This enables or disables the TTL-expiry-based VCCV control channel method (CC Type-3, per RFC 5085) for pseudowires using this VCCV profile, a mechanism that uses an artificially expired TTL to route VCCV OAM packets to the terminating PE for processing rather than having them forwarded transparently like data traffic. Whether this specific CC type is on or off determines whether VCCV ping/traceroute using the TTL-expiry method will actually work for any pseudowire referencing this profile -- if it's off but an operator attempts a TTL-based VCCV test, it will simply fail regardless of the PW's actual data-path health. An admin unable to get expected VCCV OAM results should confirm which CC type or types are actually enabled on the profile rather than assuming all VCCV mechanisms are universally available.