Applicability of Bidirectional Forwarding Detection (BFD) for Multi-point Networks in Virtual Router Redundancy Protocol (VRRP)
draft-ietf-rtgwg-vrrp-p2mp-bfd-12

RTGWG                                                          G. Mirsky
Internet-Draft                                                  Ericsson
Updates: 9568 (if approved)                                  J. Tantsura
Intended status: Standards Track                                  NVIDIA
Expires: 17 August 2025                                        G. Mishra
                                                            Verizon Inc.
                                                        13 February 2025

  Applicability of Bidirectional Forwarding Detection (BFD) for Multi-
      point Networks in Virtual Router Redundancy Protocol (VRRP)
                   draft-ietf-rtgwg-vrrp-p2mp-bfd-12

Abstract

   This document explores the applicability of Bidirectional Forwarding
   Detection (BFD) in multipoint networks to enable sub-second
   convergence in the Virtual Router Redundancy Protocol (VRRP) for
   determining the Active Router.  Additionally, it defines extensions
   to bootstrap point-to-multipoint BFD sessions using an IPv4/IPv6 VRRP
   Advertisement message, and, thus, updates RFC 9568.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 17 August 2025.

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   Please review these documents carefully, as they describe your rights

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   and restrictions with respect to this document.  Code Components
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions used in this document . . . . . . . . . . . .   3
       1.1.1.  Terminology . . . . . . . . . . . . . . . . . . . . .   3
       1.1.2.  Requirements Language . . . . . . . . . . . . . . . .   3
   2.  Applicability of p2mp BFD . . . . . . . . . . . . . . . . . .   3
     2.1.  Multipoint BFD Encapsulation  . . . . . . . . . . . . . .   5
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   The [RFC9568] is the current Virtual Router Redundancy Protocol
   (VRRP) specification for IPv4 and IPv6 networks.  VRRPv3 allows for a
   faster switchover to a Backup Router.  A router may be part of
   several Virtual Router Redundancy groups, such as Active in some and
   Backup in others.  Supporting sub-second mode for VRRPv3 [RFC9568]
   for all these roles without specialized support in the data plane may
   prove challenging because of the increased load on the control plane.
   However, it may still be possible to deploy VRRP and provide sub-
   second detection of Active Router failure by Backup Routers.

   Bidirectional Forwarding Detection (BFD) [RFC5880] had been
   originally defined to detect failure of point-to-point (p2p) paths:
   single-hop [RFC5881], multihop [RFC5883].  Single-hop BFD may enable
   a Backup router to detect a failure of the Active router within sub-
   seconds.

   [RFC8562] extends [RFC5880] for multipoint and multicast networks,
   which matches the deployment scenarios for VRRP over the LAN segment.
   This document demonstrates how point-to-multipoint (p2mp) BFD can
   enable faster detection of the Active Router failure and thus
   minimize service disruption in a VRRP domain.  It also defines the
   extension to VRRP [RFC9568] to bootstrap a VRRP Backup Router to join
   a p2mp BFD session.

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1.1.  Conventions used in this document

1.1.1.  Terminology

   BFD: Bidirectional Forwarding Detection

   p2mp: Pont-to-Multipoint

   VRRP: Virtual Router Redundancy Protocol

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 document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Applicability of p2mp BFD

   [RFC8562] may provide an efficient and scalable solution for fast-
   converging environment that uses the default route rather than
   dynamic routing.  Each redundancy group presents itself as a p2mp BFD
   session, with its Active Router being the head and Backup Routers
   being the tails of the p2mp BFD session.  Figure 1 displays the
   extension of the VRRP Advertisement packet [RFC9568] to enable a
   Backup Router, acting as a tail of the p2mp BFD session, to monitor
   the state of the Active Router, acting as the head of the p2mp BFD
   session.

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        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Version| Type  | Virtual Rtr ID|   Priority    |Count IPvX Addr|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Rsvd |B|     Max Adver Int     |          Checksum             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       +                                                               +
       |                       IPvX Address(es)                        |
       +                                                               +
       +                                                               +
       +                                                               +
       +                                                               +
       |                                                               |
       +                                                               +
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                   Active Router Discriminator                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Figure 1: Extension of the VRRP Advertisement Packet in Support
                            of P2MP BFD Session

   The new fields are interpreted as follows:

      B(FD) - a one-bit flag that indicates that the Active Router
      Discriminator field is appended to VRRP Advertisement packet
      defined in [RFC9568];

      Active Router Discriminator - the four-octet field.  The value
      MUST NOT be zero, and it equals the My Discriminator [RFC5880]
      value allocated by the head of the p2mp BFD session.

