Generic Application of Bidirectional Forwarding Detection (BFD)
RFC 5882

Internet Engineering Task Force (IETF)                           D. Katz
Request for Comments: 5882                                       D. Ward
Category: Standards Track                               Juniper Networks
ISSN: 2070-1721                                                June 2010

    Generic Application of Bidirectional Forwarding Detection (BFD)

Abstract

   This document describes the generic application of the Bidirectional
   Forwarding Detection (BFD) protocol.

Status of This Memo

   This is an Internet Standards Track document.

   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).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc5882.

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   Copyright (c) 2010 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
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   described in the Simplified BSD License.

Katz & Ward                  Standards Track                    [Page 1]
RFC 5882               Generic Application of BFD              June 2010

Table of Contents

   1. Introduction ....................................................3
      1.1. Conventions Used in This Document ..........................3
   2. Overview ........................................................3
   3. Basic Interaction between BFD Sessions and Clients ..............4
      3.1. Session State Hysteresis ...................................4
      3.2. AdminDown State ............................................5
      3.3. Hitless Establishment/Reestablishment of BFD State .........5
   4. Control Protocol Interactions ...................................6
      4.1. Adjacency Establishment ....................................6
      4.2. Reaction to BFD Session State Changes ......................7
           4.2.1. Control Protocols with a Single Data Protocol .......7
           4.2.2. Control Protocols with Multiple Data Protocols ......8
      4.3. Interactions with Graceful Restart Mechanisms ..............8
           4.3.1. BFD Fate Independent of the Control Plane ...........9
           4.3.2. BFD Shares Fate with the Control Plane ..............9
      4.4. Interactions with Multiple Control Protocols ..............10
   5. Interactions with Non-Protocol Functions .......................10
   6. Data Protocols and Demultiplexing ..............................11
   7. Multiple Link Subnetworks ......................................11
      7.1. Complete Decoupling .......................................12
      7.2. Layer N-1 Hints ...........................................12
      7.3. Aggregating BFD Sessions ..................................12
      7.4. Combinations of Scenarios .................................12
   8. Other Application Issues .......................................13
   9. Interoperability Issues ........................................13
   10. Specific Protocol Interactions (Non-Normative) ................13
      10.1. BFD Interactions with OSPFv2, OSPFv3, and IS-IS ..........14
           10.1.1. Session Establishment .............................14
           10.1.2. Reaction to BFD State Changes .....................14
           10.1.3. OSPF Virtual Links ................................15
      10.2. Interactions with BGP ....................................15
      10.3. Interactions with RIP ....................................15
   11. Security Considerations .......................................16
   12. References ....................................................16
      12.1. Normative References .....................................16
      12.2. Informative References ...................................16

Katz & Ward                  Standards Track                    [Page 2]
RFC 5882               Generic Application of BFD              June 2010

1.  Introduction

   The Bidirectional Forwarding Detection [BFD] protocol provides a