iers, audit telephone bills for customers, and coordinate resolution of repair problems with carriers. This is attractive to customers who want an organization that can recognize and separate outside network issues from telephone system issues. A value-added reseller might sell an IP telephony system at below its own cost in anticipation of profits from managed services, ongoing fees for maintenance contracts, and add-on voice and data peripherals such Wi-Fi and videoconferencing systems. The Technology behind IP Telephony THE TECHNOLOGY BEHIND IP TELEPHONY Converged phone systems use IP technology to convert analog voice signals to digital bits, compress that data, and then bundle the compressed, digitized bits into packets. Data, voice, and video packets often share the same Local-Area Network (LAN) infra- structure as that used for normal data traffic. However, voice and video are not like regular data. They need to be sent in real time. Impairments such as delay and packet loss caused by network congestion are often not noticeable with data traffic. However, these problems noticeably degrade voice and video quality. Thus, network capacity is critical for sustaining voice quality. Greater LAN capac- ity and faster Digital Signal Processors (DSPs) as well as protocols for Quality of Ser- vice (QoS) enable data networks to carry high-quality voice and video. Even though voice quality is generally good in IP systems, the aforementioned problems can occur. Therefore, packets with voice and video are given priority over packets containing bits that are less time-sensitive, such as e-mail. Voice QoS and Security Keeping networks secure is a difficult, ongoing challenge. Security needs to be installed in IP telephony system servers, and in all of the Layer 2 and Layer 3 switches, the rout- ers, and the firewalls. In particular, many IP systems use common protocols. These protocols are wide open in the sense that many hackers know how they work and put a great deal of effort into finding their vulnerabilities. Organiz