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Re: TCP and WAN issue
- From: Marshall Eubanks
- Date: Wed Mar 28 08:38:37 2007
On Mar 28, 2007, at 5:12 AM, Andre Oppermann wrote:
Marshall Eubanks wrote:
You might want to look at this classic by Stanislav Shalunov
The description on this website is very good.
Disclaimer: I'm a FreeBSD TCP/IP network stack kernel hacker.
To quickly sum up the facts and to dispell some misinformation:
- TCP is limited the delay bandwidth product and the socket buffer
- for a T3 with 70ms your socket buffer on both endss should be
- TCP is also limited by the round trip time (RTT).
- if your application is working in a request/reply model no
bandwidth will make a difference. The performance is then entirely
dominated by the RTT. The only solution would be to run multiple
sessions in parallel to fill the available bandwidth.
- Jumbo Frames have definately zero impact on your case as they don't
change any of the limiting parameters and don't make TCP go faster.
There are certain very high-speed and LAN (<5ms) case where it may
make a difference but not here.
- Your problem is not machine or network speed, only tuning.
Change these settings on both ends and reboot once to get better
"SackOpts"=dword:0x1 (enable SACK)
"TcpWindowSize"=dword:0x7D000 (512000 Bytes)
"Tcp1323Opts"=dword:0x3 (enable window scaling and timestamps)
"GlobalMaxTcpWindowSize"=dword:0x7D000 (512000 Bytes)
And, of course, if you have Ethernet duplex or other mismatch issues
anywhere along the
path, performance will be bad.
On Mar 27, 2007, at 4:26 PM, Philip Lavine wrote:
I have an east coast and west coast data center connected with a
DS3. I am running into issues with streaming data via TCP and
was wondering besides hardware acceleration, is there any
options at increasing throughput and maximizing the bandwidth?
How can I overcome the TCP stack limitations inherent in Windows
(registry tweaks seem to not functions too well)?
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