An FDDI system and method for transmitting to an optical medium, upon receipt of token, frames of synchronous data and frames of asynchronous data having different levels of priority. The network on which the FDDI is implemented includes a plurality of processors each having a system for storing the frames of data in queues corresponding to priority, and an output buffer configured to have a plurality of logical FIFOs corresponding to the queues. Data is transferred one queue at a time from the system memory to the output buffer through a single physical FIFO. To prevent the FIFO from "locking-up" as a result of any residual data remaining therein following each transfer of a frame to the output buffer, storage remaining available for a particular queue of the output buffer to be transmitted to the medium is detected. Data is transferred from the system memory to the FIFO memory only if the storage remaining available is at least equal to the storage capacity of the FIFO memory.