[95487] in North American Network Operators' Group
Re: TCP and WAN issue
daemon@ATHENA.MIT.EDU (Andre Oppermann)
Wed Mar 28 05:13:40 2007
Date: Wed, 28 Mar 2007 11:12:45 +0200
From: Andre Oppermann <nanog-list@nrg4u.com>
To: Philip Lavine <source_route@yahoo.com>
Cc: Marshall Eubanks <tme@multicasttech.com>, nanog <nanog@merit.edu>
In-Reply-To: <A498C58E-0CFC-429F-BEE5-3A30DDBEF192@multicasttech.com>
Errors-To: owner-nanog@merit.edu
Marshall Eubanks wrote:
>
> You might want to look at this classic by Stanislav Shalunov
>
> http://shlang.com/writing/tcp-perf.html
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 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 of
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 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
--
Andre
> Marshall
>
>
> 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
>
>
>
>
