BFD for Multipoint Networks over Point-to-Multi-Point MPLS LSP
draft-mirsky-mpls-p2mp-bfd-01

Abstract

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

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on December 30, 2017.

Copyright Notice

Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved.

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Table of Contents

• 1. Introduction
• 2. Conventions used in this document
• 2.1. Terminology
• 2.2. Requirements Language
• 3. Multipoint BFD Encapsulation
• 3.1. IP Encapsulation of Multipoint BFD
• 3.2. Non-IP Encapsulation of Multipoint BFD
• 4. Bootstrapping Multipoint BFD
• 4.1. LSP Ping
• 4.2. Control Plane
• 5. Security Considerations
• 6. IANA Considerations
• 6.1. Source MEP ID IP Address Type
• 7. Acknowledgements
• 8. Normative References
• Author's Address

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 the tail of multipoint BFD session demultiplexes received BFD control packet based not on Your Discriminator, as defined in [RFC5880], but using 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.

3.1. IP Encapsulation of Multipoint BFD

IP/UDP encapsulation for multipoint BFD over p2mp MPLS LSP follows the same rules as defined in Section 7 [RFC5884] for BFD over p2p LSP:

• UDP destination port MUST be set to 3784;
• destination IP address MUST be from the 127/8 range for IPv4 and from the 0:0:0:0:0:FFFF:7F00/104 range for IPv6;
• if multiple alternative paths for the given p2mp LSP Forwarding Equivalence Class(FEC) exist, the MultipointHead SHOULD use Entropy Label [RFC6790] used for LSP Ping [RFC8029] to exercise that particular alternative path;
• or the MultipointHead MAY use, as destination IP address, the IP address discovered by LSP Ping traceroute [RFC8029] to exercise that particular alternate path.

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.

7. Acknowledgements

8. Normative References

Author's Address