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)
Let us learn more about Telnet:
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
Microsoft proprietary protocol (no formal RFC)
MS-RDP Protocol Documentation: https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rdpbcgr/
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
RFB (Remote Framebuffer) Protocol is the core VNC protocol
Specification available at RealVNC: https://www.realvnc.com/en/connect/docs/
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