USB Tethering MTU?

[technoid]

Hi, not sure which category to post this in...

I use USB tethering between my Motorola smartphone & laptop (Windows 7) for Internet.   I am wondering if I could help optimize & speed up downloads/uploads by changing the MTU.  I have 3 devices in Networking Connection on the laptop.   I checked the current MTU of all 3 devices & they were all at 1500.  I tested my highest MTU without fragmenting using PING & it would be 1440 with 0% loss.  So I just changed one device to 1440 with TCP Optimizer (TCPO) & then rebooted & TCPO works, but I changed it on a device that is not connected.  Before that, I tried using NETSH but it kept saying my syntax was invalid so I downloaded latest TCPO to change MTU.   The device that seems to be the Tethering is currently called "Local Area Connection 2" under "Remote NDIS based Internet Sharing Device".  The MTU for this is 1500.  However, I am afraid to change that to 1440 yet as I am unfamiliar with any changes to the network parameters of tethering.  Does anyone know if it's ok to change the MTU of this NDIS from 1500 to 1440?  And if so, will it optimize the speed?  Right now, tethering looks good, but my cell reception is not really good, so just wanting to see if mtu can help it just a little more if possible.

[jumper]

My T-Mobile hotspot has an MTU of 1440. I changed my machines to match. No danger, they can always be changed again.

 

[technoid]

Thanks,  I actually did change it to 1440 yesterday & I noticed a nice little improvement when it came to watching video streams, such as Youtube.  Before, watching Youtube at 480p would freeze maybe every 5 to 10 seconds because my slow connection from a weak reception was trying to keep up.  I would then always have to step down to 360p or 240p.   Now at 1440, it's much smoother at 480p.   I would not see short freezes for maybe until 30 seconds, or a minute or 2, or more, later.  I would need more testing, but at the moment, I think I don't really have to, the eyeball results tell me something better is working at 1440.  I believe the usb tether & wifi hotspot are throttled anyways by the phone service , so every little thing like adjusting the MTU can help it along the way.  If I needed faster Internet, I would have to shell out even more money per month to the company, but my service is grandfathered from nearly 15 years ago, when we had slider phones, back when most of our service was 2G.  But a couple years ago the phone company gave us a free offer & increased our Internet speed to 4G at no additional monthly cost.  I think this meets our needs nicely in the middle, i.e. good usable highspeed internet at low monthly cost.  My next attempt is to try to add more gain to the signal reception.  I'm thinking either modifying the antenna in the smartphone, perhaps into some sort of biquad shape, or maybe build some some of cellphone inductive cradle booster, idk. 

[jumper]

To combat variable cellular network delays, I also used a receive window of about 256K.

 

[technoid]

Is that the RWIN value?  How do I check the current rwin value my computer is set at?

[jumper]

Yes. TCPO will tell you the RWIN if it is set in the registry. If not set, it defaults to about 8K. The Optimize button will calculate a good value and set it for you. Go through all the tabs and run the various tests to determine what numbers to use.