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

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

gregimirsky@gmail.com

Oracle

nagendrakumar.nainar@gmail.com

Huawei Technologies

mach.chen@huawei.com

VMware

santosh.pallagatti@gmail.com

RTG bier BIER OAM 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 .

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Table of Contents

. Introduction
- . Conventions Used in This Document
  - . Terminology
  - . Requirements Language
  - . Acronyms
. Requirements
. IANA Considerations
. Security Considerations
. References
- . Normative References
- . Informative References
Acknowledgements
Contributors
Authors' Addresses

Introduction 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 ) 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.

Conventions Used in This Document

Terminology The reader is expected to be familiar with:

, 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 .
The definitions, applicability, and examples of the Continuity Check and Connectivity Verification mechanisms, components of the Fault Management OAM, can be found in , , and .
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 .
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 .
Ingress endpoint is a router that encapsulates a packet in a BIER header .
A BIER OAM session is a communication established between Bit-Forwarding Routers (BFR) to perform OAM functions like fault detection, performance monitoring, and localization . These sessions can be proactive (continuous, persistent configuration) or on-demand (manual, temporary diagnostics).

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 when, and only when, they appear in all capitals, as shown here. The requirements language is used in and applies to implementations of BIER OAM conformant to the listed requirements.

Acronyms

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

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

The listed requirements MUST be supported with any routing underlay over which the BIER layer can be realized.
It MUST be possible to initialize a BIER OAM session from any BFR of the given BIER domain.
It MUST be possible to initialize a BIER OAM session from a controller.
BIER OAM MUST support proactive OAM monitoring and measurement methods.
BIER OAM MUST support on-demand OAM monitoring and measurement methods.
BIER OAM MUST support active performance measurement methods .
BIER OAM MUST support passive performance measurement methods .
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 is an example of a protocol that provides notifications about the loss of connectivity in a multicast distribution tree.
BIER OAM MUST support downstream path continuity checking. Bidirectional Forwarding Detection (BFD) is an example of a protocol that monitors the continuity of a multicast distribution tree.
BIER OAM MUST support downstream performance measurement. Simple Two-way Active Measurement Protocol (STAMP) is an example of a protocol that supports measurement of performance metrics, e.g., packet loss ratio, delay, and delay variation.
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).
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 is an example of the bidirectional mechanism of continuity checking.
BIER OAM MUST support Path Maximum Transmission Unit Discovery (PMTUD). The PMTUD using ICMP is an example of the mechanism.
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 , is an example of the RDI mechanism.
BIER OAM MUST support downstream performance measurement method(s) that (together) calculate performance metrics, e.g., throughput, loss, delay, and delay variation metrics . STAMP ( and ) 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 and , is an example of a hybrid measurement method that may be applied in a BIER domain.
BIER OAM MUST support defect notification mechanism(s). Alarm Indication Signal is an example of the defect notification mechanism.
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. provides an example of a Fault Management messaging mechanism.
BIER OAM MUST support methods to enable the survivability of a BIER layer. Protection switching and restoration are examples of survivability methods.

IANA Considerations This document has no IANA actions.

Security Considerations This document lists the OAM requirements for a BIER-enabled domain and it thus inherits the security considerations discussed in and . Another general security aspect results from using active OAM protocols 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 and LSP Ping . 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.

