sfc                                                         M. Boucadair
Internet-Draft                                                    Orange
Updates: 8300 (if approved)                                25 April 2022
Intended status: Standards Track
Expires: 27 October 2022


      OAM Packet and Behavior in the Network Service Header (NSH)
                      draft-ietf-sfc-oam-packet-01

Abstract

   This document clarifies an ambiguity in the Network Service Header
   (NSH) specification related to the handling of O bit.  In particular,
   this document clarifies the meaning of "OAM packet".

   This document updates RFC 8300.

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 27 October 2022.

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
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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Revised BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  An Update to RFC8300  . . . . . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   This document clarifies an ambiguity related to the definition of
   Operations, Administration, and Maintenance (OAM) packet discussed in
   [RFC8300].

   The processing of the O bit in the Network Service Header (NSH) must
   follow the updated behavior specified in Section 3.

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 [RFC7665] and
   [RFC8300].

   The document defines the following terms:

   SFC data plane element:  refers to SFC-aware SF, SFF, SFC Proxy, or
      Classifier as defined in the SFC data plane architecture [RFC7665]
      and further refined in [RFC8300].

   OAM control element:  an NSH-aware element that is capable of
      generating NSH OAM packets.  An SFC data plane element may behave
      as an OAM control element.

   SFC OAM data:  refers to an OAM request (e.g., Connectivity
      Verification and Continuity Checks [RFC7276]), any data that
      influences how to execute a companion OAM request (e.g., identity
      of a terminating Service Function (SF)), the output data of an OAM
      request, and any combination thereof.



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   User data:  refers to user packets cited in Section 5.7 of [RFC7665].

3.  An Update to RFC8300

   This document updates Section 2.2 of [RFC8300] as follows:

OLD:

   O bit:  Setting this bit indicates an OAM packet (see [RFC6291]).
      The actual format and processing of SFC OAM packets is outside the
      scope of this specification (for example, see [SFC-OAM-FRAMEWORK]
      for one approach).

      The O bit MUST be set for OAM packets and MUST NOT be set for
      non-OAM packets.  The O bit MUST NOT be modified along the SFP.

      SF/SFF/SFC Proxy/Classifier implementations that do not support
      SFC OAM procedures SHOULD discard packets with O bit set, but MAY
      support a configurable parameter to enable forwarding received SFC
      OAM packets unmodified to the next element in the chain.
      Forwarding OAM packets unmodified by SFC elements that do not
      support SFC OAM procedures may be acceptable for a subset of OAM
      functions, but it can result in unexpected outcomes for others;
      thus, it is recommended to analyze the impact of forwarding an OAM
      packet for all OAM functions prior to enabling this behavior.  The
      configurable parameter MUST be disabled by default.

NEW:

   O bit:  Setting this bit indicates an NSH OAM packet.  Such a packet
      is any NSH-encapsulated packet that exclusively includes SFC OAM
      data.  SFC OAM data can be included in the Fixed-Length Context
      Header, optional Context Headers, and/or the inner packet.

      The O bit is typically set by an OAM controller or a final
      destination of an NSH OAM packet that triggers a response (e.g., a
      specific SFC-aware SF, the last SFF of an SFP).

      The O bit MUST be set for NSH OAM packets and MUST NOT be set for
      non-OAM packets.  The O bit MUST NOT be modified along the SFP.

      NSH-encapsulated packets that include user data are not considered
      as NSH OAM packets even if some SFC OAM data (e.g., record route)
      is also supplied in the packet.

      When SFC OAM data is included in the inner packet, the Next
      Protocol field is set to reflect the structure of that inner OAM
      packet.  The setting and processing of the O bit neither assumes



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      nor expects detailed analysis of the content of any inner IP
      packet carried by the NSH.  As such, SFFs, SFC-aware SFs, and SFC
      Proxies SHOULD discard any NSH packets with the O bit set and Next
      Protocol set to something that is not itself an OAM protocol.
      This includes discarding the packet when the O bit is set and the
      Next Protocol is set to 0x01 (IPv4), 0x02 (IPv6), 0x03 (MPLS), or
      0x05 (Ethernet).

      An NSH OAM packet MAY include optional Context Headers (e.g., a
      subscriber identifier [RFC8979] or a flow identifier
      [I-D.ietf-sfc-nsh-tlv]) that are used to influence the processing
      of the packet by SFC data plane elements.

