IP-QoS: Scalable and Flexible Qualiy-of-Service with Differentiated Services

In the last decade, the Internet community spent a lot of research efforts in investigating various approaches and mechanisms in order to provide better Quality of Service than the traditional best effort delivery. The Differentiated Services (DiffServ) architecture developed by the Internet Engineering Task Force (IETF) seems to be the final conclusion in this long process. In contrast to previously proposed architectures, the DiffServ approach was designed with the goals of scalability and flexibility in mind. The main focus was put on avoiding the maintenance of per flow state information in core network routers. To achieve this, so-called behavior aggregates were defined merging all flows that should perceive the same service class into a simple aggregate, thus significantly decreasing state and management overhead within the network. This chapter gives an overview of the main concepts of the Differentiated Services architecture and shows how value-added services can be realized in a scalable and flexible way