Switching to VoIP

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Chapter 13

CHAPTER 13

Network Infrastructure for VoIP

In earlier chapters, we’ve talked about dial-plan design, PSTN trunks, and dial-tone

services. We’ve covered some of the equipment used to link VoIP-based networks

with legacy telephony systems: equipment like media gateways and ATAs. Signaling

protocols like SIP, media protocols like RTP, and quality of service have been

described. Each of these elements is dedicated to a specific, tactical duty in your tele-

phony system.

But the “big picture” that contains and unifies all of these disparate technology

objects together into a functional system is topology: the lay of the telephony land. At

the base of this functional system is infrastructure. The transport, security, and direc-

tory services elements enabling your voice applications on the IP network are your

VoIP infrastructure. Topology includes geographical issues, too—the physical loca-

tions of voice resources and connectivity maps of your wide area network.

There’s quite a bit to take into account. In this chapter, we’ll talk about methods for

building a reliable VoIP infrastructure. We’ll cover general IP WAN layouts, the use

of private trunks to link PBX systems, disaster recovery and survivability, choosing a

location for PSTN connect points, optimizing VoIP WAN links, ...