broadband tweaks

  harps1h 20:20 29 Jun 2004

can anyone tell me if there are any tweaks to speed up my connection?
and if so do they make any discernable difference

  Dipso 22:04 29 Jun 2004

Check out this site click here

I tweaked my connection and improved my download speed from 470 average to 478.

You really need to experiment with the MTU and RWIN figures though. There is a formula somewhere in the FAQ's on this site which allows you to work out which figures would work best with your connection.

  Pesala 23:24 29 Jun 2004
  reddwarfcrew 23:31 29 Jun 2004

Be wary of some of the Internet tune-up utilities you can find on the Web. Many are old, and not very professionally written. They don't check what version of Windows they are running under. Windows XP (and 2000 for that matter) have a more advanced TCP/IP than Windows 98/Me, so if you used tools that were only designed for Windows 95/Me, they probably changed values in the Registry that Windows XP never looks at.
The most common cause of sub-optimal Internet speeds is that your PC sends data in blocks (called "packets") that are larger than the maximum size a router between you and the destination site can handle. When this happens, the data has to be "fragmented", in other words, broken into smaller packets which are then reassembled at the receiving end. This is inefficient. It's better if packets are created and sent the largest size that allows them to complete their journey intact. This size, whatever it is, is called the Maximum Transmission Unit (MTU), and the first thing you need to do is determine its value.

There are tools that claim to determine and then set the best value of MTU, but it's quite easy to do it manually, and then you can be sure what is going on. Open a command window (in XP, click Start, Run, type "cmd" and hit Enter) and then type the command "ping click here -f -l 1472". If you see the reply "Packet needs to be fragmented but DF set" try lower values until you find the largest number that can be sent without this message appearing. [Screenshot: H97-3a.tif] Now add 28 to the number you used. This is the optimum MTU. The value 1500 (1472 + 28) is the maximum possible MTU. (Users of BT-based networks may find the maximum they can use is only 1458.)

Readers with external broadband routers should note that if the MTU they determine is less than 1500, it might be their own router that is limiting it to a lower value. If the router's MTU is equal to the value you obtained in the test, try increasing it and then repeat the "ping" test until it is clear that the MTU is being limited by devices beyond your control. Router settings aren't something that Regedit or a tuning utility can tweak, so you'll have to consult your router's manual to find out how to change them. Most modern broadband routers have a configuration interface that you access using your web browser.

The best and simplest way to speed up your XP Internet connection may be to enable path MTU discovery, which means that Windows tries to determine the optimum MTU value itself. The value of this, rather than setting a fixed MTU value, is that if your ISP upgrades its equipment so that a higher MTU can be used, Windows will automatically take advantage of it. To do this, start Regedit, expand HKEY_LOCAL_MACHINE, System, CurrentControlSet, Services, Tcpip and select the Parameters folder. Right-click in the right-hand pane and select New, DWORD value, and name the value "EnablePMTUDiscovery". Then double-click the new value and set it to 1. Better still, use the file "EnablePMTUDiscovery.reg" on your cover disc. Restart Windows before testing the effect of this.

If this doesn't help, it may be that Windows is discovering the wrong value for some reason. In that case, you can try setting the MTU value yourself. Under XP, the MTU can be set for each network interface, and Windows will then use the lowest of the discovered value or the one set for that device. If you don't want that to happen because you suspect that the discovered value is too low, you can turn off Path MTU Discovery by setting "EnablePMTUDiscovery" to 0. But you should then note that Windows will then use a low default value of 576 for any adapter whose value you haven't specifically set.

Setting the MTU for each device using RegEdit isn't all that easy to do, as the settings are stored in a folders with names consisting of long strings of gibberish. We recommend using Dr. TCP, which you can get from click here. [Screenshot: H97-3b.tif] Select the adapter that connects you to the Internet under "Adapter Settings", then enter the MTU value in the adjacent field and click Save.

Dr. TCP can be used to change Path MTU Discovery and a number of other settings, too. We don't advise wholesale tweaking (and creating a system restore point would be a good idea before trying any of this), but you might get a further performance increase by setting a value of "TCP Receive Window" and turning Window Scaling on. We won't attempt to explain what these terms mean, but to determine a good TCP Receive Window value to use, find the largest multiple of (MTU - 40) that's less than 65535 and then multiply it by 4. For an MTU of 1500, that works out to 256960.

  Dipso 21:45 30 Jun 2004

...I referred you to a second link which enables you to calculate your ideal RWIN but didn't put it in! click here

Before you start tweaking, it is advisable to run the Tweak Test on the same site.
click here

  Dipso 21:49 30 Jun 2004

Got them the wrong way around but you get my drift...

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