Network Service Header (NSH) Encapsulation for In Situ OAM (IOAM) Data
draft-ietf-sfc-ioam-nsh-13

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.

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   This Internet-Draft will expire on 6 November 2023.

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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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