Internet DRAFT - draft-ietf-sfc-ioam-nsh
draft-ietf-sfc-ioam-nsh
SFC F. Brockners, Ed.
Internet-Draft Cisco
Intended status: Standards Track S. Bhandari, Ed.
Expires: 6 November 2023 Thoughtspot
5 May 2023
Network Service Header (NSH) Encapsulation for In-situ OAM (IOAM) Data
draft-ietf-sfc-ioam-nsh-13
Abstract
In-situ Operations, Administration, and Maintenance (IOAM) is used
for recording and collecting operational and telemetry information
while the packet traverses a path between two points in the network.
This document outlines how IOAM data fields are encapsulated with the
Network Service Header (NSH).
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
Task Force (IETF). Note that other groups may also distribute
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 6 November 2023.
Copyright Notice
Copyright (c) 2023 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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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. IOAM encapsulation with NSH . . . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Appendix A. Discussion of the IOAM encapsulation approach . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
IOAM, as defined in [RFC9197], is used to record and collect OAM
information while the packet traverses a particular network domain.
The term "in-situ" refers to the fact that the OAM data is added to
the data packets rather than is being sent within packets
specifically dedicated to OAM. This document defines how IOAM data
fields are transported as part of the Network Service Header (NSH)
[RFC8300] encapsulation for the Service Function Chaining (SFC)
Architecture [RFC7665]. The IOAM-Data-Fields are defined in
[RFC9197].
2. Conventions
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.
Abbreviations used in this document:
IOAM: In-situ Operations, Administration, and Maintenance
NSH: Network Service Header
OAM: Operations, Administration, and Maintenance
SFC: Service Function Chaining
TLV: Type, Length, Value
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3. IOAM encapsulation with NSH
The NSH is defined in [RFC8300]. IOAM-Data-Fields are carried as NSH
payload using a next protocol header which follows the NSH headers.
An IOAM header is added containing the IOAM-Data-Fields. The IOAM-
Data-Fields MUST follow the definitions corresponding to IOAM-Option-
Types (e.g., see Section 4 of [RFC9197] and Section 3.2 of
[RFC9326]). In an administrative domain where IOAM is used,
insertion of the IOAM header in NSH is enabled at the NSH tunnel
endpoints, which also serve as IOAM encapsulating/decapsulating nodes
by means of configuration. The operator MUST ensure that SFC-aware
nodes along the Service Function Path support IOAM, otherwise packets
might be dropped (see Section 3 further below, as well as [RFC8300]
Section 2.2). The IOAM transit nodes (e.g., an Service Function
Forwarder) MUST process all the IOAM headers that are relevant based
on its configuration. See [RFC9378] for a discussion of deployment
related aspects of IOAM-Data-fields.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
|Ver|O|U| TTL | Length |U|U|U|U|MD Type| NP = TBD_IOAM | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ N
| Service Path Identifier | Service Index | S
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ H
| ... | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
| IOAM-Type | IOAM HDR len | Reserved | Next Protocol | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ I
! | O
! | A
~ IOAM Option and Optional Data Space ~ M
| | |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
| |
| |
| Payload + Padding (L2/L3/...) |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The NSH header and fields are defined in [RFC8300]. The O-bit MUST
be handled following the rules in [I-D.ietf-sfc-oam-packet]. The
"NSH Next Protocol" value (referred to as "NP" in the diagram above)
is TBD_IOAM.
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The IOAM related fields in NSH are defined as follows:
IOAM-Type: 8-bit field defining the IOAM-Option-Type, as defined
in the IOAM Option-Type Registry specified in [RFC9197].
IOAM HDR Len: 8-bit field that contains the length of the IOAM
header in multiples of 4-octets, including the "IOAM-Type" and
"IOAM HDR Len" fields.
Reserved bits: Reserved bits are present for future use. The
reserved bits MUST be set to 0x0 upon transmission and ignored
upon receipt.
Next Protocol: 8-bit unsigned integer that determines the type of
header following IOAM. The semantics of this field are
identical to the Next Protocol field in [RFC8300].
IOAM Option and Data Space: IOAM-Data-Fields as specified by the
IOAM-Type field. IOAM-Data-Fields are defined corresponding to
the IOAM-Option-Type (e.g., see Section 4 of [RFC9197] and
Section 3.2 of [RFC9326]) and are always aligned by 4 octets,
thus there is no padding field.
