Bidirectional Forwarding Detection (BFD) on Multi-chassis Ling Aggregation Group (MC-LAG) Interfaces in IP/MPLS Networks

The defines use of Bidirectional Forwarding Detection (BFD) on Link Aggregation Group (LAG) interfaces. Multi-chassis LAG (MC-LAG) is type of LAG with member links terminated on separate chassis. does not specify MC-LAG but doesn't preclude it either. Link Aggregation Control Protocol (LACP), also defined in , can work with MC-LAG but, as in LAG case, can detect link failure only in range of single seconds. This document defines how mechanism defined to work on LAG interfaces can be adopted to MC-LAG case to enable sub-second detection of member link failure.

ACH: Associated Channel Header BFD: Bidirectional Forwarding Detection BoS: Bottom of the Stack G-ACh: Generic Associated Channel GAL: Generic Associated Label LAG: Link Aggregation Group LACP: Link Aggregation Control Protocol MC-LAG: Multi-chassis Link Aggregation Group MPLS: Multi-Protocol Label Switching

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 .

does not specify selection of the destination IP address for the BFD control packet. The only requirement related to the selection is in Section 2.1 stating that the use of address family across all member links of the given LAG MUST be consistent across all the links. Thus it is implied that the same unicast IP address will be used on all member links of the LAG as use of different destination addresses would defeat the purpose of transforming the case into set of single-hop BFD sessions . But single unicast IP address may not work in MC-LAG case as the member links are terminated on the separate chassis. This document proposes how to overcome this problem if using IP or Multi-Protocol Label Switching (MPLS) data plane encapsulation.

There are more optional encapsulation formats for the case of micro-BFD on MC-LAG over IP/MPLS data plane: defined special purpose Generic Associated channel Label (GAL) that MAY be used in MPLS encapsulation of the micro-BFD control packet over MPSL data plane. Depending on the channel type specified in the Associated Channel Header (ACH) that immediately follows after the GAL, micro-BFD MAY use IP/UDP, as displayed in or BFD format, i.e. BFD control packet without IP and UDP headers.

If IP/UDP format of BFD over MC-LAG interfaces is used, then for IPv4 address family the destination IP address MUST be selected from 127/8 range , and if IPv6 address family is used, then the destination IP address MUST be selected from 0:0:0:0:0:FFFF:127/104 range.

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

Security considerations discussed in apply to this document.