In a communications network, which may be a federated network such as the
Internet, a tariff is distributed via the network to customer terminals.
At each terminal a charge for use of the network is calculated by using
the tariff. Different tariffs may be communicated for different services
and a respective tariff may be varied depending upon the operational
condition of the service. Different tariffs may be calculated for
different customers and the tariffs may be varied in dependence upon the
loading of network resources and different tariffs may have different
volatilities. Part of the traffic from a user to the network may be
sampled and the status of the user may be amended when a discrepancy is
detected between the sampled parameters and the contracted parameters in
the users contract.