 3.2 for DM, or       |
    . Message as specified in RFC 6374 Section 3.1 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 RFC 6374 Section 3.2 for DM, or       |
    . Message as specified in RFC 6374 Section 3.1 for LM           .
    .                                                               .
    +---------------------------------------------------------------+




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   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

   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].

3.2.1.1.  Probe Response Message to Controller

   As shown in 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].

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
   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



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   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

   All Segments in Segment List can be one of following Types:

   o  RPSL Type (value TBA3) carrying SR-MPLS Labels

   o  RPSL Type (value TBA4) carrying SRv6 Segments

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

   o  RPSL Type (value TBA6) carrying SRv6 Binding 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
   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



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   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 stack in
   the probe response message SRH 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                                                    .
    .                                                               .
    +---------------------------------------------------------------+

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


3.3.  ECMP Support

   An SR Policy can have a number of end-to-end forwarding paths due to



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   presence of Equal Cost Multipaths (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 forwarding paths and measure performance of all
   end-to-end forwarding paths of an SR Policy.

   Forwarding planes have 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 ECMP path taken by them.

   o  For IPv4 and SR-MPLS, the mechanisms described in [RFC8029] for
      handling ECMPs are also applicable to the performance measurement.
       For IPv4 and SR-MPLS, in IP/UDP header of the PM probe messages,
      different Destination Addresses in the range of 127/8 [RFC8029] or
      different Source Addresses or different Source UDP ports, etc. can
      be used.

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

   o  For IPv6, as specified in [RFC6437], 3-tuple of Flow Label, Source
      Address and Destination Address fields in the IPv6 header of 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.


3.4.  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.  The format of the 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                           |
    .                                                               .



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    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 10: Sequence Number TLV

   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 messages and ignore other
   Sequence Number TLVs if present.


4.  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.


5.  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 Segment List of the Reverse SR Policy

      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 PM probe query and
   response messages:

      o  Type TBA7: Sequence Number TLV




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6.  References

6.1.  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.

6.2.  Informative References

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

   [RFC4656]  Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
              Zekauskas, "A One-way Active Measurement Protoco (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.

   [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



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
































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Acknowledgments

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


Contributors

   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


   Sagar Soni
   Cisco Systems, Inc.
   Email: sagsoni@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





































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