VPWS creates pseudowires that emulate layer 2 circuits. A virtual private LAN service
(VPLS) network is similar to VPWS, but provides point-to-multipoint traffic forwarding
in contrast to the VPWS L2VPN’s point-to-point traffic forwarding.
VPWS provides the same services as layer 2 over MPLS except for CE-side load-balancing.
The main differences between the VPWS and L2 over MPLS services are signaling,
autodiscovery, and configuration.
A VPWS L2VPN can have either a full-mesh or a hub-and-spoke topology. The tunneling
mechanism in the core network typically is MPLS. However, VPWS can also use other
tunneling protocols, such as GRE. VPWS is similar to Martini layer 2 services over MPLS,
and employs a similar encapsulation scheme for forwarding traffic.
Figure 131 on page 640 illustrates an example of a simple VPWS L2VPN topology.
Figure 131: VPWS Sample Topology
In this example, the service provider offers VPWS services to Customer A and Customer
B. Customer A wants to create a full mesh of point-to-point links between Westford and
Bangalore. Customer B needs only a single point-to-point link between Westford and
Sunnyvale. The service provider uses BGP and MPLS signaling in the core, and creates a
set of unidirectional pseudowires at each provider edge (PE) router to separately
cross-connect each customer’s layer 2 circuits.
In order to provision this service, the provider configures two VPWS L2VPNs, L2VPN A
and L2VPN B. An encapsulation type is configured for each VPWS L2VPN. All interfaces
in a given VPWS L2VPN must be configured with the VPWS L2VPN’s encapsulation type.
The layer 2 interfaces that connect the PE router and CE device pairs are configured to
be members of the corresponding VPWS L2VPN, L2VPN A or L2VPN B.
Copyright © 2010, Juniper Networks, Inc.640
JunosE 11.2.x BGP and MPLS Configuration Guide
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