Efficiency of Asynchronous Transfer Mode Networks
           in Transporting Wide-Area Data Traffic

                       Ramon Caceres

                 Computer Science Division
                  University of California
                    Berkeley  CA  94720
                  ramon@tenet.berkeley.edu

     For performance and economic reasons, ATM networks must
efficiently  support  the  Internet family of protocols.  We
calculate the transmission efficiency achieved by a range of
ATM-related  protocols  when  transporting TCP and UDP wide-
area traffic.  We also compare  the  efficiency  effects  of
several  non-standard  compression techniques.  To assure an
accurate workload characterization, we drive these  calcula-
tions  with millions of wide-area packet lengths measured on
the current Internet.

     We find that networks using standard ATM procedures are
dismally  inefficient in carrying traditional data traffic -
depending on the protocols used, efficiency as  seen  by  an
application  program  ranges  between 40 and 53%.  Moreover,
due to interaction between TCP-IP datagram lengths  and  ATM
cell  padding,  efficiency  responds  abruptly to changes in
certain protocol parameters - for example, a 4-byte increase
in  ATM  cell payload size can yield a 10% increase in effi-
ciency.  Using one compression technique  in  isolation  can
improve  efficiency  by  12%, and simultaneously using three
techniques can improve it by 34%.  These  issues  should  be
considered when designing future ATM netPapers/