Vista Gigabit Networking

HEADRAT

HEADRAT

HEADRAT

Soldato
Joined
18 Oct 2002
Posts
21,499
Location
Cambridge, UK
Hi,

I've got a Vista Ultimate box and 2 x MCE2005 linked up via a Gigabit network, now the transfer rates between the 2 x MCE2005 boxes are fine and if I push a file from the MCE2005 boxes to the Vista box again the transfer rate is what I expect (approx 20/30%)

Now if I try and push a file from Vista to either of the MCE2005 boxes then I get a throughput of about 6%!!

Anybody seen similar behaviour?

I've tried loads of different things but my Gigabit network just crawls.

1. Latest drivers for NIC's
2. Turning Remote Differential Compression off (no difference)
3. Settiing "netsh int tcp set global autotuninglevel=disabled" (no difference)
4. Hotfix KB931770 isn't really my problem, just slow throughput.

I'm at a loss, I have a Gigabit network that runs at 10Mbps.

I have tried both a Linksys EG1032 v2 and Marvell Yukon 88e8001/8003/8010
NIC with my Netgear GS605 v2 5 port Gigabit switch but it's terrible!

HELP!

HEADRAT
 
Some info I saved off another site

“netsh interface tcp show global”

http://support.microsoft.com/kb/224829

It appears that some routers are having problems with “TCP Windows Scaling.” Essentially, the TCP spec limits a TCP packet to 64KB, since faster networks allow for more data transfer, 64KB is a tad on the small side. TCP windows scaling involves negotiating a larger packet size between the client and the server during connection by the client sending a special SYN packet and waiting for an acknowledgment. Problem is, some routers (mine for example) strip the SYN acknowledgment packet. The sever thinks that scaling is enabled and starts sending data back, meanwhile the client waits for it’s SYN acknowledgment that it never receives, and eventually times out.

By default Windows 2003 does not send Windows Scaling SYN ack packets unless the client requests scaling (known as auto-tuning). Vista, now uses auto-tuning in it’s TCP stack, where as XP did not.

So why does IE7 work? Windows scaling requires a scale factor to determine how much extra data can be squeezed into TCP packet (typically 64K * 2 ^ factor). IE7 forces a scale factor of 2, which seems to work through my router, whereas other applications, such as FF2 use a default factor of 8.

Turning auto-tuning off on Vista is a quick fix but not ideal. Replacing my router with one that does not strip out the SYN packets is another quick fix. Since other readers of my site may be using a buggy router and an installation of vista the only proper fix is to prevent the server from sending SYN packets


Is it your router?
 
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