Remote Connection Protocols

These protocols play key roles in network communication by establishing sessions and enabling secure or remote access to devices and systems.

Protocol

Description

Use Case

Telnet

A legacy protocol that provides remote command-line access over TCP port 23. Telnet transmits data—including usernames and passwords—in plaintext, making it vulnerable to interception. Due to lack of encryption, Telnet is mostly replaced by SSH in secure environments.

Remote management of legacy devices and network equipment, mainly in trusted or isolated networks.

SSH (Secure Shell)

Provides encrypted remote shell access over TCP port 22. SSH offers strong authentication and secure data transmission, replacing Telnet for secure remote administration.

Secure remote server and network device management.

RDP (Remote Desktop Protocol)

Microsoft protocol for remote graphical desktop access over TCP port 3389. Enables users to control Windows desktops remotely with GUI support.

Remote desktop access for Windows environments.

VNC (Virtual Network Computing)

Platform-independent protocol for remote desktop sharing via TCP ports 5900+. Shares graphical desktop for remote control and support.

Cross-platform desktop sharing and remote technical support.

Main Features

  • Provides remote command-line access over TCP port 23

  • Transmits data, including usernames and passwords, in plaintext

  • Simple and widely supported on legacy devices

  • Does not provide encryption or strong authentication

RFC References

  • RFC 854 – Telnet Protocol Specification

  • RFC 855 – Telnet Options

Use Cases

  • Remote management of legacy network devices

  • Access in trusted or isolated network environments

  • Basic command-line access where security is not a concern

Alternative Protocols

  • SSH – Encrypted remote shell access

  • Console access via serial or out-of-band management

  • Remote desktop protocols for GUI access (RDP, VNC)

Main Features

  • Provides encrypted remote shell access over TCP port 22

  • Supports strong authentication methods (password, keys)

  • Ensures confidentiality and integrity of data

  • Supports secure file transfers (SCP, SFTP)

RFC References

  • RFC 4251 – SSH Protocol Architecture

  • RFC 4252 – Authentication Protocol

  • RFC 4253 – Transport Layer Protocol

  • RFC 4254 – Connection Protocol

Use Cases

  • Secure remote server and network device administration

  • Automated secure scripting and file transfers

  • Replacing Telnet in all secure remote access scenarios

Alternative Protocols

  • Telnet – Legacy, insecure alternative

  • RDP – Remote GUI desktop access for Windows

  • VPN with remote shell access for enhanced security

Main Features

  • Remote graphical desktop access over TCP port 3389

  • Supports full Windows desktop GUI control

  • Includes features like audio redirection, clipboard sharing, multi-monitor support

  • Optimized for Windows environments

RFC References

Use Cases

  • Remote desktop access for Windows systems

  • IT support and remote administration with GUI

  • Remote working environments and virtual desktops

Alternative Protocols

  • VNC – Cross-platform remote desktop sharing

  • TeamViewer, AnyDesk – Proprietary remote access solutions

  • SSH with X11 forwarding – GUI access on Unix/Linux

Main Features

  • Platform-independent remote desktop sharing over TCP ports starting at 5900

  • Shares graphical desktops for remote control and support

  • Simple, lightweight, but typically unencrypted

  • Works across multiple operating systems

RFC References

Use Cases

  • Cross-platform remote technical support and desktop sharing

  • Remote access to Unix/Linux desktops and mixed environments

  • Training and collaborative screen sharing

Alternative Protocols

  • RDP – Windows-focused remote desktop with advanced features

  • TeamViewer, AnyDesk – Enhanced secure remote desktop solutions

  • SSH with X11 forwarding – Unix/Linux GUI applications over secure channels