VPN (Virtual Private Network)

kc@example.com (kc kim) — Mon, 11 Jul 2022 09:48:00 +0900

What Is a VPN (Virtual Private Network)?

A VPN (Virtual Private Network) is a technology that extends a virtual private network so that private networks, which cannot be accessed by third parties, can communicate securely with one another.

As in the following examples, VPNs are used to communicate securely between geographically remote networks.

Securely access a company’s private network from a home private network
Securely access the private network of a Busan branch office from the private network of a Seoul branch office

VPNs are used for the following reasons.

The common way to communicate between geographically separated networks is the internet
However, the internet, which anyone can access, is insecure from a security perspective
Therefore, using a VPN, which extends a virtual private network over the internet, increases communication security
Although the above says that the common way to communicate between geographically separated networks is the internet, there are also several other methods

Communication Methods Between Private Networks

There are three typical methods for communication between private networks.

Provider dedicated line (a dedicated optical cable, exclusively used by the subscriber)
Provider closed network + VPN (a closed network owned by a single provider)
Internet + VPN (a collection of routers from multiple providers, accessible by anyone)

Provider Dedicated Line

A provider dedicated line is a line used exclusively by the subscriber, allowing secure communication between private networks. However, the circuit cost is high.

Provider Closed Network + VPN

A “provider closed network” shares the line among multiple subscribers, so public IP addresses are required to distinguish subscribers, and private networks cannot communicate with one another as they are.

Internet + VPN

Because anyone can use the “internet” line, it has the following two issues.

Public IP addresses are required to distinguish users, and private networks cannot communicate with one another as they are.
Because anyone can use the line, there is a possibility of attack by malicious third parties.