1. Development history of VPN
The emergence of virtual dedicated networks, also known as virtual private networks (VPNs), originates from customer needs, wanting to have effective connectivity between subscriber switchboards (PBXs). ) via wide area network (WAN). In the past, group telephone systems or local area networks (LANs) often used leased lines to organize a dedicated network and transmit information.

The important milestones in the development of VPN are as follows:
-1975: Franch Telecom launched the Colisee service, providing lines for large customers, providing specialized calling methods and management features.
-1985: AT&T introduced a VPN service called SDN.
-1986: Sprint launched Vnet, Telefonica Spain introduced Ibercom.
-1988: Conflicting VPN service fees in the US stimulated the expansion of VPN use, helping to save costs.
-1989: AT&T introduced IVPN international service called GSDN.
-1990: Australia's Telstra launched the first VPN service in the Asia-Pacific region.
-1992: Dutch Telecom and Swedish Telia established Unisource, providing VPN services.
-1993: AT&T, KDD and Singapore telecommunications established the Worldpartners Global Alliance, providing VPN services.
-In 1994: BT and MCI established Concert company, providing VPN and frame relay services.
-1995: ITU-T issued recommendation F-16 on global VPN services (GVPNS).
-In 1996: Sprint and German Telecom and French Telecom combined to form the Global One alliance.
-1997: Considered an innovative year for VPN technology, appearing in many magazines and conferences, VPN networks built on public Internet infrastructure opened up new possibilities and new perspectives. for VPN.
VPN technology is currently the optimal solution for companies and organizations with many offices and branches. Not limited to voice, VPNs are now widely used for data, video and multimedia services.
2. Function of VPN
VPN provides three main functions, including Authentication, Integrity, and Confidentiality.
- Authenticity
To establish a VPN connection, both parties must authenticate each other to ensure that the information exchanged between them is with their intended partner, not a third party.
- Integrity
This function ensures that data has not been changed or disturbed during transmission. This ensures the integrity of the information, keeping it from unauthorized alteration.
-Security
The sender can encrypt data packets before transmitting over the public network, and only the receiver has the ability to decrypt them. Through the encryption and decryption process, it is ensured that data cannot be accessed without authorization, and even if information is obtained, it cannot be read without authorization.
3. Benefits of VPN
A VPN, at its core, is a local area network that uses an existing public network like the Internet to connect remote offices and employees. Instead of using dedicated and direct connections between offices through leased lines, VPN (virtual private network) uses virtual connections established in the Internet environment from the company's private network. company to geographically distant offices and employees.

- Benefits for the company
Expand connections to many regions and around the world.
Enhance network security.
Reduced costs compared to setting up a traditional WAN.
Supports remote working, reduces transportation costs and increases interaction.
Simplify the network architecture model.
Provides global networking opportunities.
Supports remote working and is compatible with broadband networks.
Helps recover capital faster than traditional WAN networks.
Easy management with the ability to flexibly manage the number of users.
Ability to choose speeds from 9.6 Kbit/s to T1/E1 or use DSL technology.
Ability to deliver services quickly over an integrated IP network.
- Benefits for service providers
Increase revenue from traffic and value-added services.
Increase the efficiency of using the current internet network.
Consulting on network design for customers, creating close relationships.
Invest effectively and open new business areas for service providers.
Use equipment effectively for VPN networks.
4. Advantages of VPN
- Cut the cost
Using VPN helps companies reduce investment and recurring costs. The total cost of a VPN network shrinks, as fewer payments are needed for bandwidth rental, network equipment, and system maintenance. LAN-to-LAN connection costs are reduced by 20% to 30% compared to using traditional leased lines, and remote access costs are reduced by 60% to 80%.
- Flexible in operation and use
Flexibility not only occurs in operations but also in usage requirements. Customers can use a variety of connection types, from T1, T3 to other connections such as 56 kbit/s modem, ISDN 128 kbit/s, xDSL, and T1, T3. This brings diverse and convenient choices to users.
- Expand the system
VPNs are built on public network infrastructure, so they can be deployed anywhere there is a public network. Public networks are available everywhere, so VPN scalability is very flexible. Connecting to a remote office is easy via phone line or DSL, and the VPN can be conveniently removed when needed. Bandwidth scalability is also easy when an office requires more traffic.
-Minimize technical support
Standardizing connectivity and security requirements has reduced the need for technical support for VPN networks. Support from service providers increasingly takes on more tasks, reducing the need for technical support from users.
-Reduce equipment requirements
VPN, as a single solution for Internet access, requires less equipment and simplifies maintenance. This eliminates the need to maintain separate modems, compatible cards for terminal devices, and remote access servers. Businesses can easily set up customer devices for a simple environment, like a T1 environment, with the ISP doing the rest of the connection.
- Serving commercial needs
VPN products and services follow common standards, ensuring compatibility and performance. This helps create strong relationships between service providers and customers, with standardization, governance, scalability, and network integration.