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Internet Engineering Task Force (IETF)                    G. Mirsky, Ed.
Request for Comments: 9974                                   Independent
Category: Informational                                         N. Kumar
ISSN: 2070-1721                                                   Oracle
                                                                 M. Chen
                                                     Huawei Technologies
                                                      S. Pallagatti, Ed.
                                                                  VMware
                                                               June 2026

Operations, Administration, and Maintenance (OAM) Requirements for the

Bit Index Explicit Replication (BIER) Layer

Abstract

This document specifies a list of functional requirements for Operations, Administration, and Maintenance mechanisms, protocols, and tools that support operations in the Bit Index Explicit Replication layer of a network.

Status of This Memo

This document is not an Internet Standards Track specification; it is published for informational purposes.

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are candidates for any level of Internet Standard; see Section 2 of RFC 7841.

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc9974.

Copyright Notice

Copyright © 2026 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
     1.1.  Conventions Used in This Document
       1.1.1.  Terminology
       1.1.2.  Requirements Language
       1.1.3.  Acronyms
   2.  Requirements
   3.  IANA Considerations
   4.  Security Considerations
   5.  References
     5.1.  Normative References
     5.2.  Informative References
   Acknowledgements
   Contributors
   Authors' Addresses

1. Introduction

[RFC8279] specifies a Bit Index Explicit Replication (BIER) architecture and how it supports forwarding of multicast data packets.

This document lists the Operations, Administration, and Maintenance (OAM) requirements for the BIER layer (see Section 4.2 of [RFC8279]) of the multicast domain. The list can further be used for gap analysis of available OAM tools to identify whether possible enhancements of existing or new OAM tools are required to support proactive and on-demand path monitoring and service validation.

1.1. Conventions Used in This Document

1.1.1. Terminology

The reader is expected to be familiar with: 

   *  [RFC7799], particularly definitions of Active, Passive, and Hybrid
   
      measurement methods and metrics.
  • The definitions and calculation of performance metrics, e.g., throughput, loss, delay, and delay variation metrics, are defined in [RFC6374].
  • The definitions, applicability, and examples of the Continuity Check and Connectivity Verification mechanisms, components of the Fault Management OAM, can be found in [RFC5860], [RFC6371], and [RFC7276].
  • A multicast domain is a network segment that defines the scope for multicast traffic, allowing it to be exchanged only among systems within the domain [RFC8279].
  • The term "BIER OAM" is used in this document interchangeably with "a set of OAM protocols, methods, and tools for the BIER layer".
  • Downstream is the direction from the ingress toward the egress endpoints of a multicast distribution tree.
  • Egress endpoint is a router to which the packet needs to be sent [RFC8279].
  • Ingress endpoint is a router that encapsulates a packet in a BIER header [RFC8279].
  • A BIER OAM session is a communication established between Bit- Forwarding Routers (BFR) to perform OAM functions like fault detection, performance monitoring, and localization [RFC7276]. These sessions can be proactive (continuous, persistent configuration) or on-demand (manual, temporary diagnostics).

1.1.2. Requirements Language

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.

The requirements language is used in Section 2 and applies to implementations of BIER OAM conformant to the listed requirements.

1.1.3. Acronyms

   BFD:  Bidirectional Forwarding Detection [RFC8562]
   
   BFR:  Bit-Forwarding Router [RFC8279]
   
   BFER:  Bit-Forwarding Egress Router [RFC8279]
   
   BIER:  Bit Index Explicit Replication [RFC8279]
   
   OAM:  Operations, Administration, and Maintenance [RFC6291]
   
   PMTUD:  Path Maximum Transmission Unit Discovery [RFC1191]
   
   P2MP:  Point-to-Multipoint [RFC8562]
   
   RDI:  Remote Defect Indication [RFC6428]
   
   STAMP:  Simple Two-way Active Measurement Protocol [RFC8762]

2. Requirements

This section lists the requirements for OAM of the BIER layer: 

   1.   The listed requirements MUST be supported with any routing
        underlay [RFC8279] over which the BIER layer can be realized.
   
   2.   It MUST be possible to initialize a BIER OAM session from any
        BFR of the given BIER domain.
   
   3.   It MUST be possible to initialize a BIER OAM session from a
        controller.
   
   4.   BIER OAM MUST support proactive OAM monitoring and measurement
        methods.
   
   5.   BIER OAM MUST support on-demand OAM monitoring and measurement
        methods.
   
   6.   BIER OAM MUST support active performance measurement methods
        [RFC7799].
   
   7.   BIER OAM MUST support passive performance measurement methods
        [RFC7799].
   
   8.   BIER OAM MUST support the ability of any BFR in the given BIER
        domain to proactively monitor Bit-Forwarding Egress Router
        (BFER) availability.

