Applicability of Bidirectional Forwarding Detection (BFD) for Multi-point Networks in Virtual Router Redundancy Protocol (VRRP)
draft-ietf-rtgwg-vrrp-p2mp-bfd-02
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| Authors | Greg Mirsky , Jeff Tantsura , Gyan Mishra | ||
| Last updated | 2022-03-31 | ||
| Replaces | draft-mtm-rtgwg-vrrp-p2mp-bfd | ||
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draft-ietf-rtgwg-vrrp-p2mp-bfd-02
BFD Working Group G. Mirsky
Internet-Draft Ericsson
Updates: 5798 (if approved) J. Tantsura
Intended status: Standards Track Microsoft
Expires: 2 October 2022 G. Mishra
Verizon Inc.
31 March 2022
Applicability of Bidirectional Forwarding Detection (BFD) for Multi-
point Networks in Virtual Router Redundancy Protocol (VRRP)
draft-ietf-rtgwg-vrrp-p2mp-bfd-02
Abstract
This document discusses the applicability of Bidirectional Forwarding
Detection (BFD) for multipoint networks to provide Virtual Router
Redundancy Protocol (VRRP) with sub-second convergence of the Active
router and defines the extension to bootstrap point-to-multipoint BFD
session.
This draft updates RFC 5798.
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
Task Force (IETF). Note that other groups may also distribute
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 2 October 2022.
Copyright Notice
Copyright (c) 2022 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 publication of this document.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used in this document . . . . . . . . . . . . 2
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 [RFC5798] 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 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 [RFC5798] to bootstrap a VRRP Backup
router to join in a p2mp BFD session.
1.1. Conventions used in this document
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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 [RFC5798] for all these roles without specialized support
in the data plane may prove challenging. 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 [RFC5798] 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
[RFC5798];
Active Router Discriminator - the four-octet field. The value
MUST NOT be zero, and it equals the My Discriminator 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
VRID 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 VRID 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, it re-
evaluates its role in the VRID. As a result, the Backup router may
become the Active router of the given VRID or continue as a Backup
router. If the former is the case, then the new Active router MUST
select My Discriminator and start transmitting p2mp BFD control
packets using Active router IP address as the source IP address for
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p2mp BFD control packets. If the latter is the case, then 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
[RFC5798], to accelerate detecting a failure that affects VRRP
functionality using p2mp BFD. The operation of either protocol is
not changed.
Security considerations discussed in [RFC5798], [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>.
[RFC5798] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP)
Version 3 for IPv4 and IPv6", RFC 5798,
DOI 10.17487/RFC5798, March 2010,
<https://www.rfc-editor.org/info/rfc5798>.
[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
Jeff Tantsura
Microsoft
Email: jefftant.ietf@gmail.com
Gyan Mishra
Verizon Inc.
Email: gyan.s.mishra@verizon.com
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