Separating Abstraction from Implementation
              in Communication Network Design


                       Ramon Caceres
                 Computer Science Division
                  University of California
                     Berkeley, CA 94720


                          ABSTRACT


     Datagrams and virtual circuits are not disjoint concep-
tual  models  for data communication, but rather inhabitants
of a wide design space containing many other viable network-
ing solutions.  Many design choices often closely associated
with these two communication styles can  be  decoupled  from
the  datagram and virtual circuit abstractions, and combined
to form new and  effective  network  implementations.   This
paper examines several key elements of network architecture.
For each element, it shows how certain characteristics often
thought  to differentiate datagrams and virtual circuits are
independent of these two concepts and  form  a  multi-valued
spectrum of design choices.  This discussion is motivated by
the current drive to design a new generation  of  high-speed
wide-area  networks,  and  the  observation that this effort
would benefit from a more systematic evaluation of  existing
and future network design alternatives.




























                     November 16, 1993