This requirement provides helpful clarification to the combination of Requirements 2 and 4. The Point-to-Multipoint (P2MP) BFD with active tail support [RFC9780] is an example of a protocol that provides notifications about the loss of connectivity in a multicast distribution tree. 

   9.   BIER OAM MUST support downstream path continuity checking.

Bidirectional Forwarding Detection (BFD) [RFC8562] is an example of a protocol that monitors the continuity of a multicast distribution tree.

  1. BIER OAM MUST support downstream performance measurement.

Simple Two-way Active Measurement Protocol (STAMP) [RFC8762] is an example of a protocol that supports measurement of performance metrics, e.g., packet loss ratio, delay, and delay variation.

  1. In the downstream direction, a BIER OAM solution MUST support transmission of OAM packets to traverse the same set of nodes and links and receive the same forwarding treatment (including QoS) as the monitored BIER flow.

In some cases, e.g., when monitoring a composite data flow that includes several sub-flows characterized by different Class-of- Service (CoS) marking, an operator may choose to monitor the continuity of the path at the highest CoS, not at every CoS value in the data flow. In that case, BIER OAM packets traverse the same set of nodes and links as the composite data flow while receiving the same forwarding treatment as the highest CoS sub- flow. In this scenario, the state of path continuity for lower CoS sub-flows can be derived from the state of the highest CoS, as determined by the BIER OAM protocol performing continuity verification (e.g., BFD).

  1. BIER OAM MUST support bidirectional OAM methods. In the downstream direction, these methods of monitoring or measurement MUST conform to Requirement 11. In the reverse direction (i.e., from the egress toward the ingress endpoint of the BIER OAM test session), BIER OAM packets MAY deviate from traversing the same set of nodes and links, or receive a different forwarding treatment (including QoS) as the monitored BIER flow.

The P2MP BFD with active tail [RFC9780] is an example of the bidirectional mechanism of continuity checking.

  1. BIER OAM MUST support Path Maximum Transmission Unit Discovery (PMTUD).

The PMTUD using ICMP [RFC1191] is an example of the mechanism.

  1. BIER OAM MUST support an RDI mechanism to notify the BFR, the source of the continuity checking by BFERs.

The Diagnostic field in P2MP BFD with active tail support, as described in Section 5 of [RFC9780], is an example of the RDI mechanism.

  1. BIER OAM MUST support downstream performance measurement method(s) that (together) calculate performance metrics, e.g., throughput, loss, delay, and delay variation metrics [RFC6374].

STAMP ([RFC8762] and [RFC8972]) is an example of an active performance measurement method of performance metrics that may be applied in a BIER domain. The Alternate-Marking Method, described in [RFC9341] and [RFC9342], is an example of a hybrid measurement method [RFC7799] that may be applied in a BIER domain.

  1. BIER OAM MUST support defect notification mechanism(s).

Alarm Indication Signal [RFC6427] is an example of the defect notification mechanism.

  1. BIER OAM MUST support a way for any BFR in the given BIER domain to originate a fault management message addressed to any subset of BFRs within the domain.

[RFC6427] provides an example of a Fault Management messaging mechanism.

  1. BIER OAM MUST support methods to enable the survivability of a BIER layer.

Protection switching and restoration are examples of survivability methods.

3. IANA Considerations

This document has no IANA actions.

4. Security Considerations

This document lists the OAM requirements for a BIER-enabled domain and it thus inherits the security considerations discussed in [RFC8279] and [RFC8296]. Another general security aspect results from using active OAM protocols [RFC7799] in a multicast network.

Active OAM protocols inject specially constructed test packets. Some active OAM protocols exchange echo requests/replies using test packets, e.g., ICMPv6 [RFC4443] and LSP Ping [RFC8029]. In the multicast network, test packets are replicated as data packets, thus creating a possible amplification effect of multiple echo replies being transmitted to the sender of the echo request. Therefore, the following security-related requirements are defined for BIER OAM:

  • A BIER OAM solution MUST protect the control plane by controlling the rate of echo request transmission.
  • A BIER OAM solution MUST provide control of the number of BIER OAM messages sent to the control plane.

5. References

5.1. Normative References

   [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>.
   
   [RFC6374]  Frost, D. and S. Bryant, "Packet Loss and Delay
              Measurement for MPLS Networks", RFC 6374,
              DOI 10.17487/RFC6374, September 2011,
              <https://www.rfc-editor.org/info/rfc6374>.
   
   [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>.
   
   [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>.
   
   [RFC8279]  Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
              Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
              Explicit Replication (BIER)", RFC 8279,
              DOI 10.17487/RFC8279, November 2017,
              <https://www.rfc-editor.org/info/rfc8279>.
   
   [RFC8296]  Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
              Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation
              for Bit Index Explicit Replication (BIER) in MPLS and Non-
              MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January
              2018, <https://www.rfc-editor.org/info/rfc8296>.

