RFC 9974

Operations, Administration, and Maintenance (OAM) Requirements for the Bit Index Explicit Replication (BIER) Layer

📅 published June 2026, from ietf

RFC 9974: Operations, Administration, and Maintenance (OAM) Requirements for the Bit Index Explicit Replication (BIER) Layer 🎀

  • Stream: IETF 🌸
  • Request for Comments: 9974
  • Category: Informational (not Internet Standards Track, just published for info) 📚
  • ISSN: 2070-1721
  • Date: June 2026 📅
  • Authors: G. Mirsky, Ed. (Independent), N. Kumar (Oracle), M. Chen (Huawei Technologies), S. Pallagatti, Ed. (VMware) 🫶
  • Obsoletes / Updates: the title block doesn't list anything this one obsoletes or updates 🦋

Abstract 💖

okay so this doc is a wishlist of functional requirements for OAM mechanisms, protocols, and tools that keep the BIER layer of a network running smoothly ✨

Status of This Memo 💅

not gonna lie, this one is not an Internet Standards Track spec. it's published purely for info 📚

it's a product of the IETF, so it represents the consensus of the IETF community. it got public review and was approved for publication by the IESG. not every IESG-approved doc is a candidate for any level of Internet Standard, so see Section 2 of RFC 7841 for that tea 🍵

want the current status, errata, or a way to send feedback? head to https://www.rfc-editor.org/info/rfc9974 🔗

Copyright (c) 2026 IETF Trust and the persons identified as the document authors. All rights reserved. 💜

this doc is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) as in effect on the date of publication. please actually read those, bestie, because they spell out your rights and restrictions for this doc 🙈 Code Components pulled out of this doc must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions, and they come 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 🦋

okay so [RFC8279] is the one that specifies the Bit Index Explicit Replication (BIER) architecture and how it supports forwarding of multicast data packets. main character of this whole doc 👑

this doc 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 also be used for gap analysis of the OAM tools already out there. the goal is to figure out whether existing or brand-new OAM tools need upgrades to support proactive and on-demand path monitoring and service validation 🔍✨

1.1. Conventions Used in This Document 🎀

1.1.1. Terminology 📖

before we go any further, you should be comfy with these:

  • [RFC7799], especially the definitions of Active, Passive, and Hybrid measurement methods and metrics 💜
  • the definitions and calculations of performance metrics, like throughput, loss, delay, and delay variation, are in [RFC6374] 📊
  • the definitions, applicability, and examples of the Continuity Check and Connectivity Verification mechanisms (components of Fault Management OAM) live in [RFC5860], [RFC6371], and [RFC7276] 🧩
  • a multicast domain is a network segment that defines the scope for multicast traffic, so the traffic can only be exchanged among systems inside the domain [RFC8279] 🌐
  • "BIER OAM" is used in this doc 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 that the packet needs to be sent to [RFC8279] 🚪
  • Ingress endpoint is a router that encapsulates a packet in a BIER header [RFC8279] 🎁
  • a BIER OAM session is a communication set up between Bit-Forwarding Routers (BFR) to do OAM stuff 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 doc are to be read as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they show up in all capitals, just like shown here 💅

the requirements language is used in Section 2 and applies to implementations of BIER OAM that conform 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 is the big list of requirements for OAM of the BIER layer, and it's where the requirements language from Section 1.1.2 actually kicks in 💖

  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 one is extra helpful clarification for the combo of Requirements 2 and 4. P2MP BFD with active tail support [RFC9780] is an example of a protocol that gives notifications about loss of connectivity in a multicast distribution tree 🌳

  1. 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 measuring 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 that traverse the same set of nodes and links and receive the same forwarding treatment (including QoS) as the monitored BIER flow. 🎯

sometimes, e.g., when monitoring a composite data flow with several sub-flows marked with different Class-of-Service (CoS) values, an operator may choose to monitor path continuity at the highest CoS instead of at every CoS value in the flow. in that case, BIER OAM packets traverse the same set of nodes and links as the composite flow while getting the same forwarding treatment as the highest CoS sub-flow. here, the path continuity state for lower CoS sub-flows can be derived from the state of the highest CoS, as determined by the BIER OAM protocol doing 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) than the monitored BIER flow. 🔄

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

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

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 for 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 a 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] gives 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 doc has no IANA actions. nothing to register, nothing to update, iykyk 🫶

4. Security Considerations 🔐

Okay so this doc is a list of OAM requirements for a BIER-enabled domain, which means it inherits all the security drama from [RFC8279] and [RFC8296]. There's also a separate general security thing that comes from using active OAM protocols [RFC7799] in a multicast network. Let's get into it 👀

Active OAM protocols inject specially made test packets 🧪. Some of them do echo requests and replies using those test packets, like ICMPv6 [RFC4443] and LSP Ping [RFC8029]. In a multicast network, the test packets get replicated just like data packets do. That can create an amplification effect, where lots of echo replies get sent back to whoever sent the echo request. Major yikes 😭 So these 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. 🚦
Honestly, these two MUST requirements are the whole point of this section. If a BIER OAM solution doesn't rate-limit the echo requests and cap how many OAM messages reach the control plane, the amplification problem can run wild. Don't skip them, bestie 💅

5. References ✨

5.1. Normative References

These are the ones you need to read to fully understand the spec 📚:

[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

These are the extra-credit reads that give you more background 🧠✨:

[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 want to give a big shoutout to Gunter van de Velde for the comments and suggestions that helped make this document better 🌸

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
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