3. Architectures

3.1 Hub & spoke connectivity

VPLS can support hub & spoke (H & S) connectivity. A spoke-PE is only connected (via a pseudowire) to a hub-PE in the same way as in hierarchical VPLS (which we'll discuss in the next paragraph), but without an intermediate PE. In addition, H & S VPLS can prevent customers from having direct connections via a VSI, which is normally done if both CEs are connected to the same VPLS PE. In our case, the only way to connect these two CEs is via the CE hub, as shown in figure 12 .

The PE hub always applies a split-horizon between spoke-PWs to prevent two clients from communicating directly without passing through the hub. Similarly, split-horizon...