First, telnet and ssh are the connection protocol for remote computer, you can complete control of the computer to complete, and easy maintenance. Second, they are based in the TCP / IP protocol, so all you need to know the target URL or domain name, the third channel they are connected to a remote host connection, the aim is to complete the same, but the means are not Like it.
Telnet connection computer requires the following processes:
Client establishes a TCP connection with a remote host; notification client receives the remote unit is connected, wait for an input; clients gather user input after receiving the notification, the character string input into a standard format and transmitted to the remote machine; accepted by the remote command input, and performs output obtained results to the client; client after receiving echoed on the display screen.
It is noteworthy that, when a telnet connection direct TCP connection is established, all transmitted data are transmitted in the clear, it is an unsafe manner.
SSH is an abbreviation Secrue Shell and SSH protocol for establishing security at the application layer basis, it is more reliable and secure protocols.
Version number negotiation, SSH currently includes SSH1 and SSH2 two versions, both sides determined using negotiate a version
Key and algorithm negotiation, SSH supports a variety of encryption algorithms, and algorithms parties according to the local peer support, the final negotiation algorithm used
Certification stage, SSH client initiates an authentication request to the server, the server to authenticate the client
Session request, after the authentication, the client sends a session request to the server.
Interactive session after the session request by the server and client interaction information
It is noteworthy that, due to the encrypted ssh encryption algorithm, to close the message needs to be decrypted, transmitters text to be encrypted, leading to its transmission speed, efficiency is much lower than the telnet, however, it does have telnet does not have security.