Charging ABR from an operator's and from a user's view

Available bit rate (ABR) is one of the ATM transfer capabilities as standardised by the ITU-T and specified by the ATM Forum. It is intended for sources that have the ability to reduce or increase their information rate in response to control signals from the network. A unique property of ABR is once the connection has been established, the network may change the ATM layer transfer characteristics, i.e. the cell rate that can be supported. The network provides feedback to the user about these characteristics. A user adapting its traffic accordingly, expects a low cell loss ratio. This paper addresses some of the challenges related to charging ABR connections. Different categories of ABR users are introduced, indicating that within the framework of ABR as currently standardised, there are some degrees of freedom for allocating the ABR capacity, which are believed relevant to charging. The effect of three different charging schemes are described: (1) charging proportional to the connection duration (time only); (2) charging proportional to the number of cells offered to the network (volume only); and (3) charging based on a combination of both variables (time and volume). It is shown that the allocation policy used may be relevant for which charging scheme may be applied. Therefore, each of these basic charging schemes are assessed for a particular allocation policy.