prevent flooding the LAN with TCP re-transmission

[duser]

Hi 

My network is sometimes flooded with TCP re-transmission from outside servers, which make internet connection very slow, even the access to firewall through Https.

I use NAT, and there is no public address IP in my LAN.

It looks like these servers are waiting for an acknowledgment from inside clients.

Is there any solutions in firewall to prevent this kind of flooding ?

Regards