Chapter 26. Telephony and VoIP
IN THIS CHAPTER
Telephone service and protocols
PBX telephone systems
VoIP
Computer telephony integration
Video telephony in action
Telephony is the marriage of computers and telephones, enabled by two different types of networks. Telephony covers a broad range of multimedia applications, including voice, video, business, and pleasure. It is always an area of great innovation and is supported natively in network operating systems by application programming interfaces, or APIs.
You can create a network of telephones using a Private Branch Exchange (PBX) System as a management server. PBXs can network with public switched telephone network (PSTN) telephones over phone lines or with IP-enabled phones over Ethernet. Two PBX server systems are considered in detail: the open source Asterisk system and Cisco Unified Communications Manager.
Voice over Internet Protocol, or VoIP, is a rapidly developing area of technology. VoIP can be implemented in software as a softphone, using IP phones, or by adapting an existing telephone using an Analog Telephone Adapter (ATA) to connect it to an IP network. This chapter discusses the properties of IP phones.
VoIP uses a special set of protocols to send and manage communications that are described in detail in this chapter. Session protocols include Session Initiation Protocol (SIP) and Skinny Call Control Protocol (SCCP), and packets are often in Real-Time Transport Protocol (RTP) format. The problems with firewalls and NAT (Network ...
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