BFD Working Group G. Mirsky
Internet-Draft ZTE Corp.
Intended status: Standards Track February 15, 2018
Expires: August 19, 2018

BFD for Multipoint Networks over Point-to-Multi-Point MPLS LSP


This document describes procedures for using Bidirectional Forwarding Detection (BFD) for multipoint networks to detect data plane failures in Multiprotocol Label Switching (MPLS) point-to-multipoint (p2mp) Label Switched Paths (LSPs). It also describes applicability of out-band solutions to bootstrap a BFD session in this environment.

Status of This Memo

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This Internet-Draft will expire on August 19, 2018.

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Table of Contents

1. Introduction

[I-D.ietf-bfd-multipoint] defines a method of using Bidirectional Detection (BFD) [RFC5880] to monitor and detect unicast failures between the sender (head) and one or more receivers (tails) in multipoint or multicast networks. This document describes procedures for using such mode of BFD protocol to detect data plane failures in Multiprotocol Label Switching (MPLS) point-to-multipoint (p2mp) Label Switched Paths (LSPs). The document also describes applicability of out-band solutions to bootstrap a BFD session in this environment.

2. Conventions used in this document

2.1. Terminology

MPLS: Multiprotocol Label Switching

LSP: Label Switched Path

BFD: Bidirectional Forwarding Detection

p2mp: Point-to-Multipoint

FEC: Forwarding Equivalence Class

G-ACh: Generic Associated Channel

ACH: Associated Channel Header

GAL: G-ACh Label

2.2. 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.

3. Multipoint BFD Encapsulation

[I-D.ietf-bfd-multipoint] defines how the tail of multipoint BFD session demultiplexes received BFD control packet when Your Discriminator is not set, i.e. equals zero. Because [I-D.ietf-bfd-multipoint] uses BFD in Demand mode the head of BFD multipoint session transmits BFD control packets with Your Discriminator set to zero. As result, a tail cannot demultiplex BFD sessions using Your Discriminator, as defined in [RFC5880]. [I-D.ietf-bfd-multipoint] requires that in order to demultiplex BFD sessions the tail uses source IP address, My Discriminator and the identity of the multipoint tree which the Multipoint BFD Control packet was received from. The identity of the multipoint tree MAY be provided by the p2mp MPLS LSP label in case of inclusive p-tree or upstream assigned label in case of aggregate p-tree. The source IP address MAY be drawn from the IP header, if BFD control packet transmitted by the head using IP/UDP encapsulation as described in Section 3.1. Non-IP encapsulation case described in Section 3.2.

3.1. IP Encapsulation of Multipoint BFD

[I-D.ietf-bfd-multipoint] defines IP/UDP encapsulation for multipoint BFD over p2mp MPLS LSP:

This specification further clarifies that:

3.2. Non-IP Encapsulation of Multipoint BFD

Non-IP encapsulation for multipoint BFD over p2mp MPLS LSP MUST use Generic Associated Channel (G-ACh) Label (GAL) [RFC5586] at the bottom of the label stack followed by Associated Channel Header (ACH). Channel Type field in ACH MUST be set to BFD CV [RFC6428]. To provide identity of the MultipointHead for the particular multipoint BFD session this document defines new Source MEP ID type TBA1 Section 6.1 IP Address. If the Length value is 4, then the Value field contains IPv4 address. If the Length value is 16, then the Value field contains IPv6 address. Any other value of the Length field MUST be considered as error and the BFD control packet MUST be discarded.

4. Bootstrapping Multipoint BFD

4.1. LSP Ping

MaultipointHead MAY use LSP Ping [RFC8029] using in Target FEC TLV, as appropriate, sub-TLVs defined in Section 3.1 [RFC6425].

4.2. Control Plane

BGP-BFD Attribute [I-D.ietf-bess-mvpn-fast-failover] MAY be used to bootstrap multipoint BFD session on a tail.

5. Security Considerations

This document does not introduce new security aspects but inherits all security considerations from [RFC5880], [RFC5884], [RFC7726], [I-D.ietf-bfd-multipoint], [RFC8029], and [RFC6425].

6. IANA Considerations

6.1. Source MEP ID IP Address Type

IANA is required to allocate value (TBD) for the Source Source MEP ID IP Address type from the "CC/CV MEP-ID TLV" registry which is under the "Pseudowire Associated Channel Types" registry.

Source MEP ID IP Address TLV Type
Value Description Reference
TBA1 IP Address This document

7. Acknowledgements

8. Normative References

[I-D.ietf-bess-mvpn-fast-failover] Morin, T. and R. Kebler, "Multicast VPN fast upstream failover", Internet-Draft draft-ietf-bess-mvpn-fast-failover-02, March 2017.
[I-D.ietf-bfd-multipoint] Katz, D., Ward, D., Networks, J. and G. Mirsky, "BFD for Multipoint Networks", Internet-Draft draft-ietf-bfd-multipoint-13, January 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC5586] Bocci, M., Vigoureux, M. and S. Bryant, "MPLS Generic Associated Channel", RFC 5586, DOI 10.17487/RFC5586, June 2009.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010.
[RFC5884] Aggarwal, R., Kompella, K., Nadeau, T. and G. Swallow, "Bidirectional Forwarding Detection (BFD) for MPLS Label Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884, June 2010.
[RFC6425] Saxena, S., Swallow, G., Ali, Z., Farrel, A., Yasukawa, S. and T. Nadeau, "Detecting Data-Plane Failures in Point-to-Multipoint MPLS - Extensions to LSP Ping", RFC 6425, DOI 10.17487/RFC6425, November 2011.
[RFC6428] Allan, D., Swallow, G. and J. Drake, "Proactive Connectivity Verification, Continuity Check, and Remote Defect Indication for the MPLS Transport Profile", RFC 6428, DOI 10.17487/RFC6428, November 2011.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W. and L. Yong, "The Use of Entropy Labels in MPLS Forwarding", RFC 6790, DOI 10.17487/RFC6790, November 2012.
[RFC7726] Govindan, V., Rajaraman, K., Mirsky, G., Akiya, N. and S. Aldrin, "Clarifying Procedures for Establishing BFD Sessions for MPLS Label Switched Paths (LSPs)", RFC 7726, DOI 10.17487/RFC7726, January 2016.
[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Kumar, N., Aldrin, S. and M. Chen, "Detecting Multiprotocol Label Switched (MPLS) Data-Plane Failures", RFC 8029, DOI 10.17487/RFC8029, March 2017.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017.

Author's Address

Greg Mirsky ZTE Corp. EMail: