tailieunhanh - Cisco AVVID and IP Telephony P2

Old World Technologies end user to operate and because it integrates so well with the additional services promised by the over IP (VoIP) is the common term used for these systems. For completeness, and to simplify installation, IP was selected, as it is the most common protocol in the current networking world. | 4 Chapter 1 Old World Technologies end user to operate and because it integrates so well with the additional services promised by the over IP VoIP is the common term used for these systems. For completeness and to simplify installation IP was selected as it is the most common protocol in the current networking world. Note In subsequent chapters you will likely find that many of the problems encountered with VoIP systems including latency queuing and routing are related to the early decision of using IP as a protocol. Designing with Legacy Systems in Mind Before you tackle the converged world of Cisco s AVVID even if you configure PBX systems daily it may be a good idea to read this chapter to renew your understanding of what a PBX is and how it works. Note_ Please note that this chapter is written from the Cisco AVVID perspective as it relates to PBX systems and telephony and as such some definitions and concepts will differ from the phone company or PBX system origins. These are not errors but rather are simplifications of these terms and ideas to a common related reference point. For example FXS and FXO in carrier terms can refer to other companies and their respective connections. However before we enter the world of the PBX there is a legacy system that needs introduction. This is the key system. A key system is a multiline phone historically found in offices with up to ten users. It is best thought of as those old clicking phones with the large lit buttons. It is possible to find such systems servicing up to 100 users however modern economics and the lack of advanced features makes these installations less common and well-suited for replacement. As contrasted with the PBX these systems function by placing a single line on more than one physical phone and typically a one-for-one relationship is Old World