VCCV

Virtual circuit connectivity verification (VCCV) is an end-to-end fault detection and diagnostic mechanism for a PW. VCCV is, in its simplest description, a control channel between a PW's ingress and egress points over which connectivity verification messages can be sent.

VCCV can detect and diagnose the connectivity of the forwarding paths on a PW.

A Label Mapping packet uses the BFD CV Type field to indicate whether a PW supports BFD fault detection. The BFD CV Type can be 0x04, 0x08, or 0x10. By default, the BFD CV Type is 0x08. If a remote peer does not support the 0x08 BFD CV Type, change the BFD CV Type in the Label Mapping packet.

0x04: supports BFD IP/UDP encapsulation, used for PW fault detection only.
0x08: supports BFD IP/UDP encapsulation, used in PW fault detection and AC/PW fault status signaling.
0x10: supports BFD PW-ACH encapsulation, used in PW fault detection only.

VCCV ping, an extension to LSP ping, is a tool used to manually test the connectivity of a VC. VCCV defines a series of messages exchanged between PEs for PW connectivity verification. To ensure that VCCV packets and PW data packets are transmitted along the same path, VCCV packets must be encapsulated in the same way and transmitted over the same tunnel as PW data packets.