This node is part of an A10-NSP development.
Carrier networks tend to stack three or more tags for internal purposes and therefore hiding the service tags deep inside of the stack. When decomposing such an access network frame, the processing order is typically reversed: First distinguish by service, than by other means.
This new netgragh node allows to bring the relevant VLAN in front (to the out-most position). This way other netgraph nodes (like ng_vlan) can operate on this specific type.