Bidirectional Forwarding Detection (BFD) for Multi-point Networks and Virtual Router Redundancy Protocol (VRRP) Use Case
draft-mirsky-bfd-p2mp-vrrp-use-case-06
BFD Working Group G. Mirsky
Internet-Draft ZTE Corp.
Updates: 5798 (if approved) J. Tantsura
Intended status: Standards Track Juniper Networks
Expires: 27 September 2021 G. Mishra
Verizon Inc.
26 March 2021
Bidirectional Forwarding Detection (BFD) for Multi-point Networks and
Virtual Router Redundancy Protocol (VRRP) Use Case
draft-mirsky-bfd-p2mp-vrrp-use-case-06
Abstract
This document discusses the use of Bidirectional Forwarding Detection
(BFD) for multipoint networks to provide Virtual Router Redundancy
Protocol (VRRP) with sub-second Master convergence 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
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This Internet-Draft will expire on 27 September 2021.
Copyright Notice
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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 . . . . . . . . . . . . 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 [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 Master 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 Master router
within 100 msec or faster.
[RFC8562] extends [RFC5880] for multipoint and multicast networks,
which is precisely characterizes deployment scenarios for VRRP over
LAN segment. This document demonstrates how point-to-multipoint
(p2mp) BFD can enable faster detection of Master 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 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
Master in some and as Backup in others. Supporting sub-second mode
for VRRPv3 [RFC5798] for all these roles without specialized support
in 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 Master being the root and Backup routers being tails
of the p2mp BFD session. Figure 1 displays the extension of VRRP
[RFC5798] to bootstrap tail of the p2mp BFD session. Master
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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) |
+ +
+ +
+ +
+ +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Master Discriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: VRRP Extension to Bootstrap P2MP BFD session
where new fields are interpreted as:
B(FD) - a one-bit flag that indicates that the Master
Discriminator field is appended to VRRP packet defined in
[RFC5798];
Master Discriminator - My Discriminator value allocated by the
root of the p2mp BFD session.
The Master router that is configured to use p2mp BFD to support
faster convergence of VRRP starts transmitting BFD control packets
with VRID as a source IP address and My Discriminator. The same
value of My Discriminator MUST be set as the value of the Master
Discriminator field. The BFD flag MUST be set in the VRRP packet.
Backup router demultiplexes p2mp BFD test sessions based on VRID that
it been configured with and the My Discriminator value it learns from
the received VRRP packet. When a Backup router detects the failure
of the Master router it re-evaluates its role in the VRID. As a
result, the Backup router may become the Master router of the given
VRID or continue as a Backup router. If the former is the case, then
the new Master router MUST select My Discriminator and start
transmitting p2mp BFD control packets using Master IP address as the
source IP address for p2mp BFD control packets. If the latter is the
case, then the Backup router MUST wait for the VRRP packet from the
new VRRP Master router that will bootstrap the new p2mp BFD session.
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3.1. Multipoint BFD Encapsulation
The MultipointHead of p2mp BFD session when transmitting BFD control
packet:
MUST set TTL value to 1 (though note that VRRP packets have TTL
set 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 Master 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
Security considerations discussed in [RFC5798], [RFC5880], and
[RFC8562], apply to this document.
6. Acknowledgements
7. 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>.
[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>.
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[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
ZTE Corp.
Email: gregimirsky@gmail.com, gregory.mirsky@ztetx.com
Jeff Tantsura
Juniper Networks
Email: jefftant.ietf@gmail.com
Gyan Mishra
Verizon Inc.
Email: gyan.s.mishra@verizon.com
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