Bidirectional Forwarding Detection (BFD) Directed Return Path for MPLS Label Switched Paths (LSPs)
draft-ietf-mpls-bfd-directed-15

Document Type Active Internet-Draft (mpls WG)
Authors Greg Mirsky  , Jeff Tantsura  , Ilya Varlashkin  , Mach Chen 
Last updated 2020-08-04
Replaces draft-mirsky-mpls-bfd-directed
Stream IETF
Intended RFC status Proposed Standard
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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

   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
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   This Internet-Draft will expire on February 5, 2021.

Copyright Notice

   Copyright (c) 2020 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

Mirsky, et al.          Expires February 5, 2021                [Page 1]
Internet-Draft   BFD Directed Return Path for MPLS LSPs      August 2020

   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   described in the Simplified BSD License.

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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