Multiple IOAM-Option-Types MAY be included within the NSH
encapsulation. For example, if a NSH encapsulation contains two
IOAM-Option-Types before a data payload, the Next Protocol field of
the first IOAM option will contain the value of TBD_IOAM, while the
Next Protocol field of the second IOAM-Option-Type will contain the
"NSH Next Protocol" number indicating the type of the data payload.
The applicability of the IOAM Active and Loopback flags [RFC9322] is
outside the scope of this document and may be specified in the
future.
In case the IOAM Incremental Trace Option-Type is used, an SFC-aware
node that serves as an IOAM transit node, needs to adjust the "IOAM
HDR Len" field accordingly, see Section 4.4 in [RFC9197].
Per Section 2.2 of [RFC8300], packets with Next Protocol values not
supported SHOULD be silently dropped by default. Thus, when a packet
with IOAM is received at an NSH based forwarding node such as an
Service Function Forwarder (SFF) that does not support the IOAM
header, it SHOULD drop the packet. The mechanism to maintain and
notify of such events are outside the scope of this document.
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4. IANA Considerations
IANA is requested to allocate a code point for IOAM in the "NSH Next
Protocol" registry (https://www.iana.org/assignments/nsh/
nsh.xhtml#next-protocol):
+---------------+---------------------+---------------+
| Next Protocol | Description | Reference |
+---------------+---------------------+---------------+
| TBD_IOAM | IOAM (Next protocol | This document |
| | is an IOAM header) | |
+---------------+---------------------+---------------+
5. Security Considerations
IOAM is considered a "per domain" feature, where the operator decides
on leveraging and configuring IOAM according to the operator's needs.
The operator needs to properly secure the IOAM domain to avoid
malicious configuration and use, which could include injecting
malicious IOAM packets into a domain. For additional IOAM related
security considerations, see Section 9 in [RFC9197]. For additional
OAM and NSH related security considerations see Section 5 of
[I-D.ietf-sfc-oam-packet].
6. Acknowledgements
The authors would like to thank Eric Vyncke, Nalini Elkins, Srihari
Raghavan, Ranganathan T S, Karthik Babu Harichandra Babu, Akshaya
Nadahalli, Stefano Previdi, Hemant Singh, Erik Nordmark, LJ Wobker,
Andrew Yourtchenko, Greg Mirsky and Mohamed Boucadair for the
comments and advice.
7. Contributors
In addition to editors listed on the title page, the following people
have contributed to this document:
Vengada Prasad Govindan
Cisco Systems, Inc.
Email: venggovi@cisco.com
Carlos Pignataro
Cisco Systems, Inc.
7200-11 Kit Creek Road
Research Triangle Park, NC 27709
United States
Email: cpignata@cisco.com
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Hannes Gredler
RtBrick Inc.
Email: hannes@rtbrick.com
John Leddy
Email: john@leddy.net
Stephen Youell
JP Morgan Chase
25 Bank Street
London E14 5JP
United Kingdom
Email: stephen.youell@jpmorgan.com
Tal Mizrahi
Huawei Network.IO Innovation Lab
Israel
Email: tal.mizrahi.phd@gmail.com
David Mozes
Email: mosesster@gmail.com
Petr Lapukhov
Facebook
1 Hacker Way
Menlo Park, CA 94025
US
Email: petr@fb.com
Remy Chang
Barefoot Networks
2185 Park Boulevard
Palo Alto, CA 94306
US
8. References
8.1. Normative References
[I-D.ietf-sfc-oam-packet]
Boucadair, M., "OAM Packet and Behavior in the Network
Service Header (NSH)", Work in Progress, Internet-Draft,
draft-ietf-sfc-oam-packet-03, 26 March 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-sfc-oam-
packet-03>.
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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>.
[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>.
[RFC9197] Brockners, F., Ed., Bhandari, S., Ed., and T. Mizrahi,
Ed., "Data Fields for In Situ Operations, Administration,
and Maintenance (IOAM)", RFC 9197, DOI 10.17487/RFC9197,
May 2022, <https://www.rfc-editor.org/info/rfc9197>.
8.2. Informative References
[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>.