      An NSH OAM packet MAY include SFC OAM data in both Context Headers
      and the inner packet.  The processing (including the order) of the
      SFC OAM data SHOULD be specified in the relevant OAM or Context
      Header specification.

      SFC-aware SF/SFF/SFC Proxy/Classifier implementations that do not
      support SFC OAM procedures SHOULD discard packets with O bit set,
      but MAY support a configurable parameter to enable forwarding
      received NSH OAM packets unmodified to the next element in the
      chain.  Forwarding NSH OAM packets unmodified by SFC data plane
      elements that do not support SFC OAM procedures may be acceptable
      for a subset of OAM functions, but it can result in unexpected
      outcomes for others; thus, it is recommended to analyze the impact
      of forwarding an NSH OAM packet for all OAM functions prior to
      enabling this behavior.  The configurable parameter MUST be
      disabled by default.

      The actual format and additional processing of NSH OAM packets is
      outside the scope of this specification.


4.  IANA Considerations

   This document does not make any request to IANA.

5.  Security Considerations

   Data plane SFC-related security considerations, including privacy,
   are discussed in Section 6 of [RFC7665] and Section 8 of [RFC8300].
   Additional security considerations related to SFC OAM are discussed
   in Section 9 of [RFC8924].

   Any data included in an NSH OAM packet SHOULD be integrity-protected
   [RFC9145].




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6.  Acknowledgments

   Thanks to Jim Guichard, Greg Mirsky, Joel Halpern, Christian
   Jacquenet, Dirk von-Hugo, Carlos Pignataro, and Frank Brockners for
   the comments.

7.  References

7.1.  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>.

   [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>.

   [RFC8300]  Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed.,
              "Network Service Header (NSH)", RFC 8300,
              DOI 10.17487/RFC8300, January 2018,
              <https://www.rfc-editor.org/info/rfc8300>.

   [RFC9145]  Boucadair, M., Reddy.K, T., and D. Wing, "Integrity
              Protection for the Network Service Header (NSH) and
              Encryption of Sensitive Context Headers", RFC 9145,
              DOI 10.17487/RFC9145, December 2021,
              <https://www.rfc-editor.org/info/rfc9145>.

7.2.  Informative References

   [I-D.ietf-sfc-nsh-tlv]
              Wei, Y., Elzur, U., Majee, S., Pignataro, C., and D. E.
              Eastlake, "Network Service Header (NSH) Metadata Type 2
              Variable-Length Context Headers", Work in Progress,
              Internet-Draft, draft-ietf-sfc-nsh-tlv-15, 20 April 2022,
              <https://www.ietf.org/archive/id/draft-ietf-sfc-nsh-tlv-
              15.txt>.

   [RFC6291]  Andersson, L., van Helvoort, H., Bonica, R., Romascanu,
              D., and S. Mansfield, "Guidelines for the Use of the "OAM"
              Acronym in the IETF", BCP 161, RFC 6291,
              DOI 10.17487/RFC6291, June 2011,
              <https://www.rfc-editor.org/info/rfc6291>.






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   [RFC7276]  Mizrahi, T., Sprecher, N., Bellagamba, E., and Y.
              Weingarten, "An Overview of Operations, Administration,
              and Maintenance (OAM) Tools", RFC 7276,
              DOI 10.17487/RFC7276, June 2014,
              <https://www.rfc-editor.org/info/rfc7276>.

   [RFC7665]  Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
              Chaining (SFC) Architecture", RFC 7665,
              DOI 10.17487/RFC7665, October 2015,
              <https://www.rfc-editor.org/info/rfc7665>.

   [RFC8924]  Aldrin, S., Pignataro, C., Ed., Kumar, N., Ed., Krishnan,
              R., and A. Ghanwani, "Service Function Chaining (SFC)
              Operations, Administration, and Maintenance (OAM)
              Framework", RFC 8924, DOI 10.17487/RFC8924, October 2020,
              <https://www.rfc-editor.org/info/rfc8924>.

   [RFC8979]  Sarikaya, B., von Hugo, D., and M. Boucadair, "Subscriber
              and Performance Policy Identifier Context Headers in the
              Network Service Header (NSH)", RFC 8979,
              DOI 10.17487/RFC8979, February 2021,
              <https://www.rfc-editor.org/info/rfc8979>.

Author's Address

   Mohamed Boucadair
   Orange
   35000 Rennes
   France
   Email: mohamed.boucadair@orange.com





















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