sfc F. Brockners
Internet-Draft S. Bhandari
Intended status: Standards Track V. Govindan
Expires: September 4, 2018 C. Pignataro
Cisco
H. Gredler
RtBrick Inc.
J. Leddy
Comcast
S. Youell
JMPC
T. Mizrahi
Marvell
D. Mozes
P. Lapukhov
Facebook
R. Chang
Barefoot Networks
March 3, 2018
NSH Encapsulation for In-situ OAM Data
draft-brockners-sfc-ioam-nsh-01
Abstract
In-situ Operations, Administration, and Maintenance (OAM) 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
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."
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This Internet-Draft will expire on September 4, 2018.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. IOAM data fields encapsulation in NSH . . . . . . . . . . . . 3
4. Considerations . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Discussion of the encapsulation approach . . . . . . . . 5
4.2. IOAM and the use of the NSH O-bit . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
In-situ OAM (IOAM) 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.
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].
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2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Abbreviations used in this document:
IOAM: In-situ Operations, Administration, and Maintenance
NSH: Network Service Header
OAM: Operations, Administration, and Maintenance
TLV: Type, Length, Value
3. IOAM data fields encapsulation in NSH
NSH is defined in [RFC8300]. IOAM data fields are carried in NSH
using a next protocol header which follows the NSH MDx metadata TLVs.
An IOAM header is added containing the different IOAM data fields
defined in [I-D.ietf-ippm-ioam-data]. 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.
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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|C|R|R|R|R|R|R| Length | MD Type | NP = TBD_IOAM | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ N
| Service Path Identifer | 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:
IOAM-Type: 8-bit field defining the IOAM Option type, as defined in
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 protocol.
IOAM Option and Data Space: IOAM option header and data is present
as specified by the IOAM-Type field, and is defined in Section 4
of [I-D.ietf-ippm-ioam-data].
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Multiple IOAM options MAY be included within the NSH encapsulation.
For example, if a NSH encapsulation contains two IOAM options 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 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 is to support the working group discussion in selecting
the most appropriate approach for encapsulating IOAM data fields in
NSH.
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 three option
categories: Trace, proof-of-transit, and edge-to-edge. Each of
these three 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 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
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 of
IOAM data were to be encapsulated in the packet.
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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 data field option (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 data field option (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.
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 |
+---------------+-------------+---------------+
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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.
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. References
8.1. 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., Chang, R., and d. daniel.bernier@bell.ca, "Data Fields
for In-situ OAM", draft-ietf-ippm-ioam-data-01 (work in
progress), October 2017.
[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>.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
DOI 10.17487/RFC2784, March 2000, <https://www.rfc-
editor.org/info/rfc2784>.
[RFC3232] Reynolds, J., Ed., "Assigned Numbers: RFC 1700 is Replaced
by an On-line Database", RFC 3232, DOI 10.17487/RFC3232,
January 2002, <https://www.rfc-editor.org/info/rfc3232>.
[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>.
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8.2. 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>.
Authors' Addresses
Frank Brockners
Cisco Systems, Inc.
Hansaallee 249, 3rd Floor
DUESSELDORF, NORDRHEIN-WESTFALEN 40549
Germany
Email: fbrockne@cisco.com
Shwetha Bhandari
Cisco Systems, Inc.
Cessna Business Park, Sarjapura Marathalli Outer Ring Road
Bangalore, KARNATAKA 560 087
India
Email: shwethab@cisco.com
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
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John Leddy
Comcast
Email: John_Leddy@cable.comcast.com
Stephen Youell
JP Morgan Chase
25 Bank Street
London E14 5JP
United Kingdom
Email: stephen.youell@jpmorgan.com
Tal Mizrahi
Marvell
6 Hamada St.
Yokneam 20692
Israel
Email: talmi@marvell.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
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