6man                                                              Z. Ali
Internet-Draft                                               C. Filsfils
Intended status: Standards Track                           Cisco Systems
Expires: October 1, December 14, 2020                                 S. Matsushima
                                                                Softbank
                                                                D. Voyer
                                                             Bell Canada
                                                                 M. Chen
                                                                  Huawei
                                                          March 30,
                                                           June 12, 2020

  Operations, Administration, and Maintenance (OAM) in Segment Routing
                  Networks with IPv6 Data plane (SRv6)
                   draft-ietf-6man-spring-srv6-oam-04
                   draft-ietf-6man-spring-srv6-oam-05

Abstract

   This document defines building blocks for Operations, Administration,
   and Maintenance (OAM) in Segment Routing Networks with describes how the existing IPv6 Dataplane
   (SRv6). OAM mechanisms can be
   used in an SRv6 network.  The document also describes some SRv6 introduces enhancements
   for controller-based OAM mechanisms. mechanisms for SRv6 networks.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on October 1, December 14, 2020.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.
     1.2.  Abbreviations . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.
     1.3.  Terminology and Reference Topology  . . . . . . . . . . . . .   3
   5.
   2.  OAM Mechanisms  . . . . . . . . . . . . . . . . . . . . . . .   5
     5.1.
     2.1.  O-flag in Segment Routing Header  . . . . . . . . . . . .   5
       5.1.1.
       2.1.1.  O-flag Processing . . . . . . . . . . . . . . . . . .   5
     5.2.  OAM Segments  . . . . . . . . . . . . . . . . . . . . . .   6
     5.3.  End.OP: OAM Endpoint with Punt  . . . . . . . . . . . . .   6
   6.
   3.  Illustrations . . . . . . . . . . . . . . . . . . . . . . . .   7
     6.1.
     3.1.  Ping in SRv6 Networks . . . . . . . . . . . . . . . . . .   7
       6.1.1.
       3.1.1.  Classic Ping  . . . . . . . . . . . . . . . . . . . .   7
       6.1.2.
       3.1.2.  Pinging a SID . . . . . . . . . . . . . . . . . . . .   9
     6.2.
     3.2.  Traceroute  . . . . . . . . . . . . . . . . . . . . . . .   9
       6.2.1.  10
       3.2.1.  Classic Traceroute  . . . . . . . . . . . . . . . . .  10
       6.2.2.
       3.2.2.  Traceroute to a SID . . . . . . . . . . . . . . . . .  11
     6.3.
     3.3.  A Controller-Based Passive Hybrid OAM Using O-flag  . . . . . . .  13
     6.4.
     3.4.  Monitoring of SRv6 Paths  . . . . . . . . . . . . . . . .  15
   7.
   4.  Implementation Status . . . . . . . . . . . . . . . . . . . .  16
   8.
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
   9.
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
     9.1.  ICMPv6 type Numbers Registry  . . . . . . . . . . . . . .  16
     9.2.  SRv6 OAM Endpoint Types . . . . . . . . . . . . . . . . .  17
     9.3.
     6.1.  Segment Routing Header Flags  . . . . . . . . . . . . . .  17
   10.
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  17
   11.
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  17
   12.
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     12.1.
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  18
     12.2.
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  19  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20

1.  Introduction

   This document defines building blocks for Operations, Administration,
   and Maintenance (OAM) in

   As Segment Routing Networks with IPv6 Dataplane
   (SRv6).

2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to data plane (SRv6) simply adds a new type
   of Routing Extension Header, existing IPv6 OAM mechanisms can be interpreted as described in [RFC2119], [RFC8174].

3.  Abbreviations

   The following abbreviations are used
   in this document:

      SID: Segment ID.

      SL: Segments Left.

      SR: Segment Routing.

      SRH: Segment Routing Header.

      SRv6: Segment Routing with IPv6 Data plane.

      TC: Traffic Class.

      ICMPv6: ICMPv6 Specification [RFC4443].

4.  Terminology and Reference Topology an SRv6 network.  This document uses describes how the existing IPv6
   mechanisms for ping and trace route can be used in an SRv6 network.

   The document also introduces enhancements for controller-based OAM
   mechanism for SRv6 networks.  Specifically, the document describes an
   OAM mechanism for performing controllable and predictable flow
   sampling from segment endpoints using, e.g., IP Flow Information
   Export (IPFIX) protocol [RFC7011].  The document also outlines how
   centralized OAM technique in [RFC8403] can be extended for SRv6 to
   perform a path continuity check between any nodes within an SRv6
   domain from a centralized monitoring system, with minimal or no
   control plane intervene on the nodes.

1.1.  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].

1.2.  Abbreviations

   The following abbreviations are used in this document:

      SID: Segment ID.

      SL: Segments Left.

      SR: Segment Routing.

      SRH: Segment Routing Header.

      SRv6: Segment Routing with IPv6 Data plane.

      TC: Traffic Class.

      ICMPv6: ICMPv6 Specification [RFC4443].

1.3.  Terminology and Reference Topology

   This document uses the terminology defined in [I-D.ietf- spring-srv6-
   network-programming].  The readers are expected to be familiar with
   the same.

   Throughout the document, the following simple topology is used for
   illustration.

   +--------------------------| N100 |---------------------------------+
   |                                                                   |
   |  ====== link1====== link3------ link5====== link9------   ======  |
      ||N1||------||N2||------| N3 |------||N4||------| N5 |---||N7||
      ||  ||------||  ||------|    |------||  ||------|    |---||  ||
      ====== link2====== link4------ link6======link10------   ======
         |            |                      |                   |
      ---+--          |       ------         |                 --+---
      |CE 1|          +-------| N6 |---------+                 |CE 2|
      ------            link7 |    | link8                     ------
                              ------

                           Figure 1 Reference Topology

   In the reference topology:

      Node k has a classic IPv6 loopback address A:k::/128. 2001:DB8:A:k::/128.

      Nodes N1, N2, and N4 are SRv6 capable nodes.

      Nodes N3, N5 and N6 are IPv6 nodes that are not SRv6 capable.
      Such nodes are referred as classic IPv6 nodes.

      A SID at node k with locator block B 2001:DB8:B::/48 and function F
      is represented by B:k:F::. 2001:DB8:B:k:F::.

      Node N100 is a controller.