References Normative References Key words for use in RFCs to Indicate Requirement Levels In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. Packet Loss and Delay Measurement for MPLS Networks Many service provider service level agreements (SLAs) depend on the ability to measure and monitor performance metrics for packet loss and one-way and two-way delay, as well as related metrics such as delay variation and channel throughput. This measurement capability also provides operators with greater visibility into the performance characteristics of their networks, thereby facilitating planning, troubleshooting, and network performance evaluation. This document specifies protocol mechanisms to enable the efficient and accurate measurement of these performance metrics in MPLS networks. [STANDARDS-TRACK] Active and Passive Metrics and Methods (with Hybrid Types In-Between) This memo provides clear definitions for Active and Passive performance assessment. The construction of Metrics and Methods can be described as either "Active" or "Passive". Some methods may use a subset of both Active and Passive attributes, and we refer to these as "Hybrid Methods". This memo also describes multiple dimensions to help evaluate new methods as they emerge. Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Multicast Using Bit Index Explicit Replication (BIER) This document specifies a new architecture for the forwarding of multicast data packets. It provides optimal forwarding of multicast packets through a "multicast domain". However, it does not require a protocol for explicitly building multicast distribution trees, nor does it require intermediate nodes to maintain any per-flow state. This architecture is known as "Bit Index Explicit Replication" (BIER). When a multicast data packet enters the domain, the ingress router determines the set of egress routers to which the packet needs to be sent. The ingress router then encapsulates the packet in a BIER header. The BIER header contains a bit string in which each bit represents exactly one egress router in the domain; to forward the packet to a given set of egress routers, the bits corresponding to those routers are set in the BIER header. The procedures for forwarding a packet based on its BIER header are specified in this document. Elimination of the per-flow state and the explicit tree-building protocols results in a considerable simplification. Encapsulation for Bit Index Explicit Replication (BIER) in MPLS and Non-MPLS Networks Bit Index Explicit Replication (BIER) is an architecture that provides optimal multicast forwarding through a "multicast domain", without requiring intermediate routers to maintain any per-flow state or to engage in an explicit tree-building protocol. When a multicast data packet enters the domain, the ingress router determines the set of egress routers to which the packet needs to be sent. The ingress router then encapsulates the packet in a BIER header. The BIER header contains a bit string in which each bit represents exactly one egress router in the domain; to forward the packet to a given set of egress routers, the bits corresponding to those routers are set in the BIER header. The details of the encapsulation depend on the type of network used to realize the multicast domain. This document specifies a BIER encapsulation that can be used in an MPLS network or, with slight differences, in a non-MPLS network. Informative References Path MTU discovery This memo describes a technique for dynamically discovering the maximum transmission unit (MTU) of an arbitrary internet path. It specifies a small change to the way routers generate one type of ICMP message. For a path that passes through a router that has not been so changed, this technique might not discover the correct Path MTU, but it will always choose a Path MTU as accurate as, and in many cases more accurate than, the Path MTU that would be chosen by current practice. [STANDARDS-TRACK] Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification This document describes the format of a set of control messages used in ICMPv6 (Internet Control Message Protocol). ICMPv6 is the Internet Control Message Protocol for Internet Protocol version 6 (IPv6). [STANDARDS-TRACK] Requirements for Operations, Administration, and Maintenance (OAM) in MPLS Transport Networks This document lists architectural and functional requirements for the Operations, Administration, and Maintenance of MPLS Transport Profile. These requirements apply to pseudowires, Label Switched Paths, and Sections. [STANDARDS-TRACK] Guidelines for the Use of the "OAM" Acronym in the IETF At first glance, the acronym "OAM" seems to be well-known and well-understood. Looking at the acronym a bit more closely reveals a set of recurring problems that are revisited time and again. This document provides a definition of the acronym "OAM" (Operations, Administration, and Maintenance) for use in all future IETF documents that refer to OAM. There are other definitions and acronyms that will be discussed while exploring the definition of the constituent parts of the "OAM" term. This memo documents an Internet Best Current Practice. Operations, Administration, and Maintenance Framework for MPLS-Based Transport Networks The Transport Profile of Multiprotocol Label Switching (MPLS-TP) is a packet-based transport technology based on the MPLS Traffic Engineering (MPLS-TE) and pseudowire (PW) data-plane architectures. This document describes a framework to support a comprehensive set of Operations, Administration, and Maintenance (OAM) procedures that fulfill the MPLS-TP OAM requirements for fault, performance, and protection-switching management and that do not rely on the presence of a control plane. This document is a product of a joint Internet Engineering Task Force (IETF) / International Telecommunications Union Telecommunication Standardization Sector (ITU-T) effort to include an MPLS Transport Profile within the IETF MPLS and Pseudowire Emulation Edge-to-Edge (PWE3) architectures to support the capabilities and functionalities of a packet transport network as defined by the ITU-T. This document is not an Internet Standards Track