May be I don't understand your question completely. A Putty tunnel is made to a remote SSH server. The port forwarding aspect in this case it that you connect to a port created by Putty on your local computer which is forwarded to the SSH server.
The router might forward SSH connections to a SSH server in the remote network. Or other specific connection requests at standard ports (e.g. (s)ftp, (s)http, etc.) or specifically assigned ports to a computers in the remote network.
port forwarding "in a telnet connection" makes no sense.