      The IPv6 address of the nth Link between node X and Y at the X
      side is represented as 2001:DB8:X:Y:Xn::, e.g., the IPv6 address
      of link6 (the 2nd link) between N3 and N4 at N3 in Figure 1 is
      2001:DB8:3:4:32::.  Similarly, the IPv6 address of link5 (the 1st
      link between N3 and N4) at node 3 is 2001:DB8:3:4:31::.

      B:k:Cij::

      2001:DB8:B:k:Cij:: is explicitly allocated as the END.X function
      at node k towards neighbor node i via jth Link between node i and
      node k.  e.g., B:2:C31:: 2001:DB8:B:2:C31:: represents END.X at N2 towards
      N3 via link3 (the 1st link between N2 and N3).  Similarly, B:4:C52::
      2001:DB8:B:4:C52:: represents the END.X at N4 towards N5 via
      link10.

      A SID list is represented as <S1, S2, S3> where S1 is the first
      SID to visit, S2 is the second SID to visit and S3 is the last SID
      to visit along the SR path.

      (SA,DA) (S3, S2, S1; SL)(payload) represents an IPv6 packet with:

      *  IPv6 header with source address SA, destination addresses DA
         and SRH as next-header

      *  SRH with SID list <S1, S2, S3> with SegmentsLeft = SL

      *  Note the difference between the < > and () symbols: <S1, S2,
         S3> represents a SID list where S1 is the first SID and S3 is
         the last SID to traverse.  (S3, S2, S1; SL) represents the same
         SID list but encoded in the SRH format where the rightmost SID
         in the SRH is the first SID and the leftmost SID in the SRH is
         the last SID.  When referring to an SR policy in a high-level
         use-case, it is simpler to use the <S1, S2, S3> notation.  When
         referring to an illustration of the detailed packet behavior,
         the (S3, S2, S1; SL) notation is more convenient.

      *  (payload) represents the the payload of the packet.

      SRH[SL] represents the SID pointed by the SL field in the first
      SRH.  In our example SID list (S3, S2, S1; SL), SRH[2] represents
      S1, SRH[1] represents S2 and SRH[0] represents S3.

5.

2.  OAM Mechanisms

   As Segment Routing with IPv6 data plane (SRv6) simply adds a new type
   of Routing Extension Header, existing IPv6 OAM mechanisms can be used
   in an SRv6 network.

   This section defines OAM enhancement for the SRv6 networks.
   Specifically, it defines the O-flag for implementing a controller
   based passive OAM mechanism and an OAM SID to more closely examine
   the contents of packet at a segment endpoint for active OAM.

5.1.

2.1.  O-flag in Segment Routing Header

   [I-D.ietf-6man-segment-routing-header]

   [RFC8754] describes the Segment Routing Header (SRH) and how SR
   capable nodes use it.  The SRH contains an 8-bit "Flags" field.  This
   document defines the following bit in the SRH.Flags to carry the
   O-flag:

                  0 1 2 3 4 5 6 7
                 +-+-+-+-+-+-+-+-+
                 |   |O|         |
                 +-+-+-+-+-+-+-+-+

   Where:

      O-flag: OAM flag.  When set, it indicates that this packet is an
      Operation Administration and Maintenance (OAM) packet.  This
      document defines the usage of the O-flag in the SRH.Flags.

   The document does not define any other flag in the SRH.Flags and
   meaning and processing of any other bit in SRH.Flags is outside of
   the scope of this document.

5.1.1.

2.1.1.  O-flag Processing

   The SRH.Flags.O-flag implements the "punt O-flag in SRH is used as a timestamped copy of marking-bit in the
   packet" behavior.  This enables an SRv6 Endpoint node user packets to send a
   timestamped copy of the packets marked with o-flag to a local OAM
   process.  To prevent multiple evaluations of the datagram, the OAM
   process MUST NOT process the packet or respond to any upper-layer
   header (like ICMP, UDP, etc.) payload.  However, the OAM process MAY
   export the time-stamped copy of
   trigger the packet to a controller using
   e.g., IPFIX [RFC7011].  If telemetry data from collection and export at the last node in segment
   endpoints.

   Without the segment-
   list (Egress node) loss of generality, this document assumes IP Flow
   Information Export (IPFIX) protocol [RFC7011] is desired, the ingress uses an Ultimate Segment
   Pop (USP) SID advertised by the Egress node.  To avoid hitting any
   performance impact, used for exporting
   the processing node SHOULD rate-limit traffic flow information from the number
   of packets punted network devices to the OAM process.  Specification of the OAM
   process or the external a controller operations
   for monitoring and analytics.  The requested information elements are beyond the scope of
   this document.  Section 6 illustrates use of
   configured by the SRH.Flags.O-flag for
   implementing a controller-based passive OAM mechanism. management plane through data set templates (e.g.,
   as in IPFIX [RFC7012]).

   Implementation of the O-flag is OPTIONAL.  If a node does not support
   the O-flag, then upon reception it simply ignores it.  If a node
   supports the O-flag, it can optionally advertise its potential via node capability advertisement in IGP [I-D.ietf-isis-
   srv6- extensions] and BGP-LS [I-D.ietf-idr-bgpls-srv6-ext].
   control plan protocol(s).

   When N receives a packet whose IPv6 DA is S and S is a local SID, the
   line S01 of the pseudo-code associated with the SID S, as defined in
   section 4.3.1.1 of [I-D.ietf-6man-segment-routing-header], [RFC8754], is modified as follows for the O-flag
   processing.

      S01.1. IF SRH.Flags.O-flag is set and local configuration permits
             O-flag processing THEN
                a. Make a copy of the packet.
                b. Send the copied packet, along with a timestamp
                to the OAM process. process for telemetry data collection
                and export.      ;; Ref1
      Ref1: An implementation SHOULD copy and record the timestamp as
      soon as possible during packet processing. Timestamp or any other
      metadata is not
      carried in the packet forwarded to the next hop.

   Please note that the O-flag processing happens before execution of
   regular processing of the local SID S.

5.2.  OAM Segments

   The presence of an OAM SID in the Destination address of

   Based on the IPv6
   header instructs requested information elements configured by the segment endpoint implementing
   management plane through data set templates [RFC7012], the OAM SID that
   process exports the content requested information elements.  The information
   elements include parts of the packet is header and/or parts of interest.

   The document defines OAM Endpoint with Punt action.  Additional OAM
   SIDs may be defined in future documents.

