Aserver s is designed for computers to test if they are located behind nats or not. the server has two public ip addresses, i1 and i2, and has allocated two ports, p1 and p2 (either udp or tcp port), for this purpose. note that the ip address and the port numbers are known to every computer which wants to use this service. (a) design your protocol so that a computer a, by exchanging packets with s, can test if it is located behind an nat or not. (b) assume it is behind an nat. repeat (a) if computer a needs to determine if the nat is a symmetric type or not.