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LLC encapsulation allows multiple protocols to share a single ATM connection. The ATM connection request is initiated only when the first protocol requests a connection to a remote end station. After a connection is set up, any other protocols requesting a connection to the same remote end station will not cause additional connection setup messages to be sent. Instead, a call confirmation is generated by the local system. At the remote end station, an incoming call signal is generated when it receives the first data packet, then the call is established.
The ATM connection is taken down only when the last referencing protocol of an established ATM connection requests takedown of its connection. If the protocol requesting the disconnect is not the last one referencing the ATM connection, the call is disconnected only at the local system. If the user does not manually reestablish the call within 15 minutes, the remote system will disconnect the call for the protocol. Therefore, the user might see one end station showing a call as disconnected, although the other end station shows the connection as still up until the 15-minute timeout has expired.
The advantage of LLC encapsulation over VC-based multiplexing is reduced VC count.
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