There are two basic types of VPNs:

Remote access VPN allows a user to connect to a private network and access its services and resources remotely. The connection between the user and the private network occurs over the internet and the connection is completely secure. Remote Access VPNs are very convenient for employees and those who use VPNs at home. While traveling, a company employee uses VPN to connect to his company's private network and access files and resources on the private network remotely. Home users or private VPN users primarily need VPN service to bypass regional restrictions on the internet and access blocked websites.

Site-to-Site VPN is also called Router-to-Router VPN and is mostly used in companies. Companies with offices in different geographic locations use Site-to-site VPN to connect the network of one office location to the network of another office location. When multiple offices of the same company are connected using the Site-to-Site VPN type, it is called Intranet-based VPN. When companies use the site-to-site type of VPN to connect to another company's office, it is called Extranet-based VPN. Essentially, site-to-site VPN creates a virtual bridge between networks in geographically distant offices and connects them via the internet, enabling secure and private communication between networks.

These two types of VPNs mentioned are based on different VPN security protocols. Each of these VPN protocols offers different features and levels of security.

Internet Protocol Security or IPSec is used to secure Internet communications over an IP network. IPSec protects Internet Protocol communications by authenticating the session and encrypting each data packet during the connection. IPSec operates in two modes to protect data transfer between two different networks:

Transport mode and Tunnel mode.

Transport mode encrypts the message in the data packet and tunnel mode encrypts the entire data packet.

IPSec can also be used with other security protocols to enhance the security system.

L2TP or Layer 2 Tunneling Protocol is a tunneling protocol that is often combined with another VPN security protocol such as IPSec to create a highly secure VPN connection. L2TP creates a tunnel between two L2TP ports, and the IPSec protocol encrypts the data and manages secure communication between the tunnel.

PPTP or Point-to-Point Tunneling Protocol creates a tunnel and encapsulates the data packet. It uses Point-to-Point Protocol (PPP) to encrypt data between connections. PPTP is one of the most widely used VPN protocols.

SSL (Secure Sockets Layer) and TLS (Transport Layer Security) create a VPN connection where the web browser acts as a client and user access is restricted to specific applications rather than the entire network. SSL and TLS protocol are most used by online shopping websites and service providers. Because web browsers integrate with SSL and TLS, web browsers switch to SSL easily and with almost no action required by the user. SSL connections have https at the beginning of the URL instead of http.

OpenVPN is an open source VPN useful for creating Point-to-Point and Site-to-Site connections. It uses a special security protocol based on SSL and TLS protocol. It is among the essential protocols of some VPNs.

Secure Shell or SSH creates the VPN tunnel through which data transfer occurs and also ensures encryption of the tunnel. SSH connections are created by an SSH client and data is transferred to the remote server via an encrypted tunnel from a local port.

What we have presented above are the VPN protocols and security structures used in most places. Apart from these, there are many other VPN protocols.

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