Speed - optimal settings: RWIN, MTU etc...

ic

ic

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I've been messing with RWIN and MTU on my PCs, running online tests etc.

So far all I've managed to do is sort out ICS by decreasing MTU size on all PCs to 1492 (max PPPoE).

RWIN on ICS gateway PC to 32767
(<i>not happy with that figure, but it is based on calculations with MSS of 1452</i>).

I know there are lots of factors that make these settings fairly unique to each of our setups, but what does evryone else find works best[?]

Apart from using RegEdt32 or RegEdit or DrTCP.exe, are there any other utils out there that allow you to change everything all at once[?]
 
I got best result at 1370, anything higher fragmented, then again i'm quite far from the tower.
 
We have found that people using a router and having connection problems to some websites and mail should change there MTU to 1399. it seemed to fix my problem.

Dylan
 
Guys, please help me... I wanna change my MTU. Apparently I have to go here:

System Key: [HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters\
Interfaces\[Adapter ID]]

The thing is, when I open Interfaces there are 7 different folders with names like {712DB115-1270-44C7-A102-B0237F454F4A}

How do I ascertain what the correct adapter ID is?
 
How2-Set-iBurst-MTU-4-Windows2000Professional

Related thread(s):
  • [thread=16395]Internet Connection Sharing (ICS)[/thread]
Yep, ok, I simply edit the registry with RegEdit or RegEdt32, but I'm using Win2KP and I don't know whether the settings are in the same place under WinXP-H/P +SP2.

You can try using http://www.dslreports.com/drtcp to change your MTU, I don't recommend using it to change any of the other settings it allows- note your user account will need Administrative privelleges to run DrTCP as it writes to the registry.

Alternatively, if you are ok with editing the registry, try finding something similar in XP to this (2KP):
Code: 
HKEY_LOCAL_MACHINE\
   SYSTEM\
      CurrentControlSet\
         Services\
            Tcpip\
               Parameters\
                  Interfaces\
                     {526421A4-C42F-47DA-969A-507AD0A797CD}
Now look for a DWORD value with the name MTU, set that to 570 hex or 1392 decimal. You can then reconnect, or to be sure do a restart.

PS: While you are about, please join the testing programme, click the testing link in my siggy.
 
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Thanks ic, tried DrTCP. Hope it works. Also posted my link on the other thread.
 
Windows2000: "iBurst_Terminal Connect UTL"

Totally by accident, I discovered something new today:

The iBurst software that you install on Windows 2000 Professional creates the iBurst_Terminal Connect UTL which we already know, what I for one did not know is that it has a trick that allows you to set MTU & monitor MTU for a particular IP address.

How2 set MTU in W2KP using iBurst_Terminal Connect UTL:
  1. Establish your iBurst connection by using iBurst_Terminal Connect UTL to connect.
  2. Once you have a connection, simply run iBurst_Terminal Connect UTL a second time (your iBurst connection must already be established).
  3. You will be presented with a new mystery dialog box that has buttons: MTU Setting; Property; Disconnect; Cancel.
  4. Click MTU Setting, now set MTU to 1392.
  5. You will be asked/told to reboot.

Note that you must start the iBurst_Terminal Connect UTL with administrative priveleges, use RunAs (shift+rightclick on shortcut, then Run as) if you don't login with an administrators account.
 
for the (MTU) record...

lowered my MTU again. started off with MTU 1390. got good speed in the iburst good ol' days - dec 2004.

lowered it to 1370 some time in jan 2005.

last week some sites (most notably slashdot and mybroadband.coza) stopped working. i could still ping them - classic MTU problem

i'm on 1350 at the moment and things look better. still not great, but at least most sites are working again.

chz,
kk
 
How do I change the MTU using a mac and router

Hi All,

Hope you can help. How do I change the MTU if my UTD is connected to a router? I'm running a Mac and want to try to optimise the connection.

Regards,

Michael
 
Out of my depth here, but I assume your router is establishing the connection on its own, correct? There must be a router config option somewhere to "clamp" your MTU.

If not, are you using the iBurst software for the MAC to establish a PPPoE connection with the UTD via the router?
 
Interesting???

Has anybody ever tried the ping -f -l test to try and work out what your optimal mtu setting is? I did it on the recommendation of a post here.

Initially it calculated in beautifully at 1392 as per the recommendation, I tried it again earlier and it worked out at 1352.

I'd really like to know what's happening here - does the test actually work?

For a side note (off topic) the abominal plague of bad service seems to have swept down and hit Durban :(
 
twixt said:
Has anybody ever tried the ping -f -l test to try and work out what your optimal mtu setting is? I did it on the recommendation of a post here.

Initially it calculated in beautifully at 1392 as per the recommendation, I tried it again earlier and it worked out at 1352.

I'd really like to know what's happening here - does the test actually work?

For a side note (off topic) the abominal plague of bad service seems to have swept down and hit Durban :(
Click to expand...
Dylan posted one of those morsels for us wild dogs / dingos to fight over, I quoted him in the sticky Comms thread as saying they are testing 1352 - whatever that means...
 
ic said:
Out of my depth here, but I assume your router is establishing the connection on its own, correct? There must be a router config option somewhere to "clamp" your MTU.

If not, are you using the iBurst software for the MAC to establish a PPPoE connection with the UTD via the router?
Click to expand...

Hi IC,

Thanks for your help. The router is establishing a connection on its own. I found the configuration option and set the MTU to 1352. Range is from 1000 to 1500.

I saw somwhere else in the thread that the correct value can be calculated - but could not see how. Can someone either repost or point me to the message?

Regards,

Michael

PS - My connectivity is extremely variable today.
 
michael said:
Hi IC,

Thanks for your help. The router is establishing a connection on its own. I found the configuration option and set the MTU to 1352. Range is from 1000 to 1500.

I saw somwhere else in the thread that the correct value can be calculated - but could not see how. Can someone either repost or point me to the message?

Regards,

Michael

PS - My connectivity is extremely variable today.
Click to expand...
No problemo, glad u found the setting.

Yes, MTU can definitely be calculated, it is very easy, and I know I need to put a proper how2 up here, but in the meantime forage here: http://dslnuts.com/ping.shtml

Basically open a cmd prompt, then do a ping as per above url with:
Code: 
ping -f -l xxxx 196.30.31.100
Start out with a value of 1410 for xxxx, you should see a msg saying packet needs to be fragmented but df flag set. Then you repeat but with xxxx-10 (i.e. 1400 next) until the df msg goes away, then you repeat with xxxx+1 until it says df flag msg again, and the last one that worked without the msg is what's called MSS, so the MSS==xxxx max that didn't need fragmentation, and MTU==MSS+28. If all works well then MTU of 1352 should mean that your xxxx value is 1352-28==1324==xxxx highest MSS that works without df msg.
 
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On the link i posted above you can download TCPOptimiser - it finds the max mtu by pinging a specified address with different size packets until it fragments.
It's the first link.
 
MaD said:
On the link i posted above you can download TCPOptimiser - it finds the max mtu by pinging a specified address with different size packets until it fragments.
It's the first link.
Click to expand...
Geez, some people just don't appreciate a command prompt :D I will bookmark that url for future foraging ;)
 
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