In a sense, the IP Diffserv concept 'exploits' important technological trends like growing processing and transmission speeds and decreasing costs of bandwidth. This enables QoS provisioning with less complex traffic management mechanisms than used in other broadband multi-service networks like ATM and IP Intserv. Roughly, one can say that the need for traffic management on small time scales (e.g. sophisticated packet scheduling) becomes smaller, while the role of traffic management on larger time scales (e.g. bandwidth provisioning based on network load measurements) becomes more important. In particular, we argue that admission control in IP Diffserv can be performed on aggregate flow level (important for scalability!) instead of on individual flows as in ATM or IP Intserv, while still guaranteeing suitable QoS levels. We also discuss the related issue of network dimensioning and point out possible dimensioning approaches for IP Diffserv networks.