MBI Corporation uses cc:mail, which is not Internet standard. The company also uses Novell LAN. Novell has Internet Exchange Protocol, IPX (connectionless datagram service), as its equivalent to Internet TCP/IP. As you know well, most of the global email traffic is on the Internet with SMTP as the mail protocol. Figure 1.28 shows the high-level configuration of the two networks connected through a gateway. Fill in the protocol layers of the gateway.