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Export of Segment Routing over IPv6 Information in IP Flow Information Export (IPFIX)
draft-ietf-opsawg-ipfix-srv6-srh-13

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 9487.
Authors Thomas Graf , Benoît Claise , Pierre Francois
Last updated 2023-05-25 (Latest revision 2023-05-23)
Replaces draft-tgraf-opsawg-ipfix-srv6-srh
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Document shepherd Mohamed Boucadair
Shepherd write-up Show Last changed 2023-05-05
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Needs 2 more YES or NO OBJECTION positions to pass.
Responsible AD Robert Wilton
Send notices to mohamed.boucadair@orange.com
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draft-ietf-opsawg-ipfix-srv6-srh-13
Network Working Group                                            T. Graf
Internet-Draft                                                  Swisscom
Intended status: Standards Track                               B. Claise
Expires: 25 November 2023                                         Huawei
                                                             P. Francois
                                                               INSA-Lyon
                                                             24 May 2023

           Export of Segment Routing over IPv6 Information in
                   IP Flow Information Export (IPFIX)
                  draft-ietf-opsawg-ipfix-srv6-srh-13

Abstract

   This document introduces new IP Flow Information Export (IPFIX)
   Information Elements to identify a set of Segment Routing over IPv6
   (SRv6) related information such as data contained in a Segment
   Routing Header (SRH), the SRv6 control plane, and the SRv6 endpoint
   behavior that traffic is being forwarded with.

Status of This Memo

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

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

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

   This Internet-Draft will expire on 25 November 2023.

Copyright Notice

   Copyright (c) 2023 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components

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   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  New IPFIX IPv6 SRH Information Elements . . . . . . . . . . .   4
   4.  Sample Use Cases  . . . . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     5.1.  New IPFIX IPv6 SRH Information Elements . . . . . . . . .   6
       5.1.1.  srhFlagsIPv6  . . . . . . . . . . . . . . . . . . . .   7
       5.1.2.  srhTagIPv6  . . . . . . . . . . . . . . . . . . . . .   8
       5.1.3.  srhSegmentIPv6  . . . . . . . . . . . . . . . . . . .   8
       5.1.4.  srhActiveSegmentIPv6  . . . . . . . . . . . . . . . .   9
       5.1.5.  srhSegmentIPv6BasicList . . . . . . . . . . . . . . .   9
       5.1.6.  srhSegmentIPv6ListSection . . . . . . . . . . . . . .   9
       5.1.7.  srhSegmentsIPv6Left . . . . . . . . . . . . . . . . .  10
       5.1.8.  srhIPv6Section  . . . . . . . . . . . . . . . . . . .  10
       5.1.9.  srhIPv6ActiveSegmentType  . . . . . . . . . . . . . .  11
       5.1.10. srhSegmentIPv6LocatorLength . . . . . . . . . . . . .  11
       5.1.11. srhSegmentIPv6EndpointBehavior  . . . . . . . . . . .  11
     5.2.  New IPFIX IPv6 SRH Segment Type Subregistry . . . . . . .  12
   6.  Operational Considerations  . . . . . . . . . . . . . . . . .  13
     6.1.  SRv6 Segment List . . . . . . . . . . . . . . . . . . . .  13
     6.2.  Compressed SRv6 Segment List Decomposition  . . . . . . .  14
     6.3.  Multiple Segment Routing Headers  . . . . . . . . . . . .  14
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   8.  Implementation Status . . . . . . . . . . . . . . . . . . . .  14
     8.1.  FD.io VPP . . . . . . . . . . . . . . . . . . . . . . . .  15
     8.2.  Huawei VRP  . . . . . . . . . . . . . . . . . . . . . . .  15
     8.3.  Pmacct Data Collection  . . . . . . . . . . . . . . . . .  15
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  16
     10.2.  Informative References . . . . . . . . . . . . . . . . .  17
   Appendix A.  IPFIX Encoding Examples  . . . . . . . . . . . . . .  18
     A.1.  Three Observed SRH Headers and their Routing Protocol . .  19
       A.1.1.  Template Record and Data Set with Segment Basic
               List  . . . . . . . . . . . . . . . . . . . . . . . .  19
       A.1.2.  Template Record and Data Set with Segment List
               Section . . . . . . . . . . . . . . . . . . . . . . .  21
       A.1.3.  Template Record and Data Set with SRH Section . . . .  24
     A.2.  Options Template Record and Data Set for SRv6 Segment End
           Point behavior and Locator Length . . . . . . . . . . . .  26
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  28

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1.  Introduction

   A dedicated Routing Extension Header, called Segment Routing Header
   (SRH), is defined in [RFC8754] for use of Segment Routing (SR) over
   IPv6 data plane.

