Advanced services are differentiating factors and
crucial to service providers' survival and success. Examples are credit card
calling, call forwarding, and toll-free calling. In classical telephony's early
days, their implementation was embedded in switching software, and this
hindered fast deployment. A more modern architecture known as the intelligent
network (IN) was born in the 1980s, allowing implementation in separate nodes,
resulting in faster deployment of new services. Two tracks are emerging for Internet
telephony: one from the ITU-T and the other from the IETF. As far as advanced
services are concerned, the ITU-T track offers a rather archaic architecture,
reminiscent of the early days of classical telephony. On the other hand, the
IETF architecture, although more modern, does have a few pitfalls. There is
plenty of room for improvement to both. This article scrutinizes the ITU-T and
IETF advanced services architectures for Internet telephony. Salient features
are reviewed and weaknesses pinpointed. Although these architectures are
constantly evolving, alternatives may emerge. In the conclusion of this article
we provide a very brief discussion of two potential alternatives: IN-based
architectures and mobile-agent-based architectures.