With up-coming Quality of Service (QoS) requirements raised by a wide range of communication-intensive, real-time multimedia applications, resource reservation is one of the approaches to satisfy requested QoS. Resource ReSerVation Protocol (RSVP) is a well-known signaling protocol for bandwidth reservation in the Internet. However, the current reservation protocols like RSVP do not present the maximum flow acceptance rate solution. The problem of finding the maximum reserved flow acceptance rate and minimizing the effects of crank-back procedure is called the New Killer Reservation Problem (NKR, Section IIB). In this paper, we study the NKR problem and answer two questions: (1) under what scenarios does the NKR problem become a serious problem; and (2) how can we solve this problem. We introduce the Marginable Bandwidth Reservation Protocol (MBR) as a solution to the NKR problem. The results show that MBR protocol yields the desired improvement of flow acceptance rate at a low cost.