5.2. Informative References

   [RFC1191]  Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
              DOI 10.17487/RFC1191, November 1990,
              <https://www.rfc-editor.org/info/rfc1191>.
   
   [RFC4443]  Conta, A., Deering, S., and M. Gupta, Ed., "Internet
              Control Message Protocol (ICMPv6) for the Internet
              Protocol Version 6 (IPv6) Specification", STD 89,
              RFC 4443, DOI 10.17487/RFC4443, March 2006,
              <https://www.rfc-editor.org/info/rfc4443>.
   
   [RFC5860]  Vigoureux, M., Ed., Ward, D., Ed., and M. Betts, Ed.,
              "Requirements for Operations, Administration, and
              Maintenance (OAM) in MPLS Transport Networks", RFC 5860,
              DOI 10.17487/RFC5860, May 2010,
              <https://www.rfc-editor.org/info/rfc5860>.
   
   [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>.
   
   [RFC6371]  Busi, I., Ed. and D. Allan, Ed., "Operations,
              Administration, and Maintenance Framework for MPLS-Based
              Transport Networks", RFC 6371, DOI 10.17487/RFC6371,
              September 2011, <https://www.rfc-editor.org/info/rfc6371>.
   
   [RFC6427]  Swallow, G., Ed., Fulignoli, A., Ed., Vigoureux, M., Ed.,
              Boutros, S., and D. Ward, "MPLS Fault Management
              Operations, Administration, and Maintenance (OAM)",
              RFC 6427, DOI 10.17487/RFC6427, November 2011,
              <https://www.rfc-editor.org/info/rfc6427>.
   
   [RFC6428]  Allan, D., Ed., Swallow, G., Ed., and J. Drake, Ed.,
              "Proactive Connectivity Verification, Continuity Check,
              and Remote Defect Indication for the MPLS Transport
              Profile", RFC 6428, DOI 10.17487/RFC6428, November 2011,
              <https://www.rfc-editor.org/info/rfc6428>.
   
   [RFC7276]  Mizrahi, T., Sprecher, N., Bellagamba, E., and Y.
              Weingarten, "An Overview of Operations, Administration,
              and Maintenance (OAM) Tools", RFC 7276,
              DOI 10.17487/RFC7276, June 2014,
              <https://www.rfc-editor.org/info/rfc7276>.
   
   [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>.
   
   [RFC8562]  Katz, D., Ward, D., Pallagatti, S., Ed., and G. Mirsky,
              Ed., "Bidirectional Forwarding Detection (BFD) for
              Multipoint Networks", RFC 8562, DOI 10.17487/RFC8562,
              April 2019, <https://www.rfc-editor.org/info/rfc8562>.
   
   [RFC8762]  Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple
              Two-Way Active Measurement Protocol", RFC 8762,
              DOI 10.17487/RFC8762, March 2020,
              <https://www.rfc-editor.org/info/rfc8762>.
   
   [RFC8972]  Mirsky, G., Min, X., Nydell, H., Foote, R., Masputra, A.,
              and E. Ruffini, "Simple Two-Way Active Measurement
              Protocol Optional Extensions", RFC 8972,
              DOI 10.17487/RFC8972, January 2021,
              <https://www.rfc-editor.org/info/rfc8972>.
   
   [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>.
   
   [RFC9342]  Fioccola, G., Ed., Cociglio, M., Sapio, A., Sisto, R., and
              T. Zhou, "Clustered Alternate-Marking Method", RFC 9342,
              DOI 10.17487/RFC9342, December 2022,
              <https://www.rfc-editor.org/info/rfc9342>.
   
   [RFC9780]  Mirsky, G., Mishra, G., and D. Eastlake 3rd,
              "Bidirectional Forwarding Detection (BFD) for Multipoint
              Networks over Point-to-Multipoint MPLS Label Switched
              Paths (LSPs)", RFC 9780, DOI 10.17487/RFC9780, May 2025,
              <https://www.rfc-editor.org/info/rfc9780>.

Acknowledgements

The authors would like to thank Gunter van de Velde for the comments and suggestions that helped improve this document.

Contributors

Erik Nordmark
Email: nordmark@acm.org 

   Sam Aldrin
   Google
   Email: aldrin.ietf@gmail.com

Lianshu Zheng
Email: veronique_cheng@hotmail.com 

   Nobo Akiya
   Email: nobo.akiya.dev@gmail.com

Authors' Addresses

   Greg Mirsky (editor)
   Independent
   Email: gregimirsky@gmail.com
   
   Nagendra Kumar
   Oracle
   Email: nagendrakumar.nainar@gmail.com
   
   Mach Chen
   Huawei Technologies
   Email: mach.chen@huawei.com
   
   Santosh Pallagatti (editor)
   VMware
   Email: santosh.pallagatti@gmail.com