ISDN tweak guide (Windows 98 & ME) Posted on July 02, 2001 by Toby Crundwell & Thomas McGuire Now
that it has become economically viable (& available), many people are
choosing ISDN. ISDN Terminal Adapters (TAs) are rather more limited in how they
can be tweaked. However there are still several things you can do to improve
performance. Updating
drivers/Identifying the TA First
of all you should update your drivers. If you know how to do this then skip the
next section. Hold ALT & double click on my computer, select
the Device Manager tab & open up the Network Adapters tree.
You
should see your ISDN card listed. Remember your exact model, as many
manufacturers release several different versions of the same card, each needing
different drivers. You should be able to find all the drivers you need at Windrivers.
Update your driver using the instructions provided; some cards (like my one, for
instance) have to have the old drivers uninstalled before the new ones can be
installed. If
you are using Windows 95 or 98 still then you should be sure to install the Dial-Up
Networking 1.4 upgrade. This includes an updated TCP/IP stack (For Windows
95) as well as other improvements to stability & security (e.g. 128-bit
encryption). General
tweaking Once your drivers are updated open My Computer & go into the Dial-Up Networking folder. Right click on the appropriate Dial-up connection & select Properties.
You
should connect using your primary channel (0), for the sake of simplicity. Click
on configure and make sure Only connect at this speed is not
checked. If it is you will not have the option of connecting at 128k.
Click
Ok and move on to the Server types tab. As far as I can tell
enabling Software compression does not speed up transfer rates at all, so
its best to disable it to avoid excess CPU usage. If you choose to Log onto
network connections will be about 3 seconds slower than they need to be, I
would recommend disabling this. Some servers may require an encrypted password,
this will add a second or two to connection times. The other Advanced options
should be left blank, unless you have a specific need for them (e.g.
recording a log file to analyse connections). You can safely disable (Untick)
NetBEUI & IPX/SPX if these protocols aren’t installed on your system.
128k
connections Windows
9x/Me is unfortunately very clumsy when setting up 128k access. Move to the Multilink
tab.
You
should set up an option to enable 128k even if you don’t plan to use it so its
there just in case you need it. Click on Add & verify the number is
correct. If you’ve specified to use an area code in the General
section, the number added should not have an area code prefix. If,
however, you did not specify the dialing properties with an area code/prefix,
you should add it into the new number here. The device should be the second (1)
channel, for simplicity. Click Ok, then Ok again.
However,
this alone doesn’t automatically enable connections of 128k.You will still
only connect at 64k. To activate the second channel, you first need to connect. Double
click on the connected icon in the taskbar, & click on Details.
To activate the other channel & give you 128k you need to click Resume.
The second channel can be disconnected at any time by following the previous
steps, but clicking on the Suspend button (it will change from Suspend to
Resume & back again as you click on it).
128k
is nearly always noticeably faster than 64k, & for most of you I would
recommend connecting at 128k all the time. However, this also costs double the
amount that a 64k connection does, & as such some may want to be a bit more
conservative with this option. Windows
9x/Me unfortunately does not support bandwidth on demand, like Windows
2000 does.
MTU, TTL & More First a few definitions... MTU.
Maximum Transmission Unit.
This specifies the maximum transmission unit size of a packet. A packet larger
than the MTU size will be fragmented into smaller packets. Using the (Maximum)
MTU your ISP allows can result in less fragmentation of packets. TTL.
Time To Live.
This sets the number of hops a packet is allowed to pass between "you"
& it's destination. DefaultRcvWindow.
This sets the size of the TCP send & receives windows, which is the amount
of data that can be accepted in a single transaction. Before setting your MTU
you must find it. To start with you
should set your MTU to a high value.
This way the following procedure will be accurate, i.e. If you MTU is currently
576 then the procedure won't find an MTU an larger than 576. Basically skip to
the Setting MTU/TTL/RWIN section
& set your MTU to 1500 or
greater. Then Reboot for the changes
to take effect, then return to this section. You will now be able to get an
accurate indication of your MTU. Click on Start,
Programs, Accessories, MS-DOS prompt
once connected to the Internet. Type in ping
–f –l xxxx www.yourisp.com. Replace www.yourisp.com
with whatever address your ISP’s is (Or the IP address). Replace xxxx
with numeric values until you get the message Packet
needs to be fragmented by DF set. Use whatever the largest
value is before that error message
& add 28 to it to find your MTU. –f.
Sets a Don’t Fragment flag in packet. –l
xxxx. This sends a buffer
sized xxxx. E.g. ping
–f –l 1472 194.145.128.1
1472
+ 28 = 1500. As a result I’d set my MTU to 1500 as higher values return the fragment message. 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 the following formula to get a value for it. Ideally the factor of multiplication (X) should result in: MTU – 40 * X = Connect speed/10 or thereabouts, e.g. In my case that is 1500-40 * 3 = (circa) 45333/10. 4380 = (circa) 4533.
Now change the MTU & TTL (Maximum segment size, or MSS is not settable in Windows 9x/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. Find the key [HKEY_LOCAL_MACHINE\Enum\Root\Net\000x] & within there will be one or more sub-keys such as 0000, 0001, etc. 2. Open each key & find the one that contains the value of DeviceDesc equal to Dial-Up Adapter. 3. 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. 4. 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. 5. 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. 6. 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. 7. 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. 8.
Next go into
[HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\
Class\Net\ 9. 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). 10.
Go
into [HKEY_LOCAL_MACHINE\System\CurrentControlSet\ 11. Exit the registry & restart your computer for the changes to take effect. You can
change the settings as necessary.
Timeouts This tweak can reduce the amount of Timeouts you may experience when online. 1. Open Regedit (Click on Start, Run, type in regedit & hit Enter), go to [HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\Net\000x]. Where x represents the folder with the Slownet entry. 2. In the right hand pane, right click on Slownet & select Modify, change the value from 01 to 00. Conclusion Hopefully
now your connections will be quicker, downloads faster, ping times lower etc. If
you have any questions or comments feel free to email me. |
