Network Working Group                                            T. Graf
Internet-Draft                                                  Swisscom
Intended status: Standards Track                               B. Claise
Expires: 15 May 2023                                              Huawei
                                                             P. Francois
                                                               INSA-Lyon
                                                        11 November 2022


           Export of Segment Routing over IPv6 Information in
                   IP Flow Information Export (IPFIX)
                  draft-ietf-opsawg-ipfix-srv6-srh-04

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 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 15 May 2023.

Copyright Notice

   Copyright (c) 2022 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.  IPFIX Information Elements  . . . . . . . . . . . . . . . . .   4
   4.  Sample Use Cases  . . . . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     5.1.  srhFlagsIPv6  . . . . . . . . . . . . . . . . . . . . . .   8
     5.2.  srhTagIPv6  . . . . . . . . . . . . . . . . . . . . . . .   8
     5.3.  srhSegmentIPv6  . . . . . . . . . . . . . . . . . . . . .   8
     5.4.  srhActiveSegmentIPv6  . . . . . . . . . . . . . . . . . .   9
     5.5.  srhSegmentIPv6BasicList . . . . . . . . . . . . . . . . .   9
     5.6.  srhSegmentIPv6ListSection . . . . . . . . . . . . . . . .  10
     5.7.  srhSegmentIPv6sLeft . . . . . . . . . . . . . . . . . . .  10
     5.8.  srhSectionIPv6  . . . . . . . . . . . . . . . . . . . . .  10
     5.9.  srhActiveSegmentIPv6Type  . . . . . . . . . . . . . . . .  11
       5.9.1.  IPFIX IPv6 SRH Segment Type Subregistry . . . . . . .  11
     5.10. srhSegmentLocatorLength . . . . . . . . . . . . . . . . .  12
     5.11. srhSegmentEndpointBehavior  . . . . . . . . . . . . . . .  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.  Implementation Status . . . . . . . . . . . . . . . . . . . .  14
     7.1.  FD.io VPP . . . . . . . . . . . . . . . . . . . . . . . .  14
     7.2.  Huawei VRP  . . . . . . . . . . . . . . . . . . . . . . .  15
     7.3.  Pmacct Data Collection  . . . . . . . . . . . . . . . . .  15
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  15
     10.2.  Informative References . . . . . . . . . . . . . . . . .  16
   Appendix A.  IPFIX Encoding Examples  . . . . . . . . . . . . . .  18
     A.1.  Three Observed SRH Headers and their Routing Protocol . .  18
       A.1.1.  Template Record and Data Set with Segment Basic
               List  . . . . . . . . . . . . . . . . . . . . . . . .  18
       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
   [I-D.ietf-lsr-isis-srv6-extensions] and BGP Prefix Segment
   Identifiers(Prefix-SIDs) [RFC9252] 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 are defined in [RFC8986] and describe
   how packets should be processed by SRv6 Segment Endpoint Nodes.

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

   These IEs are used to export SRv6 active segment and its control
   plane protocol, the SRv6 segment list, the next SRv6 node and its
   type, and then 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.  IPFIX Information Elements

   This section specifies the new SRv6 IPFIX 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 an 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
      Exposes the SRH Segment List as defined in Section 2 of [RFC8754]
      as series of n octets in IPFIX.

   srhSegmentIPv6sLeft
      8-bit unsigned integer defining the number of segments remaining
      to reach the end of the segment list.

   srhSectionIPv6
      Exposes the SRH and its TLVs as specified in Section 2 of
      [RFC8754] as series of n octets in IPFIX.

   srhActiveSegmentIPv6Type
      Name of the routing protocol or PCEP extension from where the
      active SRv6 segment has been learned from.

   srhSegmentLocatorLength
      The number of significant bits.  Together with srhSegmentIPv6 it
      enables the calculation of the SRv6 Locator.