   Also, three routing protocol extensions, OSPFv3
   [I-D.ietf-lsr-ospfv3-srv6-extensions], IS-IS [RFC9352] and BGP Prefix
   Segment Identifiers(Prefix-SIDs) [RFC8669] and Path Computation
   Element Communication Protocol (PCEP) Extension
   [I-D.ietf-pce-segment-routing-ipv6] and Segment Routing Policy
   [RFC9256] are defined to propagate Segment Identifiers (SIDs).

   SRv6 segment endpoint behaviors describe how packets should be
   processed by SRv6 Segment Endpoint Nodes.  Such behaviors are defined
   in [RFC8986].

   This document specifies eleven new IPFIX Information Elements (IEs)
   and one new subregistry within the "IPFIX Information Elements"
   registry [RFC7012], for SRv6 purposes.

   These IEs are used to export the SRv6 active segment and its control
   plane protocol, the SRv6 Segment List, the next SRv6 node and its
   type, and the numbers of SRv6 segments left.

   Some examples are provided in Appendix A.

2.  Terminology

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

   This document makes use of the terms defined in [RFC7011], [RFC8402]
   and [RFC8754].

   The following terms are used as defined in [RFC7011]:

   *  IPFIX

   *  IPFIX Information Elements

   *  Template

   *  Template Record

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   *  Options Template

   *  Options Template Record

   *  Data Record

   *  Data Set

   The following terms are used as defined in [RFC8402]:

   *  Segment Routing (SR)

   *  Segment

   *  Segment List

   *  Active Segment

   *  Segment Identifier (SID)

   *  SRv6

   *  SRv6 SID

   The following terms are used as defined in [RFC8754]:

   *  Segment Routing Header (SRH)

   *  SR Source Node

   *  Transit Node

   *  SR Segment Endpoint Node

   *  Reduced SRH

   *  Segments Left

   *  Last Entry

3.  New IPFIX IPv6 SRH Information Elements

   This section specifies the new IPFIX IPv6 SRH IEs.

   srhFlagsIPv6
      8-bit flags defined in the SRH (Section 2 of [RFC8754]).

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   srhTagIPv6
      16-bit tag field defined in the SRH (Section 2 of [RFC8754]).  A
      tag is used to mark a packet as part of a class or group of
      packets sharing the same set of properties.

   srhSegmentIPv6
      128-bit IPv6 address that represents a SRv6 segment.

   srhActiveSegmentIPv6
      128-bit IPv6 address that represents the active SRv6 segment.

   srhSegmentIPv6BasicList
      Ordered basicList [RFC6313] of zero or more 128-bit IPv6 addresses
      in the SRH that represents the SRv6 Segment List.  As specified in
      Section 2 of [RFC8754], the Segment List is encoded starting from
      the last segment of the SR Policy.  That is, the first element of
      the Segment List (Segment List[0]) contains the last segment of
      the SR Policy, the second element contains the penultimate segment
      of the SR Policy, and so on.

   srhSegmentIPv6ListSection
      The SRH Segment List as defined in Section 2 of [RFC8754] as a
      series of octets in IPFIX.

   srhSegmentsIPv6Left
      8-bit unsigned integer defining the number of segments remaining
      to reach the end of the Segment List from the SRH, as specified by
      the "Segments Left" field in Section 4.4 of [RFC8200] and
      mentioned part of the SRH in Section 2 of [RFC8754]).

   srhIPv6Section
      Exposes the SRH and its TLVs as specified in Section 2 of
      [RFC8754] as a series of octets in IPFIX.

   srhIPv6ActiveSegmentType
      Designator of the routing protocol or PCEP extension where the
      active SRv6 segment has been learned from.

   srhSegmentIPv6LocatorLength
      The SRH segment IPv6 locator length specified as the number of
      significant bits.  Together with srhSegmentIPv6 it enables the
      calculation of the SRv6 Locator.

   srhSegmentIPv6EndpointBehavior
      16-bit unsigned integer that represents a SRv6 Endpoint behavior
      as per Section 4 of [RFC8986].

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   Note that the srhSegmentIPv6, srhSegmentIPv6LocatorLength, and
   srhSegmentIPv6EndpointBehavior IPFIX IEs are generic fields, to be
   used in the context of IPFIX Options Templates or IPFIX Structured
   Data [RFC6313].

4.  Sample Use Cases

   The IPFIX IEs srhSegmentIPv6BasicList (TBD5) or
   srhSegmentIPv6ListSection (TBD6), srhActiveSegmentIPv6 (TBD4),
   srhSegmentsIPv6Left (TBD7), srhIPv6ActiveSegmentType(TBD9),
   forwardingStatus (89) [RFC7270] [IANA-IPFIX], and some existing
   counters information [IANA-IPFIX] allow to provide answers to the
   following questions (amongst others):

   *  How many packets steered with a SR policy are forwarded or dropped
      using SRv6 in a network?

   *  If dropped, for which reasons?

   *  What is the current active segment and its associated control
      plane protocol?

   *  What is the SRv6 Segment List?

   *  What is the next SRv6 node and its type?

   *  How many SRv6 segments are left?

