Protocol description
L2TP protocol

For a PPP session to be transported to an LNS, one of the two ends (e.g. the LAC) must request the creation of a tunnel. The other end (the LNS) then sends confirmation of the tunnel creation. The LAC responds by also sending a tunnel creation confirmation. The control connection is thus initiated on the tunnel. An L2TP session is then established by sending similar control messages (request, 1 ^re confirmation, 2 ^nde confirmation) on the control channel. Data can then be sent via the L2TP tunnel. The protocol regularly sends control messages, which must be acknowledged to ensure correct communication through...