| MPLS Working Group | G. Mirsky |
| Internet-Draft | ZTE Corp. |
| Intended status: Standards Track | October 12, 2018 |
| Expires: April 15, 2019 |
BFD for Multipoint Networks over Point-to-Multi-Point MPLS LSP
draft-mirsky-mpls-p2mp-bfd-04
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 the applicability of out-band solutions to bootstrap a BFD session in this environment.
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[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 the 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 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.
[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 a 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 the 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.
[I-D.ietf-bfd-multipoint] defines IP/UDP encapsulation for multipoint BFD over p2mp MPLS LSP:
This specification further clarifies that:
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 the identity of the MultipointHead for the particular multipoint BFD session this document defines new Source MEP ID IP Address type (TBA1) in Section 6.1. If the Length value is 4, then the Value field contains an IPv4 address. If the Length value is 16, then the Value field contains an IPv6 address. Any other value of the Length field MUST be considered as an error, and the BFD control packet MUST be discarded.
MaultipointHead MAY use LSP Ping [RFC8029] using in Target FEC TLV, as appropriate, sub-TLVs defined in Section 3.1 [RFC6425].
BGP-BFD Attribute [I-D.ietf-bess-mvpn-fast-failover] 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 [RFC5880], [RFC5884], [RFC7726], [I-D.ietf-bfd-multipoint], [RFC8029], and [RFC6425].
IANA is required to allocate value (TBD) for the 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 |
TBD