Applicability of Bidirectional Forwarding Detection (BFD) for Multi-point Networks in Virtual Router Redundancy Protocol (VRRP)
draft-ietf-rtgwg-vrrp-p2mp-bfd-09

RTGWG                                                          G. Mirsky
Internet-Draft                                                  Ericsson
Updates: 5798bis (if approved)                               J. Tantsura
Intended status: Standards Track                                  NVIDIA
Expires: 27 February 2025                                      G. Mishra
                                                            Verizon Inc.
                                                          26 August 2024

  Applicability of Bidirectional Forwarding Detection (BFD) for Multi-
      point Networks in Virtual Router Redundancy Protocol (VRRP)
                   draft-ietf-rtgwg-vrrp-p2mp-bfd-09

Abstract

   This document discusses the applicability of Bidirectional Forwarding
   Detection (BFD) for multipoint networks to provide Virtual Router
   Redundancy Protocol with sub-second convergence for the process
   determining the Active router and defines the extension to bootstrap
   point-to-multipoint BFD session.

   This draft updates RFC 5798bis [Ed.Note: When the RFC 5798bis is
   published, change to the assigned new number].

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 27 February 2025.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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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  . . . . . . . . . . . . . . . . . . . . . .   6
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The [I-D.ietf-rtgwg-vrrp-rfc5798bis] 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 [I-D.ietf-rtgwg-vrrp-rfc5798bis] 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 [I-D.ietf-rtgwg-vrrp-rfc5798bis] 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 [I-D.ietf-rtgwg-vrrp-rfc5798bis] 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
      [I-D.ietf-rtgwg-vrrp-rfc5798bis];

      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
   [I-D.ietf-rtgwg-vrrp-rfc5798bis] 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

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   former is the 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
   [I-D.ietf-rtgwg-vrrp-rfc5798bis], to accelerate detecting a failure
   that affects VRRP functionality using p2mp BFD.  The operation of
   either protocol is not changed.

   Security considerations discussed in
   [I-D.ietf-rtgwg-vrrp-rfc5798bis], [RFC5880], [RFC5881], and
   [RFC8562], apply to this document.

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6.  Acknowledgements

7.  Normative References

   [I-D.ietf-rtgwg-vrrp-rfc5798bis]
              Lindem, A. and A. Dogra, "Virtual Router Redundancy
              Protocol (VRRP) Version 3 for IPv4 and IPv6", Work in
              Progress, Internet-Draft, draft-ietf-rtgwg-vrrp-
              rfc5798bis-18, 4 January 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-rtgwg-
              vrrp-rfc5798bis-18>.

   [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>.

Authors' Addresses

   Greg Mirsky
   Ericsson
   Email: gregimirsky@gmail.com

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

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

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