ommunication infrastructure is the process
model used to communicate with all the sites in the replication group.
Each site creates a thread of control that listens on its designated
socket (as specified by the <span class="bold"><strong>-l</strong></span> command line argument) and
then creates a new channel for each site that contacts it.  In addition,
each site explicitly connects to the sites specified in the
<span class="bold"><strong>-r</strong></span> and <span class="bold"><strong>-R</strong></span>