A communication system providing telephony communication across combined circuit switched and packet switched networks, such as a telephone network and the Internet, which are connectable to terminals, such as telephones and computers, for selective communication therebetween. The communication system provides an architecture and methodology for handling resource allocation across carriers or service providers, settlements between carriers and service providers, usage accounting across carriers and service providers, and usage allocation among carriers or service providers. A first provider of packet switched services controls a directory of addresses of gateways between the packet switched and data switched networks, and an authentication database of account data. A second provider of packet switched services controls a multiplicity of the gateways and a database of addresses of authentication databases.