TURN server behind NAT with port forwarding

[lostmsu]

I have this weird setup:

Service - NAT1 - Host LAN - NAT2 - Internet - NAT3 - Browser

I believe when Service is placed in Host LAN instead WebRTC between Service and Browser succeeds using srflx, however it fails when Service is behind NAT1. I am assuming NAT1 misbehaves.

However, I know TCP from behind NAT1 works totally OK, so I want to try

Service - NAT1 - turn-rs (Host LAN) - NAT2 - Internet - NAT3 - Browser.

Here turn-rs would have TCP port T for Service to connect to, and UDP port U for Browser to connect to. Port U would be exposed to the Internet using UPnP port forwarding on NAT2. It has to be UDP over Internet due to latency constraints.

Does this setup make sense? Would turn-rs be able to successfully serve clients that connect to it via port forwarding on NAT2? Can turn-rs forward packets between clients connected via UDP and clients connected via TCP?

P.S. I have to put Service behind NAT1 as it requires sandboxing, and NAT1 is inseparable part of the sandbox.

[mycrl]

My God, it's complicated, and my advice is to try it.

For turn-rs though, each peer should be fine as long as it can communicate directly with the turn, which doesn't care much about nat structures and types.