Cisco OL-21636-01 - Manual (Page 384)

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Cisco IP Solution Center L2VPN and Carrier Ethernet User Guide, 6.0
OL-21636-01
Appendix E ISC Layer 2 VPN Concepts
VPLS Service Provisioning
Figure E-8 Frame Relay over MPLS
VPLS Service Provisioning
VPLS services are multipoint. They provide multipoint connectivity over an MPLS or an Ethernet core.
These implementations, in turn, support service types, as follows:
• VPLS over MPLS core:
– Ethernet Wire Service (EWS). This is also sometimes referred to as EMS, or Ethernet
Multipoint Service. The MEF term for this service is EP-LAN.
– Ethernet Relay Service (ERS). This is also sometimes referred to ERMS, or Ethernet Relay
Multipoint Service. The MEF term for this service is EVP-LAN.
• VPLS over Ethernet core:
– Ethernet Wire Service (EWS). The MEF term for this service is EP-LAN.
– Ethernet Relay Service (ERS). The MEF term for this service is EVP-LAN.
Instructions on creating policies and service requests for these services are provided in other chapters of
the guide.
VPLS is a multipoint Layer 2 VPN that connects two or more customer devices using EoMPLS bridging
techniques. VPLS EoMPLS is an MPLS-based provider core, that is, the PE routers have to cooperate to
forward customer Ethernet traffic for a given VPLS instance in the core. A VPLS essentially emulates
an Ethernet switch from a user’s perspective. All connections are peers within the VPLS and have direct
communications. The architecture is actually that of a distributed switch. Multiple attachment circuits
have to be joined together by the provider core. The provider core has to simulate a virtual bridge that
connects these multiple attachment circuits together. To achieve this, all PE routers participating in a
VPLS instance form emulated VCs among them.
A Virtual Forwarding Instance (VFI) is created on the PE router for each VPLS instance. PE routers
make packet-forwarding decisions by looking up the VFI of a particular VPLS instance. The VFI acts
like a virtual bridge for a given VPLS instance. More than one attachment circuit belonging to a given
Frame Relay DLCI
MPLS Core
Frame
Relay
Frame
Relay
PE PE
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