This enables or disables Ciena's proprietary out-of-band VCCV control channel method (CC Type-4) for pseudowires using this profile, an alternative to the standards-based in-band VCCV mechanisms, like the TTL-expiry method above, that instead carries OAM traffic outside the pseudowire's normal data path. Because this is a Ciena-proprietary mechanism, it will only interoperate correctly if the remote peer PE is also Ciena equipment supporting the same out-of-band scheme -- a mixed-vendor pseudowire pairing this device with non-Ciena equipment would need to rely on the standards-based CC types instead. If VCCV testing fails specifically on pseudowires terminating on third-party equipment while working fine between two Ciena devices, this proprietary out-of-band channel being enabled-but-unsupported on the far end is a plausible explanation.