VCCV has been specified to test and verify the data plane of pseudowires. VCCV entails procedures to create a control channel between the PE routers that provide the AToM service. The network layer might actually be MPLS, L2TPv3, or IP. Because this book covers only MPLS, it hereafter deals only with MPLS as the network layer when looking at VCCV. If MPLS is the network layer, VCCV re-uses MPLS LSP ping to verify the connectivity of pseudowires. VCCV creates a control channel between PE routers whereby the VCCV packets are sent across as IP packets. You can use three kinds of control channels:
TTL expiry VCCV
The first method uses the inband VCCV. Packets on the inband VCCV carry a control word. AToM data can ...