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

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



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4.  Sample Use Cases

   The IPFIX IEs srhSegmentIPv6BasicList(TBD5) or
   srhSegmentIPv6ListSection (TBD6), srhActiveSegmentIPv6 (TBD4),
   srhSegmentIPv6sLeft (TBD7), srhActiveSegmentIPv6Type(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

   This document requests IANA to create new IEs (see table 1) and three
   new subregistries called "IPFIX IPv6 SRH Flags" (table 2), "IPFIX
   IPv6 SRH Segment Type" (table 3), and "IPFIX SRv6 Endpoint Behavior"
   (table 4) under the "IPFIX Information Elements" registry [RFC7012]
   available at [IANA-IPFIX].





















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        +-------+----------------------------+
        |Element|           Name             |
        |   ID  |                            |
        +-------+----------------------------+
        | TBD1  | srhFlagsIPv6               |
        |       |                            |
        +-------+----------------------------+
        | TBD2  | srhTagIPv6                 |
        |       |                            |
        +-------+----------------------------+
        | TBD3  | srhSegmentIPv6             |
        |       |                            |
        +-------+----------------------------+
        | TBD4  | srhActiveSegmentIPv6       |
        |       |                            |
        +-------+----------------------------+
        | TBD5  | srhSegmentIPv6BasicList    |
        |       |                            |
        +-------+----------------------------+
        | TBD6  | srhSegmentIPv6ListSection  |
        |       |                            |
        +-------+----------------------------+
        | TBD7  | srhSegmentIPv6sLeft        |
        |       |                            |
        +-------+----------------------------+
        | TBD8  | srhSectionIPv6             |
        |       |                            |
        +-------+----------------------------+
        | TBD9  | srhActiveSegmentIPv6Type   |
        |       |                            |
        +-------+----------------------------+
        | TBD10 | srhSegmentLocatorLength    |
        |       |                            |
        +-------+----------------------------+
        | TBD11 | srhSegmentEndpointBehavior |
        |       |                            |
        +-------+----------------------------+

     Table 1: New IEs in the "IPFIX Information Elements" registry

   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





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5.1.  srhFlagsIPv6

   Name:  srhFlagsIPv6

   ElementID:  TBD1

   Description:  The 8-bit flags defined in the SRH.  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:  RFC8754.  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

   Reference:  [RFC-to-be]

5.2.  srhTagIPv6

   Name:  srhTagIPv6

   ElementID:  TBD2

   Description:  The 16-bit tag field defined in the SRH that marks 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:  RFC8754

   Reference:  [RFC-to-be]

5.3.  srhSegmentIPv6

   Name:  srhSegmentIPv6

   ElementID:  TBD3

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




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   Abstract Data Type:  ipv6address

   Data Type Semantics:  default

   Additional Information:  RFC8754

   Reference:  [RFC-to-be]

5.4.  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:  RFC8754

   Reference:  [RFC-to-be]

5.5.  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 described 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:  RFC8754

   Reference:  [RFC-to-be]





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5.6.  srhSegmentIPv6ListSection

   Name:  srhSegmentIPv6ListSection

   ElementID:  TBD6

   Description:  The SRH Segment List as defined in section 2 of
      [RFC8754] as series of n octets.

   Abstract Data Type:  octetArray

   Data Type Semantics:  default

   Additional Information:  RFC8754

   Reference:  [RFC-to-be]

5.7.  srhSegmentIPv6sLeft

   Name:  srhSegmentIPv6sLeft

   ElementID:  TBD7

   Description:  The 8-bit unsigned integer defining the number of route
      segments remaining to reach the end of the segment list.

   Abstract Data Type:  unsigned8

   Data Type Semantics:  quantity

   Additional Information:  RFC8754

   Reference:  [RFC-to-be]

5.8.  srhSectionIPv6

   Name:  srhSectionIPv6

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

   Abstract Data Type:  octetArray

   Data Type Semantics:  default

   Additional Information:  RFC8754

   Reference:  [RFC-to-be]



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5.9.  srhActiveSegmentIPv6Type

   Name:  srhActiveSegmentIPv6Type

   ElementID:  TBD9

   Description:  The name 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:  [RFC-to-be]

   Reference:  [RFC-to-be]

5.9.1.  IPFIX IPv6 SRH Segment Type Subregistry

   Initial values in the registry are defined by the table below.  New
   assignments of values will be administered by IANA and are subject to
   Expert Review [RFC8126].  Experts need to check definitions of new
   values for completeness, accuracy, and redundancy.


























