Chapter 3: Structuring and Modularizing the Network■ Campus Core layer: The Campus Core layer forms the network’s core. All enterprisenetwork modules are attached to it; therefore, virtually all traffic between application serversand clients traverses the Campus Core. With the advent of wire-speed multilayer gigabitswitching devices, LAN backbones have migrated to switched gigabit architectures thatcombine all the benefits of routing with wire-speed packet forwarding.■ Server Farm module: This module includes multilayer switches with redundant connectionsto redundant Cisco Unified Communications Managers, which are essential for providinghigh availability and reliability.■ Enterprise Edge: The Enterprise Edge extends IP telephony from the Enterprise Campus toremote locations via WANs, the PSTN, and the Internet.Figure 3-22 shows the voice network solution in the Cisco Enterprise Architecture. It illustrateshow a call is initiated on an IP phone, how the call setup goes through the Cisco UnifiedCommunications Manager, and how the end-to-end session between two IP phones is established.Note that Cisco Unified Communications Manager is involved in only the call setup.
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