Port forwarding is TCP "next to" TCP, so that's fine, yes! It can even be beneficial in some cases: If a host has an old/bad TCP stack not able to deal well wi

Port forwarding is TCP "next to" TCP, so that's fine, yes! It can even be beneficial in some cases: If a host has an old/bad TCP stack not able to deal well with some network situation (latency, packet loss, you name it), port forwarding from a closer/less affected host can resolve the issue. Happened to me once for the terrible old eBook delivery server from my public library when a continent away: It handled the long latency so poorly, a 30 MB download would have taken two hours. SSH forwarding brought that down to seconds.