ADSL Users - MTU Tweaks for Max Performance

Cadaver · June 03, 2003, 09:28:48 PM

I happened across this today, I don't know if any of you ADSL broadband chaps have already done this but it worked for me.

Simply follow the instructions here:

http://www.pengbo.dsl.pipex.com/ppages/tweaks.shtml

Doing so my download link speed went up from ~458kbps to 476kbps. Not a lot in the grand scheme of things, but worthwhile doing nonetheless.

Oh, if I understand it correctly, doing this won't lower your CS ping, just the download/upload rate.

And, if you decide to attempt this, make a note of the original settings in the DrTCP window, so you can put them back again in case it doesn't help any.

Anonymous · June 03, 2003, 11:03:53 PM

OK, here is some boring stuff. The internet is an ethernet, therefore your MTU should be set to 1500 and nothing else. If you have to set anything else then someone (your ISP?) is playing silly buggers. The Receive window is the only (I repeat ONLY) thing that will have any effect on a broadband connection. Have a look at http://www.dslreports.com/tweaks and pay special attention to the two coloured boxes. Also have a look at "tweakmatrix" available from the drop down box on the same page.

JB · June 03, 2003, 11:19:51 PM

Sorry to pee on your chips, but id take this word.

Gandalf · June 04, 2003, 08:09:41 AM

yep, that's correct. Until BT make changes to their routing hardware that will enable them to handle the default MTU of 1500 there will be packet fragmentation. This is causing BT's equip to CPU spike thereby increasing the time it takes to recieve said packets. This means slower downloads.

Setting your MTU at about 1458 (varies, experiment) will make sure that the packet gets passed on unmolested my BT's grubby equip, therefore less time is taken and faster downloads.

However, this isn't the case for everyone. TBH mine is the default 1500 as, A I can't be bothered to change it, and B I rarely download anyway

Anonymous · June 04, 2003, 07:51:57 PM

Quote...therefore your MTU should be set to 1500 and nothing else. If you have to set anything else then someone (your ISP?) is playing silly buggers...

I repeat!

Having to set your MTU to less than 1500 means that you are not using the internet bandwidth as economically as you could and in fact you could get a higher transfer rate if your ISP allowed an MTU of 1500. Basically, the packets you are sending are smaller than optimal. IMHO

JB · June 04, 2003, 09:08:18 PM

If someone is playing silly buggers is the entire BT network, because its them that stipulate the 1458 and not 1500.

Anonymous · June 04, 2003, 09:09:42 PM

That's what I'm trying to get to. Their (BTs) implementation of PPPoE doesn't allow a 1500 byte MTU

Aga · June 05, 2003, 10:07:19 AM

Find the link to BT's MTU adjsutment tool here http://www.broadband1.bt.com/update/index.asp#20030131

Anonymous · June 05, 2003, 07:36:24 PM

LOL! Even their explanation is confused! this is from the website:

"Fragmentation is the result of IP packets, larger than the 1500 byte maximum attempting to the pass across the network. The MTU tool enables users of Microsoft Windows based operating systems, to improve their network performance. By modifying the MTU to a setting suitable for the network, the MTU can be lowered to stop fragmentation, thereby improving the perceived performance of the network. This setting is nominally 1458 bytes."