Three Main VPN Protocols: OpenVPN, PPTP, L2TP/IPSEC

OpenVPN 

OpenVPN is better known for its cross-platform capabilities. This type of protocol makes use of robust encryption through OpenSSL. Its encryption strength is also made up of 256-bit encryption, and 128-bit encryption that is comprised of 1024 bit keys for the effective connection. OpenVPN uses a package to be put individually and * .ovpn configuration files that have a password and username combined. The speed of this type of protocol depends on several factors as well as server and computer speed. OpenVPN via UDP is usually quicker than via TCP. OpenVPN has effective stability with all kinds of networks such as mobile, LAN (wired), WLAN (wireless) among others. The protocol has reduced security problems, you must opt for this type of protocol for guaranteed VPN security. This VPN has both effective security and speed and knows several network and firewall restrictions. One of the disadvantages of the OpenVPN is that when the installation is done, separated supplied software is necessary. It is indeed true that OpenVPN is one of the best protocols in several situations as it is secure, stable, and fast. 

PPTP 

Windows first supported the PPTP protocol. PPTP performs encryption via MPPE protocol. RSA RC4 algorithm is used which features 128-bit keys. PPTP can be put in the operating system as well as use individual software during installation. The speed of PPTP is that it depends on several aspects such as the server and the computer speed. The compatibility issues associated with the PPTP makes stability difficult. Windows are often associated with multiple security vulnerabilities when using PPTP. The benefit of this VPN protocol is that it supports several devices, has good speeds, and is adjustable. On the contrary, this VPN protocol is less secure and alters stability. Hence, PPTP is less secure, less stable even though easy to install. 

L2TP / IPSEC 

L2TP / IPSEC makes use of IPSec, which has a 3DES/AES algorithm and 256 bit key for both encryption and security. L2TP / IPSEC can be put in the operating system as well as use individual software during installation. The speed of L2TP / IPSEC is that it depends on several aspects such as the server and the computer speed. Its stability depends on the network but also similar to OpenVPN. When combined with IPsec, L2TP / IPSEC is considered very secure. The benefits of L2TP / IPSEC include passing ISP and network restrictions as well as easy adjustments that can be made. Its disadvantage is that it is easier and slower to block. In conclusion, L2TP is usually slower yet by-passes blockages OpenVPN and PPTP cannot by-pass. L2TP is an alternative to OpenVPN. 

References 

https://howvpnwork.com/vpn-guides/vpn-protocols-compared.html