Win95 and TCP Window Size
Daniel Senie
Is there way to set such parameters as TCP window size using the TCP/IP
stack from Microsoft that comes with Win95? The performance of this
stack as it comes out of the box leaves a lot to be desired.
Gordon McAndrew
d...@senie.com (Daniel Senie) wrote:
;>Is there way to set such parameters as TCP window size using the TCP/IP
;>stack from Microsoft that comes with Win95? The performance of this
;>stack as it comes out of the box leaves a lot to be desired.
Below is part of my answers file.
It could be because you are still using the default settings for
DefaultRcvWindow. You will find how to change this value in the resource
kit help file on the Win95 CD under the folder Admin\Reskit\Helpfile.
The path to create the string key under is: (use REGEDIT to change it)
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\MSTCP
Add the string value DefaultRcvWindow and then modify its value to "4096"
for 14.4 modems or "5632" for 28.8 modems.
To find the section of the help that you need, in the contends screen that
comes up when you double-click on the help file, type "tcp" then click on
configuring | Display | then click on the ">>" button six times to come to
the page titled "TCP/IP Registry Entries in the MSTCP Subkey". The key you
want to edit is described on this page. Enter the new value so that it is
a number between quotes, ie "4096". Look a few pages farther on for how
to change the MTU setting.
I found that the default value of 8192 will run but it slows and comes to a
stop and then starts again. All the values between that and 4096 don't
work. 4096 works well with no rest stops<g> I have settled on 4096.
It all depends on the value of MSS that your ISP has chosen for himself.
You will have to experiment.
-------------------------------------------------------------------------------
There are only two variables to play with "DefaultRcvWindow" (RWIN) and
MaxMTU (MTU)
-------------------------------------------------------------------------------
The entries described here must be added to the following Registry key:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\MSTCP
DefaultRcvWindow= 16-bit number
Specifies the default receive window advertised by TCP. The default is
8192
--------------------------------------------------------------------------------
The entries in this section must be added to the following Registry key,
where n represents the particular TCP/IP-to-network adaptor binding.
HKEY_LOCAL_MACHINE\System\CurrentControlSet\services\Class\netTrans\000n
MaxMTU= 16-bit integer
Specifies the maximum size datagram IP that can pass to the media driver.
SNAP and source routing headers (if used on the media) are not included in
this value. For example, on an ethernet network, MaxMTU will default to
1500.
The actual value used will be the minimum of the value specified with this
parameter and the size reported by the media driver. The default is the
size reported by the media driver.
--------------------------------------------------------------------------
I had a 14.4 modem and I got good results with a value of 4095 for
DefaultRcvWindow with the MaxMTU being the default value of the one that
the line has which is 1500.
I bought a 28.8 modem and wondered about that value and whether it would
change.
So I started a cycle of tests with different values in DefaultRcvWindow.
(rebooting to get the value to take effect). The transmit rate was the
same
in all tests at 62 Kbps (as it should be if I play with a receive setting).
The tests where done with a straight text file.
DefaultRcvWindow Receive rate K bits /sec
1024 24
2048 27
3072 52.5
4096 52
5120 62
5632 62.7
6000 62
6144 59
6160 59
As you can see the peak receive speed came at 5632. So that is what I
now have it set at.
Gordon McAndrew
LAN Manager,
Alberta Environmental Centre,
Vegreville,
Alberta, Canada
gmca...@aec.env.gov.ab.ca Home
gor...@aec.env.gov.ab.ca Office