6. L2TP security

Security in L2TP consists essentially of authentication mechanisms. Transporting PPP frames, authentication at this level already provides a minimum of security, usually accompanied by authentication of the tunnel (i.e. the communicating endpoints, the LAC and the LNS). In addition, the definition of certain AVPs has reinforced this security. Finally, combinations of L2TP with well-known security mechanisms have been defined; for example, the use of L2TP with IPsec is recommended by the IETF, and the joint use of L2TP and RADIUS further enhances exchange security.