A layer 2 VPN, as the name suggests, is a link where layer 2 frames are carried transparently from one end to the other. This means that the layer 2 frames are tunneled across the service provider backbone network, by using additional encapsulation headers, and the native layer 2 frames of the user are handed back at the other end of the link. As an example, consider the network shown in the following figure. The cloud comprises a number of networking devices of the service provider network, which are interconnected. The layer 2 frames handed over to the SP at point A on the network are transported over the SP network and handed over to the user at point B:
Figure 14: Sample topology requiring a layer 2 VPN
In the preceding ...
