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Root [DEV][INFO]Motorola Triumph MTU/Tether settings ideas and info

B

BSydz

Android Expert
So after trying to figure out why tethering was messed up, I have figured some stuff out and wanted to get it out into the community.

First, the MTU is set to 1472 on the 3G side not the wifi side. I found this by going to SpeedGuide.net :: Broadband Tweaks, Tools and Info on both 3G and wifi. I have only checked with Sharp Ver7 using my new kernel so other ROMs may be different. That is why I started this thread, to get as much info as possible about all ROMs for the Triumph. Just click the link and report your findings and what ROM you are using.

Second, I found that the stock kernel has these lines in drivers/net/msm_rmnet.c and msm_rmnet_common.c :
Code: 
/* allow larger frames */
/* FXPCAYM-218: Start - Change frame size from 2000 to 1472 */
/* #define RMNET_DATA_LEN 2000 */
#define RMNET_DATA_LEN 1472
/* FXPCAYM-218: End */
instead of what it should be:
Code: 
/* allow larger frames */
#define RMNET_DATA_LEN 2000
This is the setting for 3G not wifi and it seems to reduce the ping times significantly haven't seen a ping over 350ms on 3G so far with my new kernel. Though it has not increased speeds as far as I can tell.

Third, I have found some info on how to change MTU through terminal here, I just haven't tested it yet.

Hopefully we can get some more useful info in here, but for now let me know what you guys are seeing.
 
So, I have a question for the devs and advanced users. How do we turn this into a build prop edit or script or kernel edit?

ifconfig rmnet0 mtu #### (1500 or what ever works best)

Cause it sets the MTU correctly, just use the command in terminal on the phone. And this should fix tether. I just can't test right now.
 
ifconfig rmnet0 mtu 1492
error: SIOCSIFMTU (Invalid argument)
#

I think it's also something that needs to be enabled. I use the brandom kernel and that's what I get.I know a few apps like barnacle that tries but fails to change the mtu
 
Ok I am on u9000 with b's modded kernal I entered "ifconfig rmnet0 mtu 2000" and have net access with win7 64 laptop in firefox and ie. I know there is a limit for mtu's but not sure. I did not modify mtu on client only on triumph.
 
awdark said:
ifconfig rmnet0 mtu 1492
error: SIOCSIFMTU (Invalid argument)
#

I think it's also something that needs to be enabled. I use the brandom kernel and that's what I get.I know a few apps like barnacle that tries but fails to change the mtu
Click to expand...
Try to set it lower than 1472. My new custom kernel has the code switched to what I thought it should be from comparing code with the other X6 variants. I'm not sure if this is just the upper limit or the actual setting cause with the changes my 3G MTU is still at 1472 when it reboots, but I can change it 1500 no problem. I am still trying to figure all of this out, I need to dig around in the source code and see if there is a way to set the default. Hopefully more people will chime in and we can compare results and find a good setting.
 
beaviskob1 said:
Ok I am on u9000 with b's modded kernal I entered "ifconfig rmnet0 mtu 2000" and have net access with win7 64 laptop in firefox and ie. I know there is a limit for mtu's but not sure. I did not modify mtu on client only on triumph.
Click to expand...

By default MTU should be set to 1500. However You can get crazy and set MTU to what ever you want. The problem lies in the fact that the receiving network can handle the MTU settings you set. So lets say you set MTU to 9000 which is Jumbo Frames, well if the receiving network can not handle the frames you can experience dropped packets or data loss.

I had to deal with this at my last job when I setup a (6) Node Hyper-V Cluster. The network admin swore up and down that Jumbo Frame where configured correctly for my ISCI network to the NetApp SAN. However I kept dropping luns from the Cluster and loosing Virtual Machines all the time. Long story short and 4 months worth of dealing with NetApp, and Microsoft support we found that the Jumbo frames where not configured correctly on the Cisco Switch. So be weary in what settings you are using as again the receiving network needs to be able to handle the packet flow you are sending.
 
BSydz said:
Try to set it lower than 1472. My new custom kernel has the code switched to what I thought it should be from comparing code with the other X6 variants. I'm not sure if this is just the upper limit or the actual setting cause with the changes my 3G MTU is still at 1472 when it reboots, but I can change it 1500 no problem. I am still trying to figure all of this out, I need to dig around in the source code and see if there is a way to set the default. Hopefully more people will chime in and we can compare results and find a good setting.
Click to expand...

If nothing else, seems like you could have a script fire off the "ifconfig rmnet0 mtu XXXX" command at boot...
 
I just got around to changing mtu's from 2000 to 1500 and testing it right now. The speed seams to be quicker so we will leave it like it is. I did not make a script I manually entered via android terminal.
 
I have a bash script, I just want to figure out how to get it to work at boot with out an app. I have it in init.d but, I have limited knowledge of exactly how it works. Anybody that wants to know how to make a bash script for this here are instructions.

1. Open root explorer and navigate to the folder you want the script
2. Create new file named mtu.sh
3. Open the file you just created in a text editor and enter "ifconfig rmnet0 mtu ####" without the quotes, #### is what ever you want MTU set at, 1500 is the normal default for most devices.
4. Now you have a bash script to change the MTU just select the script in root explorer and select execute.
5. Go to SpeedGuide.net :: Broadband Tweaks, Tools and make sure it stuck.
 
Here is the script for anybody that wants to try this out. Just open it in root explorer and select execute. It doesn't seem to work from the SD card, I put it in system/etc/init.d folder and it worked.

BSydz mtu 1500.sh.zip
 
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