Yes, I recognise that behaviour from when I didn't have the timer resolution workaround in cake. The PowerBook was fine (modern hardware, good timers) but the Pentium-MMX only has the basic PC-AT timer hardware, operating at 1kHz. Because ack packets end up spaced the same way, it affects download as well at a multiple of the upload effect bandwidth, even if download is not shaped. The multiple depends on how the receiving host spaces acks. - Jonathan Morton