MTU Size, Packet Fragmentation ETC. Please help

[Johnbear007]

Alright. Everytime I run a torrent file, I get a huge upload rate and like 3 - kbps download.

I am on SBC yahoo DSL, and average between 1 - 1.5 mb down, ftp and html transfers work fine.


I have tried swapping NIC's. Doesnt help.


I have tried this behind my netgear MR814, with ports 6881 - 6999 forwarded, as well as with the computer hooked up DIRECTLY to the DSL modem. I am using the speedstream 5260, and I also have a speedstream 5360 that I have tried, and get the same problem.

Any time it is hooked directly to the modem, or any time the ports are forwarded I get a slightly better upload rate, but after about 20 minutes, it locks up my entire computer.

Without the ports forwarded, behind the router, it doesnt lock up, but the download speed stays at like 1 - 3 kbps.

I thought perhaps the MTU size was too large and I was getting pack fragmentation.

I ran the ping test with directions from here:


LINK

and found that I got fragmentation until I lowered the MTU to 1472

However the guide says add 28 to your highest size without fragmentation, and that puts me at 1500, which is 8 above the 1492 I am already at.

Since I am using PPoE I cannot set it higher than 1492.

I get all of the symptoms of a non optimal MTU size but have no idea what to do now.

I have tried using various clients that allow the adjustment of upload speed, and regardless of my upload speed I still have the problem. Even if I limit it to 1 Kbps for my upload speed ( I have tried 1 - 40+ ) my upload speed will decrease but download remains unnaffected.

I also STILL get the lock up. The lock up is a huge problem.

Please not that bittorrent is NOT the only problem here. I get many classic MTU problems such as blank webpages, missing frams, slow browser access, page not found errors etc.

My service tends to 'stick' alot. This is regardless of whether it is behind a router, or directly connected to the modem.

Any advice?

 

[JackMDS]

Download DrTCP: http://www.dslreports.com/front/DRTCP021.exe

Run the program, it will show the current settings of TCP/IP parameters. Write them down.

You can change any variable that you want, click Apply, and reboot the computer, if no good; you can always change to your original values.

Start with:

MaxMTU - for DSL =1492, Cable=1500, ISDN -1322, DialUp=576

Tcp Receive - 256960 (This is the variable to play with).

Window Scaling - Yes

Time Stamping - No

Selective Acks - Yes

Path MTU Discovery - Yes.

Black Hole - NO

Max Duplicate - 2

TTL - 64

Notice it said above Start with

These settings are not written in "stone" there is variability depending on the computer other setting. So try few setting and measure your Download for each setting.

In addition, in case a person has a Router the Router's MTU if set differently can affect the general MTU.

Link: Measuring the "Speed" of Internet Connection.

:sun:

 

[cmetz]

JackMDS, something's off with your link - please check/fix.

 

[flexy]

MTU 1500 is (AFAIK) only for NON PPoE ...i am almost positive 1492 is right for PPoE.... ! leave this at 1492

also, on www.speedguide.net is a LOT of information, tweaks...otherwise www.dslreports.com of course

 

[Johnbear007]

yeah I read the DSL reports guide, thats the problem. I get fragmentation until 1472, but the speed guide says to add 28

 

[Goosemaster]

PLEASe tell me you are using that abc bittorrent client instead of that default one after having written all that...or else I'm gonna have to slap you

 

[Johnbear007]

Well, i've switched between the, and the ABC client doesnt do any better than the others.

 

[JackMDS]

Originally posted by: cmetz
JackMDS, something's off with your link - please check/fix.

Fixit.

Thanks cmetz.

 

[flexy]

Originally posted by: Johnbear007
yeah I read the DSL reports guide, thats the problem. I get fragmentation until 1472, but the speed guide says to add 28

1472+28=1500

but you need 1492 since you use PPoE

 

[flexy]

check out a program called 'cablenut' (get this and the update for it). install both and load/apply the appropriate settings.
this is an excellent program fro tweaking all tcp/ip settings