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Guidelines for Charactering "OAM"
draft-ietf-opsawg-oam-characterization-00

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Authors Carlos Pignataro , Adrian Farrel
Last updated 2024-05-10
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draft-ietf-opsawg-oam-characterization-00
OPS Area Working Group                                      C. Pignataro
Internet-Draft                                       NC State University
Updates: 6291 (if approved)                                    A. Farrel
Intended status: Best Current Practice                Old Dog Consulting
Expires: 11 November 2024                                    10 May 2024

                   Guidelines for Charactering "OAM"
               draft-ietf-opsawg-oam-characterization-00

Abstract

   As the IETF continues to produce and standardize different
   Operations, Administration, and Maintenance (OAM) protocols and
   technologies, various qualifiers and modifiers are prepended to the
   OAM acronym.  While, at first glance, the most used appear to be well
   understood, the same qualifier may be interpreted differently in
   different contexts.  A case in point is the qualifiers "in-band" and
   "out-of-band" which have their origins in the radio lexicon and which
   have been extrapolated into other communication networks.

   This document considers some common qualifiers and modifiers that are
   prepended, within the context of packet networks, to the OAM acronym,
   and lays out guidelines for their use in future IETF work.

   This document updates RFC 6291 by adding to the guidelines for the
   use of the term "OAM".

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 11 November 2024.

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Copyright Notice

   Copyright (c) 2024 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
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  In-Band and Out-of-Band OAM . . . . . . . . . . . . . . . . .   3
     2.1.  Historical Uses . . . . . . . . . . . . . . . . . . . . .   5
   3.  Active, Passive, Hybrid, and Compound OAM . . . . . . . . . .   5
   4.  Extended OAM Acronyms . . . . . . . . . . . . . . . . . . . .   6
   5.  Node Processing OAM Packets . . . . . . . . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   It is not uncommon for historical and popular terms to have
   fundamental nuances in how they are interpreted or understood.  This
   was, for example, the case with the acronym for Operations,
   Administration, and Maintenance, "OAM", and [RFC6291] provided
   guidelines for its use as well as definitions of its constituent
   parts.

   Characterizations or qualifiers for "OAM" within packet networks
   often encounter similar problems, such as with the adjective phrases
   "in-band" and "out-of- band".  This document considers some common
   qualifiers and modifiers that are prepended to the OAM acronym, and
   lays out guidelines for their use in future IETF work to achieve
   unambiguous characterization.

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   Additionally, this document recommends avoiding the creation and use
   of extended acronyms for the qualifiers of "OAM".  For example, the
   first "O" in "OOAM" could mean out-of-band, overlay, or something
   else.

   This document updates [RFC6291] by adding to the guidelines for the
   use of the term "OAM".

2.  In-Band and Out-of-Band OAM

   Historically, the terms "in-band" and "out-of-band" were used
   extensively in telephony signaling [RFC4733] and appear also in radio
   communications.  In both these cases, there is an actual "Band"
   (i.e., a "Channel" or "Frequency") to be within or outside.

   While those terms, useful in their simplicity, continued to be
   broadly used to mean "within something" and "outside said something",
   a challenge is presented for IP communications and packet switch
   networks (PSNs) which do not have a "band" per se, and, in fact, has
   multiple "somethings" that OAM can go within or outside.  A
   frequently encountered case is the use of in-band to mean either in-
   packet or in-path.

   Within the IETF, the terms "in-band" and "out-of-band" cannot be
   reliably understood consistently and unambiguously.  Context-specific
   redefinitions of these terms lack ability to be generalized, and can
   be confused by participants from other contexts.  More importantly,
   the terms are not self-defining any more and cannot be understood by
   someone exposed to them for the first time, since there is no "band"
   in IP.

   The guidance in this document is to avoid the terms "*-band" and
   instead find finer-granularity descriptive terms.  The definitions
   presented in this document are for use in all future IETF documents
   that refer to OAM, and the terms "in-band OAM" and "out-of-band OAM"
   are not to be used in future documents.

   Path:  OAM in relation to a path.

      Path-Congruent OAM:
         The OAM messages follow the exact same path as the observed
         data traffic.  This was sometimes referred to as "in-band".

