Good news. I tested new router. It was problem between router and wifi
and SLED (change one of these three components always solved my
problem). So I bought new router. Internet speed is good now.
Arnaudk93: I tried send you private message but your message box is
full.
Good news. I have nearly emptied my mailbox.
I asked the support team to take a look on your configuration. They
asked me whether a firewall or security stuffs were part of your
configuration.
I don’t have activated firewall on router. Deactivating firewall in
SLED has no effect.
Fortunately this issue hasn’t priority for me now, because new router
has solved my problem. But I can provide info for general solution,
because it seems like some SLED driver problem, because other linux or
other wifi (usb zyxel zygair) don’t has this problem.