H-VPLS (Hierarchical VPLS)
H-VPLS (Hierarchical VPLS) is the more scalable version of VPLS. Basically, H-VPLS has some architectural difference than flat VPLS.
In H-VPLS, there are some additional edge devices. These devices are u-PE (User facing Provider Edge) and n-PE (Network facing Provider Edge). By using two different Edge Devices, H-VPLS provide less overhead in n-PE devices. Because, the traffic that is coming from the user, meets with u-PE device firstly.
In the H-VPLS architecture, customer devices firstly connected to the u-PE device. u-PE devices are connected to n-PE devices with a single Pseudowire (PW). This is for each VPLS service. After that, the n-PE devices are connected as fullmesh . The conection of the n-PE devices are like flat VPLS.
For the connection of the access layer of the H-VPLS, there are two mechanisms.
• H-VPLS with Q-in-Q
• H-VPLS with MPLS
In Nokia (Formerly Alcatel-Lucent) Service Routers, we need to configure SDPs as Pseudowires (PW). In H-VPLS all the sites are not have to connect via SDPs. The connection is provided with both mesh SDPs and spoke SDPs. But as you remember, in VPLS, all sites needs to be connected as full mesh with mesh SDP.