This chapter discusses how to design the transport of voice within a network, and includes the following sections:
This chapter describes how voice can be transported along with other data within a network. We first introduce why it would be advantageous to include voice in your network design. The mechanics of voice transport, including digitization, packetization, and call processing are explained. Quality of service (QoS) for voice is reviewed. The components required in a Voice over IP (VoIP) network and those in an IP telephony network are described. The standards for how voice calls are coded and compressed are introduced, and the bandwidth requirements for voice traffic are explored. IP telephony design scenarios are examined. We conclude with an introduction to security considerations for voice. Note Appendix B, "Network Fundamentals," includes material that we assume you understand before reading the rest of the book. Thus, we encourage you to review any of the material in Appendix B that you are not familiar with before reading the rest of this chapter. While those in the networking world have been hearing about Voice over IP for quite a while now, over the past couple of years (at least within North America), the mainstream press has been introducing the term VoIP to the ordinary consumer. Although the residential market is currently small, it is growing quickly, as prices are slashed for VoIP packages that include such features as unlimited calls within the continent, low-cost international calling, voice mail, selection of your own area code, call forwarding, and call display. An enterprise might also want to implement VoIP, in other words, to use its data network to also carry its voice traffic. Referring to the discussion in Chapter 1, "Network Design," a new technology shouldn't be implemented just because it can be, but rather because it meets the network's requirements. The goal for converging an organization's voice and data networks is to positively "impact key initiatives, business processes and business results."[1] This can be accomplished in many ways, including the following:
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