5.3.  End.OP: OAM Endpoint with Punt

   When N receives a packet destined to S and S is a local End.OP SID, N
   does:

        S01.   Send the
   packet to the OAM process payload for flow identification.  The local OAM process further processes the packet, this MAY involve
   processing protocol layers above IPv6.  For example, ping uses
   information elements defined in IPFIX [RFC7011] and
   traceroute will require ICMP or UDP protocol processing.  Once PSAMP [RFC5476]
   for exporting the
   packet leaves requested sections of the IPv6 layer mirrored packets.

   If the processing telemetry data from the last node in the segment-list (egress
   node) is considered host desired, the ingress uses an Ultimate Segment Pop (USP) SID
   advertised by the egress node.

   The processing and node SHOULD rate-limit the upper layer protocols number of packets punted to
   the OAM process to avoid hitting any performance impact.

   The OAM process MUST be processed as such.

   As END.OP SID terminates NOT process the forwarding copy of the probe packets for packet or respond to
   any upper-layer header (like ICMP, UDP, etc.) payload to prevent
   multiple evaluations of the
   upper layer processing, it is used for datagram.

   Specification of the active OAM mechanisms.
   For example, process or the END.OP SID SID is not designed external controller
   operations are beyond the scope of this document.  section 3
   illustrates use of the SRH.Flags.O-flag for implementing In-
   situ a
   controller-based hybrid OAM mechanism, where the "hybrid"
   classification is based on RFC7799 [RFC7799].  The illustration is
   different than the In-situ OAM mechanisms defined in [I.D-draft-ietf-ippm-ioam-data].

6.  Illustrations [I.D-draft-ietf-ippm-ioam-
   data].  This is because In-situ OAM records operational and telemetry
   information in the packet as the packet traverses a path between two
   points in the network [I.D-draft-ietf- ippm-ioam-data].  The
   controller-based OAM mechanism using O-flag illustration in section illustrates 3
   does not require the use recording of OAM data in the packet.

3.  Illustrations

   This section shows how some of the existing IPv6 OAM mechanisms can
   be used in
   the an SRv6 network.  It also illustrates the use of the END.OP SID an OAM mechanism for
   performing controllable and
   O-flag at predictable flow sampling from segment
   endpoints.

   The document does not propose any changes to the standard ICMPv6
   [RFC4443], [RFC4884] or standard ICMPv4 [RFC792] or [RFC2151].

6.1.  How centralized OAM technique in [RFC8403] can be
   extended for SRv6 is also described in this Section.

3.1.  Ping in SRv6 Networks

   The following subsections outline some use cases of the ICMP ping in
   the SRv6 networks.

6.1.1.

3.1.1.  Classic Ping

   The existing mechanism to query liveliness of a remote IP address,
   along the shortest path, continues to work without any modification.
   The initiator may be an SRv6 node or a classic IPv6 node.  Similarly,
   the egress or transit may be an SRv6 capable node or a classic IPv6
   node.

   If an SRv6 capable ingress node wants to ping an IPv6 prefix address via an
   arbitrary segment list <S1, S2, S3>, it needs to initiate ICMPv6 ping
   with an SR header containing the SID list <S1, S2, S3>.  This is
   illustrated using the topology in Figure 1.  Assume all the links
   have IGP metric 10 except both links between node2 and node3, which
   have IGP metric set to 100.  User issues a ping from node N1 to a
   loopback of node 5, via segment list <B:2:C31, B:4:C52>. <2001:DB8:B:2:C31::,
   2001:DB8:B:4:C52::>.

   Figure 2 contains sample output for a ping request initiated at node
   N1 to the loopback address of node N5 via a segment list <B:2:C31,
   B:4:C52>.
   <2001:DB8:B:2:C31::, 2001:DB8:B:4:C52::>.

       > ping A:5:: 2001:DB8:A:5:: via segment-list B:2:C31, B:4:C52 2001:DB8:B:2:C31::,
              2001:DB8:B:4:C52::

       Sending 5, 100-byte ICMP Echos to B5::, timeout is 2 seconds:
       !!!!!
       Success rate is 100 percent (5/5), round-trip min/avg/max = 0.625
       /0.749/0.931 ms

               Figure 2 A sample ping output at an SRv6 capable node

   All transit nodes process the echo request message like any other
   data packet carrying SR header and hence do not require any change.
   Similarly, the egress node (IPv6 classic or SRv6 capable) does not
   require any change to process the ICMPv6 echo request.  Furthermore,
   there is no difference in processing of the ICMPv6 echo request at an
   IPv6 classic node or an SRv6 capable node.  For example,
   in the ping example of Figure 2:

   o  Node N1 initiates an ICMPv6 ping packet with SRH as follows
      (A:1::, B:2:C31)(A:5::, B:4:C52, B:2:C31,
      (2001:DB8:A:1::, 2001:DB8:B:2:C31::) (2001:DB8:A:5::,
      2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::, SL=2, NH = ICMPv6)(ICMPv6
      Echo Request).  If B:4:C52 2001:DB8:B:4:C52:: is a PSP SID, the OAM probes
      encodes the PSP SID in the packet (just mimicking data packets).
      No special consideration is needed to handle PSP SIDs.

   o  Node N2, which is an SRv6 capable node, performs the standard SRH
      processing.  Specifically, it executes the END.X function
      (B:2:C31)
      (2001:DB8:B:2:C31::) and forwards the packet on link3 to N3.

   o  Node N3, which is a classic IPv6 node, performs the standard IPv6
      processing.  Specifically, it forwards the echo request based on
      the DA B:4:C52 2001:DB8:B:4:C52:: in the IPv6 header.

   o  Node N4, which is an SRv6 capable node, performs the standard SRH
      processing.  Specifically, it observes the END.X function
      (B:4:C52)
      (2001:DB8:B:4:C52::) and forwards the packet on link10 towards N5.
      If
      B:4:C52 2001:DB8:B:4:C52:: is a PSP SID, The penultimate node (Node N4)
      does not, should no not and cannot differentiate between the data
      packets and OAM probes.  Specifically, if B:4:C52 2001:DB8:B:4:C52:: is a
      PSP SID, node N4 executes the SID like any other data packet with
      DA = B:4:C52 2001:DB8:B:4:C52:: and removes the SRH.

   o  The echo request packet at N5 arrives as an IPv6 packet with or
      without an SRH.  If N5 receives the packet with SRH, it skips SRH
      processing.
      processing (SL=0).  In either case, Node N5 performs the standard
      IPv6/ ICMPv6 processing on the echo request.

6.1.2.

3.1.2.  Pinging a SID

   The following illustration uses END.OP SID for pinging classic ping described in the previous section applies equally to
   ping a SID. remote SID function, as explained using an example in the
   following.