5.  IANA Considerations

   Note to the RFC-Editor:

   *  Please replace TBD1 - TBD17 with the values allocated by IANA

   *  Please replace the [RFC-to-be] with the RFC number assigned to
      this document

5.1.  New IPFIX IPv6 SRH Information Elements

   This document requests IANA to add new IEs (Section 5.1) to the
   "IPFIX Information Elements" registry [RFC7012] available at
   [IANA-IPFIX].

   Table 1 lists the new IPv6 SRH IEs:

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     +-------+--------------------------------+
     |Element|              Name              |
     |   ID  |                                |
     +-------+--------------------------------+
     | TBD1  | srhFlagsIPv6                   |
     |       |                                |
     +-------+--------------------------------+
     | TBD2  | srhTagIPv6                     |
     |       |                                |
     +-------+--------------------------------+
     | TBD3  | srhSegmentIPv6                 |
     |       |                                |
     +-------+--------------------------------+
     | TBD4  | srhActiveSegmentIPv6           |
     |       |                                |
     +-------+--------------------------------+
     | TBD5  | srhSegmentIPv6BasicList        |
     |       |                                |
     +-------+--------------------------------+
     | TBD6  | srhSegmentIPv6ListSection      |
     |       |                                |
     +-------+--------------------------------+
     | TBD7  | srhSegmentsIPv6Left            |
     |       |                                |
     +-------+--------------------------------+
     | TBD8  | srhIPv6Section                 |
     |       |                                |
     +-------+--------------------------------+
     | TBD9  | srhIPv6ActiveSegmentType       |
     |       |                                |
     +-------+--------------------------------+
     | TBD10 | srhSegmentIPv6LocatorLength    |
     |       |                                |
     +-------+--------------------------------+
     | TBD11 | srhSegmentIPv6EndpointBehavior |
     |       |                                |
     +-------+--------------------------------+

  Table 1: New IPv6 SRH IEs in the "IPFIX Information Elements" Registry

5.1.1.  srhFlagsIPv6

   Name:  srhFlagsIPv6

   ElementID:  TBD1

   Description:  The 8-bit flags defined in the SRH (Section 2 of

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      [RFC8754]).  Assigned flags and their meanings are provided in the
      "Segment Routing Header Flags" IANA registry.

   Abstract Data Type:  unsigned8

   Data Type Semantics:  flags

   Additional Information:  See the assignments in the "Segment Routing
      Header Flags" IANA registry at https://www.iana.org/assignments/
      ipv6-parameters/ipv6-parameters.xhtml#segment-routing-header-
      flags.  See also RFC8754 for the SRH specification.

   Reference:  [RFC-to-be]

5.1.2.  srhTagIPv6

   Name:  srhTagIPv6

   ElementID:  TBD2

   Description:  The 16-bit tag field defined in the SRH (Section 2 of
      [RFC8754]).  A tag is used to mark a packet as part of a class or
      group of packets sharing the same set of properties.

   Abstract Data Type:  unsigned16

   Data Type Semantics:  identifier

   Additional Information:  See Section 2 of [RFC8754] for more details
      about the tag.

   Reference:  [RFC-to-be]

5.1.3.  srhSegmentIPv6

   Name:  srhSegmentIPv6

   ElementID:  TBD3

   Description:  The 128-bit IPv6 address that represents a SRv6
      segment.

   Abstract Data Type:  ipv6address

   Data Type Semantics:  default

   Additional Information:  Specified in Section 1 of [RFC8402] and
      mentioned in "Segment List" in Section 2 of [RFC8754].

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   Reference:  [RFC-to-be]

5.1.4.  srhActiveSegmentIPv6

   Name:  srhActiveSegmentIPv6

   ElementID:  TBD4

   Description:  The 128-bit IPv6 address that represents the active
      SRv6 segment.

   Abstract Data Type:  ipv6address

   Data Type Semantics:  default

   Additional Information:  See Section 2 of [RFC8402] for the
      definition of active segment.

   Reference:  [RFC-to-be]

5.1.5.  srhSegmentIPv6BasicList

   Name:  srhSegmentIPv6BasicList

   ElementID:  TBD5

   Description:  The Ordered basicList [RFC6313] of zero or more 128-bit
      IPv6 addresses in the SRH that represents the SRv6 Segment List.
      As specified in Section 2 of [RFC8754], the Segment List is
      encoded starting from the last segment of the SR Policy.  That is,
      the first element of the Segment List (Segment List[0]) contains
      the last segment of the SR Policy, the second element contains the
      penultimate segment of the SR Policy, and so on.

   Abstract Data Type:  basicList

   Data Type Semantics:  list

   Additional Information:  See Section 2 of [RFC8754] for more details
      about the SRv6 Segment List.

   Reference:  [RFC-to-be]

5.1.6.  srhSegmentIPv6ListSection

   Name:  srhSegmentIPv6ListSection

   ElementID:  TBD6

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   Description:  The SRH Segment List as defined in Section 2 of
      [RFC8754] as a series of octets in IPFIX.

