Preemption mechanism The standard 64/65-octet encapsulation technique has been amended with a pre- emption mechanism that allows high- priority frames to interrupt the transmission of low-priority frames until the high-priority frames have been sent. Transmission of the low-priority frames is then resumed. To understand how this works, let us assume that a 1518-byte packet with internet traffic is being processed when a high-priority voice packet arrives. The preemption mechanism interrupts transmission of the 1518- byte frame, stores its current state, transmits the voice packet, and then resumes trans- mitting the packet with internet traffic.