The document discusses how Provider Backbone Bridging (PBB) can help address scaling challenges in service provider Ethernet networks. PBB introduces a backbone MAC and service identifier tag that encapsulates customer traffic. This allows hiding customer MAC addresses within the network core and provides up to 16 million service instances. The document explains how PBB can be used on its own in native Ethernet networks or combined with Hierarchical Virtual Private LAN Service (H-VPLS) to reduce the number of label switched paths and pseudowires needed for large VPLS implementations.