[RFC9322] Mizrahi, T., Brockners, F., Bhandari, S., Gafni, B., and
M. Spiegel, "In Situ Operations, Administration, and
Maintenance (IOAM) Loopback and Active Flags", RFC 9322,
DOI 10.17487/RFC9322, November 2022,
<https://www.rfc-editor.org/info/rfc9322>.
[RFC9326] Song, H., Gafni, B., Brockners, F., Bhandari, S., and T.
Mizrahi, "In Situ Operations, Administration, and
Maintenance (IOAM) Direct Exporting", RFC 9326,
DOI 10.17487/RFC9326, November 2022,
<https://www.rfc-editor.org/info/rfc9326>.
[RFC9378] Brockners, F., Ed., Bhandari, S., Ed., Bernier, D., and T.
Mizrahi, Ed., "In Situ Operations, Administration, and
Maintenance (IOAM) Deployment", RFC 9378,
DOI 10.17487/RFC9378, April 2023,
<https://www.rfc-editor.org/info/rfc9378>.
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Appendix A. Discussion of the IOAM encapsulation approach
This section lists several approaches considered for encapsulating
IOAM with NSH and presents the rationale for the approach chosen in
this document.
An encapsulation of IOAM-Data-Fields in NSH should be friendly to an
implementation in both hardware as well as software forwarders and
support a wide range of deployment cases, including large networks
that desire to leverage multiple IOAM-Data-Fields at the same time.
Hardware and software friendly implementation: Hardware forwarders
benefit from an encapsulation that minimizes iterative look-ups of
fields within the packet: Any operation which looks up the value of a
field within the packet, based on which another lookup is performed,
consumes additional gates and time in an implementation - both of
which are desired to be kept to a minimum. This means that flat TLV
structures are to be preferred over nested TLV structures. IOAM-
Data-Fields are grouped into several categories, including trace,
proof-of-transit, and edge-to-edge. Each of these options defines a
TLV structure. A hardware-friendly encapsulation approach avoids
grouping these three option categories into yet another TLV
structure, but would rather carry the options as a serial sequence.
Total length of the IOAM-Data-Fields: The total length of IOAM-Data-
Fields can grow quite large in case multiple different IOAM-Data-
Fields are used and large path-lengths need to be considered. If for
example an operator would consider using the IOAM Trace Option-Type
and capture node-id, app_data, egress/ingress interface-id, timestamp
seconds, timestamps nanoseconds at every hop, then a total of 20
octets would be added to the packet at every hop. In case this
particular deployment would have a maximum path length of 15 hops in
the IOAM domain, then a maximum of 300 octets were to be encapsulated
in the packet.
Different approaches for encapsulating IOAM-Data-Fields in NSH could
be considered:
1. Encapsulation of IOAM-Data-Fields as "NSH MD Type 2" (see
[RFC8300], Section 2.5). Each IOAM-Option-Type (e.g., trace,
proof-of-transit, and edge-to-edge) would be specified by a type,
with the different IOAM-Data-Fields being TLVs within this the
particular option type. NSH MD Type 2 offers support for
variable length meta-data. The length field is 6-bits, resulting
in a maximum of 256 (2^6 x 4) octets.
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2. Encapsulation of IOAM-Data-Fields using the "Next Protocol"
field. Each IOAM-Option-Type (e.g trace, proof-of-transit, and
edge-to-edge) would be specified by its own "next protocol".
3. Encapsulation of IOAM-Data-Fields using the "Next Protocol"
field. A single NSH protocol type code point would be allocated
for IOAM. A "sub-type" field would then specify what IOAM
options type (trace, proof-of-transit, edge-to-edge) is carried.
The third option has been chosen here. This option avoids the
additional layer of TLV nesting that the use of NSH MD Type 2 would
result in. In addition, this option does not constrain IOAM data to
a maximum of 256 octets, thus allowing support for very large
deployments.
Authors' Addresses
Frank Brockners (editor)
Cisco Systems, Inc.
Hansaallee 249, 3rd Floor
40549 DUESSELDORF
Germany
Email: fbrockne@cisco.com
Shwetha Bhandari (editor)
Thoughtspot
3rd Floor, Indiqube Orion, 24th Main Rd, Garden Layout, HSR Layout
Bangalore, KARNATAKA 560 102
India
Email: shwetha.bhandari@thoughtspot.com
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