Since TCP is not a secured transport layer protocol, SSH first uses a protocol that creates
a secured channel on the top of TCP. This new layer is an independent protocol
referred to as SSH-TRANS. When the software implementing this protocol is called,
the client and server first use the TCP protocol to establish an insecure proconnection.
Then they exchange several security parameters to establish a secure channel on the top
of the TCP. We discuss network security in Chapter 29, but we briefly list the services
provided by this protocol: