SFC                                                    F. Brockners, Ed.
Internet-Draft                                                     Cisco
Intended status: Standards Track                        S. Bhandari, Ed.
Expires: 4 August 2022                                       Thoughtspot
                                                         31 January 2022


 Network Service Header (NSH) Encapsulation for In-situ OAM (IOAM) Data
                       draft-ietf-sfc-ioam-nsh-07

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

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 4 August 2022.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   provided without warranty as described in the Revised BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  IOAM encapsulation with NSH . . . . . . . . . . . . . . . . .   3
   4.  Considerations  . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  IOAM and the use of the NSH O-bit . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   5
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Appendix A.  Discussion of the IOAM encapsulation approach  . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   In-situ OAM (IOAM), as defined in [I-D.ietf-ippm-ioam-data], 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) [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 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 different IOAM-Data-Fields.
   The IOAM-Data-Fields MUST follow the definitions corresponding to
   IOAM-Option-Types (e.g. see Section 5 of [I-D.ietf-ippm-ioam-data]
   and Section 3.2 of [I-D.ietf-ippm-ioam-direct-export]).  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.  See [I-D.ietf-ippm-ioam-deployment] 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 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



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         in the IOAM Option-Type Registry specified in
         [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-Data-Fields as specified by the
         IOAM-Type field.  IOAM-Data-Fields are defined corresponding to
         the IOAM-Option-Type (e.g. see Section 5 of
         [I-D.ietf-ippm-ioam-data] and Section 3.2 of
         [I-D.ietf-ippm-ioam-direct-export]).

   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

4.1.  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:








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                 +---------------+-------------+---------------+
                 | 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 10 in
   [I-D.ietf-ippm-ioam-data].

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,
   Andrew Yourtchenko and Greg Mirsky for the comments and advice.

8.  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

      Hannes Gredler
      RtBrick Inc.
      Email: hannes@rtbrick.com

      John Leddy
      Email: john@leddy.net






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      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

9.  References

9.1.  Normative References

   [I-D.ietf-ippm-ioam-data]
              Brockners, F., Bhandari, S., and T. Mizrahi, "Data Fields
              for In-situ OAM", Work in Progress, Internet-Draft, draft-
              ietf-ippm-ioam-data-17, 13 December 2021,
              <https://www.ietf.org/archive/id/draft-ietf-ippm-ioam-
              data-17.txt>.

   [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>.




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   [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/>.

   [I-D.ietf-ippm-ioam-deployment]
              Brockners, F., Bhandari, S., Bernier, D., and T. Mizrahi,
              "In-situ OAM Deployment", Work in Progress, Internet-
              Draft, draft-ietf-ippm-ioam-deployment-00, 19 October
              2021, <https://www.ietf.org/archive/id/draft-ietf-ippm-
              ioam-deployment-00.txt>.

   [I-D.ietf-ippm-ioam-direct-export]
              Song, H., Gafni, B., Zhou, T., Li, Z., Brockners, F.,
              Bhandari, S., Sivakolundu, R., and T. Mizrahi, "In-situ
              OAM Direct Exporting", Work in Progress, Internet-Draft,
              draft-ietf-ippm-ioam-direct-export-07, 13 October 2021,
              <https://www.ietf.org/archive/id/draft-ietf-ippm-ioam-
              direct-export-07.txt>.

   [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>.

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,



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   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.

Authors' Addresses








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   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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