FTP/SFTP stalls when transmitting files

[userwaldo]

Hello,

I'm have a very strange problem, that I can't figure out how to fix.

The problem is when I try to transmit a file via ftp or sftp, to an web server outside of my network, using Ubuntu 8.10. I previous didn't have problems with Ubuntu 7.04.

The problem is that when I try to transmit a large file, that is stall at somewhere between 1-4 MBs, and never recovers. The actual place it stalls varies each time I try to transmit the file, but it is always between 1-4MBs.

I can how ever transmit files over sftp to another computer in my own network. I tested files as larger as 800MB to see if I could reproduce the failure. I then transmitted that same large file from my other computer (MAC OSX) to the site that failed with my ubuntu install, and I have been sucessful.

So the problem seems to be with my ubuntu machine. I can't figure out why I can't transmit large files from it. I've check and I don't even have a firewall setup on my ubunut, as I thought that this might be part of the problem.

If anyone has any suggestions on how to troubleshoot this, I would really appreciate the help. I'm tempted to try going back to ubuntu 7.04.

[SpaceTeddy]

i have a (somewhat) similar problem (i think) - can you please try to drop your mtu to 1490 bytes instead of the normal 1500 on the sending machine and see if the transfers still stalls ?

make sure you drop the mtu on the source machine - NOT the router. You can drop the mtu on an ubuntu machine with this command:

sudo ifconfig %device mtu 1490

where %device is eth0, wlan0 ath0 or something like that (depending on your device)

let's see if you get the same results as me...

[userwaldo]

I tried reducing the mtu to 1490, but I still see the problem with the uploads stalling at about the same point, 1MB - 4MB.

I'm willing to try other ideas, as well.

[SpaceTeddy]

i've been searching myself a little - but i have no idea how to even start debugging that problem (apart from doing paket dumps and looking where the connections stalls, e.g. which part of the connection will suddenly not pass pakets anymore)...

i'd use wireshark or tcpdump for that - but that is really only an idea and i don't know if anything can even be seen there... really ;(

[kgibbs]

i have a (somewhat) similar problem (i think) - can you please try to drop your mtu to 1490 bytes instead of the normal 1500 on the sending machine and see if the transfers still stalls ?

make sure you drop the mtu on the source machine - NOT the router. You can drop the mtu on an ubuntu machine with this command:

sudo ifconfig %device mtu 1490

where %device is eth0, wlan0 ath0 or something like that (depending on your device)

let's see if you get the same results as me...

This did the trick for me. I have been trying to sync a few GB of files between my workstation, my laptop and my server at home. Between the workstation and the laptop (sitting across the room), no problem, between the workstation and my home server, repeated stalls even after upgrading rsync to v3.0.2(?). Setting the mtu as you suggested fixed the problem
(well, I transferred a random directory containing 60MB with no hitch).
Thanks!

- k

[hpark21]

I am running into Exactly same issue.

Uploading via FTP will stall.

Changing MTU to 1490 makes it a LITTLE better, (it does not down right cancels the upload, but it stalls about once every 30 MB transfer for about 10 seconds)

This did NOT happen with Ubuntu 6.10.

Please help.

[hpark21]

Ok, here is something new.

IF using PORT setting (and not PASV) and when I limit the upload transfer speed to 400KB/s then, stalling frequency lessens severely.
(I can transfer around 100MB before stalling out, still not good, but MAYBE tolerable)

I transfer 1GB+ regularly to my xbox from my computer and when I had 6.10, I had ZERO issues uploading.

Now, I installed the Hardy, I am having issues (upgrade was needed because I could not upgrade packages anymore for my 6.10)

I have seen another forum that this may be due to router interface. Maybe it is time for me to reboot all my routers, it has been few weeks.

[hpark21]

It has been couple of weeks and still no resolution.

I noticed that this problem worsens when there is rather moderate/heavy load on network.

Even when throttling at 350KB/sec it stalls frequently (around every 10-30MB)

Please help as I am not planning to go back to 6.10 if I can help it (maybe 7.04 may help?)

Does anyone know what changed in network/ftp side for 8.10?

Thanks.

[rushtovijay]

i have a (somewhat) similar problem (i think) - can you please try to drop your mtu to 1490 bytes instead of the normal 1500 on the sending machine and see if the transfers still stalls ?

make sure you drop the mtu on the source machine - NOT the router. You can drop the mtu on an ubuntu machine with this command:

sudo ifconfig %device mtu 1490

where %device is eth0, wlan0 ath0 or something like that (depending on your device)

let's see if you get the same results as me...

Thanks changing the mtu to 1490
fixes stall problem in ftp and http.
In both ubuntu 8.04 and ubuntu 9.04.
upload speed also improves.

[hongquan1987]

i have a (somewhat) similar problem (i think) - can you please try to drop your mtu to 1490 bytes instead of the normal 1500 on the sending machine and see if the transfers still stalls ?

make sure you drop the mtu on the source machine - NOT the router. You can drop the mtu on an ubuntu machine with this command:

sudo ifconfig %device mtu 1490

where %device is eth0, wlan0 ath0 or something like that (depending on your device)

let's see if you get the same results as me...

Thank you so much