In order to achieve better scalability, inter-domain signaling protocols rely on aggregation to reduce the amount of state information that routers are required to maintain. Nonetheless, they do not address another scalability key factor, the signaling load associated with establishing and maintaining reservations. Such load can be reduced if bandwidth is over-reserved. Over-reservation allows accommodating reservations without exchanging signaling messages, but may result in additional blocking. In this paper, we carry out a systematic investigation of the impact of over-reservation in different aggregation approaches, evaluating such impact in terms of the achieved signaling reduction, and blocking.