Chapter 3. Paving the Pathway to a Voice over IP Network

What You Will Learn

After reading this chapter, you should be able to

	Describe how VoIP can compete with the reliability of traditional PBX systems.
	Explain how to replace PBX-to-PBX connections with a VoIP network.
	Identify router interfaces used for connecting various analog devices (for example, phones and fax machines).
	Describe how voice-enabled routers connect to digital circuits (for example, T1 and E1 circuits).
	Explain how dial peers allow voice-enabled routers to forward calls to the appropriate destination.
	Discuss how VoIP can be used in the home, as opposed to traditional telephone service.

The transition from a traditional private branch exchange (PBX)-based telephony system to a Voice over IP (VoIP) system is not usually an overnight (or over-the-weekend for that matter) process. Instead, we usually take "baby steps," as they said in What About Bob? A first step might be to replace the trunk line that interconnects PBXs at remote sites with an IP wide area network (WAN) connection. A next step could be to connect existing analog phones, fax machines, and speaker phones to voice-enabled routers.

The end result of these baby steps is a telephony network, without a PBX, where voice traffic is transmitted over an IP network. In this chapter, we'll explore how to begin this migration and pave the pathway to a VoIP network.