FTP uploading to Linux host fails if file > 1.42KB

I have a very curious problem with FTP server
customersites9.easily.co.uk, which the host company do not seem able to
solve. If I upload files with a file size of anything less than 1.42Kb
(I've found this out by extensive testing), the files upload perfectly.
However, any larger file and it simply times out and doesn't upload no
matter how long I leave it. I have a number of different accounts with
the same hosting company (though not exactly the same server) and none
of these have any problems at all.

The company has just moved me onto this new server because I was having
exactly the same problem with the previous one. I'm using CuteFTP 7.1
Prof as my FTP Client, though it seems to be a problem through
www.surftp.com and a number of other clients too.

Any ideas?

Many thanks,
David.

On 6 Jul 2006, in the Usenet newsgroup comp.os.linux.networking, in article
<(E-Mail Removed) .com>,
(E-Mail Removed) wrote:

>I have a very curious problem with FTP server customersites9.easily.co.uk,
>which the host company do not seem able to solve. If I upload files with a
>file size of anything less than 1.42Kb (I've found this out by extensive
>testing), the files upload perfectly. However, any larger file and it
>simply times out and doesn't upload no matter how long I leave it.

1191 Path MTU discovery. J.C. Mogul, S.E. Deering. November 1990.
(Format: TXT=47936 bytes) (Obsoletes RFC1063) (Status: DRAFT
STANDARD)

2923 TCP Problems with Path MTU Discovery. K. Lahey. September 2000.
(Format: TXT=30976 bytes) (Status: INFORMATIONAL)

Sound like a system with an MTU less than 1500, and someone blocking ICMP
Type 3 Code 4. Quick test - on the box you are trying to upload _FROM_
set the MTU to 1480 or so (man ifconfig) and see if things start working.
If so, investigate ALL firewall setups under your control. Incidentally,
the normal way to investigate this is tcpdump. You can also use something
like tcptraceroute (not the "normal" traceroute or microsoft's horribly
broken imitation) or hping2. Remember that some routers/hosts/firewalls
treat ICMP and UDP differently than TCP.

Old guy