ATM layer 2 services over MPLS provide ATM switch-like functionality for E-series routers. This feature is useful for customers who run IP in the majority of their network but still have to carry a small amount of non-IP traffic, as in the example shown in Figure 115.
Figure 115: Common ISP Network
In this scenario, it is not economical to have special ATM switches in front of E-series routers just to accommodate the small percentage of non-IP traffic. The ATM layer 2 services over MPLS feature lets you replace the ATM traffic selector switch with an E-series router, as shown in Figure 116. The two routers pass traffic between two interfaces through an MPLS tunnel using Martini encapsulation, regardless of the contents of the packets.
Figure 116: E-series Router Replacing Remote ATM Switch
ATM layer 2 services over MPLS supports two encapsulation methods on E-series routers:
The following sections describe each of these encapsulation methods.
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