Bidirectional Forwarding Detection (BFD) Directed Return Path for MPLS Label Switched Paths (LSPs)
draft-ietf-mpls-bfd-directed-15
MPLS Working Group G. Mirsky
Internet-Draft ZTE
Intended status: Standards Track J. Tantsura
Expires: February 5, 2021 Nuage Networks
I. Varlashkin
Google
M. Chen
Huawei
August 4, 2020
Bidirectional Forwarding Detection (BFD) Directed Return Path for MPLS
Label Switched Paths (LSPs)
draft-ietf-mpls-bfd-directed-15
Abstract
Bidirectional Forwarding Detection (BFD) is expected to be able to
monitor a wide variety of encapsulations of paths between systems.
When a BFD session monitors an explicitly routed unidirectional path
there may be a need to direct egress BFD peer to use a specific path
for the reverse direction of the BFD session.
Status of This Memo
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This Internet-Draft will expire on February 5, 2021.
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Internet-Draft BFD Directed Return Path for MPLS LSPs August 2020
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used in this document . . . . . . . . . . . . 3
1.1.1. Requirements Language . . . . . . . . . . . . . . . . 3
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
3. Control of the Reverse BFD Path . . . . . . . . . . . . . . . 3
3.1. BFD Reverse Path TLV . . . . . . . . . . . . . . . . . . 3
3.2. Return Codes . . . . . . . . . . . . . . . . . . . . . . 5
4. Use Case Scenario . . . . . . . . . . . . . . . . . . . . . . 5
5. Operational Considerations . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6.1. BFD Reverse Path TLV . . . . . . . . . . . . . . . . . . 6
6.2. Return Code . . . . . . . . . . . . . . . . . . . . . . . 7
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9. Normative References . . . . . . . . . . . . . . . . . . . . 8
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
[RFC5880], [RFC5881], and [RFC5883] established the BFD protocol for
IP networks. [RFC5884] and [RFC7726] set rules for using BFD
asynchronous mode over IP/MPLS LSPs, while not defining means to
control the path an egress BFD system uses to send BFD control
packets towards the ingress BFD system.
For the case when BFD is used to detect defects of the traffic
engineered LSP the path the BFD control packets transmitted by the
egress BFD system toward the ingress may be disjoint from the LSP in
the forward direction. The fact that BFD control packets are not
guaranteed to follow the same links and nodes in both forward and
reverse directions may be one of the factors contributing to
producing false positive defect notifications, i.e., false alarms, at
the ingress BFD peer. Ensuring that both directions of the BFD
session use co-routed paths may, in some environments, improve the
determinism of the failure detection and localization.
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