und applications. When the end user, either a machine or a human, is online requesting data from remote equipment (e.g. a server), the interactive scheme applies. In a normal case the user is requesting information. During a common packet call a bursty sequence of datagrams is exchanged. This phenomenon is very important when developing a traffic model. Burstiness is an inherent feature of this class. Examples of human interaction with remote equipment are web browsing, e-learning, interactive e-mail and database retrieval. Server access is another application in this class, for example when several persons at different geographical locations play a game together supported by a game server. A third example is collaborative working, i.e. when several persons work together on the same object and exchange information on that object directly between their respective terminals. Examples of machine interaction with remote equipment are polling for measurement records and automatic database enquiries (tele-machines) Location-based services belong often to the interactive class. See below. Interactive traffic is dependent on the request response pattern of the end user. At the message destination there is an entity expecting the message (response) within a certain time. Round-trip delay time is therefore one of the key attributes. Another characteristic is that the content of the packets must be transparently transferred (with low bit error rate). For mobile systems two types of users are included, namely laptop users and mini browser users. Users referred to as mini-browser users are assumed to be running their applications over efficient protocols and are commonly known as 'thin clients'. A palmtop or pocket phone type is an example of such clients. Service session characteristics include: Duration of one session Byte volume up and down per session Packet size up and down link File size down Inter request times Number of sessions per day User access (rate, QoS) Distribution of sessions during the day Location-based Ser