QUALITY OF SERVICE IN ATM NETWORKS


            Domenico Ferrari and Dinesh C. Verma

                 Computer Science Division
 Department of Electrical Engineering and Computer Sciences
                  University of California
        and International Computer Science Institute
                Berkeley, California, U.S.A.










                          Abstract

     B-ISDN networks of  the  future  will  have  to  handle
traffic  with  a  wide  range of traffic characteristics and
performance requirements.  In view of the high bandwidth  of
these  networks and the  relatively large propagation delays
involved  in  wide-area  B-ISDN  networks,  the  performance
requirements  can only be provided by reserving resources to
communicating clients at the connection establishment  time.
However,  reservation  mechanisms  for  heterogenous  bursty
traffic usually result in a rather poor utilization of  net-
work resources.

     In this paper, we propose a  simple  admission  control
criterion  that  can be used to reserve resources for bursty
as well as smooth traffic with delay and loss sensitivities.
Our scheme leads to a reasonable value of the maximum utili-
zation of network bandwidth (about 40%) for delay  sensitive
traffic  with moderate burstiness (peak-to-average bandwidth
ratios of about 4), even under  the  worst  possible  condi-
tions.  Actual utilizations can be higher if there is smooth
traffic or traffic which is not delay-sensitive.  Our admis-
sion  control algorithm uses a well-defined traffic specifi-
cation scheme which is easy to enforce and verify, and  able
to  accommodate  arbitrary  degrees of burstiness. Extensive
simulation experiments  failed to show  that  our  admission
control criterion are incorrect, in the sense that the qual-
ity of service requirements of the traffic was  always  met,
even  in  the worst case. Moreover, the scheme is simple and
feasible at the high speeds required of B-ISDN networks.