When designing IP telephony, designers must document and evaluate the existing data infrastructure in each enterprise module to help determine upgrade requirements. Items to consider include the following:
■ Performance: Enhanced infrastructure for additional bandwidth, consistent performance, or higher availability, if required, might be necessary for the converging environment. Performance evaluation includes analyzing network maps, device inventory information, and network baseline information. Links and devices such as those with high peak or busy-hour use might have to be upgraded to provide sufficient capacity for the additional voice traffic. Devices with high CPU use, high backplane use, high memory use, queuing drops, or buffer misses might have to be upgraded.
■ Availability: Redundancy in all network modules should be reviewed to ensure that the network can meet the recommended IP telephony availability goals with the current or new network design.
■ Features: Examine the router and switch characteristics—including the chassis, module, and software version—to determine the IP telephony feature capabilities in the existing environment.
■ Capacity: Evaluate the overall network capacity and the impact of IP telephony on a module-by-module basis to ensure that the network meets capacity requirements and that there is no adverse impact on the existing network and application requirements.
■ Power: Assess the power requirements of the new network infrastructure, ensuring that the additional devices will not oversubscribe existing power. Consider taking advantage of PoE capabilities in devices.
NOTE Chapter 8, "Voice Network Design Considerations," covers voice in detail.
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