   Abstract Data Type:  octetArray

   Data Type Semantics:  default

   Additional Information:  See Section 2 of [RFC8754] for more details
      about the SRv6 Segment List.

   Reference:  [RFC-to-be]

5.1.7.  srhSegmentsIPv6Left

   Name:  srhSegmentsIPv6Left

   ElementID:  TBD7

   Description:  8-bit unsigned integer defining the number of segments
      remaining to reach the end of the Segment List in the SRH.

   Abstract Data Type:  unsigned8

   Data Type Semantics:  quantity

   Additional Information:  Specified by the "Segments Left" field in
      Section 4.4 of [RFC8200] and mentioned in Section 2 of [RFC8754]).

   Reference:  [RFC-to-be]

5.1.8.  srhIPv6Section

   Name:  srhIPv6Section

   Description:  The SRH and its TLVs as defined in Section 2 of
      [RFC8754] as a series of octets in IPFIX.

   Abstract Data Type:  octetArray

   Data Type Semantics:  default

   Additional Information:  See Section 2 of [RFC8754] for more details
      about the structure of an SRH.

   Reference:  [RFC-to-be]

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5.1.9.  srhIPv6ActiveSegmentType

   Name:  srhIPv6ActiveSegmentType

   ElementID:  TBD9

   Description:  The designator of the routing protocol or PCEP
      extension from where the active SRv6 segment has been learned
      from.  Values for this Information Element are listed in the
      "IPFIX IPv6 SRH Segment type" subregistry, see [IANA-IPFIX].

   Abstract Data Type:  unsigned8

   Data Type Semantics:  identifier

   Additional Information:  See the assigned types in [IPFIX IPv6 SRH
      Segment Type Subregistry].

   Note to IANA:  Please replace [IPFIX IPv6 SRH Segment Type
      Subregistry] with the URL of the IANA subregistry.

   Reference:  [RFC-to-be]

5.1.10.  srhSegmentIPv6LocatorLength

   Name:  srhSegmentIPv6LocatorLength

   ElementID:  TBD10

   Description:  The SRH segment IPv6 locator length specified as the
      number of significant bits.  Together with srhSegmentIPv6 it
      enables the calculation of the SRv6 Locator.

   Abstract Data Type:  unsigned8

   Data Type Semantics:  default

   Additional Information:  See Section 3.1 of [RFC8986] for more
      details about the SID format.

   Reference:  [RFC-to-be]

5.1.11.  srhSegmentIPv6EndpointBehavior

   Name:  srhSegmentIPv6EndpointBehavior

   ElementID:  TBD11

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   Description:  The 16-bit unsigned integer that represents a SRv6
      Endpoint behavior as per Section 4 of [RFC8986].  Assigned values
      and their meanings are provided in the "SRV6 Endpoint Behavior"
      registry.

   Abstract Data Type:  unsigned16

   Data Type Semantics:  identifier

   Additional Information:  See the assigned behaviors at the "SRv6
      Endpoint Behavior" registry available at
      https://www.iana.org/assignments/segment-routing/segment-
      routing.xhtml#srv6-endpoint-behaviors.  See Section 4 of [RFC8986]
      for more details about the endpoint behaviors processing.

   Reference:  [RFC-to-be]

5.2.  New IPFIX IPv6 SRH Segment Type Subregistry

   This document requests IANA to create a new subregistry called "IPFIX
   IPv6 SRH Segment Type" under the "IPFIX Information Elements"
   registry [RFC7012] available at [IANA-IPFIX].

   The allocation policy of this new subregistry is Expert Review
   (Section 4.5 of [RFC8126]).

   The designated experts for this registry should be familiar with SRH.
   The guidelines that are being followed by the designated experts for
   the IPFIX registry should be followed for this subregistry.  In
   particular, criteria that should be applied by the designated experts
   include determining whether the proposed registration duplicates
   existing entries and whether the registration description is clear
   and fits the purpose of this registry.  Within the review period, the
   designated experts will either approve or deny the registration
   request, communicating this decision to IANA.  Denials should include
   an explanation and, if applicable, suggestions as to how to make the
   request successful.

   Initial values in the registry are defined in Table 2.

