Understanding VPNs: Definition, How They Work, and Why Use Them

This article explains what a VPN is, how it works, and why you might want to use one. We’ll cover everything from the basic definition to the advantages and disadvantages of using a VPN.

VPN Definition

VPN stands for Virtual Private Network. It’s a way to browse the internet anonymously and securely. Essentially, a VPN encrypts the data you send and receive over a public or less secure internet connection. This prevents anyone from snooping on your online activity.

VPNs operate at either layer 2 or layer 3 of the OSI model. There are three main types of VPNs:

• Remote Access VPN: Allows individual users to connect to a private network (like an office network) from a remote location.
• Intranet VPN: Connects multiple offices or branches of an organization over a secure network.
• Extranet VPN: Connects an organization’s network with the network of a partner or customer.

How Does a VPN Work?

From a technical standpoint, a VPN needs the following components to function:

• VPN router or VPN switch: Hardware that manages VPN connections.
• Software: Software to create and manage secure tunnels for data transmission.
• Security Device: A firewall or similar security device to protect the network.
• Internet Connection: A stable internet connection is necessary.
• Existing Hardware: Existing servers and workstations can be utilized.

VPNs utilize layer-2 (Ethernet) and layer-3 (IP) frame formats. Tunneling is a core concept in VPNs. It allows senders to encapsulate their data in IP packets, effectively hiding the routing and switching infrastructure of the internet. This encapsulation is crucial for data security and preventing unwanted access.

From the user’s perspective, using a VPN is quite simple:

1. VPN Program/App: You need a VPN program or application installed on your computer, laptop, tablet, or mobile device.
2. Installation/Activation: Install the software or turn the app “ON”.
3. Configuration: Configure the VPN settings on your device.

Once the VPN is configured and active, your internet activity is no longer publicly accessible.

In summary, VPNs rely on three key elements:

• Protocols: VPNs use protocols like IPSec (IP Security), PPTP (Point to Point Tunneling Protocol), and L2TP (Layer-2 Tunneling Protocol). (Refer to L2TP vs PPTP for more information).
• Security: Encryption scrambles data before transmission and descrambles it upon receipt. VPNs use different key sizes for this process. User and system-level authentication add another layer of security.
• Appliances: Firewalls at the packet and application levels protect against intrusions.

VPN Ports

The following VPN ports are commonly used and need to be open on your firewall to allow VPN traffic:

• IPsec:
  • IP protocol-50 for ESP (Encapsulating Security Payload)
  • IP protocol-51 for AH (Authentication Header)
  • UDP port 500 and 4500
• SSL: TCP port 443. Also uses:
  • 465 port for secure SMTP
  • 993 port for Secure IMAP
  • 995 port for secure POP
• L2TP: TCP port 1701
• PPTP: TCP port 1723 and IP port 47 GRE

Why Use a VPN?

Here are several common reasons for using a VPN:

• Remote Access to Internal Networks: Employees working remotely can securely access company resources (intranet, accounting systems, HR systems) to update information like leave and attendance.
• Secure Internet Connection: VPNs provide a secure connection for accessing sensitive information using an Intranet VPN.
• Accessing Content from Different Regions: Using remote access or extranet VPNs, you can securely access content that might be restricted in your current location.
• Bypassing Restrictions: VPNs can help overcome government restrictions or access blocked websites and programs.

Advantages of VPNs

• Extended Geographic Connectivity: Companies can easily connect employees across different locations.
• Increased Productivity: Employees can work securely from anywhere, boosting productivity.
• Scalability: VPNs offer excellent scalability, allowing you to easily add or remove users.
• Secure Internet Access: VPNs provide a secure connection, protecting your data.
• Mobility: Users can access resources from any location.
• Reduced Telecommunication Costs: VPNs can lower long-distance communication costs.

Disadvantages of VPNs

• Complexity: Understanding the security implications can be difficult for the average user.
• Unpredictable Internet Traffic: VPN performance can be affected by internet traffic.
• Compatibility Issues: Integrating products from different vendors can sometimes be challenging.
• Lack of Standardization: A lack of universal standards can create interoperability problems.
• Security Risks with Free VPNs: Using some free VPN applications without proper research can lead to security breaches and intrusions.