שאלה | What is the "relaying" solution to the NAT traversal problem, as used in applications like Skype?

What is the "relaying" solution to the NAT traversal problem, as used in applications like Skype?

		The client and server establish direct connections, with the NAT router handling the address translation.
		The client and server communicate through a dedicated NAT traversal server that bridges the two connections.
		The NATed client establishes a connection to a relay server, and the external client then connects to that same relay, which bridges the two connections.
		The NAT router automatically configures port forwarding rules to allow the client and server to connect directly.