A population of networked Application Gateway Centers or voice centers provides telephony resources. The telephony application for a call number is typically created by a user in XML (Extended Markup Language) with predefined telephony XML tags and deployed on a website. A voice center provides facility for retrieving the associated XML application from its website and processing the call accordingly. The individual voice centers are either operated at a hosted facility or at a customer's premise. Provisioning Management Servers help to allocate telephony resources among the voice centers. This is accomplished by suitably updating a voice center directory. In this way, the original capacity at a premise, predetermined by the hardware installed, can be adjusted up or down. If the premise is under capacity, it can be supplemented by that from a hosted facility. If the premise has surplus capacity, it can be reallocated for use by others outside the premise.