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

defines a method of using Bidirectional Detection (BFD) 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.

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

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 when, and only when, they appear in all capitals, as shown here.

defines the tail of multipoint BFD session demultiplexes received BFD control packet based not on Your Discriminator, as defined in , 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.

IP/UDP encapsulation for multipoint BFD over p2mp MPLS LSP follows the same rules as defined in Section 7 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 used for LSP Ping to exercise that particular alternative path; or the MultipointHead MAY use, as destination IP address, the IP address discovered by LSP Ping traceroute to exercise that particular alternate path.

Non-IP encapsulation for multipoint BFD over p2mp MPLS LSP MUST use Generic Associated Channel (G-ACh) Label (GAL) at the bottom of the label stack followed by Associated Channel Header (ACH). Channel Type field in ACH MUST be set to BFD CV . To provide identity of the MultipointHead for the particular multipoint BFD session this document defines new Source MEP ID type TBA1 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.

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

BGP-BFD Attribute MAY be used to bootstrap multipoint BFD session on a tail.

This document does not introduce new security aspects but inherits all security considerations from , , , , , and .

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. Value Description Reference TBA1 IP Address This document