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Succeeding with Cisco IP Telephony
from a Customer's Perspective
© Ted Wallingford 2003 - 2004
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Table of Contents: i. Background
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5. Cisco 911 Responders are risky The golden rule of change is, “First, do no harm.” The change in VoIP is justified by gains in other areas: bandwidth economy, applications, and so on. In most instances, VoIP does no harm. But Cisco's Emergency 911 approach introduces risk to a critical component of telephony, and this is harmful. In order to reach a 911 dispatcher, calls must be routed through the Cisco CallManager to a separate Ethernet-enabled device called a “responder server” that facilitates the connection to the dispatcher. This adds two points of failure for E911 service that don't exist on Avaya: the responder server and the Ethernet data link. This means that if the Ethernet network was compromised, swamped, or failed, 911 service would not be available. In Avaya's and Nortel's solutions, E911 is handled via a direct connection to a phone line or through the PRI. If the softPBX inside these system fails to route calls, the port with the dialtone is passed-through automatically via a hardware switch. In this fashion, even if the phone system is down and nobody can call anybody else in the office, 911 calls are still reliably connected.
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