This mode references 802.1Q tags across L2VPN pseudowires. These tags are only significant to local and endpoint devices. Service providers must preserve the original VLAN Tag IDs passed to them from the local endpoint to the remote endpoint.
Tagged mode pseudowires have a type 0x0004, and every frame sent across a PW must have a unique VLAN for each customer. this is called the service delimiting VLAN tag.
If a frame is received from the attachment circuit and its missing a service-delimiting VLAN the PE must prepend the frame with a dummy VLAN tag before sending the frame on the PW.
In Raw mode pseudowires, the service delimiting tag has no significance. This mode has pseudowire type 0x0005, Raw mode dictates that any service delimiting tags must be removed before being transported across the L2VPN PW.