   Consider the example where the user wants to ping a remote SID
   function B:4:C52, 2001:DB8:B:4::, via B:2:C31, 2001:DB8:B:2:C31::, from node N1.  The
   ICMPv6 echo request is processed at the individual nodes along the
   path as follows:

   o  To force a punt of the ICMPv6 echo request at the node N4, node N1
      inserts the END.OP SID just before the target SID B:4:C52 in the
      SRH.  Specifically,  Node N1 initiates an ICMPv6 ping packet with SRH as follows (A:1::, B:2:C31)(B:4:C52, B:4:OP, B:2:C31; SL=2;
      (2001:DB8:A:1::, 2001:DB8:B:2:C31::) (2001:DB8:B:4::,
      2001:DB8:B:2:C31::; SL=1; NH=ICMPv6)(ICMPv6 Echo Request).  If
      2001:DB8:B:2:C31:: is a PSP SID, the OAM probes encodes the PSP
      SID in the packet (just mimicking data packets).  No special
      consideration is needed to handle PSP SIDs.

   o  Node N2, which is an SRv6 capable node, performs the standard SRH
      processing.  Specifically, it executes the END.X function
      (B:2:C31)
      (2001:DB8:B:2:C31::) on the echo request packet.

   o  Node N3 receives  If
      2001:DB8:B:2:C31:: is a PSP SID, node N4 executes the SID like any
      other data packet as follows (A:1::, B:4:OP)(B:4:C52,
      B:4:OP, B:2:C31 ; SL=1; NH=ICMPv6)(ICMPv6 Echo Request). with DA = 2001:DB8:B:2:C31:: and removes the
      SRH.

   o  Node N3, which is a classic IPv6 node, performs the standard IPv6
      processing.  Specifically, it forwards the echo request based on
      DA B:4:OP = 2001:DB8:B:4:: in the IPv6 header.

   o  When node N4 receives the packet (A:1::, B:4:OP)(B:4:C52, B:4:OP,
      B:2:C31 ; SL=1; NH=ICMPv6)(ICMPv6 Echo Request), packet, it processes the
      END.OP 2001:DB8:B:4::
      SID, as described in the pseudocode in Section 3.  The
      packet gets punted to the OAM process for processing.  The OAM
      process checks if the next SID in SRH (the target SID B:4:C52) is
      locally programmed. [I-D.ietf-spring-srv6-
      network-programming].

   o  If the next 2001:DB8:B:4:: SID is not locally programmed, the OAM process returns
      an ICMPv6 error message type 4 (parameter problem) code 0
      (erroneous header field encountered) with pointer set to the
      target SID B:4:C52 and the packet is discarded.
      discarded

   o  If the next target SID (2001:DB8:B:4::) is locally programmed, the node
      processes the upper layer header, as a host. header.  As part of the upper layer
      header
      (ICMPv6) processing node N4 sends respond to the ICMPv6 Echo Reply message
      [RFC4443].

6.2. echo request
      message.

3.2.  Traceroute

   There is no hardware or software change required for traceroute
   operation at the classic IPv6 nodes in an SRv6 network.  That
   includes the classic IPv6 node with ingress, egress or transit roles.
   Furthermore, no protocol changes are required to the standard
   traceroute operations.  In other words, existing traceroute
   mechanisms work seamlessly in the SRv6 networks.

   The following subsections outline some use cases of the traceroute in
   the SRv6 networks.

6.2.1.

3.2.1.  Classic Traceroute

   The existing mechanism to traceroute a remote IP prefix, address, along the
   shortest path, continues to work without any modification.  The
   initiator may be an SRv6 node or a classic IPv6 node.  Similarly, the
   egress or transit may be an SRv6 node or a classic IPv6 node.

   If an SRv6 capable ingress node wants to traceroute to IPv6 prefix address
   via an arbitrary segment list <S1, S2, S3>, it needs to initiate
   traceroute probe with an SR header containing the SID list <S1, S2,
   S3>.  That is illustrated using the topology in Figure 1.  Assume all
   the links have IGP metric 10 except both links between node2 and
   node3, which have IGP metric set to 100.  User issues a traceroute
   from node N1 to a loopback of node 5, via segment list <B:2:C31,
   B:4:C52>.
   <2001:DB8:B:2:C31::, 2001:DB8:B:4:C52::>.  Figure 3 contains sample
   output for the traceroute request.

   > traceroute A:5:: 2001:DB8:A:5:: via segment-list B:2:C31, B:4:C52 2001:DB8:B:2:C31::,
                2001:DB8:B:4:C52::

   Tracing the route to A:5:: 2001:DB8:A:5::
   1  2001:DB8:1:2:21:: 0.512 msec 0.425 msec 0.374 msec
            SRH: (A:5::, B:4:C52, B:2:C31,
      DA: 2001:DB8:B:2:C31::,
      SRH:(2001:DB8:A:5::, 2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::, SL=2)
   2  2001:DB8:2:3:31:: 0.721 msec 0.810 msec 0.795 msec
            SRH: (A:5::, B:4:C52, B:2:C31,
      DA: 2001:DB8:B:4:C52::,
      SRH:(2001:DB8:A:5::, 2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::, SL=1)
   3  2001:DB8:3:4:41::  2001:DB8:3:4::41:: 0.921 msec 0.816 msec 0.759 msec
            SRH: (A:5::, B:4:C52, B:2:C31,
      DA: 2001:DB8:B:4:C52::,
      SRH:(2001:DB8:A:5::, 2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::, SL=1)
   4  2001:DB8:4:5:52::  2001:DB8:4:5::52:: 0.879 msec 0.916 msec 1.024 msec
      DA: 2001:DB8:A:5::

      Figure 3 A sample traceroute output at an SRv6 capable node

   Please note that if B:4:C52 is a PSP SID, the traceroute probe
   encodes the PSP SID in the packet (just mimicking data packets).
   Likewise, if B:4:C52 is a PSP SID, node N4 executes the SID like any
   other data packet with DA = B:4:C52.  I.e., no special consideration
   is needed to handle PSP SIDs.

   Please note that information for hop2 is returned by N3, which is a
   classic IPv6 node.  Nonetheless, the ingress node is able to display
   SR header contents as the packet travels through the IPv6 classic
   node.  This is because the "Time Exceeded Message" ICMPv6 message can
   contain as much of the invoking packet as possible without the ICMPv6
   packet exceeding the minimum IPv6 MTU [RFC4443].  The SR header is
   also included in these ICMPv6 messages initiated by the classic IPv6
   transit nodes that are not running SRv6 software.  Specifically, a
   node generating ICMPv6 message containing a copy of the invoking
   packet does not need to understand the extension header(s) in the
   invoking packet.