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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="            |
  |       | Segment Routing    | I-D.ietf-lsr-isis-srv6-extensions"/>  |
  +-------+--------------------+---------------------------------------+
  | TBD17 | BGP Segment        | [RFC-to-be],                          |
  |       | Routing Prefix-SID | <xref target="RFC9252"/>              |
  +-------+--------------------+---------------------------------------+

          Table 3: "IPFIX IPv6 SRH Segment type" subregistry


5.10.  srhSegmentLocatorLength

   Name:  srhSegmentLocatorLength

   ElementID:  TBD10

   Description:  The number of significant bits and together with
      srhSegmentIPv6 enables the calculation of the SRv6 Locator.

   Abstract Data Type:  unsigned8

   Data Type Semantics:  default

   Additional Information:  RFC8986 Section 3.1

   Reference:  [RFC-to-be]

5.11.  srhSegmentEndpointBehavior

   Name:  srhSegmentEndpointBehavior

   ElementID:  TBD11




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   Description:  The 16-bit SRv6 Endpoint behavior.  Assigned values and
      their meanings are provided in the "SRV6 Endpoint Behavior" IANA
      registry [IANA-IPFIX].

   Abstract Data Type:  unsigned16

   Data Type Semantics:  identifier

   Additional Information:  RFC8986 Section 4.  See the assignments in
      the "SRV6 Endpoint Behavior" IANA registry at
      https://www.iana.org/assignments/segment-routing/segment-
      routing.xhtml#srv6-endpoint-behaviors

   Reference:  [RFC-to-be]

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
   addresses according 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.






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6.2.  Compressed SRv6 Segment List Decomposition

   The SRv6 segment list in the IPFIX IEs srhSegmentIPv6BasicList and
   srhSegmentIPv6ListSection could contain compressed-SID containers as
   described in [I-D.ietf-spring-srv6-srh-compression].  The SID
   endpoint behaviors described in section 4 of
   [I-D.ietf-spring-srv6-srh-compression] determine wherever the segment
   list is compressed or not.  The SID Locator as described in section
   3.1 [RFC8986], determines the common most significant bits.

6.3.  Multiple Segment Routing Headers

   [RFC8200] describes the support of multiple extension headers in one
   IPv6 packet.  Allowing the use of multiple SRH per SRv6 packet.  The
   export of the same IE multiple times in one data record and related
   template 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 active SRH.

7.  Implementation Status

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

7.1.  FD.io VPP

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

   *  srhActiveSegmentIPv6

   *  srhSegmentEndpointBehavior

   *  srhSegmentIPv6sLeft

   *  srhFlagsIPv6

   *  srhTagIPv6

   *  srhSegmentIPv6ListSection

   *  srhSegmentIPv6BasicList

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






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7.2.  Huawei VRP

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

   *  srhActiveSegmentIPv6

   *  srhSegmentIPv6sLeft

   *  srhFlagsIPv6

   *  srhTagIPv6

   *  srhSegmentIPv6ListSection

   The implementation was validated at the IETF 115 hackathon.

7.3.  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.

8.  Acknowledgements

   The authors would like to thank Yao Liu, Eduard Vasilenko, Bruno
   Decraene and Mohamed Boucadair for their review and valuable
   comments, and Paolo Lucente and Alex Huang Feng for the
   implementation and validation.

9.  Security Considerations

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

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>.




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   [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>.

   [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-isis-srv6-extensions]
              Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and
              Z. Hu, "IS-IS Extensions to Support Segment Routing over
              IPv6 Dataplane", Work in Progress, Internet-Draft, draft-
              ietf-lsr-isis-srv6-extensions-18, 20 October 2021,
              <https://www.ietf.org/archive/id/draft-ietf-lsr-isis-srv6-
              extensions-18.txt>.

   [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-08, 14 September
              2022, <https://www.ietf.org/archive/id/draft-ietf-lsr-
              ospfv3-srv6-extensions-08.txt>.





