Hello and welcome!
Some people`s router have a wrote connection settings that is causing this, but it`s really easy to fix. All you need to do is turn power off and on on your wireless router or internet modem (or both if separate).
If that doesn`t work, try disabling any programs and other background application that could be accessing internet while you play DoF - could be a rare port issues. And as a last report - try disabling anti-virus and firewall software to see if that makes a difference.