This is the tunnel-index component of the composite key identifying the inbound MPLS-TE tunnel delivering this pseudowire's traffic, mirroring cpwVcMplsOutboundTunnelIndex but for the receive direction, and reading zero absent a TE outer tunnel. It matters when a pseudowire is engineered to receive over a protected TE path, since this value confirms which specific inbound tunnel entry to inspect if inbound traffic drops unexpectedly. A discrepancy between the intended inbound TE tunnel and what this object actually shows would explain traffic arriving via an unprotected or unexpected path.