   The segment list information returned for hop1 is returned by N2,
   which is an SRv6 capable node.  Just like for hop2, the ingress node
   is able to display SR header contents for hop1.

   There is no difference in processing of the traceroute probe at an
   IPv6 classic node and an SRv6 capable node.  Similarly, both IPv6
   classic and SRv6 capable nodes may use the address of the interface
   on which probe was received as the source address in the ICMPv6
   response.  ICMP extensions defined in [RFC5837] can be used to also
   display information about the IP interface through which the datagram
   would have been forwarded had it been forwardable, and the IP next
   hop to which the datagram would have been forwarded, the IP interface
   upon which a datagram arrived, the sub-IP component of an IP
   interface upon which a datagram arrived.

   The information about the IP address of the incoming interface on
   which the traceroute probe was received by the reporting node is very
   useful.  This information can also be used to verify if SID functions
   B:2:C31
   2001:DB8:B:2:C31:: and B:4:C52 2001:DB8:B:4:C52:: are executed correctly by
   N2 and N4, respectively.  Specifically, the information displayed for
   hop2 contains the incoming interface address 2001:DB8:2:3:31:: at N3.
   This matches with the expected interface bound to END.X function
   B:2:C31
   2001:DB8:B:2:C31:: (link3).  Similarly, the information displayed for
   hop5 contains the incoming interface address 2001:DB8:4:5:52:: 2001:DB8:4:5::52:: at
   N5.  This matches with the expected interface bound to the END.X
   function
   B:4:C52 2001:DB8:B:4:C52:: (link10).

6.2.2.

3.2.2.  Traceroute to a SID

   The following illustration uses END.OP SID for trace-routing a SID.
   The illustration assumes classic traceroute probe is UDP encoded but described in the
   procedure is previous section applies
   equally applicable to other encoding types. traceroute a remote SID function, as explained using an
   example in the following.

   Please note that traceroute to a SID function is exemplified using
   UDP probes.  However, the procedure is equally applicable to other
   implementations of traceroute mechanism.

   Consider the example where the user wants to traceroute to a remote SID
   function B:4:C52, 2001:DB8:B:4::, via B:2:C31, 2001:DB8:B:2:C31::, from node N1.  The
   traceroute probe is processed at the individual nodes along the path
   as follows:

   o  To force a punt of the traceroute probe at the node N4, node N1
      inserts the END.OP SID just before the target SID B:4:C52 in the
      SRH.  Specifically,  Node N1 initiates a traceroute probe packet with a monotonically
      increasing value of hop-count hop count and SRH as follows (A:1::, B:2:C31)(B:4:C52, B:4:OP, B:2:C31; SL=2; (2001:DB8:A:1::,
      2001:DB8:B:2:C31::) (2001:DB8:B:4::, 2001:DB8:B:2:C31::; SL=1;
      NH=UDP)(Traceroute probe).  If 2001:DB8:B:2:C31:: is a PSP SID,
      the OAM probes encodes the PSP SID in the packet (just mimicking
      data packets).  No special consideration is needed to handle PSP
      SIDs.

   o  When node N2 receives the packet with hop-count = 1, it processes
      the hop-limit hop count expiry.  Specifically, the node N2 responses with
      the ICMPv6 message (Type: "Time Exceeded", Code: "Time to Live
      exceeded in Transit").

   o  When Node N2 receives the packet with hop-count > 1, it performs
      the standard SRv6 SID and SRH processing.  Specifically, it executes the END.X
      function (B:2:C31) (2001:DB8:B:2:C31::) on the traceroute probe.  If
      2001:DB8:B:2:C31:: is a PSP SID, node N4 executes the SID like any
      other data packet with DA = 2001:DB8:B:2:C31:: and removes the
      SRH.

   o  When node N3, which is a classic IPv6 node, receives the packet
      (A:1::, B:4:OP)(B:4:C52, B:4:OP, B:2:C31 ; HC=1, SL=1;
      NH=UDP)(Traceroute probe)
      with hop-count = 1, it processes the
      hop-limit hop count expiry.
      Specifically, the node N3 responses with the ICMPv6 message (Type:
      "Time Exceeded", Code: "Time to Live exceeded in Transit").

   o  When node N3, which is a classic IPv6 node, receives the packet
      with hop-count > 1, it performs the standard IPv6 processing.
      Specifically, it forwards the traceroute probe based on DA B:4:OP
      2001:DB8:B:4:: in the IPv6 header.

   o  When node N4 receives the packet (A:1::, B:4:OP)(B:4:C52, B:4:OP,
      B:2:C31 ; SL=1; HC=1, NH=UDP)(Traceroute probe), with DA set to the local SID
      2001:DB8:B:4::, it processes the
      END.OP END SID, as described in the
      pseudocode in Section 3, before
      hop-limit processing.  The packet gets punted to the OAM process
      for processing.  The OAM process checks if the next SID in SRH
      (the target SID B:4:C52) is locally programmed. [I-D.ietf-spring-srv6-network-programming].

   o  If the next 2001:DB8:B:4:: SID is not locally programmed, the OAM process returns
      an ICMPv6 error message type 4 (parameter problem) code 0
      (erroneous header field encountered) with pointer set to the
      target SID B:4:C52 and the packet is
      discarded.

   o  If the next target SID (2001:DB8:B:4::) is locally programmed, the node
      processes the upper layer header.  As part of the upper layer
      header processing node N4 responses with the ICMPv6 message (Type:
      Destination unreachable, Code: Port Unreachable).

   Figure 4 displays a sample traceroute output for this example.

     > traceroute srv6 B:4:C52 2001:DB8:B:4:C52:: via segment-list B:2:C31 2001:DB8:B:2:C31::

     Tracing the route to SID function B:4:C52 2001:DB8:B:4:C52::
     1  2001:DB8:1:2:21:: 0.512 msec 0.425 msec 0.374 msec
            SRH: (B:4:C52, B:4:OP, B:2:C31; SL=2)
        DA: 2001:DB8:B:2:C31::,
        SRH:(2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::; SL=1)
     2  2001:DB8:2:3:31:: 0.721 msec 0.810 msec 0.795 msec
            SRH: (B:4:C52, B:4:OP, B:2:C31; SL=1)
        DA: 2001:DB8:B:4:C52::,
        SRH:(2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::; SL=0)
     3  2001:DB8:3:4:41:: 0.921 msec 0.816 msec 0.759 msec
            SRH: (B:4:C52, B:4:OP, B:2:C31; SL=1)
        DA: 2001:DB8:B:4:C52::,
        SRH:(2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::; SL=0)

          Figure 4 A sample output for hop-by-hop traceroute to a SID

6.3.

