Many uniform total order broadcast protocols have been designed in the last 30 years. Unfortunately, none of them achieves both optimal throughput and low latency. Indeed, protocols achieving optimal throughput rely on a ring dissemination pattern, which induces high latencies. Protocols achieving low latency rely on IP multicast and fail to achieve good throughput because of message losses. In this paper, we describe FastCast, the first protocol that achieves both optimal throughput and low latency. To achieve low latency, FastCast relies on IP multicast. To achieve optimal throughput, FastCast defines a protocol responsible for dynamically computing the throughput at which processes can send IP multicast messages. Thanks to this dynamic bandwidth allocation protocol, FastCast allows multiple processes to simultaneously send messages, while avoiding message losses. An evaluation of FastCast on a cluster of 8 machines shows that it indeed achieves optimal throughput and a very low latency.