My naive understanding of how the internet works is as follow :
Physical layer (1) Link layer (2) - Inside frames IP layer (3) - Inside IPv4 or IPv6 packets Transport layer (4) - Inside TCP or UDP Application layer
Where does L2TP protocol stands? The name suggests it is a layer 2 protocol, but the wiki article says L2TP packets are inside UDP datagrams. This, to me, suggests it is an application protocol.
Is L2TP a layer 2 protocol? Is it using another "kind of frame" different thant the common one I am used to? Or is it actually an application protocol contained within "normal" frames, IP packets and UDP datagrams?