Applicability of Bidirectional Forwarding Detection (BFD) for Multi-point Networks in Virtual Router Redundancy Protocol (VRRP)
draft-ietf-rtgwg-vrrp-p2mp-bfd-10

RTGWG                                                          G. Mirsky
Internet-Draft                                                  Ericsson
Updates: 9568 (if approved)                                  J. Tantsura
Intended status: Standards Track                                  NVIDIA
Expires: 29 May 2025                                           G. Mishra
                                                            Verizon Inc.
                                                        25 November 2024

  Applicability of Bidirectional Forwarding Detection (BFD) for Multi-
      point Networks in Virtual Router Redundancy Protocol (VRRP)
                   draft-ietf-rtgwg-vrrp-p2mp-bfd-10

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

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 29 May 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.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Applicability of p2mp BFD . . . . . . . . . . . . . . . . . .   3
     3.1.  Multipoint BFD Encapsulation  . . . . . . . . . . . . . .   5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The [RFC9568] is the current specification of the Virtual Router
   Redundancy Protocol (VRRP) for IPv4 and IPv6 networks.  VRRPv3 allows
   for a faster switchover to a Backup Router.  Using such capability
   with the software-based implementation of VRRP may prove challenging.
   But it still may 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 be used
   to enable Backup Routers to detect a failure of the Active router
   within 100 msec or faster.

   [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.  The document also
   defines the extension to VRRP [RFC9568] to bootstrap a VRRP Backup
   Router to join in 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.  Problem Statement

   A router may be part of several Virtual Router Redundancy groups, as
   Active in some and as 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.  BFD already has many implementations based on
   HW that are capable of supporting multiple sub-second sessions
   concurrently.

3.  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 root and Backup Routers
   being the tails of the p2mp BFD session.  Figure 1 displays the
   extension of VRRP [RFC9568] to bootstrap a tail 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: VRRP Extension to Bootstrap 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 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 root of the p2mp BFD session.

   The Active router, configured to use p2mp BFD to support faster
   convergence of VRRP, 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 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 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

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   case, then the new Active router MUST select its new My Discriminator
   value, include that value in the VRRP 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 wait for the VRRP packet from the
   new VRRP Active router that will bootstrap the new p2mp BFD session.

3.1.  Multipoint BFD Encapsulation

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

      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;

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

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

4.  IANA Considerations

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

5.  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.

6.  Acknowledgements

7.  Normative References

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   [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>.

   [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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