Tuning of Large Send Window

[j7n]

Provider (JSC Balticom) gives us 30 MBit/s of upstream. Those speeds are normally achievable within Northern Europe only, where latency is low (<30 ms). By increasing the TCP windows and socket buffers, I am able to get those speeds with the East Coast as well (120-200 ms).

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\AFD\Parameters]
"DefaultSendWindow"=dword:00040000

Upload speed between Riga,LV<->Dallas,TX - 1.1 Megabyte/s. pic

Upload speed between Riga,LV<->Singapore - 600 kilobyte/s. pic

 

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\AFD\Parameters]
"DefaultSendWindow"=dword:00080000

Upload speed between Riga,LV<->Dallas,TX - 2.3 Megabyte/s. pic

Upload speed between Riga,LV<->Singapore - 1.1 Megabyte/s. pic

Good.

Those are my last tests here. Repeated from 2 IPs to be certain. The problem is that now connections with hosts in Europe are not stable. Upload to Amsterdam, NL ramps up to 60 MBit/s, then suddenly drops, recovers slowly, and drops again. Average speed - 1.8 Megabyte/s. Same with a test site in OVH. My browser shows the speed during an upload.

There is no problem with download, which are working well, because we get 100 MBit/s of downstream.

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\AFD\Parameters]
"DefaultReceiveWindow"=dword:0007d780

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters]
"GlobalMaxTcpWindowSize"=dword:000faf00
"TcpWindowSize"=dword:0007d780

There is a fair bit of a misinformation around the net regarding various "speed boosts", which is why I am unable to find the answer myself.

Is there a way to slow down the transmission automatically under Windows XP/2003, which is what I use? If your suggestion is to upgrade to Win Seven/2008, then do tell how it has worked well in similar situations.

[mudmanc4]

You might be better off setting a QOS in the router for this. Although this will not fix your issue , as you are aware of.

 

This sounds more like a QOS within the route itself, that should be tuned for your bandwidth package. As 30Mbps should never be controlled to 1.8 - in normal circumstances.

 

The speedboost as I am familiar with , would normally be on the downstream, allowing for fast browsing and such , making it appear the connection is much faster, though prolonged downloads will level out after the initial opening of the connection is established. This is not to say it's not being done on the upstream.

 

That said, the results seen in your tests to Dallas truly are not that bad, considering the distance.

[j7n]

I played a bit with the traffic shaper on my router with similar results to what I get without it from ISP (without consuming the router's resources). I feel like I would need to have the flow control at the sender, and am now just assuming a single Bandwidth Delay Product for all connections, which is only true for part of them.

Maybe Windows NT 6 does have better auto tuning as I heard. But even on my latest PC I've installed XP, because I am generally very satisfied with the system, and am familiar with its tweaking.

In practice the problem isn't that great if I have a few connections running (to different destinations), only one of them collapses at any given time.

The results are indeed quite good. I've read conflicting opinions about DefaultSendWindow, and it is not available for adjustment in the TCP Optimizer. But it really does have an effect. I'm observing speeds proportional to the chosen window in bittorrent, random Comcast peers now get near 1 MB/s. According to some reports, it must also be set in Vista. Not sure about later.