Switching to VoIP

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Chapter 13: Network Infrastructure for VoIP

practical. They might be needed in very demanding scenarios, such as a call center

with offices in multiple states or highly redundant military or intelligence

applications.

Quality-of-service measures must be more sophisticated when used in a highly-

meshed network. Indeed, one thing RSVP is designed to do is negotiate the best-

quality path through the network for a phone call when there are multiple potential

paths. This is quite different from dynamic routing alone, which chooses paths

across the network based on policies that have no direct relationship with the voice

application.

Layout and PBX Placement

Most networks employ a combination of distributed and client-server models for dif-

ferent applications and a combination of different layout techniques for different bal-

ances of cost and resilience to failure. As long as the total number of remote

locations is under 10 or so, a circular peer network is a great solution to the down-

time issue, because if an upstream route fails, the other arc of the circle is still up and

also leads back to the data center. This functionality is handled by—you guessed it—

IP routing. So it takes two points of failure on the circle in order to bring the voice

transport down for any one site, as