Tweaking
your modem
Last
Updated on September 18, 2000 by Thomas
McGuire - Page 3/10
Setting
MTU/TTL/RWIN
Once the value is discovered click on Start, Run, type in regedit
& hit Enter. Open the following registry key [HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\VxD\MSTCP].
Right click in the right hand pane. Select New & String value.
Make 2, one
called DefaultRcvWindow
& the other DefaultTTL.
Once they have been created right click on each of them
select Modify.
For DefaultTTL
I'd recommend selecting 32
or 64, if you cannot reach a server with 64 hops it is futile to waste
anymore on trying. For DefaultRcvWindow
I suggest using MTU-40
* 3. Ideally the factor of multiplication should result
in MTU – 3 * X = Connect speed/10 or thereabouts, e.g.
In my case that is 1500-40
* 3 = 45333/10. 4380
= 4533.
Now change the MTU & TTL (Maximum segment size, or
MSS is not
settable in Windows Me, it is automatically determined by
your MTU so don't waste time needlessly setting it). Take
the following steps. NOTE
– If you only have a single modem in your PC, i.e. No
Ethernet card installed in your machine also, then you can
skip to Step 5 as there should only be one key(s) available, 0000.
1.
You have to find the details of your Dial-Up Adapter.
2.
Find the key [HKEY_LOCAL_MACHINE\Enum\Root\Net\000x]
& within there will be one or more sub-keys such as
0000, 0001, etc.
3.
Open each key & find the one that contains the value of DeviceDesc
equal to Dial-Up
Adapter.
4.
Within that key there will also be another sub-key named Bindings.
Open the Bindings sub-key & you will find a string named MSTCP\000x.
Take note of the four-digit number after MSTCP\
(in this case 0000)
& use it in the next step.
5.
Now go to the key [HKEY_LOCAL_MACHINE\Enum\Network\MSTCP\000x]
& expand the sub-key with the same four-digit number as
from the previous step.
6.
In this key you will find a value called Driver & there will be an entry entitled NetTrans\000x. Take note of the four-digit number & use it in
the next step.
7.
Now open [HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\
Class\NetTrans\000x].
Expand the key with the value equal to the four-digit number
from the previous step.
8.
Within this key create a new string value named MaxMTU
& set it to your MTU (e.g. 1500), which you discovered
in the MTU, TTL &
DefaultRcvWindow section.
9.
Next go into [HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\
Class\Net\
000x\Ndi\params\IPMTU\enum], in here you will find
entries for Automatic,
Large, Medium & Small.
Right click in the right hand side of the box & make a New
String Value equal to your MTU e.g. 1500,
right click on this new entry & select modify,
type in Automatic
then click Ok.
Delete all the other values there, e.g. Large - Small &
the other Automatic (if any).
10.
Now
open [HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\
Class\Net\000x].
Right click on IPMTU
& select modify, change this value to whatever your
current MTU you (e.g. 1500).
11.
Go into [HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\Class\Net\0000\Ndi\params\IPMTU],
change the default
value to your current MTU (e.g. 1500).
12.
Exit the registry & restart
your computer for the changes to take effect.
You
can change the settings as necessary.
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