I have a Lync 2013 FE and Edge working to provide federated Lync service to our domain. Internal/External chat works fine but when getting on a video call with someone outside of the LAN the call will go through, video and audio, until 10 seconds have passed and the call is dropped. It is consistently 10 seconds every time and I don't know where to start in troubleshooting this.
I had exactly the same and for my environment incoming connections on UDP 3478 and TCP 443 wasn't working due to a temp. block via a firewall feature (aggressive line aging).