IP Telephony Basics

Technology, Operation, Economics, and Services
Author: Lawrence Harte, David Bowler, and Robert T. Flood
Number of Pages: 324
Number of Diagrams: 78

This book explains why and how companies are using IP Telephony equipment and software to efficiently upgrade existing telephone systems, develop their own advanced communications services, and to more easily integrate telephone network with company information systems.
IP telephony technology has become a reliable communication option that has well-established standardized communication protocol. IP Telephony systems have many low cost devices and software application development tools available compared to proprietary telephone systems and services. The use of IP Telephony products and software allows companies to cost-effectively upgrade and eventually replace existing (legacy) telephone systems with more cost effective and easy to use telephone equipment. Because IP Telephony systems commonly use standardized protocols, this allows end-users and system administrators to have more more....

Adding IP Telephony Lines to an Existing Company Data and PBX Network
This figure shows how a PBX system can be upgraded to use voice over IP (VoIP) telephone service without any significant changes to the PBX system. This example shows that a VoIP gateway is used to create addition lines for the PBX system. Because the VoIP gateway can produce standard telephone signals (standard telephone or T1/E1 lines), it can be directly connected to PBX system line cards. The PBX system administrator simply configures the PBX system to use the added lines through the same process that would be used when installing new telephone lines. The gateway is controlled to provide telephone services by a call server from a ITSP, IP Centrex or even another iPBX system.

IP Telephony Communication Servers
This figure shows the different types of servers used in some IP Telephony communication systems. This example shows that a call manager (proxy server) receives and processes call requests from communication units (IP telephones). The administrator server coordinates accounts to the system. A unit manager (location server) functions as a location server by tracking the IP address assigned to the communication units. The gateway manager identifies and coordinates communication through the available gateways. The system manager coordinates the communication between the different servers and programs available on the system.

Gateway Manager Software
This figure shows how gateway manager software can be used to configure and manage gateways that connect the SIP network to other networks such as the public switched telephone network. This example shows how the gateway manager contains the configuration information for the gateway including IP address, capabilities such as speech coders, protocols, and access control information.