LimeVPN uses PPTP, SSTP, L2TP, OpenVPN and Soft ether protocols.

PPTP

Stands for "Point-to-Point Tunneling Protocol." PPTP is a networking standard for connecting to virtual private networks, or VPNs. VPNs are secure networks that can be accessed over the Internet, allowing users to access a network from a remote location. This is useful for people who need to connect to an office network from home or access their home computer from another location.

The "point-to-point" part of the term refers the connection created by PPTP. It allows one point (the user's computer) to access another specific point (a remote network) over the Internet. The "tunneling" part of the term refers to the way one protocol is encapsulated within another protocol. In PPTP, the point-to-point protocol (PPP) is wrapped inside the TCP/IP protocol, which provides the Internet connection. Therefore, even though the connection is created over the Internet, the PPTP connection mimics a direct link between the two locations, allowing for a secure connection.

SSTP

Secure Socket Tunneling Protocol (SSTP) is a secure protocol used in VPN tunneling. The protocol, though owned by Microsoft, is available to both Linux and Mac users. SSTP uses SSL/TLS (Secure Socket Layer/Transport Layer Security) channel over TCP 443 port.

A client’s system connects to a server through a TCP (Transmission Control Port). SSL uses the 443 port to connect to the server. To confirm the connection, it requires user authentication. And, it is usually authenticated by the client. The protocol uses the server certificate for authentication.

L2TP

L2TP stands for Layer 2 Tunneling Protocol, and it’s – like the name implies – a tunneling protocol that was designed to support VPN connections. Funnily enough, L2TP is often employed by ISPs to allow VPN operations.

L2TP tunneling starts out by initiating a connection between LAC (L2TP Access Concentrator) and LNS (L2TP Network Server) – the protocol’s two endpoints – on the Internet. Once that’s achieved, a PPP link layer is enabled and encapsulated, and afterwards it’s carried over the web.

The PPP connection is then initiated by the end-user (you) with the ISP. Once the LAC accepts the connection, the PPP link is established. Afterwards, a free slot within the network tunnel is assigned, and the request is then passed on to the LNS.

Lastly, once the connection is fully authenticated and accepted, a virtual PPP interface is created. At that moment, link frames can freely be passed through the tunnel. The frames are accepted by the LNS, which then removes the L2TP encapsulation and proceeds to process them as regular frames.

OpenVPN

OpenVPN is open-source commercial software that implements virtual private network (VPN) techniques to create secure point-to-point or site-to-site connections in routed or bridged configurations and remote access facilities. It uses a custom security protocol that utilizes SSL/TLS for key exchange.

Soft Ether

SoftEther VPN is a VPN system that consists of exchanging virtual Ethernet frames and communicate by VPN among VPN Client / VPN Server / VPN Bridge. Based on TCP/IP protocol, SoftEther VPN protocol plays the role of encapsulating, encrypting and transmitting virtual Ethernet frames on a physical IP network.

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