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VPN Terminology
VPNs include the following types of network devices
(see Figure 1):
- Provider edge (PE) routers—Routers in the provider’s
network that connect to customer edge devices located at customer
sites. PE routers support VPN and label functionality. (The label
functionality can be provided either by the Resource Reservation Protocol
[RSVP] or Label Distribution Protocol [LDP].) Within a single VPN,
pairs of PE routers are connected through a tunnel, which can be either
a Multiprotocol Label Switching (MPLS) label-switched path (LSP) or
an LDP tunnel.
- Provider (P) routers—Routers within the core of
the provider’s network that are not connected to any routers
at a customer site but are part of the tunnel between pairs of PE
routers. P routers support MPLS LSP or LDP functionality, but do not
need to support VPN functionality.
- Customer edge (CE) devices—Routers or switches located
at the customer site that connect to the provider’s network.
CE devices are typically IP routers, but could also be an Asynchronous
Transfer Mode (ATM), Frame Relay, or Ethernet switch.
VPN functionality is provided by the PE routers;
the provider and CE routers have no special configuration requirements
for VPNs.
Figure 1: Routers in a VPN

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