Subject: Re: How to reach Large TCP window in Win (2000) or Linux

From: [email-masked]
Date: Tue, 29 May 2001 10:09:41 +0200

Hi,

To enable large window size in Win2000: create a reg key (DWORD):
HKEY_LOCALMACHINE\system\currentcontrolset\services\tcpip\parameters\tcpwindowsize
and set it to something larger than 65535 (I use 200000 for a RTT of approx
500ms).

On Linux: (2.2)
for send window
echo 200000 > /proc/sys/net/core/wmem_default
echo 200000 > /proc/sys/net/core/wmem_max
for receive window
echo 200000 > /proc/sys/net/core/rmem_default
echo 200000 > /proc/sys/net/core/rmem_max
Sack and timestamping are enabled by default on Linux.

note that you have to change this on both http server and client.

The TT card will download with reasonable stability up to 3 Mbit/s.

Robert

                    Dusan Statelov                                                                         
                    <statelov@maind        To:     [email-masked]                                     
                    ata.sk>                cc:                                                             
                    Sent by:               Subject:     How to reach Large TCP window in Win (2000) or     
                    owner-tcpsat@gr        Linux                                                           
                    c.nasa.gov                                                                             

                    05/28/01 05:00                                                                         
                    PM                                                                                     
                    Please respond                                                                         
                    to statelov                                                                            

Hello:

As we are now in time pressure I would like ask you for advices how to
properly configure Win2000 or Linux Http data server in order to achieve
bigger TCP window and improve Single TCP connection from poor 20-30 kbyte/s
(for RTT 240 ms) to according to us achievable 1 mbps.
We have changed "Default Receive Window", but TCP is running at only 20-30
kbyte/s what would corresponde to 8 kbyte Window rather then to 64 kbyte.
I assume there are other TCP registry entities which influence Sender
Window.

Here is a configuration emulating satellite internet:

Http Data Server [Linux or Win2000]  -> DVB/ip -> DVB-S Modulator -> L band
output -> PC DVB board [SkyMedia - Telemann, TT DVB Technotrend] ->
client PC [Win98] o---------------o  connected to DVB/ip GW in return via
LAN
LAN RTT 20 ms
Artefficial delay in DVB/ip GW 220 ms (in order to simulate long RTT for
satellite)

Windows98
Default Receive Window to max.values 65535
Data Sever Win2000
Default Receive Window to max.values 65535 (we tried even 0,5 Mbyte with no
effect)
RTT 240 ms
Single TCP connection 20 - 30 kbyte/s

Thanks in advance.

Dusan Statelov
Managing Director
Main Data,s.r.o.
mailto:[email-masked]

Tel:     +421 7 54789 586
Fax:     +421 7 54789 585
GSM:     +421 905 606 027
http://www.maindata.sk

(See attached file: statelov.vcf)

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