In this paper, we propose a novel Head of Line Priority Cell Discard (HoL-PCD) buffer management mechanism at the earth terminal buffers of broadband satellite networks, that preserves QoS for compliant traffic at the expense of non compliant traffic, and improves the overall delay performance of the network. Our simulation model includes a GEO satellite with onboard bandwidth scheduler, with multimedia earth terminals accessing the satellite by means of multiple frequency time division multiple access (MFTDMA) with combined free/demand assignment (CFDAMA). Results verify the effectiveness of the HoL-PCD scheme in increasing the amount of compliant traffic accommodated by the network while maintaining the QoS guarantees required by the users.