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  +-------+--------------------+---------------------------------------+
  | Value |     Description    |        Additional Information         |
  +-------+--------------------+---------------------------------------+
  | TBD12 | Unknown            | [RFC-to-be]                           |
  |       |                    |                                       |
  +-------+--------------------+---------------------------------------+
  | TBD13 | Segment Routing    | [RFC-to-be],                          |
  |       | Policy             | <xref target="RFC9256"/>              |
  +-------+--------------------+---------------------------------------+
  | TBD14 | Path Computation   | [RFC-to-be],<xref target="            |
  |       | Element            | I-D.ietf-pce-segment-routing-ipv6"/>  |
  +-------+--------------------+---------------------------------------+
  | TBD15 | OSPFv3             | [RFC-to-be],<xref target="            |
  |       | Segment Routing    | I-D.ietf-lsr-ospfv3-srv6-extensions"/>|
  +-------+--------------------+---------------------------------------+
  | TBD16 | IS-IS              | [RFC-to-be],<xref target="RFC9352"/>  |
  |       | Segment Routing    |                                       |
  +-------+--------------------+---------------------------------------+
  | TBD17 | BGP Segment        | [RFC-to-be],                          |
  |       | Routing Prefix-SID | <xref target="RFC8669"/>              |
  +-------+--------------------+---------------------------------------+

          Table 2: "IPFIX IPv6 SRH Segment Type" Subregistry

6.  Operational Considerations

6.1.  SRv6 Segment List

   The zero or more 128-bit IPv6 addresses in the SRH [RFC8754] can be
   exported in two different ways, with two different IPFIX IEs:

   *  srhSegmentIPv6BasicList

   *  srhSegmentIPv6ListSection

   The srhSegmentIPv6BasicList encodes the SRv6 Segment List with a
   basicList, specified in the IPFIX Structured Data [RFC6313].  This
   encoding offers the advantage to the data collection that the
   different IPv6 addresses are already structured as a list, without
   the need of post processing.  However, this method requires some
   extra processing on the exporter, to realize the BasicList data
   mapping.

   The srhSegmentIPv6ListSection, on the other hand, encodes the list of
   IPv6 addresses as an octetArray.  This doesn't impose any data flow
   manipulation on the exporter, facilitating the immediate export.
   However, the data collection MUST be able to decode the IPv6

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   addresses according to the SR specifications.  Compared to the
   srhSegmentIPv6BasicList, the srhSegmentIPv6ListSection flow records
   length is slightly reduced.

   It is not expected that an exporter would support both
   srhSegmentIPv6BasicList and srhSegmentIPv6ListSection at the same
   time.

6.2.  Compressed SRv6 Segment List Decomposition

   The SRv6 Segment List in the IPFIX IEs srhSegmentIPv6BasicList,
   srhSegmentIPv6ListSection and destinationIPv6Address could contain
   compressed-SID containers as described in
   [I-D.ietf-spring-srv6-srh-compression].  The SR Endpoint Flavors,
   described in Section 4 of [I-D.ietf-spring-srv6-srh-compression]
   defines new flavors for SID endpoint behaviors, and determine
   wherever the Segment List encoding is compressed, along with the
   flavor.  The SID Locator as described in Section 3.1 of [RFC8986],
   determines the common most significant bits.  By using described
   information from srhSegmentIPv6EndpointBehavior and
   srhSegmentIPv6LocatorLength the compressed-SID containers can be
   decoded at the data collection.

6.3.  Multiple Segment Routing Headers

   If multiple SRHs are observed (for reasons that are not detailed
   here), the export of the same IE multiple times in one data record
   and related template record is supported and the order within the
   packet SHOULD be preserved in the IPFIX export according to Section 8
   of [RFC7011].  If the network node is not capable to export IPFIX for
   more than one SRH, it MUST export IPFIX for the SRH of the active
   segment.

7.  Acknowledgements

   The authors would like to thank Yao Liu, Eduard Vasilenko, Bruno
   Decraene, Mohamed Boucadair, Kamran Raza, Qin Wu, Jim Guichard, Tero
   Kivinen, Paul Aitken, Roman Danyliw, John Scudder, Eric Vyncke and
   Erik Kline for their review and valuable comments, and Paolo Lucente
   and Alex Huang Feng for the implementation and validation.

8.  Implementation Status

   Note to the RFC-Editor: Please remove this section before publishing.

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8.1.  FD.io VPP

   INSA Lyon implemented the following IEs as part of a prototype in the
   FD.io VPP (Vector Packet Processing) platform:

   *  srhActiveSegmentIPv6

   *  srhSegmentIPv6EndpointBehavior

   *  srhSegmentsIPv6Left

   *  srhFlagsIPv6

   *  srhTagIPv6

   *  srhSegmentIPv6ListSection

   *  srhSegmentIPv6BasicList

   The open source code can be obtained here: [INSA-Lyon-VPP] and was
   validated at the IETF 115 hackathon.

8.2.  Huawei VRP

   Huawei implemented the following IEs as part of a a production
   implementation in the VRP platform:

   *  srhActiveSegmentIPv6

   *  srhSegmentsIPv6Left

   *  srhFlagsIPv6

   *  srhTagIPv6

   *  srhSegmentIPv6ListSection

   The implementation was validated at the IETF 115 hackathon.

8.3.  Pmacct Data Collection

   Paolo Lucente implemented the IE
   srhSegmentIPv6ListSection decomposition as part of a a production
   implementation in the open source Network Telemetry data collection
   project pmacct.

