R3303-HP HSR6800 Routers MPLS Configuration Guide

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As in the typical hierarchical network model, HoVPN has different requirements on the devices at
different layers of the hierarchy.
Implementation of HoVPN
Figure 78 Basic architecture of HoVPN
As shown in Figure 78, devices directly connected to CEs are called underlayer PEs (UPEs) or user-end
PEs, whereas devices that are connected to UPEs and are in the internal network are called superstratum
PEs (SPE) or service provider-end PEs.
The hierarchical PE consists of multiple UPEs and SPEs, which function together as a traditional PE.
With the HoVPN solution, PE functions are implemented hierarchically. Hence, the solution is also called
"hierarchy of PE (HoPE)."
UPEs and SPEs play the following different roles:
• A UPE allows user access. It maintains the routes of the VPN sites that are directly connected with
it, It does not maintain the routes of the remote sites in the VPN, or only maintains their summary
routes. A UPE assigns inner labels to the routes of its directly connected sites, and advertises the
labels to the SPE along with VPN routes through MP-BGP.
• An SPE manages and advertises VPN routes. It maintains all the routes of the VPNs connected
through UPEs, including the routes of both the local and remote sites. An SPE advertises routes
along with labels to UPEs, including the default routes of VPN instances or summary routes and the
routes permitted by the routing policy. By using routing policies, you can control which nodes in a
VPN can communicate with each other.
Different roles mean different requirements:
• An SPE is required to have large-capacity routing table, high forwarding performance, and fewer
interface resources.
• A UPE is required to have small-capacity routing table, low forwarding performance, but higher
access capability.
HoVPN makes full use of both the high performance of SPEs and the high access capability of UPEs.
The concepts of SPE and UPE are relative. In the hierarchical PE architecture, a PE may be the SPE of its
underlayer PEs and a UPE of its SPE at the same time.
The HoPE and common PEs can coexist in an MPLS network.