Source : Free On-Line Dictionary of Computing

protocol stack
     
         A layered set of {protocols} which work together to
        provide a set of network functions.  Each intermediate
        {protocol layer} uses the layer below it to provide a service
        to the layer above.
     
        The {OSI} seven layer model is an attempt to provide a
        standard framework within which to describe protocol stacks.
     
        (1997-12-07)