Command execution and data forwarding

As soon as the OpenSSH client (ssh) has successfully authenticated itself a dialog begins for preparing the OpenSSH session. At this point the client can, for example, request the following activities:

• Setup of a pseudo-tty

• Forwarding of TCP/IP connections

• Forwarding of the connection to an authentication agent (ssh-agent, see "ssh-agent - Authentication agent") via a secure channel

Finally ssh requests either a shell or execution of a command. Client and server are in session mode. In this mode each side can send data at any time. This data is then forwarded as follows:

• from the user terminal on the client side to the shell / command on the server side, or

• from the shell / command on the server side to the user terminal on the client side.