SummaryPrior to pseudowire emulation, Layer 2 VPN services were provided by legacy Layer 2 VPN technologies, such as ATM, Frame Relay, and VPDN, which rely on overlapping parallel network infrastructures. Pseudowire emulation is the fundamental building block of the new generation of Layer 2 VPN architectures. Many complex network applications that are to replace legacy Layer 2 VPNs or facilitate new requirements are built on top of some form of pseudowire emulation. Cisco offers AToM and L2TPv3 for pseudowire emulation. They are not designed as competing technologies; rather they are optimized for MPLS- and IP-based network infrastructures, respectively. Before determining which product to adopt, consider the technical and business factors and find the right balance between features and manageability. Each has its own merits and implications, some of which are outlined in Table 3-2.
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