Virtual Circuit Connectivity Verification (VCCV) Capability Advertisement for MPLS Transport Profile (MPLS-TP)
Extracted elements (11)
Four MPLS-TP CV types arise from the combination of two monitoring modes (coordinated and independent, per RFC 6428) with two functionality levels (fault detection only vs. fault detection plus AC/PW status signaling via RFC 6310 OAM message mapping). This matrix-based design cleanly accommodates all operational requirements.
The CV selection rules from RFC 5085 Section 7 and RFC 5885 Section 4 are augmented but not replaced; the new MPLS-TP CC-CV priority rules apply only when VCCV Control Channel Type 1 is chosen and both PEs advertise MPLS-TP CC-CV types.
If VCCV Control Channel Type 1 is selected, PEs MAY select one of the MPLS-TP CC-CV types as the VCCV CV mechanism to be used for the PW.
The Reserved field in the VCCV Extended CV Advertisement Sub-TLV MUST be set to zeroes on transmit and ignored on receive.
The VCCV Extended CV parameter sub-TLV MUST appear in combination with the VCCV parameter sub-TLV. If the VCCV parameter sub-TLV is missing, the VCCV Extended CV parameter sub-TLV SHOULD be ignored.
Four MPLS-TP CC-CV types are defined as bitmask values in the CV Type field: 0x01 (Independent mode, Fault Detection only), 0x02 (Independent mode, Fault Detection and AC/PW Fault Status Signaling), 0x04 (Coordinated mode, Fault Detection only), 0x08 (Coordinated mode, Fault Detection and AC/PW Fault Status Signaling).
When both PEs advertise a common set of proactive CV types that includes both MPLS-TP CC-CV types and BFD CV types, MPLS-TP CC-CV takes precedence over any BFD CV type. Among multiple MPLS-TP CV types, the priority order (descending) is: 0x08, 0x04, 0x02, 0x01.
A new IANA registry 'VCCV Extended CV Types' is created for 8-bit values. Values 0x01, 0x02, 0x04, and 0x08 are assigned by this document; values 0x10 through 0x80 require IETF Review (per RFC 5226) with a description and IESG-approved RFC reference.
IANA assigned PW Interface Parameters Sub-TLV type 0x19 (variable length) for the VCCV Extended CV Parameter, registered in the PW Interface Parameters Sub-TLV registry originally defined in RFC 4446.
Implementations of the new CV types are subject to the same security considerations as RFC 5085 (VCCV), RFC 5880 (BFD), RFC 5881 (BFD for IPv4/IPv6), and RFC 6428 (MPLS-TP CC/CV/RDI). No additional security issues are introduced by this specification.
The VCCV Extended CV Advertisement Sub-TLV has Type = 0x19, a variable-length Length field (minimum 4 bytes, extensions in 4-byte increments), an 8-bit CV Type bitmask, and an 8-bit Reserved field. It is a sub-TLV of the PW Interface Parameters Sub-TLV.