   The source code can be obtained here: [Paolo-Lucente-Pmacct] and was
   validated at the IETF 115 hackathon.

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9.  Security Considerations

   There exists no extra security considerations regarding allocation of
   these new IPFIX IEs compared to [RFC7012].

   The IEs described in this document export provider plane data metrics
   on how packets are being forwarded within a SRv6 network.
   Applications and operators using the IEs described in this document
   must evaluate the sensitivity of this information in their
   implementation context, and apply the data-at-rest storage guidance
   in Section 11.8 of [RFC7011] as appropriate.

10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC6313]  Claise, B., Dhandapani, G., Aitken, P., and S. Yates,
              "Export of Structured Data in IP Flow Information Export
              (IPFIX)", RFC 6313, DOI 10.17487/RFC6313, July 2011,
              <https://www.rfc-editor.org/info/rfc6313>.

   [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>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [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>.

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   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,
              <https://www.rfc-editor.org/info/rfc8200>.

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

10.2.  Informative References

   [I-D.ietf-lsr-ospfv3-srv6-extensions]
              Li, Z., Hu, Z., Talaulikar, K., and P. Psenak, "OSPFv3
              Extensions for SRv6", Work in Progress, Internet-Draft,
              draft-ietf-lsr-ospfv3-srv6-extensions-11, 2 May 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-lsr-
              ospfv3-srv6-extensions-11>.

   [I-D.ietf-pce-segment-routing-ipv6]
              Li, C., Negi, M. S., Sivabalan, S., Koldychev, M.,
              Kaladharan, P., and Y. Zhu, "Path Computation Element
              Communication Protocol (PCEP) Extensions for Segment
              Routing leveraging the IPv6 dataplane", Work in Progress,
              Internet-Draft, draft-ietf-pce-segment-routing-ipv6-16, 6
              March 2023, <https://datatracker.ietf.org/doc/html/draft-
              ietf-pce-segment-routing-ipv6-16>.

   [I-D.ietf-spring-srv6-srh-compression]
              Cheng, W., Filsfils, C., Li, Z., Decraene, B., and F.
              Clad, "Compressed SRv6 Segment List Encoding in SRH", Work
              in Progress, Internet-Draft, draft-ietf-spring-srv6-srh-
              compression-04, 31 March 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-spring-
              srv6-srh-compression-04>.

   [IANA-IPFIX]
              "IANA, "IP Flow Information Export (IPFIX) Entities"",
              <https://www.iana.org/assignments/ipfix/ipfix.xhtml>.

   [INSA-Lyon-VPP]
              "INSA Lyon, FD.io VPP implementation",
              <https://github.com/network-analytics/vpp-srh-onpath-
              telemetry>.

   [Paolo-Lucente-Pmacct]
              "Paolo Lucente, Pmacct open source Network Telemetry Data
              Collection", <https://github.com/pmacct/pmacct>.

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   [RFC7270]  Yourtchenko, A., Aitken, P., and B. Claise, "Cisco-
              Specific Information Elements Reused in IP Flow
              Information Export (IPFIX)", RFC 7270,
              DOI 10.17487/RFC7270, June 2014,
              <https://www.rfc-editor.org/info/rfc7270>.

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

   [RFC8669]  Previdi, S., Filsfils, C., Lindem, A., Ed., Sreekantiah,
              A., and H. Gredler, "Segment Routing Prefix Segment
              Identifier Extensions for BGP", RFC 8669,
              DOI 10.17487/RFC8669, December 2019,
              <https://www.rfc-editor.org/info/rfc8669>.

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

   [RFC9256]  Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
              A., and P. Mattes, "Segment Routing Policy Architecture",
              RFC 9256, DOI 10.17487/RFC9256, July 2022,
              <https://www.rfc-editor.org/info/rfc9256>.

   [RFC9352]  Psenak, P., Ed., Filsfils, C., Bashandy, A., Decraene, B.,
              and Z. Hu, "IS-IS Extensions to Support Segment Routing
              over the IPv6 Data Plane", RFC 9352, DOI 10.17487/RFC9352,
              February 2023, <https://www.rfc-editor.org/info/rfc9352>.

Appendix A.  IPFIX Encoding Examples

   This appendix represents three different encodings for the newly
   introduced IEs, for the example values in Table 3.  The three
   different encodings use the following IEs, respectively:
   srhSegmentIPv6BasicList, srhSegmentIPv6ListSection, and
   srhIPv6Section.

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   +-----+------+-----+----------------+--------------------------|
   | SRH | SRH  | SRH | Active Segment |       Segment List       |
   | Nr  | Flags| Tag | Type           |                          |
   +-----+------+-----+----------------+--------------------------+
   | 1   | 0    | 123 | IS-IS          | 2001:db8::1, 2001:db8::2,|
   |     |      |     |                | 2001:db8::3              |
   +-----+------+-----+----------------+--------------------------+
   | 2   | 0    | 456 | IS-IS          | 2001:db8::4, 2001:db8::5 |
   +-----+------+-----+----------------+--------------------------+
   | 3   | 0    | 789 | IS-IS          | 2001:db8::6              |
   +-----+------+-----+----------------+--------------------------+

     Table 3: Three Observed SRH headers and Their Associated Routing Protocol

A.1.  Three Observed SRH Headers and their Routing Protocol

A.1.1.  Template Record and Data Set with Segment Basic List

   With encoding in Figure 1, the examples in Table 3 are represented
   with the following IEs: “=>” is used to indicate which IE is mapped
   to a given information.