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   The Active Router, configured to use p2mp BFD to support faster
   convergence of VRRP, MUST transmit VRRP Advertisement as shown in
   Figure 1.  Allso, the Active Router starts transmitting BFD control
   packets with IPvX address associated with the Virtual Router
   [RFC9568] as a source IP address and the locally allocated value as
   the value of the My Discriminator field ([RFC5880]).  The same non-
   zero value of My Discriminator MUST be set as the value of the Active
   Router Discriminator field.  The BFD flag MUST be set in the VRRP
   Advertisement packet.  A Backup Router demultiplexes p2mp BFD test
   sessions based on IPvX address associated with the Virtual Router
   that it has been configured with and the non-zero My Discriminator
   value it learns from the received VRRP Advertisement packet.  When a
   Backup router detects the failure of the Active Router, according to
   the Section 5.11 [RFC8562], it re-evaluates its role in the Virtual
   Router.  As a result, the Backup Router may become the Active router
   of the given Virtual Router or continue as a Backup Router.

      If the former is the case, then the new Active router MUST select
      its new My Discriminator value, include that value in the VRRP
      Advertisement packet to bootstrap a new p2mp BFD session, and
      start transmitting p2mp BFD control packets using the Active
      Router IP address as the source IP address for p2mp BFD control
      packets and its new My Discriminator value.

      If the latter is the case, the Backup Router MUST close and remove
      the p2mp BFD session associated with the failed Active Router.
      The VRRP Advertisement packet from the new VRRP Active Router will
      bootstrap the new p2mp BFD session.

2.1.  Multipoint BFD Encapsulation

   The MultipointHead of p2mp BFD session when transmitting BFD control
   packet:

      Set the source MAC address according to rules in Section 7.3 of
      [RFC9568];

      MUST set TTL or Hop Limit value to 255 (Section 5 [RFC5881]).
      Similarly, all received BFD Control packets that are demultiplexed
      to the session MUST be discarded if the received TTL or Hop Limit
      is not equal to 255;

      SHOULD use group address VRRP ('224.0.0.18' for IPv4 and
      'FF02:0:0:0:0:0:0:12' for IPv6) as destination IP address;

      MAY use network broadcast address for IPv4 or link-local all nodes
      multicast group for IPv6 as destination IP address;

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      MUST set destination UDP port value to 3784 when transmitting BFD
      control packets, as defined in [RFC8562];

      Source UDP port value selection follows the rules defined in
      Section 4 of [RFC5881];

      MUST use the Active Router IP address as the source IP address.

3.  IANA Considerations

   This document makes no requests for IANA allocations.  This section
   may be deleted by RFC Editor.

4.  Security Considerations

   This document defines an alternative way, to the one defined in
   [RFC9568], to accelerate detecting a failure that affects VRRP
   functionality using p2mp BFD.  The operation of either protocol is
   not changed.

   Security considerations discussed in [RFC9568], [RFC5880], [RFC5881],
   and [RFC8562], apply to this document.

5.  Acknowledgements

6.  Normative References

   [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>.

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
              <https://www.rfc-editor.org/info/rfc5880>.

   [RFC5881]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881,
              DOI 10.17487/RFC5881, June 2010,
              <https://www.rfc-editor.org/info/rfc5881>.

   [RFC5883]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883,
              June 2010, <https://www.rfc-editor.org/info/rfc5883>.

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   [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>.

   [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>.

   [RFC9568]  Lindem, A. and A. Dogra, "Virtual Router Redundancy
              Protocol (VRRP) Version 3 for IPv4 and IPv6", RFC 9568,
              DOI 10.17487/RFC9568, April 2024,
              <https://www.rfc-editor.org/info/rfc9568>.

Authors' Addresses

   Greg Mirsky
   Ericsson
   Email: gregimirsky@gmail.com

   Jeff Tantsura
   NVIDIA
   Email: jefftant.ietf@gmail.com

   Gyan Mishra
   Verizon Inc.
   Email: gyan.s.mishra@verizon.com

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