Abstract. In Optical Burst-Switched networks, the so-called BurstControl Packet is sent a given offset-time ahead of the optical data burst to advertise the imminent burst arrival, and reserve a time-slot at each intermediate node to allocate the incoming optical burst. This work proposes a methodology to estimate the number of packets to arrive in a given amount of time, in order to make it possible to send the BCP packet straightafter the first packet arrival and reduce the latency experienced during the burst-assembly process. The following studies the impact of a wrong guess in terms of overreservation of resources and waiting-time at the assembler, providing a detailed characterisation of their probability density functions. Additionally, a case example in a scenario with non-homogeneous Poisson arrivals is analysed and it is shown how to choose the appropriate burst-assembly algorithm values to never exceed a given over-reservation amount.