[FONT='Verdana','sans-serif']Mark Russinovich, one of our Technical Fellows and a prominent member of the Windows community,
posted today on a topic that's received much discussion in the past few days -- that being the manner in which Windows Vista throttles network traffic on gigabit Ethernet networks when the user is engaged in multimedia playback.[/font]
[FONT='Verdana','sans-serif']As Mark puts it, "many people have correctly surmised that the degradation in network performance during multimedia playback is directly connected with mechanisms employed by the Multimedia Class Scheduler Service (MMCSS), a feature new to Windows Vista." This throttling of network traffic is mainly apparent on networks with infrastructure allowing gigabit throughput and is experienced by a user receiving, as opposed to sending, data.[/font]
[FONT='Verdana','sans-serif']The explanation is quite technical and rather esoteric, but the gist is that when receiving data on faster networks, the number of system interrupts is increased and because network-driven system interrupts are handled at higher priority than media playback, multimedia playback can be affected if the number of network-driven interrupts outpaces content refilling the multimedia playback buffer. Mark's full explanation is quite a bit more detailed -- I've only described it here in outline.[/font]
[FONT='Verdana','sans-serif']While this behavior is by design, [FONT='Verdana','sans-serif']the throttling parameters as shipped caused greater-than-anticipated degradation on gigabit Ethernet systems. In addition, t[/font]here's also a related bug we've identified in scenarios involving multiple NICs but for which we're scheduling a fix. If you'd like all the details in their technical glory,
visit Mark's blog. He'll have more news on this topic as it develops.[/font]
http://windowsvistablog.com/aggbug.aspx?PostID=487649
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