adam's notes

Remote Terminal Access Servers

A remote terminal server allows a host to accept connections to its command shell or graphical desktop from across the network.

  • name terminal comes from the early days of computing where configuration was performed by a teletype (TTY) device
  • TTY is the terminal or endpoint for communication between the computer and the user
    • handles text input and output between the user and the shell, or command environment
  • Where the terminal accepts input and displays output, the shell performs the actual processing
  • A terminal emulator is any kind of software that replicates this TTY input/output function
    • terminal emulator application might support connections to multiple types of shells
  • remote terminal emulator allows you to connect to the shell of a different host over the network

Secure Shell

Secure Shell (SSH) is the principal means of obtaining secure remote access to UNIX and Linux servers and to most types of network appliances (switches, routers, and firewalls).

  • can be used for
    • encrypted terminal emulation
    • SFTP
    • to achieve many other network configurations
  • Numerous commercial and open source SSH servers and terminal emulation clients are available for all the major NOS platforms
  • SSH server listens on port TCP/22 by default

Telnet

Telnet is both a protocol and a terminal emulation software tool that transmits shell commands and output between a client and the remote host.

  • server listens on port TCP/23
  • interface can be password protected, but the password and other communications are not encrypted
    • could be vulnerable to packet sniffing and replay
  • provided a simple means to configure switch and router equipment, but only secure access methods should be used for these tasks now

Remote Desktop Protocol

  • Telnet and SSH provide terminal emulation for command-line shells
    • sufficient for most administrative tasks, but where users want to connect to a desktop, they usually prefer to work with a graphical interface
  • A GUI remote administration tool sends screen and audio data from the remote host to the client and transfers mouse and keyboard input from the client to the remote host.
  • Remote Desktop Protocol (RDP) is Microsoft’s protocol for operating remote GUI connections to a Windows machine
    • uses port TCP/3389
    • administrator can specify permissions to connect to the server via RDP and can configure encryption on the connection\
    • RDP clients are available for other OSs, including Linux, macOS, iOS, and Android
      • so you can connect to a Windows desktop remotely using a non-Windows device
  • are also open-source RDP server products, such as xrdp (xrdp.org)

Graph View

Backlinks