After I had my problems in Vista64 with my gigabit adapter apparently working as a 100 Mbps one, I found some interesting articles about "Netowrk Throttling", a technique developed by Microsoft to hard-limit the bandwidth for processes using Gigabit networks when other concurring processes involve audio, video and multimedia resources.
I'm sorry for the double post, but I think it could be interesting for everybody, so I decided to start a new topic on this topic.
First of all: what is Network Throttling?
Mark Russinovich, Microsoft Fellow, explained that network performance was hard-coded to cap at 10,000 packets per second if any MMCSS-enabled application came on (apparently even if no audio or video is being played) and demanded CPU priority. The hard-coded rate limit essentially limits network performance to around 15 MB/sec (megabytes per second) because 1500 bytes per packet times 10,000 packets equals 15 million bytes per second. 15 MB/sec works out to be 120 mbps (megabits per second) and most 10/100 networks top out around 90 mbps while most broadband connections are capped to 1.5 mbps. Even most so-called gigabit NAS (Network Attached Storage) devices have a performance cap of around 120 mbps so very few people will even notice the MMCSS induced throttling in the first place.
And now, some articles and solutions to limit or completely get rid of the Network Throttling effect.
"Playing music severely degrades network transfer performance in Vista"
http://blogs.zdnet.com/hardware/?p=702&tag=rbxccnbzd1
About Netowrk Throttling and Multimedia Class Scheduler Service (MMCSS)
http://blogs.zdnet.com/Ou/?p=711
How to manage Network Throttling Index
http://www.vistarevisited.com/2008/05/24/how-to-improve-network-performance-in-windows-vista/
How to disable Multimedia Class Scheduler Service
http://forums.nvidia.com/index.php?showtopic=36178&st=0&p=332216&#entry332216
Hope this can help.
Luigi.