3.3.  A Controller-Based Passive Hybrid OAM Using O-flag

   This section illustrates a controller-based passive OAM mechanism
   using

   Consider the SRH.Flags.O-flag.

   The mechanism is different than example where the passive In-situ OAM defined in
   [I.D-draft-ietf-ippm-ioam-data].  This is because In-situ OAM records
   operational and telemetry information in user wants to monitor sampled IPv4 VPN
   100 traffic going from CE1 to CE2 via a low latency SR policy P
   installed at Node N1.  To exercise a low latency path, the packet as the packet
   traverses a path between two points in the network [I.D-draft-ietf-
   ippm-ioam-data].  The controller-based OAM mechanism using O-flag
   described in this section does not require the recording of OAM data
   in the packet.  Instead, a copy of the packet with the SRH.O-flag set
   is sent to a local OAM process.  The OAM process adds the required
   metadata to the packet and sends the packet to a controller for
   further processing.  Specification of how the OAM process computes
   the metadata and how the controller correlates and processes the copy
   of the packets from different segment endpoints is beyond the scope
   of this document.

   Consider the example where the user wants to monitor sampled IPv4 VPN
   100 traffic going from CE1 to CE2 via a low latency SR policy P
   installed at Node N1.  To exercise a low latency path, the SR Policy
   P forces SR Policy
   P forces the packet via segments B:2:C31 2001:DB8:B:2:C31:: and B:4:C52.
   2001:DB8:B:4:C52::.  The VPN SID at N7 associated with VPN100 is B:7:DT100.  B:7:DT100
   2001:DB8:B:7:DT100::.  2001:DB8:B:7:DT100:: is a USP SID.  N1, N4,
   and N7 are capable of processing SRH.Flags.O-flag but N2 is not
   capable of processing SRH.Flags.O-flag.  N100 is the centralized
   controller capable of processing and correlating the copy of the
   packets sent from nodes N1, N4, and N7.  N100 is aware of
   SRH.Flags.O-flag processing capabilities.  Controller N100 with the
   help from nodes N1, N4, N7 and implements a passive hybrid OAM mechanism
   using the SRH.Flags.O-flag as follows:

   o  A packet P1:(IPv4 header)(payload) is sent from CE1 to Node N1.

   o  Node N1 steers the packet P1 through the Policy P.  Based on a
      local configuration, Node N1 also implements logic to sample
      traffic steered through policy P for passive hybrid OAM purposes.
      Specification for the sampling logic is beyond the scope of this
      document.  Consider the case where packet P1 is classified as a
      packet to be monitored via the passive hybrid OAM.  Node N1 sets
      SRH.Flags.O-flag during encapsulation required by policy P.  As
      part of setting the SRH.Flags.O-flag, node N1 also send a
      timestamped copy of the packet P1: (A:1::, B:2:C31)(B:7:DT100,
      B:4:C52, B:2:C31; (2001:DB8:A:1::,
      2001:DB8:B:2:C31::) (2001:DB8:B:7:DT100::, 2001:DB8:B:4:C52::,
      2001:DB8:B:2:C31::; SL=2; O-flag=1; NH=IPv4)(IPv4 header)(payload)
      to a local OAM process.  The local OAM process sends a full or
      partial copy of the packet P1 to the controller N100.  The OAM
      process includes the recorded timestamp, additional OAM
      information like incoming and outgoing interface, etc. along with
      any applicable metadata.  Node N1 forwards the original packet
      towards the next segment B:2:C31. 2001:DB8:B:2:C31::.

   o  When node N2 receives the packet with SRH.Flags.O-flag set, it
      ignores the SRH.Flags.O-flag.  This is because node N2 is not
      capable of processing the O-flag.  Node N2 performs the standard
      SRv6 SID and SRH processing.  Specifically, it executes the END.X
      function (B:2:C31) (2001:DB8:B:2:C31::) and forwards the packet P1 (A:1::,
      B:4:C52)(B:7:DT100, B:4:C52, B:2:C31;
      (2001:DB8:A:1::, 2001:DB8:B:4:C52::) (2001:DB8:B:7:DT100::,
      2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::; SL=1; O-flag=1;
      NH=IPv4)(IPv4 header)(payload) over link 3 towards Node N3.

   o  When node N3, which is a classic IPv6 node, receives the packet P1
      , it performs the standard IPv6 processing.  Specifically, it
      forwards the packet P1 based on DA B:4:C52 2001:DB8:B:4:C52:: in the IPv6
      header.

   o  When node N4 receives the packet P1 (A:1::, B:4:C52)(B:7:DT100,
      B:4:C52, B:2:C31; (2001:DB8:A:1::,
      2001:DB8:B:4:C52::) (2001:DB8:B:7:DT100::, 2001:DB8:B:4:C52::,
      2001:DB8:B:2:C31::; SL=1; O-flag=1; NH=IPv4)(IPv4
      header)(payload), it processes the SRH.Flags.O-flag.  As part of
      processing the O-flag, it sends a timestamped copy of the packet
      to a local OAM process.  The local OAM process sends a full or
      partial copy of the packet P1 to the controller N100.  The OAM
      process includes the recorded timestamp, additional OAM
      information like incoming and outgoing interface, etc. along with
      any applicable metadata.  Node N4 performs the standard SRv6 SID
      and SRH processing on the original packet P1.  Specifically, it
      executes the END.X function
      (B:4:C52) (2001:DB8:B:4:C52::) and forwards the
      packet P1 (A:1::, B:7:DT100)(B:7:DT100,
      B:4:C52, B:2:C31; (2001:DB8:A:1::, 2001:DB8:B:7:DT100::)
      (2001:DB8:B:7:DT100::, 2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::;
      SL=0; O-flag=1; NH=IPv4)(IPv4 header)(payload) over link 10
      towards Node N5.

   o  When node N5, which is a classic IPv6 node, receives the packet
      P1, it performs the standard IPv6 processing.  Specifically, it
      forwards the packet based on DA B:7:DT100 2001:DB8:B:7:DT100:: in the IPv6
      header.