specification; it is published for informational purposes. MPLS Fault Management Operations, Administration, and Maintenance (OAM) This document specifies Operations, Administration, and Maintenance (OAM) messages to indicate service disruptive conditions for MPLS-based transport network Label Switched Paths. The notification mechanism employs a generic method for a service disruptive condition to be communicated to a Maintenance Entity Group End Point. This document defines an MPLS OAM channel, along with messages to communicate various types of service disruptive conditions. [STANDARDS-TRACK] Proactive Connectivity Verification, Continuity Check, and Remote Defect Indication for the MPLS Transport Profile Continuity Check, Proactive Connectivity Verification, and Remote Defect Indication functionalities are required for MPLS Transport Profile (MPLS-TP) Operations, Administration, and Maintenance (OAM). Continuity Check monitors a Label Switched Path for any loss of continuity defect. Connectivity Verification augments Continuity Check in order to provide confirmation that the desired source is connected to the desired sink. Remote Defect Indication enables an end point to report, to its associated end point, a fault or defect condition that it detects on a pseudowire, Label Switched Path, or Section. This document specifies specific extensions to Bidirectional Forwarding Detection (BFD) and methods for proactive Continuity Check, Continuity Verification, and Remote Defect Indication for MPLS-TP pseudowires, Label Switched Paths, and Sections using BFD as extended by this memo. [STANDARDS-TRACK] An Overview of Operations, Administration, and Maintenance (OAM) Tools Operations, Administration, and Maintenance (OAM) is a general term that refers to a toolset for fault detection and isolation, and for performance measurement. Over the years, various OAM tools have been defined for various layers in the protocol stack. This document summarizes some of the OAM tools defined in the IETF in the context of IP unicast, MPLS, MPLS Transport Profile (MPLS-TP), pseudowires, and Transparent Interconnection of Lots of Links (TRILL). This document focuses on tools for detecting and isolating failures in networks and for performance monitoring. Control and management aspects of OAM are outside the scope of this document. Network repair functions such as Fast Reroute (FRR) and protection switching, which are often triggered by OAM protocols, are also out of the scope of this document. The target audience of this document includes network equipment vendors, network operators, and standards development organizations. This document can be used as an index to some of the main OAM tools defined in the IETF. At the end of the document, a list of the OAM toolsets and a list of the OAM functions are presented as a summary. Detecting Multiprotocol Label Switched (MPLS) Data-Plane Failures This document describes a simple and efficient mechanism to detect data-plane failures in Multiprotocol Label Switching (MPLS) Label Switched Paths (LSPs). It defines a probe message called an "MPLS echo request" and a response message called an "MPLS echo reply" for returning the result of the probe. The MPLS echo request is intended to contain sufficient information to check correct operation of the data plane and to verify the data plane against the control plane, thereby localizing faults. This document obsoletes RFCs 4379, 6424, 6829, and 7537, and updates RFC 1122. Bidirectional Forwarding Detection (BFD) for Multipoint Networks This document describes extensions to the Bidirectional Forwarding Detection (BFD) protocol for its use in multipoint and multicast networks. This document updates RFC 5880. Simple Two-Way Active Measurement Protocol This document describes the Simple Two-way Active Measurement Protocol (STAMP), which enables the measurement of both one-way and round-trip performance metrics, like delay, delay variation, and packet loss. Simple Two-Way Active Measurement Protocol Optional Extensions This document describes optional extensions to Simple Two-way Active Measurement Protocol (STAMP) that enable measurement of performance metrics. The document also defines a STAMP Test Session Identifier and thus updates RFC 8762. Alternate-Marking Method This document describes the Alternate-Marking technique to perform packet loss, delay, and jitter measurements on live traffic. This technology can be applied in various situations and for different protocols. According to the classification defined in RFC 7799, it could be considered Passive or Hybrid depending on the application. This document obsoletes RFC 8321. Clustered Alternate-Marking Method This document generalizes and expands the Alternate-Marking methodology to measure any kind of unicast flow whose packets can follow several different paths in the network; this can result in a multipoint-to-multipoint network. The network clustering approach is presented and, for this reason, the technique described here is called "Clustered Alternate Marking". This document obsoletes RFC 8889. Bidirectional Forwarding Detection (BFD) for Multipoint Networks over Point-to-Multipoint MPLS Label Switched Paths (LSPs) This document describes procedures for using Bidirectional Forwarding Detection (BFD) for multipoint networks to detect data plane failures in point-to-multipoint MPLS Label Switched Paths (LSPs) and Segment Routing (SR) point-to-multipoint policies with an SR over MPLS (SR-MPLS) data plane. Furthermore, this document updates RFC 8562 by recommending the use of an IPv6 address from the Dummy IPv6 Prefix address block 100:0:0:1::/64 and discouraging the use of an IPv4 loopback address mapped to IPv6. In addition, this document describes the applicability of LSP Ping (as an in-band solution) and the control plane (as an out-of-band solution) to bootstrap a BFD session. The document also describes the behavior of the active tail for head notification.

Acknowledgements The authors would like to thank for the comments and suggestions that helped improve this document.

Contributors

nordmark@acm.org

Google

aldrin.ietf@gmail.com

veronique_cheng@hotmail.com

nobo.akiya.dev@gmail.com