A Study of QoS Sensitive Pricing for IP Telephony

While Internet Telephony (IP Telephony) encompasses many different architectures and services, the key idea is the transport of real-time voice traffic over the Internet. IP Telephony architecture [2] allows the entire end-to-end path or a portion thereof to be routed over the Internet. The endpoints are regular personal computers (PCs) that are equipped with IP Telephony software which allows them to interface with the existing Public Switched Telephone Network (PSTN) through an Internet Telephony Gateway (ITG). The only delay suffered by the voice traffic in the PSTN network is the propagation delay which is fixed once the circuit has been established. On the other hand, the Internet is still inherently a best-effort network and provides no end-to-end bandwidth guarantees. Thus, transporting packetized voice over the Internet can result not only in variable delays but also losses which may cause poor audio quality at the receiver. Furthermore, these losses and delays can increase as the number of hops traversed by the voice packets increase. As a result, the quality of the received audio can degrade as the distance traversed by voice packets over the Internet increases.