   o  When node N7 receives the packet P1 (A:1::, B:7:DT100)(B:7:DT100,
      B:4:C52, B:2:C31; (2001:DB8:A:1::,
      2001:DB8:B:7:DT100::) (2001:DB8:B:7:DT100::, 2001:DB8:B:4:C52::,
      2001:DB8:B:2:C31::; SL=0; O-flag=1; NH=IPv4)(IPv4
      header)(payload), it processes the SRH.Flags.O-flag.  As part of
      processing the O-flag, it sends a timestamped copy of the packet
      to a local OAM process.  The local OAM process sends a full or
      partial copy of the packet P1 to the controller N100.  The OAM
      process includes the recorded timestamp, additional OAM
      information like incoming and outgoing interface, etc. along with
      any applicable metadata.  Node N4 performs the standard SRv6 SID
      and SRH processing on the original packet P1.  Specifically, it
      executes the VPN SID
      (B:7:DT100) (2001:DB8:B:7:DT100::) and based on lookup in
      table 100 forwards the packet P1 (IPv4 header)(payload) towards CE
      2.

   o  The controller N100 processes and correlates the copy of the
      packets sent from nodes N1, N4 and N7 to find segment-by-segment
      delays and provide other passive hybrid OAM information related to packet
      P1.

   o  The process continues for any other sampled packets.

6.4.

3.4.  Monitoring of SRv6 Paths

   In the recent past, network operators are interested in performing
   network OAM functions in a centralized manner.  Various data models
   like YANG are available to collect data from the network and manage
   it from a centralized entity.

   SR technology enables a centralized OAM entity to perform path
   monitoring from centralized OAM entity without control plane
   intervention on monitored nodes.  [RFC 8403]  [RFC8403] describes
   such a centralized OAM mechanism.  Specifically, the draft document
   describes a procedure that can be used to perform path continuity
   check between any nodes within an SR domain from a centralized
   monitoring system, with minimal or no control plane intervene on the
   nodes.  However, the draft document focuses on SR networks with MPLS data
   plane.  The same
   concept applies to the SRv6 networks.  This document describes how
   the concept can be used to perform path monitoring in an SRv6
   network.  This document describes how the concept can be used to
   perform path monitoring in an SRv6 network as follows. from the centralized
   controller.

   In the above reference topology, topology in Figure 1, N100 is uses an IGP protocol like
   OSPF or ISIS to get the centralized monitoring
   system implementing topology view within the IGP domain.  N100
   can also use BGP-LS to get the complete view of an inter-domain
   topology.  The controller leverages the visibility of the topology to
   monitor the paths between the various endpoints without control plane
   intervention required at the monitored nodes.

   The controller N100 advertises an END function B:100:1::. In SID 2001:DB8:B:100:1::. To
   monitor any arbitrary SRv6 paths, the controller can create a
   loopback probe that originates and terminates on Node N100.  For
   example, in order to verify a segment list <B:2:C31, B:4:C52>, <2001:DB8:B:2:C31::,
   2001:DB8:B:4:C52::>:

   o  N100 generates a probe an OAM packet with
   SRH set to (B:100:1::, B:4:C52, B:2:C31, SL=2). (2001:DB8:A:100::,
      2001:DB8:B:2:C31::)(2001:DB8:B:100:1::, 2001:DB8:B:4:C52::,
      2001:DB8:B:2:C31::, SL=2)(OAM Payload).  The controller routes the
      probe packet towards the first segment, which is B:2:C31.
      2001:DB8:B:2:C31::.

   o  Node N2 performs executes the standard SRv6 SID and SRH processing END.X function (2001:DB8:B:2:C31::) and forward it
   over link3 with
      forwards the DA of IPv6 packet set (2001:DB8:A:100::,
      2001:DB8:B:4:C52::)(2001:DB8:B:100:1::, 2001:DB8:B:4:C52::,
      2001:DB8:B:2:C31::, SL=1)(OAM Payload) on link3 to B:4:C52.  N4 also N3.

   o  Node N3, which is a classic IPv6 node, performs the normal SRH processing and forward standard IPv6
      processing.  Specifically, it over link10 with forwards the packet based on the DA of
      2001:DB8:B:4:C52:: in the IPv6 header.

   o  Node N4 executes the END.X function (2001:DB8:B:4:C52::) and
      forwards the packet set (2001:DB8:A:100::,
      2001:DB8:B:100:1::)(2001:DB8:B:100:1::, 2001:DB8:B:4:C52::,
      2001:DB8:B:2:C31::, SL=0)(OAM Payload) on link10 to B:100:1::. This makes N5.

   o  Node N5, which is a classic IPv6 node, performs the probe loops
   back to standard IPv6
      processing.  Specifically, it forwards the centralized monitoring system.

   In packet based on the reference topology DA
      2001:DB8:B:100:1:: in Figure 1, N100 uses an IGP protocol like
   OSPF or ISIS to get the topology view within the IGP domain. IPv6 header.

   o  Node N100
   can also use BGP-LS to get executes the complete view of an inter-domain
   topology.  In other words, standard SRv6 END function.  It
      decapsulates the controller leverages header and consume the visibility of probe for OAM processing.
      The information in the topology OAM payload is used to monitor detect any missing
      probes, round trip delay, etc.

   The OAM payload type or the paths between information carried in the various endpoints
   without control plane intervention required OAM probe is a
   local implementation decision at the monitored nodes.

7. controller and is outside the
   scope of this document.

4.  Implementation Status

   This section is to be removed prior to publishing as an RFC.

   See [I-D.matsushima-spring-srv6-deployment-status] for updated
   deployment and interoperability reports.

8.

5.  Security Considerations

   This document does not define any new protocol extensions and relies
   on existing procedures defined for ICMP.  This document does not
   impose any additional security challenges to be considered beyond
   security considerations described in RFC4884, RFC4443, RFC792, RFCs
   that updates these RFCs, [I-D.ietf-6man-segment-routing-header] [RFC4884], [RFC4443], [RFC0792],
   and
   [I-D.ietf-spring-srv6-network-programming].

9. [RFC8754].

6.  IANA Considerations

9.1.  ICMPv6 type Numbers Registry

   This document defines one ICMPv6 type Number in the "ICMPv6 'type'
   Numbers" registry of [RFC4443].  Specifically, the document requests
   to add the following ICMPv6 type Number to the "ICMPv6 Type Numbers"
   registry:

      TBA (suggested value: 162) SRv6 OAM Message.

