BFD Working Group G. Mirsky
Internet-Draft J. Tantsura
Intended status: Informational Ericsson
Expires: January 7, 2016 July 6, 2015

Bidirectional Forwarding Detection (BFD) for Multi-point Networks and Virtual Router Redundancy Protocol (VRRP) Use Case


This document discusses use of Bidirectional Forwarding Detection (BFD) for multi-point networks to provide Virtual Router Redundancy Protocol (VRRP) with sub-second Master convergence.

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Table of Contents

1. Introduction

The [RFC5798] is the current specification of the Virtual Router Redundancy Protocol (VRRP) for IPv4 and IPv6 networks. VRRPv3 allows for faster switchover to a Backup router. Using such capability with software-based implementation of VRRP is 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 failure of the Master router within 100 msec or faster. [I-D.nitish-vrrp-bfd] demonstrates how, with some extenstions to [RFC5798], that can be achieved.

[I-D.ietf-bfd-multipoint] extends [RFC5880] for multipoint and multicast networks, which is precisely characterizes deployment scenarios for VRRP over LAN segment.

1.1. Conventions used in this document

1.1.1. Terminology

BFD: Bidirectional Forwarding Detection

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 [RFC2119].

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 to be very challenging. BFD already has many implementations based on HW that are capable to support multiple sub-second session concurrently.

3. Applicability of p2mp BFD

[I-D.ietf-bfd-multipoint] may provide the efficient and scaleable solution for fast-converging environment that uses default route rather than dynamic routing. Each redundancy group presents itself as p2mp BFD session with its Master being the root and Backup routers being tails of the p2mp BFD session. The Master router starts transmitting BFD control packets with VRID as source IP address. Backup router demultiplexes p2mp BFD test sessions based on VRID that it been configured with. Once Backup router accepts p2mp session from the new Master router backup router the Backup router MAY use My Discriminator from received p2mp BFD control packet to demultiplex p2mp BFD sessions. When a Backup router detects failure of the Master router it re-evaluates its role in the VRID. As 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 source IP address fro p2mp BFD control packets. If the latter is the case, then the Backup router MUST wait for p2mp BFD control packet with source IP address set to VRID.

4. IANA Considerations

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

5. Security Considerations

Secuirity considerations discussed in [RFC5798], [RFC5880], and [I-D.ietf-bfd-multipoint], apply to this document.

6. Acknowledgements

7. Normative References

[I-D.ietf-bfd-multipoint] Katz, D., Ward, D. and J. Networks, "BFD for Multipoint Networks", Internet-Draft draft-ietf-bfd-multipoint-06, May 2015.
[I-D.nitish-vrrp-bfd] Gupta, N., Dogra, A. and C. Docherty, "Fast failure detection using peer learning in VRRP with BFD", Internet-Draft draft-nitish-vrrp-bfd-01, June 2015.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5798] Nadas, S., "Virtual Router Redundancy Protocol (VRRP) Version 3 for IPv4 and IPv6", RFC 5798, March 2010.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD)", RFC 5880, June 2010.
[RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, June 2010.
[RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD) for Multihop Paths", RFC 5883, June 2010.

Authors' Addresses

Greg Mirsky Ericsson EMail:
Jeff Tantsura Ericsson EMail: