Layer Two Tunneling Protocol (L2TP) is a combination of PPTP and Layer 2 Forwarding (L2F), a technology developed by Cisco Systems, Inc. Rather than having two incompatible tunneling protocols competing in the marketplace and causing customer confusion, the Internet Engineering Task Force (IETF) mandated that the two technologies be combined into a single tunneling protocol that represents the best features of PPTP and L2F. L2TP is described in RFC 2661 in the IETF RFC Database.
Due to licensing restrictions, iOS developers previously couldn’t implement OpenVPN connections directly inside their applications. Since that changed in mid-2018, a few providers, including IVPN and PrivateInternetAccess, have added native OpenVPN support to their apps. This makes a secure connection on any Apple device much easier than the old method that required a clunky third-party application and complicated connection profiles. Though we haven’t done performance tests on any updated iOS apps yet, our limited use of the updated IVPN app worked without any problems. Going forward, we wouldn’t consider a VPN provider that doesn’t include native OpenVPN support on iOS.
Agree expressvpn is an absolute winner, even though nordvpn has more than twice servers (around 5000) it still loses in download speed and therefore streaming. One remark I noticed when tested average speed of different vpns is that the closer your own location is to vpn server you choose the better the speed and it seems to be obvious. The only big cons for expressvpn is of course the price but it seems that the guys from the company knows the best can’t be cheap  I would also like to share a good source for online vpn comparison chart I have found, check it here
Are you so used to your data traveling over Wi-Fi that you've stopped worrying about the security of that data—and about who else might be spying on it, or even stealing it for nefarious purposes? If so, you are—sadly—in the majority, and you ought to consider using a viritual private network, or VPN. In fact, when PCMag conducted a survey on VPN usage, we found that a dismal 71 percent of the 1,000 respondents had never used a VPN. Even among those who support net neutrality—who you might think would tend to be well informed on technology and privacy issues—only 45 percent had used a VPN.