Verizon 4G/LTE USB Device with TCP Window Size Set to 128 or Higher

[laurend_vzw]

If you recently purchased a 4G/LTE USB device from Verizon Wireless, read on to optimize data throughput in your computer:

Certain Internet parameters and configurations (such as TCP settings) are preset by your operating system; to optimize the data throughput, set the TCP window size to at least 128K.

Instructions on how to set this window size are found in Microsoft's support webpages.

In addition, third party software (such as TCP optimizers) may be available to configure your operating system to be optimized for Mobile Broadband service. Verizon Wireless does not support any 3rd party software applications or the configuration of specific operating system settings at this time.

Please let us know if you have any additional questions, thanks.

[toughbook]

Thank you for pointing us to the link. However, it explains many TCP settings. Which one should we be looking for? Also, this article is for XP, what about other OS systems such as Vista and W7?

Thanks Again.

[#3]

He says "TCP window size."

[jgaona3]

If you do not know what you are doing. It is better to just leave it alone. Here is another link so you can read up on it. 

speedquide.net tcp info

[MojaveMoon_]

The Microsoft Kin Two(m) has a menu that lets you adjust the TCP Window Size. Someone reported that it's 32K by default. Would it be beneficial to adjust it to at least 128K ?

[whatsupdoc]

Windows Vista and 7 dynamically adjust the TCP Receive Window (RWIN).  This adjustment would only be used for Windows XP systems.

Instructions for determining and adjusting the TCP window using Dr. TCP (freeware) is available from broadbandreports.com:

http://www.broadbandreports.com/faq/tweaks/5.+RWIN#6181

[whatsupdoc]

On a similar subject, the MTU size set for the LGE LTE USB NDIS Network Connection Driver as found in the Windows Device manager is set at 1428.  The Verizon 4G LTE modem is a PPPoE connection, therefore, a setting of 1492 works just fine (I tested it and it works fine) and will provide better throughput of data.  This is on Windows XP, Vista and 7 systems and can be changed on every LGE LTE USB NDIS Network Connection Driver found in the Device Manager (there will be as many devices as there are USB ports that the USB modem has been plugged into and installed.

Once changed the network connection will need to either be disconnected and restarted or reboot the PC for changes to take effect.

[Prolixium]

---

whatsupdoc wrote:

On a similar subject, the MTU size set for the LGE LTE USB NDIS Network Connection Driver as found in the Windows Device manager is set at 1428.  The Verizon 4G LTE modem is a PPPoE connection, therefore, a setting of 1492 works just fine (I tested it and it works fine) and will provide better throughput of data.  This is on Windows XP, Vista and 7 systems and can be changed on every LGE LTE USB NDIS Network Connection Driver found in the Device Manager (there will be as many devices as there are USB ports that the USB modem has been plugged into and installed.

Once changed the network connection will need to either be disconnected and restarted or reboot the PC for changes to take effect.

---

I'd be weary of doing this under normal circumstances.  Do you have performance data indicating this does indeed increase performance?

I'm under the impression that the MTU is being set to 1428 to avoid link-layer fragementation on the way onto the LTE network.  An MTU of 1492 (or even 1500, which is used on Linux by default with the LG VL600 modem) may appear to work fine, but could cause fragmentation when the packets are transmitted onto the RF network, therefore hurting performance instead.

Although, that being said, I haven't read over the LTE spec. to understand what type of MTU will cause link-layer fragmentation, but I have a feeling it's not being set to 1428 arbitrarily or to "slow down" clients

- Mark

[whatsupdoc]

Mark,

You bring up a very good point and I should be able to test this next week. I used the standard ping tests in Windows XP to arrive at this conclusion using various packet lengths until this setting was reached without any fragmenting or timing out.

I can say though that my download speeds are consistently in the 20-22 MB range and my upload speeds are consistently in the 4-5 MB range using this setting - absolutely tremendous for 4G LTE service and faster than my RoadRunner Turbo service.

~ Chris

[whatsupdoc]

I performed the MTU DOS ping test and found that I could ping using a value of 1464 bytes without fragmenting:

Microsoft Windows XP [Version 5.1.2600](C) Copyright 1985-2001 Microsoft Corp.

C:\>ping www.yahoo.com -f -l 1464

Pinging any-fp3-real.wa1.b.yahoo.com [69.147.125.65] with 1464 bytes of data:

Reply from 69.147.125.65: bytes=1464 time=87ms TTL=50

Reply from 69.147.125.65: bytes=1464 time=94ms TTL=50

Reply from 69.147.125.65: bytes=1464 time=96ms TTL=50

Reply from 69.147.125.65: bytes=1464 time=95ms TTL=50
Ping statistics for 69.147.125.65: 

        Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

Approximate round trip times in milli-seconds:

        Minimum = 87ms, Maximum = 96ms, Average = 93ms
C:\>

Adding the standard number of 28 to this would equate to an MTU value of 1492.

Keeping the MTU value at 1492 I performed a speed test and got 20.27 MB down and 7.43 MB up with 75ms latentcy:

http://www.speedtest.net/result/1414929750.png

Then I logged out of the network and changed the MTU value to 1428 and performed a speed test and got 20.62 MB down and 7.90 MB up with 95ms latentcy.:

http://www.speedtest.net/result/1414950008.png

The results are very similiar so it appears that at least for me, it did not make any realy difference whether an MTU value of 1428 or 1492 was used.  The lower MTU value actually produced slightly better results but this was only one test.

Nevertheless I'm thrilled with the results!