SFC F. Brockners, Ed.
Internet-Draft S. Bhandari, Ed.
Intended status: Standards Track Cisco
Expires: December 18, 2020 June 16, 2020
Network Service Header (NSH) Encapsulation for In-situ OAM (IOAM) Data
draft-ietf-sfc-ioam-nsh-04
Abstract
In-situ Operations, Administration, and Maintenance (IOAM) records
operational and telemetry information in the packet while the packet
traverses a path between two points in the network. This document
outlines how IOAM data fields are encapsulated in the Network Service
Header (NSH).
Status of This Memo
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This Internet-Draft will expire on December 18, 2020.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. IOAM data fields encapsulation in NSH . . . . . . . . . . . . 3
4. Considerations . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Discussion of the encapsulation approach . . . . . . . . 4
4.2. IOAM and the use of the NSH O-bit . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1. Normative References . . . . . . . . . . . . . . . . . . 8
9.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
In-situ OAM (IOAM), as defined in [I-D.ietf-ippm-ioam-data], records
OAM information within the packet 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) [RFC7665]. The IOAM-Data-Fields are defined in
[I-D.ietf-ippm-ioam-data]. An implementation of IOAM which leverages
NSH to carry the IOAM data is available from the FD.io open source
software project [FD.io].
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
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TLV: Type, Length, Value
3. IOAM data fields encapsulation in NSH
The NSH is defined in [RFC8300]. IOAM-Data-Fields are carried in NSH
using a next protocol header which follows the NSH MD context
headers. An IOAM header is added containing the different IOAM-Data-
Fields. The IOAM-Data-Fields MUST follow the definitions in
[I-D.ietf-ippm-ioam-data]. If "proof-of-transit" is used in
conjunction with NSH, the implementation of proof of transit MUST
follow [I-D.ietf-sfc-proof-of-transit]. 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.
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 Data Space ~ M
| | |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
| |
| |
| Payload + Padding (L2/L3/ESP/...) |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The NSH header and fields are defined in [RFC8300]. The "NSH Next
Protocol" value (referred to as "NP" in the diagram above) is
TBD_IOAM.
The IOAM related fields in NSH are defined as follows:
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IOAM-Type: 8-bit field defining the IOAM-Option-Type, as defined
in the IOAM Option-Type Registry (see Section 7.2 of
[I-D.ietf-ippm-ioam-data]).
IOAM HDR Len: 8 bit Length field contains the length of the IOAM
header in 4-octet units.
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-Option-Type and IOAM-Data-Field
as specified by the IOAM-Type field are present (see Section 4
of [I-D.ietf-ippm-ioam-data]).
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.
4. Considerations
This section summarizes a set of considerations on the overall
approach taken for IOAM data encapsulation in NSH, as well as
deployment considerations.
4.1. Discussion of the encapsulation approach
This section discusses several approaches for encapsulating IOAM-
Data-Fields in 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
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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.
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.
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4.2. IOAM and the use of the NSH O-bit
[RFC8300] defines an "O bit" for OAM packets. Per [RFC8300] the O
bit must be set for OAM packets and must not be set for non-OAM
packets. Packets with IOAM data included MUST follow this
definition, i.e. the O bit MUST NOT be set for regular customer
traffic which also carries IOAM data and the O bit MUST be set for
OAM packets which carry only IOAM data without any regular data
payload.
5. IANA Considerations
IANA is requested to allocate protocol numbers for the following "NSH
Next Protocol" related to IOAM:
+---------------+-------------+---------------+
| Next Protocol | Description | Reference |
+---------------+-------------+---------------+
| x | TBD_IOAM | This document |
+---------------+-------------+---------------+
6. Security Considerations
IOAM is considered a "per domain" feature, where one or several
operators decide on leveraging and configuring IOAM according to
their needs. Still, operators need 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 8 in
[I-D.ietf-ippm-ioam-data]. For proof of transit related security
considerations, see Section 7 in [I-D.ietf-sfc-proof-of-transit].
7. 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,
and Andrew Yourtchenko for the comments and advice.
8. Contributors
In addition to editors listed on the title page, the following people
have contributed to this document:
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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
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
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Remy Chang
Barefoot Networks
2185 Park Boulevard
Palo Alto, CA 94306
US
9. References
9.1. Normative References
[I-D.ietf-ippm-ioam-data]
Brockners, F., Bhandari, S., Pignataro, C., Gredler, H.,
Leddy, J., Youell, S., Mizrahi, T., Mozes, D., Lapukhov,
P., remy@barefootnetworks.com, r., daniel.bernier@bell.ca,
d., and J. Lemon, "Data Fields for In-situ OAM", draft-
ietf-ippm-ioam-data-09 (work in progress), March 2020.
[I-D.ietf-sfc-proof-of-transit]
Brockners, F., Bhandari, S., Mizrahi, T., Dara, S., and S.
Youell, "Proof of Transit", draft-ietf-sfc-proof-of-
transit-05 (work in progress), May 2020.
[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>.
9.2. Informative References
[FD.io] "Fast Data Project: FD.io", <https://fd.io/>.
[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>.
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Authors' Addresses
Frank Brockners (editor)
Cisco Systems, Inc.
Hansaallee 249, 3rd Floor
DUESSELDORF, NORDRHEIN-WESTFALEN 40549
Germany
Email: fbrockne@cisco.com
Shwetha Bhandari (editor)
Cisco Systems, Inc.
Cessna Business Park, Sarjapura Marathalli Outer Ring Road
Bangalore, KARNATAKA 560 087
India
Email: shwethab@cisco.com
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