Vpls Operational Principle - 3Com 8807 Configuration Manual

VPLS Operational
Principle
VPLS Basic Transmission
Components
Figure 153 Hierarchical VPLS network architecture
As shown in Figure 153, the network topology of the VPLS network is hierarchical,
and the access range of the network is expansible. The core devices (NPEs) in the
core network require high performance because VPN traffic concentrates there,
while the edge devices (UPEs) require lower performance because they are mainly
used for VPN service access. In addition, you can back up the links between NPEs
and UPEs to make the network more robust. The access networks between UPEs
and NPEs can be either a MPLS edge network connected by LSP, or a simple
Ethernet network for VLAN-VPN user access.
As shown in the following figure, the whole VPLS network is just like a huge
switch. For each VPN, it sets up PWs between the sites of the VPN on MPLS
tunnels and transparently transmits user's layer 2 packets from one site to another
through these PWs. In this network, PEs forward packets, learn source MAC
addresses, create MAC forwarding entries, and map the MAC addresses to
corresponding ACs and PWs. While, the P devices (provider routers, that is, core
switches in the backbone network), only implement MPLS forwarding according
to MPLS labels without considering layer 2 user data encapsulated in MPLS
packets.

VPLS Operational Principle

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