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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
L2VPN Service Provisioning
This VLAN-VC ID mapping lets the service provider reuse VLAN IDs in Access Domains. (See
Figure E-6.)
Figure E-6 VLAN-VC ID Mapping
The VLAN IDs allocated and used at each access domain do not have to be the same.
ATM over MPLS (ATMoMPLS)
With Cisco ATM over MPLS (ATMoMPLS), Cisco supports ATM Adaptation Layer 5 (AAL5) transport
and Cell Relay over MPLS.
AAL5
AAL5 allows you to transport AAL5 PDUs from various customers over an MPLS backbone. ATM
AAL5 extends the usability of the MPLS backbone by enabling it to offer Layer 2 services in addition
to already existing Layer 3 services. You can enable the MPLS backbone network to accept AAL5 PDUs
by configuring the provider edge (PE) routers at both ends of the MPLS backbone.
To transport AAL5 PDUs over MPLS, a virtual circuit is set up from the ingress PE router to the egress
PE router. This virtual circuit transports the AAL5 PDUs from one PE router to the other. Each AAL5
PDU is transported as a single packet.
Cell Relay over MPLS
Cell Relay over MPLS allows you to transport ATM cells from various customers over an MPLS
backbone. ATM Cell Relay extends the usability of the MPLS backbone by enabling it to offer Layer 2
services in addition to already existing Layer 3 services. You can enable the MPLS backbone network
to accept ATM cells by configuring the provider edge (PE) routers at both ends of the MPLS backbone.
To transport ATM cells over MPLS, a virtual circuit is set up from the ingress PE router to the egress PE
router. This virtual circuit transports the ATM cells from one PE router to the other. Each MPLS packet
can contain one or more ATM cells. The encapsulation type is AAL0.
Topology for ATMoMPLS
Only the single PE scenario is supported. (See Figure E-7.)
138359
PE_AGG
N_PE1
10.1.1.1
N_PE2
10.2.2.2
Site A
CE
Site B
CE
VC ID
200
VC ID
200
VLAN 100
U_PE
U_PE
MPLS Core
Mapping
VLAN ID to VC ID
Mapping
VLAN ID to VC ID
VLAN 200