1. Simple, classless Queueing Disciplines 1.1 pfifo_fast
This queue is, as the name says, First In, First Out, which means that no packet receives special treatment. At least, not quite. This queue has 3 so called ’bands’. Within each band, FIFO rules apply. However, as long as there are packets waiting in band 0, band 1 won’t be processed. Same goes for band 1 and band 2.
The kernel honors the so called Type of Service flag of packets, and takes care to insert ’minimum delay’ packets in band 0.