Summary

In this chapter, you learned about voice design principles, with a focus on the following topics:

■ Analog and digital signaling, including the process to convert between the two

■ The features of and similarities and differences between PBXs and PSTN switches

■ The connections and signaling between the various devices in a traditional telephony network

■ PSTN numbering plans and various PSTN services

■ The H.323 standard for packet-based audio, video, and data communications across IP-based networks, including H.323 components

■ The concepts of VoIP and IP telephony, including the components and sample design scenarios

■ Protocols used to transport all control (signaling) and voice conversation traffic

■ Voice quality issues, including delay, jitter, packet loss, and echo

■ Voice coding and compression standards

■ Bandwidth considerations and requirements for integrated networks

■ QoS mechanisms for voice

■ Voice traffic engineering to select the correct number of lines and the proper types of service, including the use of Erlang tables to calculate trunk capacity for voice calls.

NOTE This chapter introduced voice design principles; additional resources, such as voice-related Cisco Press books and documents on http://www.cisco.com/, are required to successfully integrate voice services into a network.

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