I didn't know where to post this issue. because Parsix GNU/Linux is not in the linuxquestions forums. It's a Debian base distro so I post my issue here.

As I noticed in parsix 3 and 3.5 and ubuntu 9.10, uploading files decrases the internet speed and after about 1.5 mb uploading, the connection failes!
When I'm uploading a ie.3 mb file, I see outgoing terrafic (as it should be) and also some incomming terrafic!!! I mean both incomming and outgoing packages during uploading a file!!! and that incommings decreases the speed, even I must "wait" for google.com!!

and after some minutes, connection failes because of uploading that file. But in small files (less than 1mb) the connectioan does not fail!

I tested this issue with Arch linux, and I didn't have this problems! it shows my connection is healthy!

kernel version is: 2.6.32-11
Connection is an ADSL

( I didn'd get answer from parsix forums)

Thanking you in advance!

1. ADSL has asynchronous speeds - up != down.
2. ADSL upload speed is << than download speed. For example i have 6 Mbit down/ 0.5 Mbit up - thats effectively ~650 KiB down / ~53 KiB up.
3. Transferring files via TCP generates traffic in both directions - the effective data (in packages) goes one way, the acknowledgements for those packages come back - this is for error corrections because some data might be lost on the way - so the lost packages are re-sent.

Uploading files may "freeze" your net connection temporarily - because the upload channel is overcrowded a bit - this means some data (such as web browsing) that doesnt belong to the upload will have to wait in the line to be transmitted - this in turn might lead to some http connections timing out because they assume your browser isnt working anymore.
Using torrents for example is known to "freeze" connections even if smaller amount data is transferred, because of larger overhead activity. Try playing some online games and you will see your "ping" and "packet loss" increasing dramatically in this case.

Solution: get a (preferably) synchronous and better net connection (of course, this is theoretical) or be patient for the upload to finish. It should eventually finish, but bear in mind that the upload speed is smaller than the download by about 10x factor. If it doesnt and drops connection, it is a problem with your ADSL line/modem.

I don't think the problem is in my ADSL line/modem, because I upload the files with windows xp. but here in debian (parsix) cannot handle uploading files larger than 1 or 1.5 mb.

I have noticed something in my modem's LEDs: during uploading. modem's LEDs in linux blinks very very fast, but in windows they blinks slower.

maybe making some short breaks during upload solves the problem, I mean, is there any way to tell linux upload a specific amount of data (for example 500kb) then pause it for only 1 or 2 seconds, and then continue the next 500 kb, and again another pause and so on... ???? is it technically possible?!!

What you mean is MTU (Maximum Transmission Unit), and you can set it for the relevant interface in /etc/network/interfaces like so
However, I doubt that the problem lies on some mtu value. I am almost certain that it lies on how many connections can your os or browser or modem/router handle.

How can I change the number of connections made by browser or modem?

In ff go to about:config and search for "network.http". The settings and their values are almost self explained.

In opera they are somewhere inside the advanced settings tab.

I have no idea where are they in chrome or midori or any other browser.

I changed MTU, but it didn't solve the problem.

then I changed the max connections in firefox, from 30 to 10 !! again it didn't solve the problem.

The point is that this problem does not exist in ArchLinux and windows XP ( I used them) and ubuntu 8.10. but in the newer versions of ubuntu, and debian, I have this problem. and IT IS KILLING MY NERVE !!!

can you reinstall the device ??is it a usb modem or a combo router??

it's a USB modem, (ASUS). what do you mean by reinstalling it? it works fine in downloading. how should I reinstall it?! reinstall what?

Its a plug and play device .Try to find separate linux drivers for the device for your linux dist.As it is clear there is no problem with internet connection and issue is at OS level .If you could find linux drivers for then install them and try again .

I had a similar issue a couple of yrs ago with ktorrent, it would randomly kill my connection. Never could figure out why switching to deluge solved whatever was causing the issue.

there is not any ASUS AM602 dsl modem driver for linux
It's really odd

Does anyone know how can I limit amount of packages send/receive over my connection?
maybe there is something wrong with TCP ?

finally, I found a package which can sets the upload and download speed limits like piece of a cake! and it solved my problem! just install "trickle" by "sudo apt-get install trickle" and use these command to do the job:

for example:

trickle -u 10 firefox =>> limits the upload speed to 10kb but does not affect download speed.
trickle -u 10 -d 50 firefox =>> limits both dl/up speeds.
trickle -d 50 firefox =>> just limits the download speed.

you can use any program instead of firefox, like opera, midori, gftp ... and you can change the speed amounts by yourself.

interesting. isn't it?