Operations, Administration, and Maintenance (OAM) Packet and Behavior in the Network Service Header (NSH)
draft-ietf-sfc-oam-packet-03

sfc                                                         M. Boucadair
Internet-Draft                                                    Orange
Updates: 8300 (if approved)                                26 March 2023
Intended status: Standards Track                                        
Expires: 27 September 2023

      OAM Packet and Behavior in the Network Service Header (NSH)
                      draft-ietf-sfc-oam-packet-03

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 September 2023.

Copyright Notice

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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 . . . . . . . . . . . . . . . . . . .   5
   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 Service Function (SF),
      Service Function Forwarder (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

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

   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.

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         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 nor expects detailed analysis of the content of any
         inner IP packet carried by the NSH.  In order to prevent non
         deterministic behaviors, SFC data plane elements MAY support a
         configuration parameter to filter valid Next Protocol values in
         NSH OAM packets.  Absent explicit configuration, 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 [RFC9263])
         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 the
         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.

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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].

6.  Acknowledgments

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

   Thanks to Barry Leiba for the art directorate review and Russ Housley
   for the security directorate review.

   Thanks to Alvaro Retana and Robert Wilton for the IESG review.

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

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   [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>.

   [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>.

   [RFC9263]  Wei, Y., Ed., Elzur, U., Majee, S., Pignataro, C., and D.
              Eastlake 3rd, "Network Service Header (NSH) Metadata Type
              2 Variable-Length Context Headers", RFC 9263,
              DOI 10.17487/RFC9263, August 2022,
              <https://www.rfc-editor.org/info/rfc9263>.

Author's Address

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

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