Overview
Virtual Private Networks (VPNs) provide secure, private communication over public networks by encrypting traffic between a client and a VPN server. VPNs enhance privacy, anonymity, and security — but only encrypt traffic between the client and server, not beyond it.
Terminology
| Term | Definition |
|---|---|
| VPN (Virtual Private Network) | Encrypted tunnel between a client and server over a public network |
| VPN Client | Software on the user’s device that encrypts outgoing traffic |
| VPN Server | Receives encrypted traffic, decrypts it, and forwards to the destination |
| Tunneling | Encapsulating one protocol inside another for secure transmission |
| PPP (Point-to-Point Protocol) | Authentication and encryption foundation used by VPN technologies |
| PPTP (Point-to-Point Tunneling Protocol) | Encapsulates PPP packets for transmission over IP networks |
| IPSec (Internet Protocol Security) | Encrypts and authenticates data using the standard IP framework |
| Split Tunneling | VPN configuration where only some traffic routes through the VPN |
Core Concepts
How VPNs Work
Basic VPN Layout VPN Traffic Flow
- VPN client encrypts outgoing data on the user’s device
- Encrypted traffic travels over the public network to the VPN server
- VPN server decrypts the traffic and forwards it to its destination
- Return traffic is encrypted at the server and sent back to the client
Important Limitation
Only traffic between client and VPN server is encrypted — traffic beyond the server is unencrypted
Single Device VPN
Single Device With VPN
- Protects a single device’s traffic
- Common for personal privacy and secure browsing on public networks
VPN Technologies
| Protocol | Description |
|---|---|
| PPP | Authentication and encryption foundation; used by higher-level VPN protocols |
| PPTP | Encapsulates PPP packets for IP network transmission; older standard |
| IPSec | Encrypts data at the IP layer; widely used in enterprise and site-to-site VPNs |
Common VPN Use Cases
- Remote work — secure access to internal company resources
- Public network protection — encrypts traffic on untrusted networks
- Network tunneling — connects remote sites securely
- Privacy — masks user IP and location from destination servers
Related Concepts
Related Techniques
References / Images
- Basic VPN Layout
- VPN Traffic Flow
- Single Device With VPN
- RFC 2637 (PPTP), RFC 4301 (IPSec)
- OpenVPN and WireGuard documentation