OPSAWG                                                            Y. Liu
Internet-Draft                                                       ZTE
Intended status: Standards Track                                   Z. Li
Expires: 4 September 2025                                         Y. Liu
                                                            China Mobile
                                                                  C. Lin
                                                    New H3C Technologies
                                                            3 March 2025


         Export of Path Segment Identifier Information in IPFIX
                 draft-liu-opsawg-ipfix-path-segment-01

Abstract

   This document introduces a new IPFIX Information Element to identify
   the Path Segment Identifier(PSID) in the SRH for SRv6 path
   identification purpose.

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
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   This Internet-Draft will expire on 4 September 2025.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.











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   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
   extracted from this document must include Revised BSD License text as
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   4.  Operational Considerations  . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   [RFC9487] introduces new IP Flow Information Export (IPFIX)
   Information Elements (IEs) to identify a set of information related
   to Segment Routing over IPv6 (SRv6).  For the SRv6 segment list, two
   IPFIX IPv6 SRH IEs are defined in [RFC9487], srhSegmentIPv6BasicList
   (elementID:496) and srhSegmentIPv6ListSection (elementID:497), both
   encoding the Segment List in the SRH starting from Segment List[0].

   When monitoring a traffic flow in an SR network, a typical use case
   is to answer the following questions:

   *  How many packets are steered into an certain SR path ?

   *  Which SR Policy or candidate path or segment list this SR path
      belongs to ?

   To answer these questions, when exporting the flow record using IPFIX
   messages, the SR path information needs to be included.

   An SRv6 path could be identified by the content of a segment list in
   IPFIX using IE496 or IE497, but the segment list is not always the
   best key identifier due to the following reasons:

   *  When a segment list contains many SIDs, the size of IPFIX message
      (especially the data record) would be large, making the collecting
      and analyzing of flow records inefficient.



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   *  In the cases that different SRv6 policies use the same segment
      list for traffic steering, it is difficult to distinguish the
      traffic flow of different SRv6 policies.

   *  An SRv6 path may not be identified by the segment list carried by
      the SRH in reduced mode [RFC8754] as the first SID is not present
      in the SRH.

   Path Segment is a type of Segment Routing (SR) segment, and a Path
   Segment Identifier (PSID) is used to identify an SR path.  PSID in
   SRv6 networks is defined in [I-D.ietf-spring-srv6-path-segment].  In
   SRH, the PSID appears as the last entry in the segment list.

   This document introduces a new IPFIX Information Element to identify
   the Path Segment Identifier(PSID) in the SRH for SRv6 path
   identification purpose.

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

   *  Metering Process

   *  Template Record

   *  Data Record

   *  Collector

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

   *  Segment Routing (SR)

   *  Segment List




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   *  SRv6

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

   *  SRH

   *  Last Entry

3.  IANA Considerations

   This document requests IANA to create one new IE under the "IPFIX
   Information Elements" registry [RFC7012] available at [IANA-IPFIX].

                   +-------+--------------------------------+
                   |Element|              Name              |
                   |   ID  |                                |
                   +-------+--------------------------------+
                   | TBD1  |      srhPSID                   |
                   +-------+--------------------------------+


   ElementID:  TBD1
   Name:  srhPSID
   Abstract Data Type:  ipv6Address
   Data Type Semantics:  default
   Description:  The 128-bit IPv6 address that represents an SRv6 PSID.
   Additional Information:  Specified in Section 3 of
      [I-D.ietf-spring-srv6-path-segment].
   Reference:  This document

4.  Operational Considerations

   As specified in [I-D.ietf-spring-srv6-path-segment], the P-flag in
   the SRH is set to indicate the presence of PSID.  In order to
   generate Flow Records with PSID included, the metering process MUST
   understand the P-flag.  Only when the P-flag is set SHOULD the
   metering process capture the last entry in the SRH to get the PSID.
   If the P-flag in the packet is unset, when the srhPSID appears in the
   template record, the corresponding field in the data record is
   RECOMMENDED to set to all zero.

   After decoding the IPFIX messages to get the flow record with PSID
   included in it at the collector, the collector might process the flow
   record locally or send it to an analyzer for further analysis
   purpose.  In order to recognize the SR path, the analysis node SHOULD
   be aware of which SR path the PSID identifies.  How to get this
   information the is out of the scope of this document.




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   The IE srhPSID can be used together with srhSegmentIPv6BasicList or
   srhSegmentIPv6ListSection.  As in [I-D.ietf-spring-srv6-path-segment]
   section 3, the PSID allocate metering is depending on the use case,
   including:

   *  each segment list may have its own PSID with different value;

   *  the same PSID may be used for some or all the segment list under a
      Candidate path;

   *  the same PSID may be used for some or all Candidate Path within an
      SRv6 policy.

   So if srhPSID and srhSegmentIPv6BasicList/
   srhSegmentIPv6ListSection appear together, the srhPSID MAY be used to
   identify an SR Policy or candidate path, and the information carried
   in srhSegmentIPv6BasicList/srhSegmentIPv6ListSection shows the
   detailed segment list belonging to this SR Policy or candidate path.
   This document does not limit how to use srhPSID and the detail is out
   of scope.

5.  Security Considerations

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

   Other security considerations for SRv6 PSID described in
   [I-D.ietf-spring-srv6-path-segment] apply to this document.

6.  References

6.1.  Normative References

   [I-D.ietf-spring-srv6-path-segment]
              Li, C., Cheng, W., Chen, M., Dhody, D., and Y. Zhu, "Path
              Segment Identifier (PSID) in SRv6 (Segment Routing in
              IPv6)", Work in Progress, Internet-Draft, draft-ietf-
              spring-srv6-path-segment-11, 18 September 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-spring-
              srv6-path-segment-11>.

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







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   [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>.

   [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>.

   [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>.

   [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>.

   [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>.

6.2.  Informative References

   [RFC9487]  Graf, T., Claise, B., and P. Francois, "Export of Segment
              Routing over IPv6 Information in IP Flow Information
              Export (IPFIX)", RFC 9487, DOI 10.17487/RFC9487, November
              2023, <https://www.rfc-editor.org/info/rfc9487>.

Authors' Addresses

   Yao Liu
   ZTE
   Nanjing
   China
   Email: liu.yao71@zte.com.cn


   Zhenqiang Li
   China Mobile



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   Email: lizhenqiang@chinamobile.com


   Yisong Liu
   China Mobile
   Email: liuyisong@chinamobile.com


   Changwang Lin
   New H3C Technologies
   Email: linchangwang.04414@h3c.com








































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