Layer 2 Tunnel Protocol version 3 (L2TPv3) is an extension of regular L2TP that allows transport of data-link traffic other than PPP. The differences between version 3, defined in RFC 3931, and its previous incarnation are relatively minor and generally involve making the protocol less PPP specific. RFC 3931 lists the major differences from the original specification (RFC 2661, which we probably now need to refer to as L2TPv2):
Separation of all PPP-related AVPs [attribute-value pair], references, etc., including a portion of the L2TP data header that was specific to the needs of PPP.
Transition from a 16-bit Session ID and Tunnel ID to a 32-bit Session ID and Control Connection ID, respectively.
Extension of ...