), and different types of conferencing, including audioconferencing, video- conferencing, and Web/data conferencing. As carriers consolidate and wireless broadband networks are deployed, a major challenge will be developing viable business models to market, bill, provision, and provide excellent customer care for all these services. Many incumbent carriers are choosing to initially implement IP-based services on an overlay network. Carriers that take this approach do not have to replace circuit-switched network elements, which usually have minimal ongoing operational expenses. In an overlay network scenario, the packet-switched network is isolated from the circuit-switched network, and the two are connected via a gateway. IPT has been drawing a lot of attention in the past couple years, and terminology in this area is confusing, with VoIP being the most common expression, even though there are in fact technical differences between IPT (the umbrella term), VoIP (IPT over private IP networks), and Internet telephony (voice over the Inter- net). The following sections cover the types of applications anticipated for IPT as well as what network elements are required in order to make IPT work and provide similar capabilities to what we are used to from the PSTN. Although IPT has a very important place, it is not yet taking over the tradi- tional circuit-switched approach to accommodating voice telephony. The truly exciting future of IPT, or VoIP, lies in advanced and interesting new applications, an environment where voice is but one of the information streams comprising a rich media application. While such applications are being developed, there are other compelling reasons to adopt IPT, including the reduction of toll and interna- tional calling charges, which makes a strong argument for many businesses and consumers. The network-specific cost for VoIP on dedicated networks is quite a bit lower than the cost of calls on circuit-switched networks, not to mention the bene- fit an average residential user, with family m