psftp stalls when trying to upload

[jschwepp]

Anyone have any idea why psftp would stall when trying to upload a
file over 8k. When trying to upload from this one particular machine
I always get: Fatal: Network error: Software caused connection abort.
All other machines with the same setup work fine, and in fact this one
was working fine until last friday and then all of the sudden it
started giving me this error message. I can ssh to the box and I can
sftp and browse and download, but anytime I try to upload anything
over 8k it stalls and gives me the Fatal Network error message. There
are no firewalls on the machine, I have no idea what could be causing
this.

[Nico Kadel-Garcia]

What does WinSCP report? Or sftp under CygWin? And what OpenSSH or SSH
server are you contacting, under what OS? Is that server different
from the other servers? Is there another network difference on that
server (behind a NAT or something)?

[Doug Freyburger]

This happens when some network along the routing path switches to/from
Jumbo Frames or other MTU change. Packets over a certain size get
rejected and if ICMP along the path is blocked the ICMP messages used to
negnotiate smaller packets don't work.

So get the path to unblock ICMP and change the network parameters to
always use smaller packets. Thus losing any throughput advantage of
Jumbo frames, sigh.

[jschwepp]

WinSCP gives the error message: Host is not communicating for more
than 15 seconds. Still waiting... Warning: Aborting this operation
will close connection! I'll try a different server to see if that
might be causing the problem.

[jschwepp]

This is interesting, do I have to contact their ISP to get this
fixed? I somehow dread trying to work my way through AT&T's customer
support to get them to make these changes.