The final step in the handshaking process is to send an MNP packet containing the "SABME" command, short for "set asynchronous balanced mode extended". This is sent by the originator, containing a number of data fields indicating the exact protocols it can support. The answering system responds with a modified version of the same packet, switching bits in the data to indicate it is successful. From that point on, the two systems exchange data using the error correcting packet protocol. If this last step does not complete during timer T401, the originator sends L-RELEASE and returns to a non-MNP link.
