The SSH transport layer handles algorithm negotiation between the server and client over TCP/IP. Negotiation begins when the SSH client and server send each other textual information that identifies their SSH version. If they both agree that the versions are compatible, the client and server exchange lists that specify the algorithms that they support for key exchange, encryption and data integrity via a message authentication code (MAC). These lists are protected by their own encryption algorithms. The Mac Algorithms in the left column are available, the ones in the right column are enabled.