With Hierarchical VPLS (H-VPLS), the PE routers are no longer directly attached to the customer equipment. Hierarchy is introduced by adding another layer in the access layer toward the customer equipment. H-VPLS has two forms:
H-VPLS with dot1q tunneling in the access layer
H-VPLS with MPLS in the access layer
Figure 11-7 shows H-VPLS.
There are now N-PE and U-PE routers. The N-PE routers are network-facing PE routers, whereas the U-PE routers are user-facing PE routers. The hierarchy provides the benefits of less signaling in the MPLS core network and less packet replication on the ...