In some guaranteed data delivery scenarios, servers can quickly and carefully allocate the available bandwidth among the requests of the users to reduce rejections. This is particularly important when reservations are higher than minimum required delivery rate (semi-elastic reservations). As an example, when semi-elastic reservations utilize all the available server bandwidth and a new flow reservation arrives, it is useful to reallocate current reservations to accept the new one. The RSVP protocol is receiver oriented and it is in charge of setting up these reservations. However, in some cases, to reallocate bandwidth in a receiver riented way could delay the required sender reservation adjustments. This paper presents a new extension of the RSVP signaling messages that allows the server to adjust and modify these reservations. The performance evaluation of the extended and the native RSVP signaling protocols when used to manage the access bandwidth of a semi elastic flows server shows the benefits of the extensions. In particular, the use of resource reservation is reduced because of a more efficient bandwidth usage. In addition, the blocking probability is also reduced because of a more flexible bandwidth reallocation situation. The authors believe that this procedure is an intermediate step to improve the lack of flexibility that RSVP presents.