Microsoft Responds To Vista's Network and Audio Problems Vista News Discuss Microsoft Responds To Vista's Network and Audio Problems in the Windows Vista forums; With the discovery last week of the connection between Vista's poor networking performance and audio activities, word quickly spread around the Net. No doubt this got Microsoft's attention, ...

[Snuffy]

With the discovery last week of the connection between Vista's poor networking performance and audio activities, word quickly spread around the Net. No doubt this got Microsoft's attention, and they have responded to the issue. Thanks to pacpis for this news.

Microsoft states that 'some of what we are seeing is expected behavior, and some of it is not'; and that they are working on technical documentation, as well as applying a slight sugar coating to the symptoms.

Apparently they believe an almost 90% drop in networking performance is 'slight,' only affects reception of data, and that this performance trade-off is necessary to simply play an MP3.

Adrian Kingsley-Hughes: I have received a response to the Vista network performance issue from Microsoft. Here are some points of interest:

* “We have been looking into this problem and are working on a doc that will go into the technical details of what we have found.”
* “Please note that some of what we are seeing is expected behavior, and some of it is not. In certain circumstances Windows Vista will trade off network performance in order to improve multimedia playback. This is by design.”
* “The connection between media playback and networking is not immediately obvious. But as you know, the drivers involved in both activities run at extremely high priority. As a result, the network driver can cause media playback to degrade. This shows up to the user as things like popping and crackling during audio playback. Users generally hate this, hence the trade off.”
* “In most cases the user does not notice the impact of this as the decrease in network performance is slight. Of course some users, especially ones on Gigabit based networks, are seeing a much greater decrease than is expected and that is clearly a problem that we need to address.”
* “Two other things to note. First, we have not seen any cases where a users internet performance would be degraded, in our tests this issue only shows up with local network operations.”
* “Second, this trade-off scheme only kicks in on the receive side. Transmit is not affected.”

I’ve been doing some more research into this and I’m coming to the conclusion that the issue is related somehow to Multimedia Class Scheduler service (MMCSS). This is a service that makes sure that multimedia applications have prioritized access to CPU resources. I can’t prove my theory because killing MMCSS also disables Windows audio.

[Snuffy]

Russinovich confirms Vista network-killing bug
by Justin Mann on August 29, 2007, 5:54 PM |
An interesting Vista bug has been brought to light that many have wondered about, but had not yet until now been confirmed. Mark Russinovich has documented the steps needed to reproduce a bug in Vista in which you can cause the machines networking capabilities to slow down or even halt altogether, due to a Vista feature called MMCSS.

This feature was intended to improve the quality of your “media experience” when playing audio or video. It may have accomplished that at the cost of other resources:

Its mission is to automatically prioritize the playback of audio and video to prevent skipping, sputtering and other unseemly glitches. Unfortunately, it ends up fixing a problem that was largely non-existent and leaving in its place a major headache for many sysadmins.

The bug is such an issue, it seems, that even playing files as innocent as the Windows error beeps can cause serious network degradation. The problem is also seen in games and meda suites such as Real Player.

Just how bad can it be? Apparently, it can be a network killer:

Russinovich documents how a throughput of about 20 percent on his 1Gb local area network dropped to about 6 percent simply by trying to pass the time by playing a tune in Windows Media Player. Effects like that will also be felt on 100MB networks.

This is definitely interesting. According to the article, Microsoft developers are at least aware of the problem. There is no official acknowledgment of the issue yet, however, which has been a bone of contention for some. A workaround has been posted that seems to cure the issue, by simply disabling MMCS. That's not, of course, an official fix.