RAN (see section 2.3.4.1) or using Pseudo Wire Emulation Edge-to-Edge (PWE3) technology to emulate ATM over Ethernet or other packet switched networks like Asymmetric Digital Subscriber Line (ADSL) (see section 2.3.4.2). The resulting system requires a modified dimensioning paradigm. The lub transport cannot be modeled as a set of dedicated point-to-point links between RNC and Node B pairs anymore, but as a complex topology, where traffic going to different destinations is competing for the system resources with connections having mutual impact on each other. Quality of Service Requirements One of the most essential features of UMTS is its multi-service support to provide adequate service-specific QoS for a wide range of applications and services. The following fundamental QoS functionalities will have to be realized in the UMTS networks: Differentiated service treatment: in order to offer several classes of QoS, UMTS has to be able to distinguish different service classes and handle them in a differentiated way, corresponding to the class of service they belong to. Resource reservation and admission control: whenever network resources are limited and strict QoS requirements have to be met, the usage of resources needs to be controlled, monitored, and regulated. End-to-end service provisioning: QoS has to be provided on an end-to-end basis, making it necessary to coordinate service provisioning across multiple domains and provider networks. Over the past years, numerous QoS mechanisms have been developed, which provide fundamental building blocks for the overall QoS framework [LF03]. Furthermore, various concepts have been introduced, which incorporate fundamental QoS schemes within one network architecture to realize comprehensive QoS-enabled networks. For the ATM transport networks, a number of QoS categories are defined by the ATM forum [ATM96] and various QoS mechanisms are suggested such as call admission control. For the IP transport networks, examples are the Internet Engineering Task Force (IETF)'s Integr