Cisco Architecture Evolution
Figures 1-2 and 1-3 represent the evolution of the Cisco architecture and the migration of the technology. Figure 1-2 provides a view of how the network architecture looked in 2001 at the beginning of the migration. Figure 1-3 demonstrates how calls come in to the network, how they tandem through the PBX, and how voice mail and intercluster calling are performed.
Figure 1-2 Traffic Flow Example of Voice Mail and Intercluster Calling