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   [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-ipv6-15, 23
              October 2022, <https://www.ietf.org/archive/id/draft-ietf-
              pce-segment-routing-ipv6-15.txt>.

   [I-D.ietf-spring-srv6-srh-compression]
              Cheng, W., Filsfils, C., Li, Z., Decraene, B., Cai, D.,
              Voyer, D., Clad, F., Zadok, S., Guichard, N., Aihua, L.,
              Raszuk, R., and C. Li, "Compressed SRv6 Segment List
              Encoding in SRH", Work in Progress, Internet-Draft, draft-
              ietf-spring-srv6-srh-compression-02, 11 July 2022,
              <https://www.ietf.org/archive/id/draft-ietf-spring-srv6-
              srh-compression-02.txt>.

   [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/insa-unyte/vpp>.

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

   [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>.

   [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>.

   [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>.






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   [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>.

   [RFC9252]  Dawra, G., Ed., Talaulikar, K., Ed., Raszuk, R., Decraene,
              B., Zhuang, S., and J. Rabadan, "BGP Overlay Services
              Based on Segment Routing over IPv6 (SRv6)", RFC 9252,
              DOI 10.17487/RFC9252, July 2022,
              <https://www.rfc-editor.org/info/rfc9252>.

   [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>.

Appendix A.  IPFIX Encoding Examples

   This appendix represents three different encodings for the newly
   introduced IEs, for the example values in Table 5.  The three
   different encodings use the following IEs, respectively:
   srhSegmentIPv6BasicList, srhSegmentIPv6ListSection, and
   srhSectionIPv6.

      +-----+------+-----+----------------+--------------------------|
      | 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 5: three observed SRH headers and their 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 5 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 => srhActiveSegmentIPv6Type (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


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



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      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             Segment List[1] = 2001:db8::2                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             Segment List[2] = 2001:db8::3                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | srhFlagsIPv6  |        srhTagIPv6 = 456       | srhActiveSegme|
      | = 0           |                               | ntIPv...=TBD16|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      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|



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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      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 5 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 => srhActiveSegmentIPv6Type (TBD9)

   *  Segment List => srhSegmentIPv6ListSection (TBD6)




















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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 = 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 (see https://www.rfc-
   editor.org/rfc/rfc7011.html#section-7)

   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                                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      ...      |   2001:db8::2                                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      ...      |   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 5 are represented
   with the following IEs: "=>" is used to indicate which IE is mapped
   to a given information.

   *  SR Flags + SR Tag + Segment List => srhSectionIPv6 (TBD8)

   *  Active Segment Type => srhActiveSegmentIPv6Type (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|    srhSectionIPv6 = 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 srhSectionIPv6 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 (see https://www.rfc-editor.org/rfc/
   rfc7011.html#section-7)

   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 = 258          |           Length = (*)        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        srhActiveSegmentIPv6Type = TBD16       |  Length = (*) |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Next Header   |  Hdr Ext Len  | Routing Type  | Segments Left |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Last Entry   |     Flags     |              Tag              |



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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Segment List[0] 2001:db8::1                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Segment List[1] 2001:db8::2                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Segment List[2] 2001:db8::3                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~          Optional Type Length Value objects (variable)        ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        srhActiveSegmentIPv6Type = TBD16       |    0xFFFF     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Next Header   |  Hdr Ext Len  | Routing Type  | Segments Left |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Last Entry   |     Flags     |              Tag              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Segment List[0] 2001:db8::4                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Segment List[1] 2001:db8::5                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              ...                              |



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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~          Optional Type Length Value objects (variable)        ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        srhActiveSegmentIPv6Type = 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 12.  In the Options
   Template case, the srhActiveSegmentIPv6 Information Element is a
   Scope field

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

        Figure 7: three observed SRv6 Segment End Point Behaviors





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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 = 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|srhSegmentLocatorLength=TBD10|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       Field Length = 4        |           Padding             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


          Figure 8: 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:

       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 9: Data Set Encoding Format for SRH Section






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   (*) 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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