% $Id$
%
% Earth System Modeling Framework
% Copyright (c) 2002-2023, University Corporation for Atmospheric Research, 
% Massachusetts Institute of Technology, Geophysical Fluid Dynamics 
% Laboratory, University of Michigan, National Centers for Environmental 
% Prediction, Los Alamos National Laboratory, Argonne National Laboratory, 
% NASA Goddard Space Flight Center.
% Licensed under the University of Illinois-NCSA License.

%\subsection{Use and Examples}

A Component Tunnel connects a {\em dual} Component to an {\em actual} Component. This connection can be based on a number of different low level implementations, e.g. VM-based or socket-based. VM-based Component Tunnels require that both dual and actual Components run within the same application (i.e. execute under the same MPI\_COMM\_WORLD). Fault-tolerant Component Tunnels require that dual and actual Components run in separate applications, under different MPI\_COMM\_WORLD communicators. This mode is implemented in the socket-based Component Tunnels.
