Downstream Tag Allocation on Demand Scheme

For each route in its FIB a switch requests (via TDP) the next hop (associated with the route) to provide the switch with the tag binding information
When the next hop receives the request, it:
- allocates a tag
- creates an entry in its TIB with the incoming tag set to the allocated tag
- returns the binding to the requester
When the requester receives the tag binding information for a route from the next hop for that route, the requester places the tag into the outgoing tag of the TIB entry associated with the route