Basic Web traffic counts, sometimes identifying business and consumer users, are raw ingredients for usage-based accounting. Part of the problem is semantics, once again. The only real parameters are time and simple aggregates of distance predefined by the phone company to suit tariff requirements. Bandwidth is not an issue. Compare this with accounting for networked data services.
Services vary by type across a range of application and access choices.
They vary by transport type and user priority. Bandwidth very much comes into play. There is no single source - rather, just the opposite. Database and directory services for associating user names with addresses. Ports for application identification.