Resource reservation in a packed switched telecommunications network is provided. System and method are directed to make resource reservation especially in an Internet Protocol (IP) network for achieving Quality of Service (QoS) requirements controlling traffic preferable in a Terrestrial Radio Access Network (UTRAN) of a Universal Mobile Telecommunications Network (UMTS). A sub-object of source statistics description characterizes the statistical behavior of a traffic source for example the average length of ON and OFF periods. The sub-object is used to reserve resources in a per-flow reservation method or for calculation of the number of resource units in edge nodes in case of an aggregated reservation method.