Internet DRAFT - draft-boucadair-sfc-oam-packet
draft-boucadair-sfc-oam-packet
sfc M. Boucadair
Internet-Draft Orange
Updates: 8300 (if approved) 24 February 2022
Intended status: Standards Track
Expires: 28 August 2022
An Update to the OAM Behavior in the Network Service Header (NSH)
draft-boucadair-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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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 28 August 2022.
Copyright Notice
Copyright (c) 2022 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 . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 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 elements that is capable of
generating NSH OAM packets. An SFC data plane element may behave
as an OAM control element.
OAM data: refers to an OAM command (e.g., Connectivity Verification
and Continuity Checks [RFC7276]), any data that influences how to
execute a companion OAM command (e.g., identity of a terminating
Service Function (SF)), the output data of an OAM command, 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 SFC OAM packet. Such a packet
is any NSH-encapasulated packet that exclusively includes OAM
data. An 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 an ultimate
target of an SFC OAM packet that triggers a response (e.g., a
sepcific SFC-aware SF, the last SFF of an SFP).
The O bit MUST be set for SFC 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 SFC OAM packets even if some OAM data (e.g., record route) is
also supplied in the packet.
When an 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 SFC 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 SFC OAM packet MAY include OAM data in both Context Headers and
the inner packet. The processing (including the order) of the 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 SFC OAM packets unmodified to the next element in the
chain. Forwarding SFC 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 SFC 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 SFC 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].
Data icnluded in an SFC OAM packet SHOULD be integrity-protected
[RFC9145].
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6. Acknowledgements
Thanks to Jim Guichard, Greg Mirsky, and Joel Halpern 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 Metadata Type 2
Variable-Length Context Headers", Work in Progress,
Internet-Draft, draft-ietf-sfc-nsh-tlv-13, 26 January
2022, <https://www.ietf.org/archive/id/draft-ietf-sfc-nsh-
tlv-13.txt>.
[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>.
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[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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