Current Quality of Service models such as those embodied in the Differentiated Services proposals, rely on data path aggregation to achieve scalability. Data path aggregation bundles into a single aggregate multiple individual flows with the same quality requirements, hence decreasing the amount of state that needs to be kept along a path. A similar scalability concern exists on the control path, where the state required to account for individual reservations needs to be minimized. There have been a number of proposals aimed at control path aggregation, and the goal of this report is to expand on these works in an attempt to gain a better understanding of the various parameters that influence the efficiency of different approaches. In particular, we focus on inter-domain control aggregation, and compare an Autonomous System (AS) sink-tree based approach with several examples of a shared AS segment based approach. The comparison is done in terms of the amount of state that is kept, ...