   *  SR Flags => srhFlagsIPv6 (TBD1)

   *  SR Tag => srhTagIPv6 (TBD2)

   *  Active Segment Type => srhIPv6ActiveSegmentType (TBD9)

   *  Segment List => srhSegmentIPv6BasicList (TBD5)

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          SET ID = 2           |       Length = 24             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Template ID = 256        |      Field Count = 4          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|     srhFlagsIPv6 = TBD1     |      Field Length = 1         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|      srhTagIPv6 = TBD2      |      Field Length = 2         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|srhActiveSegmentIPv... = TBD9|      Field Length = 1         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|srhSegmentIPv6BasicList= TBD5|      Field Length = 0xFFFF    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure 1: Template Record with Basic List Encoding Format

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   In this example, the Template ID is 256, which will be used in the
   Data Record.  The field length for srhSegmentIPv6BasicList is 0xFFFF,
   which means the length of this IE is variable, and the actual length
   of this IE is indicated by the List Length field in the basicList
   format as per [RFC6313].

   The data set is represented as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         SET ID = 256          |           Length = 136        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | srhFlagsIPv6  |        srhTagIPv6 = 123       | srhActiveSegme|
      | = 0           |                               | ntIPv...=TBD16|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      255      |        List Length = 53       |semantic=      |
      |               |                               |ordered        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     srhSegmentIPv6 = TBD3     |        Field Length = 16      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             Segment List[0] = 2001:db8::1                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             Segment List[1] = 2001:db8::2                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             Segment List[2] = 2001:db8::3                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | srhFlagsIPv6  |        srhTagIPv6 = 456       | srhActiveSegme|
      | = 0           |                               | ntIPv...=TBD16|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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      |      255      |        List Length = 37       |semantic=      |
      |               |                               |ordered        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     srhSegmentIPv6 = TBD3     |        Field Length = 16      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             Segment List[0] = 2001:db8::4                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             Segment List[1] = 2001:db8::5  (16 bytes)         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | srhFlagsIPv6  |        srhTagIPv6 = 789       | srhActiveSegme|
      | = 0           |                               | ntIPv...=TBD16|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      255      |        List Length = 21       |semantic=      |
      |               |                               |ordered        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     srhSegmentIPv6 = TBD3     |        Field Length = 16      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             Segment List[0] = 2001:db8::6  ...                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 2: Data Set Encoding Format for Basic List

A.1.2.  Template Record and Data Set with Segment List Section

   With encoding in Figure 3, the examples in Table 3 are represented
   with the following IEs: “=>” is used to indicate which IE is mapped
   to a given information.

   *  SR Flags => srhFlagsIPv6 (TBD1)

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   *  SR Tag => srhTagIPv6 (TBD2)

   *  Active Segment Type => srhIPv6ActiveSegmentType (TBD9)

   *  Segment List => srhSegmentIPv6ListSection (TBD6)

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          SET ID = 2           |       Length = 24             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      Template ID = 257        |      Field Count = 4          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0|     srhFlagsIPv6 = TBD1     |      Field Length = 1         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0|      srhTagIPv6 = TBD2      |      Field Length = 2         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0|srhActiveSegmentIPv... = TBD9|      Field Length = 1         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0|     srhSegmentIPv6List      |      Field Length = 0xFFFF    |
     | |     Section=TBD6            |                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Figure 3: Template Record with Segment List Section Encoding Format

   In this example, the Template ID is 257, which will be used in the
   Data Record.  The field length for srhSegmentIPv6ListSection in the
   Template Record is 0xFFFF, which means that the length of this IE is
   variable: its actual length is encoded in the Data Set. Note that,
   with an actual length inferior to 255 in the Data Record example, the
   length field is encoded in 8 bits (Section 7 of [RFC7011]).

   The data can be represented as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         SET ID = 257          |           Length = 116        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | srhFlagsIPv6  |        srhTagIPv6 = 123       | srhActiveSegme|
      | = 0           |                               | ntIPv...=TBD16|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Length = 48   |   2001:db8::1                                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |

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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      ...      |   2001:db8::2                                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      ...      |   2001:db8::3                                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      ...      | srhFlagsIPv6  |        srhTagIPv6 = 456       |
      |               | = 0           |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | srhActiveSegme| Length = 32   |   2001:db8::4                 |
      | ntIPv...=TBD15|               |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      ...                      |   2001:db8::5                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      ...                      |srhFlagsIPv6=0 | srhTagIPv6... |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | = 789         |         srhActiveSegment      | Length = 16   |
      |               |         IPv6Type=TBD16        |               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        2001:db8::6 ...                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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

        Figure 4: Data Set Encoding Format for Segment List Section

A.1.3.  Template Record and Data Set with SRH Section

   With encoding in Figure 5, the examples in Table 3 are represented
   with the following IEs: “=>” is used to indicate which IE is mapped
   to a given information.