   The document also requests the creation of a new IANA registry to the
   "ICMPv6 'Code' Fields" against the "ICMPv6 Type Numbers TBA - SRv6
   OAM Message" with the following codes:

       Code  Name                                     Reference
       --------------------------------------------------------
        0     No Error                                This document
        1     SID is not locally implemented          This document

9.2.  SRv6 OAM Endpoint Types

   This I-D requests to IANA to allocate, within the "SRv6 Endpoint
   Behaviors Registry" sub-registry belonging to the top-level "Segment-
   routing with IPv6 data plane (SRv6) Parameters" registry [I-D.ietf-
   spring- srv6-network-programming], the following allocations:

           +------------------+-------------------+-----------+
           | Value (Suggested | Endpoint Behavior | Reference |
           | Value)           |                   |           |
           +------------------+-------------------+-----------+
           | TBA (40)         |        End.OP     | [This.ID] |
           +------------------+-------------------+-----------+

9.3.
6.1.  Segment Routing Header Flags

   This I-D requests to IANA to allocate bit position 2, within the
   "Segment Routing Header Flags" registry defined in [I-D.draft-ietf-
   6man-segment-routing-header].

10. [RFC8754].

7.  Acknowledgements

   The authors would like to thank Joel M.  Halpern, Greg Mirsky, Bob
   Hinden, Loa Andersson and Gaurav Naik for his their review comments.

11.

8.  Contributors

   The following people have contributed to this document:

      Robert Raszuk
      Bloomberg LP
      Email: robert@raszuk.net

      John Leddy
      Individual
      Email: john@leddy.net

      Gaurav Dawra
      LinkedIn
      Email: gdawra.ietf@gmail.com

      Bart Peirens
      Proximus
      Email: bart.peirens@proximus.com

      Nagendra Kumar
      Cisco Systems, Inc.
      Email: naikumar@cisco.com

      Carlos Pignataro
      Cisco Systems, Inc.
      Email: cpignata@cisco.com
      Rakesh Gandhi
      Cisco Systems, Inc.
      Canada
      Email: rgandhi@cisco.com

      Frank Brockners
      Cisco Systems, Inc.
      Germany
      Email: fbrockne@cisco.com

      Darren Dukes
      Cisco Systems, Inc.
      Email: ddukes@cisco.com

      Cheng Li
      Huawei
      Email: chengli13@huawei.com

      Faisal Iqbal
      Individual
      Email: faisal.ietf@gmail.com

12.

9.  References

12.1.

9.1.  Normative References

   [I-D.ietf-6man-segment-routing-header]

   [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>.

   [RFC8754]  Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
              Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
              (SRH)", draft-ietf-6man-segment-routing-header-26 (work in
              progress), October 2019. RFC 8754, DOI 10.17487/RFC8754, March 2020,
              <https://www.rfc-editor.org/info/rfc8754>.

9.2.  Informative References

   [I-D.ietf-spring-srv6-network-programming]
              Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
              Matsushima, S., and Z. Li, "SRv6 Network Programming",
              draft-ietf-spring-srv6-network-programming-15 (work in
              progress), March 2020.

   [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>.

12.2.  Informative References

   [I-D.matsushima-spring-srv6-deployment-status]
              Matsushima, S., Filsfils, C., Ali, Z., and Z. Li, Z., and K.
              Rajaraman, "SRv6 Implementation and Deployment Status", draft-matsushima-
              spring-srv6-deployment-status-06
              draft-matsushima-spring-srv6-deployment-status-07 (work in
              progress), March April 2020.

   [RFC0792]  Postel, J., "Internet Control Message Protocol", STD 5,
              RFC 792, DOI 10.17487/RFC0792, September 1981,
              <https://www.rfc-editor.org/info/rfc792>.

   [RFC4443]  Conta, A., Deering, S., and M. Gupta, Ed., "Internet
              Control Message Protocol (ICMPv6) for the Internet
              Protocol Version 6 (IPv6) Specification", STD 89,
              RFC 4443, DOI 10.17487/RFC4443, March 2006,
              <https://www.rfc-editor.org/info/rfc4443>.

   [RFC4884]  Bonica, R., Gan, D., Tappan, D., and C. Pignataro,
              "Extended ICMP to Support Multi-Part Messages", RFC 4884,
              DOI 10.17487/RFC4884, April 2007,
              <https://www.rfc-editor.org/info/rfc4884>.

   [RFC5476]  Claise, B., Ed., Johnson, A., and J. Quittek, "Packet
              Sampling (PSAMP) Protocol Specifications", RFC 5476,
              DOI 10.17487/RFC5476, March 2009,
              <https://www.rfc-editor.org/info/rfc5476>.

   [RFC5837]  Atlas, A., Ed., Bonica, R., Ed., Pignataro, C., Ed., Shen,
              N., and JR. Rivers, "Extending ICMP for Interface and
              Next-Hop Identification", RFC 5837, DOI 10.17487/RFC5837,
              April 2010, <https://www.rfc-editor.org/info/rfc5837>.

   [RFC7011]  Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
              "Specification of the IP Flow Information Export (IPFIX)
              Protocol for the Exchange of Flow Information", STD 77,
              RFC 7011, DOI 10.17487/RFC7011, September 2013,
              <https://www.rfc-editor.org/info/rfc7011>.

   [RFC7012]  Claise, B., Ed. and B. Trammell, Ed., "Information Model
              for IP Flow Information Export (IPFIX)", RFC 7012,
              DOI 10.17487/RFC7012, September 2013,
              <https://www.rfc-editor.org/info/rfc7012>.

   [RFC7799]  Morton, A., "Active and Passive Metrics and Methods (with
              Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
              May 2016, <https://www.rfc-editor.org/info/rfc7799>.

   [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>.

   [RFC8403]  Geib, R., Ed., Filsfils, C., Pignataro, C., Ed., and N.
              Kumar, "A Scalable and Topology-Aware MPLS Data-Plane
              Monitoring System", RFC 8403, DOI 10.17487/RFC8403, July
              2018, <https://www.rfc-editor.org/info/rfc8403>.

Authors' Addresses

   Zafar Ali
   Cisco Systems

   Email: zali@cisco.com

   Clarence Filsfils
   Cisco Systems

   Email: cfilsfil@cisco.com

   Satoru Matsushima
   Softbank

   Email: satoru.matsushima@g.softbank.co.jp

   Daniel Voyer
   Bell Canada

   Email: daniel.voyer@bell.ca

   Mach Chen
   Huawei

   Email: mach.chen@huawei.com