qualified logical link control (SNA) (QLLC)
The QLLC protocol was defined by IBM for communication from the SNA architecture via X.25 networks. A virtual end-to-end connection under Qualified Logical Link Control (QLLC) corresponds to an X.25 connection. A QLLC connection is comparable to an SDLC connection over X.25. The QLLC protocol can be used to emulate SDLC data communication over an X.25 network.