Enlightenment needed on file transfer

[Xavier Cazin]

Hello,

I'm experiencing strange behavior on ssh-enabled file transfers (scp
and rsync): 

When connecting to the Internet through an RTC PPP link to a certain
provider, file transfers from a remote host (debian potato) to my local
host (debian woody) get immediately stuck when issued from the local host,
while they work very well when issued from the remote host. 

On the other hand, no problem with shell connections nor with rsync
dry-runs. Also, if I connect to another provider, everything works as
expected. Do you have any idea of what might happen? 

Thank you very much in advance,
Xavier