Internet DRAFT - draft-ietf-sfc-oam-packet
draft-ietf-sfc-oam-packet
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.
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This Internet-Draft will expire on 27 September 2023.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Please review these documents carefully, as they describe your rights
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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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