      Non-Path-Congruent OAM:
         The OAM messages do not follow the same path as the observed
         data traffic.  This was sometimes referred to as "out-of-band".

      [RFC6669] gives an example of "Path-Congruent OAM", and further

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      describes that the OAM Packets "share their fate with data
      packets."

   Packet:  OAM in relation to a user data packet.

      In-Packet OAM:
         The OAM messages are carried as part of data traffic.  This was
         sometimes referred to as "in-band".

      Dedicated-Packet OAM:
         The OAM messages have their own OAM packets, separate from data
         traffic.  This was sometimes referred to as "out-of-band".

      The MPLS echo request/reply messages [RFC8029] are an example of
      "Dedicated-Packet OAM", since they are described as "An MPLS echo
      request/reply is a (possibly labeled) IPv4 or IPv6 UDP packet".

      In Situ OAM [RFC9197] is an example of "In-Packet OAM", given that
      it '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 being sent within packets specifically dedicated to OAM.'

      Initially "In Situ OAM" [IETF96-In-Band-OAM] was also referred to
      as "In-band OAM", but was renamed due to the overloaded meaning of
      "in-band OAM".  Further, [RFC9232] also intertwines the terms "in-
      band" with "in situ", though [I-D.song-opsawg-ifit-framework]
      settled on using "In Situ".  Other similar uses, including
      [P4-INT-2.1] and [I-D.kumar-ippm-ifa], still use variations of
      "in-band", "in band", or "inband".

   Packet Treatment:  OAM in relation to the treatment of user data
      packets, as for example QoS treatment.

      Equal-QoS-Treatment OAM:
         The OAM packets receive the same QoS treatment as user data
         packets.  This was sometimes referred to as "in-band".

      Different-QoS-Treatment OAM:
         The OAM packets receive different QoS treatment as user data
         packets.  This was sometimes referred to as "out-of-band".

      For a case of either "Non-Path-Congruent OAM" or "Different-QoS-
      Treatment OAM", [I-D.ietf-detnet-oam-framework] says "Out-of-band
      OAM is an active OAM whose path through the DetNet domain is not
      topologically identical to the path of the monitored DetNet flow,
      or its test packets receive different QoS and/or PREOF treatment,
      or both."  [I-D.ietf-raw-architecture] uses similar text.

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   Combined:  OAM in relation to multiple criteria.  For example, in
      relation to both topological congruence and packet treatment.
      Examples include [I-D.ietf-detnet-oam-framework] and
      [I-D.ietf-raw-architecture].

      [I-D.ietf-detnet-oam-framework] uses Combined OAM when it says
      "In-band OAM is an active OAM that is in-band within the monitored
      DetNet OAM domain when it traverses the same set of links and
      interfaces receiving the same QoS and Packet Replication,
      Elimination, and Ordering Functions (PREOF) treatment as the
      monitored DetNet flow".  [I-D.ietf-raw-architecture] uses similar
      text.

2.1.  Historical Uses

   There are many examples of "in-band OAM" and "out-of-band OAM" in
   published RFCs.  While interpreting those, it is important to
   understand the semantics of what "band" is a proxy for, and to be
   more explicit if those documents are updated.  This document does not
   change the meaning of any terms in any prior RFCs.

   For example, [RFC5085] says "as in-band traffic with the PW's data,
   or out-of-band", and "in-band (i.e., following the same data-plane
   faith as PW data)".  Hence, the term "band" refers to the "Pseudowire
   data".

3.  Active, Passive, Hybrid, and Compound OAM

   [RFC7799] provides clear definitions for active and passive
   performance assessment such that the construction of metrics and
   methods can be described as either "Active" or "Passive".  Even
   though [RFC7799] does not include the specific terms "Active",
   "Passive", or "Hybrid" as modifiers of "OAM", the following terms are
   used in many RFCs and are provided here for use in all future IETF
   documents that refer to OAM.

   Active OAM:
      Depends on dedicated instrumented OAM packets.

   Passive OAM:
      Depends solely on the observation of one or more existing data
      packet streams, and does not use dedicated OAM packets.