   *  SR Flags + SR Tag + Segment List => srhIPv6Section (TBD8)

   *  Active Segment Type => srhIPv6ActiveSegmentType (TBD9)

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          SET ID = 2           |       Length = 16             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Template ID = 258        |      Field Count = 2          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0| srhActiveSegmentIP... = TBD9|      Field Length = 1         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|    srhIPv6Section = TBD8    |      Field Length = 0xFFFF    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Figure 5: Template Record with SRH Section Encoding Format

   In this example, the Template ID is 258, which will be used in the
   Data Record.  The field length for srhIPv6Section in the Template
   Record is 0xFFFF, which means that the length of this IE is variable:
   its actual length is encoded in the Data Set. Note that, with an
   actual length inferior to 255 in the Data Record example, the length
   field is encoded in 8 bits (Section 7 of [RFC7011]).

   The data can be represented as follows:

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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         SET ID = 258          |           Length = (*)        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        srhIPv6ActiveSegmentType = TBD16       |  Length = (*) |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Next Header   |  Hdr Ext Len  | Routing Type  | Segments Left |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Last Entry   |     Flags     |              Tag              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Segment List[0] 2001:db8::1                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Segment List[1] 2001:db8::2                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Segment List[2] 2001:db8::3                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~          Optional Type Length Value objects (variable)        ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        srhIPv6ActiveSegmentType = TBD16       |    0xFFFF     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Next Header   |  Hdr Ext Len  | Routing Type  | Segments Left |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Last Entry   |     Flags     |              Tag              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Segment List[0] 2001:db8::4                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |

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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Segment List[1] 2001:db8::5                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~          Optional Type Length Value objects (variable)        ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        srhIPv6ActiveSegmentType = TBD16       |    0xFFFF     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Next Header   |  Hdr Ext Len  | Routing Type  | Segments Left |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Last Entry   |     Flags     |              Tag              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Segment List[0] 2001:db8::6                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~          Optional Type Length Value objects (variable)        ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

             Figure 6: Data Set Encoding Format for SRH Section

   (*) The Length must be calculated to include the optional Type Length
   Value objects.

A.2.  Options Template Record and Data Set for SRv6 Segment End Point
      behavior and Locator Length

   This appendix provides an SRv6 EndPoint Bevahior Options Template
   example, for the values presented in Table 4.  In the Options
   Template case, the srhActiveSegmentIPv6 Information Element is a
   Scope field

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      +-------+-------------+-------------------------+----------------+
      | Entry | SRH End     | SRH End                 | SRH Segment    |
      | Nr    | Point IPv6  | Point Behavior          | Locator Length |
      +-------+-------------+-------------------------+----------------+
      | 1     | 2001:db8::1 | End [1]                 | 48             |
      +-------+-------------+-------------------------+----------------+
      | 2     | 2001:db8::4 | End with NEXT-CSID [43] | 48             |
      +-------+-------------+-------------------------+----------------+
      | 3     | 2001:db8::6 | End.DX6 [16]            | 48             |
      +-------+-------------+-------------------------+----------------+

        Table 4: Three Observed SRv6 Segment End Point Behaviors

         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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Set ID = 3            |          Length = 24          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       Template ID 259         |        Field Count = 3        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Scope Field Count = 1     |0| srhActiveSegmentIPv6 = TBD4 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Scope 1 Field Length = 4    |0|srhSegmentEndpointBeh..=TBD11|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       Field Length = 1        |0|srhSegmentIPv6Lo.Length=TBD10|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       Field Length = 4        |           Padding             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Figure 7: Template Record with SRH Section Encoding Format

   In this example, the Template ID is 259, which will be used in the
   Data Record.

   The data set is represented as follows:

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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         SET ID = 259          |           Length = 28         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         2001:db8::1                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             End [1]           |               48              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        2001:db8::4                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    End with NEXT-CSID [43]    |               48              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         2001:db8::6                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             End.DX6 [16]      |               48              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 8: Data Set Encoding Format for SRH Section

   (*) The Length must be calculated to include the optional Type Length
   Value objects.

Authors' Addresses

   Thomas Graf
   Swisscom
   Binzring 17
   CH-8045 Zurich
   Switzerland
   Email: thomas.graf@swisscom.com

   Benoit Claise
   Huawei
   Email: benoit.claise@huawei.com

   Pierre Francois
   INSA-Lyon
   Lyon
   France
   Email: pierre.francois@insa-lyon.fr

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