What is VPN(Virtual Private network)

A virtual private network (VPN) extends a  across a public network, and enables users to send and receive data across shared or public networks as if their computing devices were directly connected to the private network. Applications running on a computing device, e.g., a laptop, desktop, smartphone, across a VPN may therefore benefit from the functionality, security, and management of the private network.

VPN technology was developed to allow remote users and branch offices to access corporate applications and resources. To ensure security, the private network connection is established using an encrypted layered tunneling protocol, and VPN users use authentication methods, including passwords or certificates, to gain access to the VPN. In other applications, Internet users may secure their connections with a VPN to circumvent geo-restrictions and censorship or to connect to proxy servers to protect personal identity and location to stay anonymous on the Internet. Some websites, however, block access to known VPN technology to prevent the circumvention of their geo-restrictions, and many VPN providers have been developing strategies to get around these roadblocks.

A VPN is created by establishing a virtual point-to-point connection through the use of dedicated circuits or with tunneling protocols over existing networks. A VPN available from the public Internet can provide some of the benefits of a wide area network (WAN). From a user perspective, the resources available within the private network can be accessed remotely.

 Early data networks allowed VPN-style connections to remote sites through dial-up modem or through leased line connections utilizing X.25, Frame Relay and Asynchronous Transfer Mode (ATM) virtual circuits provided through networks owned and operated by telecommunication carriers. These networks are not considered true VPNs because they passively secure the data being transmitted by the creation of logical data streams. They have been replaced by VPNs based on IP and IP/Multi-protocol Label Switching (MPLS) Networks, due to significant cost-reductions and increased bandwidth provided by new technologies such as digital subscriber line (DSL) and fiber-optic networks.

VPNs can be characterized as host-to-network or remote access by connecting a single computer to a network or as site-to-site for connecting two networks. In a corporate setting, remote-access VPNs allow employees to access the company's intranet from outside the office. Site-to-site VPNs allow collaborators in geographically disparate offices to share the same virtual network. A VPN can also be used to interconnect two similar networks over a dissimilar intermediate network, such as two IPv6 networks connected over an IPv4 network.

VPN systems may be classified by:

·         the tunneling protocol used to tunnel the traffic

·         the tunnel's termination point location, e.g., on the customer edge or network-provider edge

·         the type of topology of connections, such as site-to-site or network-to-network

·         the levels of security provided

·         the OSI layer they present to the connecting network, such as Layer 2 circuits or Layer 3 network connectivity

·         the number of simultaneous connections

VPNs cannot make online connections completely anonymous, but they can usually increase privacy and security. To prevent disclosure of private information, VPNs typically allow only authenticated remote access using tunneling protocols and encryption techniques.

The VPN security model provides:

·         confidentially such that even if the network traffic is sniffed at the packet level, an attacker would see only encrypted data

·         sender authentication to prevent unauthorized users from accessing the VPN

·         Message integrity to detect any instances of tampering with transmitted messages.

 Secure VPN protocols include the following:

·         Internet Protocol Security was initially developed by the Internet Engineering Task Force (IETF) for IPv6, which was required in all standards-compliant implementations of IPv6 before RFC 6434 made it only a recommendation.^[7] This standards-based security protocol is also widely used with IPv4 and the Layer 2 Tunneling Protocol. Its design meets most security goals: availability, integrity, and confidentiality. IPsec uses encryption, encapsulating an IP packet inside an IPsec packet. De-encapsulation happens at the end of the tunnel, where the original IP packet is decrypted and forwarded to its intended destination.

·         Transport Layer Security (SSL/TLS) can tunnel an entire network's traffic (as it does in the OpenVPN project and SoftEther VPN project^[8]) or secure an individual connection. A number of vendors provide remote-access VPN capabilities through SSL. An SSL VPN can connect from locations where IPsec runs into trouble with Network Address Translation and firewall rules.

·         Datagram Transport Layer Security (DTLS) – used in Cisco AnyConnect VPN and in OpenConnect VPN^[9] to solve the issues SSL/TLS has with tunneling over TCP (tunneling TCP over TCP can lead to big delays and connection aborts^[10]).

·         Microsoft Point-to-Point Encryption (MPPE) works with the Point-to-Point Tunneling Protocol and in several compatible implementations on other platforms.

·         Microsoft Secure Socket Tunneling Protocol (SSTP) tunnels Point-to-Point Protocol (PPP) or Layer 2 Tunneling Protocol traffic through an SSL 3.0 channel (SSTP was introduced in Windows Server 2008 and in Windows Vista Service Pack 1).

·         Multi Path Virtual Private Network (MPVPN). Ragula Systems Development Company owns the registered trademark "MPVPN".^[11]

·         Secure Shell (SSH) VPN – OpenSSH offers VPN tunneling (distinct from port forwarding) to secure remote connections to a network or to inter-network links. OpenSSH server provides a limited number of concurrent tunnels. The VPN feature itself does not support personal authentication.^[12][13][14]

·         WireGuard