nanog mailing list archives
Re: TCP and WAN issue
From: Marshall Eubanks <tme () multicasttech com>
Date: Wed, 28 Mar 2007 08:34:04 -0400
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 http://shlang.com/writing/tcp-perf.htmlThe 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 sizes. - for a T3 with 70ms your socket buffer on both endss should be 450-512KB.- TCP is also limited by the round trip time (RTT).- if your application is working in a request/reply model no amount ofbandwidth 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 throughput:[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip \Parameters]"SackOpts"=dword:0x1 (enable SACK) "TcpWindowSize"=dword:0x7D000 (512000 Bytes) "Tcp1323Opts"=dword:0x3 (enable window scaling and timestamps) "GlobalMaxTcpWindowSize"=dword:0x7D000 (512000 Bytes)
http://www.microsoft.com/technet/network/deploy/depovg/tcpip2k.mspx
And, of course, if you have Ethernet duplex or other mismatch issues anywhere along the
path, performance will be bad. Regards Marshall
-- AndreMarshall On Mar 27, 2007, at 4:26 PM, Philip Lavine wrote:To all,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)?Philip____________________________________________________________________ __ ______________Need Mail bonding? Go to the Yahoo! Mail Q&A for great tips from Yahoo! Answers users. http://answers.yahoo.com/dir/?link=list&sid=396546091
Current thread:
- Re: Jumbo frames, (continued)
- Re: Jumbo frames Andy Davidson (Mar 29)
- RE: Jumbo frames michael.dillon (Mar 29)
- Re: Jumbo frames Stephen Sprunk (Mar 30)
- RE: Jumbo frames Hank Nussbacher (Mar 27)
- Re: Perry Lorier (Mar 27)
- Re: TCP and WAN issue Mikael Abrahamsson (Mar 27)
- RE: TCP and WAN issue Lincoln Dale (Mar 27)
- Re: TCP and WAN issue Steve Meuse (Mar 27)
- Re: TCP and WAN issue Marshall Eubanks (Mar 27)
- Re: TCP and WAN issue Andre Oppermann (Mar 28)
- Re: TCP and WAN issue Marshall Eubanks (Mar 28)
- Re: TCP and WAN issue Simon Leinen (Mar 28)
- Re: TCP and WAN issue Andre Oppermann (Mar 28)
- Re: TCP and WAN issue Philip Lavine (Mar 27)
- Re: TCP and WAN issue Roland Dobbins (Mar 27)
- RE: TCP and WAN issue michael.dillon (Mar 27)
- Re: TCP and WAN issue Roland Dobbins (Mar 27)
- Re: TCP and WAN issue Roland Dobbins (Mar 27)
- Re: TCP and WAN issue Adrian Chadd (Mar 27)
- Re: TCP and WAN issue Leo Bicknell (Mar 27)
- Re: TCP and WAN issue Eric A. Hall (Mar 27)
- Re: TCP and WAN issue Joe Maimon (Mar 27)