   Hybrid OAM:
      Uses instrumentation or modification of data packets themselves.
      [RFC9341] and [RFC9197] are examples labeled "Hybrid OAM" under
      this definition.

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   Compound OAM:
      Uses a combination of at least two of Active OAM, Passive OAM, and
      Hybrid OAM (i.e., a combination of atomic OAM packets, data packet
      modification for OAM, and no OAM packet).  Note that [RFC7799]
      also uses the term "Hybrid" to refer to metric types in-between
      active and passive, for OAM there are no in-betweens per se, only
      active, passive, hybrid, or a combination.

      Compound OAM can further be characterized in a more explicit way,
      for nuanced use-cases.

      *  Active-Passive OAM.

      *  Active-Hybrid OAM.

      *  Hybrid-Passive OAM.

      *  Active-Hybrid-Passive OAM.

   [RFC7799] adds to the confusion by describing "passive methods" as
   "out of band".  Following the guidelines of this document, OAM may be
   qualified according to the terms described in Sections 2 and 3 of
   this document, and the term "out of band OAM" is not to be used in
   future documents.

4.  Extended OAM Acronyms

   This document recommends avoiding the creation and use of extended
   acronyms for the qualifiers of "OAM".  For example, the first "O" in
   "OOAM" could mean out-of-band, overlay, or something else.

   [RFC9197] currently uses the acronym "IOAM" for In Situ Operations,
   Administration, and Maintenance.  While this document does not
   obsolete that acronym, it still recommends that "In situ OAM" is used
   instead to avoid potential ambiguity.

5.  Node Processing OAM Packets

   There are multiple processing capabilities that nodes processing OAM
   packets can utilize.  Some of those capabilities are explained in
   [RFC9197] for In situ OAM, and are further generalized in this
   document.

   Depending on the Type of OAM processing, nodes are chategorized as
   follows.  Please note that this characterization exists within the
   context of a particular OAM protocol instance, and a given node can
   support multiple types:

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   *  Hybrid OAM instruments or modifies data packet themselves.
      Consequently:

      Encapsulating Node:
         Adds OAM information to data packets.

      Transit Node:
         Processes OAM information in data packets.

      Transparent Node:
         Does not process OAM information in data packets.

      Decapsulating Node:
         Removes OAM information to data packets.

   *  Active OAM uses dedicated OAM packets, outside data packets.
      Consequently:

      Source Node:
         Creates and injects OAM packets into a flow.

      Sink Node:
         Processes and removes OAM packets from a flow.

      A node could be source and sink of Active OAM packets
      simultaneously.

6.  Security Considerations

   Security is improved when the terms used and their definitions are
   unambiguous.

7.  Acknowledgements

   The creation of this document was triggered when observing one of
   many on-mailing-list discussions of what these terms mean, and how to
   abbreviate them.  Participants on that mailing thread include,
   alphabetically: Adrian Farrel, Alexander Vainshtein, Florian Kauer,
   Frank Brockners, Greg Mirsky, Italo Busi, Loa Andersson, Med
   Boucadair, Michael Richardson, Quan Xiong, Stewart Bryant, Tom Petch,
   Eduard Vasilenko, and Xiao Min.

   The authors wish to thank Hesham Elbakoury, Michael Richardson,
   Stewart Bryant, Greg Mirsky, Med Boucadair, Loa Andersson, Thomas
   Graf, and Alex Huang Feng for their thorough review and very useful
   comments that improved this document.

8.  References

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8.1.  Normative References

   [RFC6291]  Andersson, L., van Helvoort, H., Bonica, R., Romascanu,
              D., and S. Mansfield, "Guidelines for the Use of the "OAM"
              Acronym in the IETF", BCP 161, RFC 6291,
              DOI 10.17487/RFC6291, June 2011,
              <https://www.rfc-editor.org/info/rfc6291>.

   [RFC7799]  Morton, A., "Active and Passive Metrics and Methods (with
              Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
              May 2016, <https://www.rfc-editor.org/info/rfc7799>.

