We are writing for managers of enterprise IT departmentsand for their managers, up to the CIO level. We are also writing for networking professionals, technology experts, and systems integrators who are embarking on the big effort to deploy voice on an IP network. And we have included material that will be useful to the folks on the other side of the big knowledge gap that we are trying to bridge; it seems few professionals in the telephony community know much about the data-networking community, and vice versa.