>>1042163
>I don't see what the problem is with PPP then
There is nothing wrong with PPP itself, it's just that it is not necessary for IP tunnelling case.
>Isn't the whole point of it being Layer 2 Tunneling Protocol that it tunnels the network layer?
Network level is 3 (ip). Level 2 is data link (ethernet, ppp).
Yes, it is (assuming s/network/link/).
>Is it because it's low-level instead of application layer like openvpn or whatever else?
Application level is, surprisingly, specific application protocols. HTTP, SMTP, etc. OpenVPN's tunnelling is network level (but it can also work as level 2 (ethernet) tunnel).
Yes, because it's too low level, in sense that is has to emulate details that are irrelevant for common usage. Basically, you need L3TP in majority of cases - but L2TP is widely used for historic reasons.
L2TP is non-properierary, but supported by equipment manufacturers; works over UDP (as opposed to stuff like GRE, that works over bare IP packets); works together with IPsec terminating equipment and ppp access/billing infrastructure. For ISPs and business such factors are more important than protocol cleanness and simplicity.
But for personal cases, without burden of legacy and need to integrate with RADIUS server that serviced dial up customers for 15 years, there is no reason to use L2TP.