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3. Motivation

SR P2MP Policies are usually provisioned by a controller, NETCONF/YANG, or CLI. Because there is no underlay signaling protocol that distributes the SR P2MP Policy from the Root to Leaf routers, ping and traceroute are needed to isolate faults along the multicast tree.

RFC 6425 procedures apply to SR P2MP Policy, with SR-specific considerations. Egress Address P2MP Responder sub-TLVs SHOULD NOT be used when an echo request carries an SR P2MP Policy MPLS CP FEC. SR P2MP Policies SHOULD follow common RFC 6425 P2MP MPLS LSP procedures. Implementations MUST account for multiple CPs and PTIs, and SHOULD support testing each CP and PTI individually. A downstream node that understands the Replication-SID MUST process and respond even when the CP/PTI is not the active path.

For non-adjacent Replication segments connected by a unicast path, SR P2MP Policy OAM verifies the P2MP parts, while unicast OAM verifies the connecting unicast path. For P2MP tree traceroute, TTL mode MUST be Pipe Mode at the router where the unicast path starts.

The echo request message MUST include a Target FEC Stack TLV specifying the CP and PTI under test. RFC 9961 introduces the SR MPLS P2MP Policy Tree Instance sub-TLV:

Sub-TypeLengthValue Field
41VariableSR MPLS P2MP Policy Tree Instance
0                   1                   2                   3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|        Address Family         | Address Length|   Reserved    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
~                            Root                               ~
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                         Tree-ID                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Instance-ID               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  • Address Family: 2 octets, IPv4/IPv6 Address Family Numbers from [IANA-AF].
  • Address Length: 1 octet, 4 octets for IPv4 and 16 octets for IPv6.
  • Reserved: MUST be set to zero by the sender and ignored by the receiver.
  • Root: variable length, the Root node of the SR P2MP Policy.
  • Tree-ID: 4 octets.
  • Instance-ID: 2 octets, identifying the specific Path-Instance.

Response scope follows RFC 6425 P2MP Responder Identifier TLV mechanisms for IPv4/IPv6 egress and node address sub-TLVs.

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