8.2.  Informative References

   [I-D.ietf-detnet-oam-framework]
              Mirsky, G., Theoleyre, F., Papadopoulos, G. Z., Bernardos,
              C. J., Varga, B., and J. Farkas, "Framework of Operations,
              Administration and Maintenance (OAM) for Deterministic
              Networking (DetNet)", Work in Progress, Internet-Draft,
              draft-ietf-detnet-oam-framework-11, 8 January 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-detnet-
              oam-framework-11>.

   [I-D.ietf-raw-architecture]
              Thubert, P., "Reliable and Available Wireless
              Architecture", Work in Progress, Internet-Draft, draft-
              ietf-raw-architecture-17, 4 March 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-raw-
              architecture-17>.

   [I-D.kumar-ippm-ifa]
              Kumar, J., Anubolu, S., Lemon, J., Manur, R., Holbrook,
              H., Ghanwani, A., Cai, D., Ou, H., Li, Y., and X. Wang,
              "Inband Flow Analyzer", Work in Progress, Internet-Draft,
              draft-kumar-ippm-ifa-08, 26 April 2024,
              <https://datatracker.ietf.org/doc/html/draft-kumar-ippm-
              ifa-08>.

   [I-D.song-opsawg-ifit-framework]
              Song, H., Qin, F., Chen, H., Jin, J., and J. Shin,
              "Framework for In-situ Flow Information Telemetry", Work
              in Progress, Internet-Draft, draft-song-opsawg-ifit-
              framework-21, 23 October 2023,
              <https://datatracker.ietf.org/doc/html/draft-song-opsawg-
              ifit-framework-21>.

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   [IETF96-In-Band-OAM]
              Brockners, F., Bhandari, S., Dara, S., Pignataro, C.,
              Gedler, H., Youell, S., and J. Leddy, "IETF 96, OPSWG: In-
              Band OAM", IETF-96 Proceedings, IETF-96 slides-96-opsawg-
              8.pdf, 19 July 2016,
              <https://www.ietf.org/proceedings/96/slides/slides-96-
              opsawg-8.pdf>.

   [P4-INT-2.1]
              "In-band Network Telemetry (INT) Dataplane Specification,
              Version 2.1", 11 November 2020,
              <https://p4.org/p4-spec/docs/INT_v2_1.pdf>.

   [RFC4733]  Schulzrinne, H. and T. Taylor, "RTP Payload for DTMF
              Digits, Telephony Tones, and Telephony Signals", RFC 4733,
              DOI 10.17487/RFC4733, December 2006,
              <https://www.rfc-editor.org/info/rfc4733>.

   [RFC5085]  Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual
              Circuit Connectivity Verification (VCCV): A Control
              Channel for Pseudowires", RFC 5085, DOI 10.17487/RFC5085,
              December 2007, <https://www.rfc-editor.org/info/rfc5085>.

   [RFC6669]  Sprecher, N. and L. Fang, "An Overview of the Operations,
              Administration, and Maintenance (OAM) Toolset for MPLS-
              Based Transport Networks", RFC 6669, DOI 10.17487/RFC6669,
              July 2012, <https://www.rfc-editor.org/info/rfc6669>.

   [RFC8029]  Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
              Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
              Switched (MPLS) Data-Plane Failures", RFC 8029,
              DOI 10.17487/RFC8029, March 2017,
              <https://www.rfc-editor.org/info/rfc8029>.

   [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>.

   [RFC9232]  Song, H., Qin, F., Martinez-Julia, P., Ciavaglia, L., and
              A. Wang, "Network Telemetry Framework", RFC 9232,
              DOI 10.17487/RFC9232, May 2022,
              <https://www.rfc-editor.org/info/rfc9232>.

   [RFC9341]  Fioccola, G., Ed., Cociglio, M., Mirsky, G., Mizrahi, T.,
              and T. Zhou, "Alternate-Marking Method", RFC 9341,
              DOI 10.17487/RFC9341, December 2022,
              <https://www.rfc-editor.org/info/rfc9341>.

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Authors' Addresses

   Carlos Pignataro
   North Carolina State University
   United States of America
   Email: cpignata@gmail.com, cmpignat@ncsu.edu

   Adrian Farrel
   Old Dog Consulting
   United Kingdom
   Email: adrian@olddog.co.uk

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