From: stevemc@ICSI.Berkeley.EDU (Steven McKearney)
Newsgroups: ba.seminars
Subject: 1/11/93 Christopher Lindemann Talk at ICSI
Date: 5 Jan 1993 00:12:52 GMT
Organization: International Computer Science Institute, Berkeley, CA, U.S.A.
Distribution: ba
NNTP-Posting-Host: icsid.icsi.berkeley.edu
Keywords: Performance Modeling of Communication Systems with Deterministic and Stochastic Petri Nets

            The International Computer Science Institute
                    is pleased to present a talk:

                 Monday, January 11, 1993  2:00 p.m.

                        CHRISTOPHER LINDEMANN
                    Technical University of Berlin
                               GERMANY
                        lind@cs.tu-berlin.de

         ``Performance Modeling of Communication Systems with
                Deterministic and Stochastic Petri Nets''

Deterministic and  Stochastic  Petri  Nets  (DSPNs) are  a numerically
solvable   modeling   formalism   which  include   both  exponentially
distributed and constant timing.  Thus, DSPNs are well suited to model
discrete-event  dynamic  systems  in  which  some  activities  have  a
constant duration.  As  examples, we would  like  to mention  transfer
times of data packets of fixed size in distributed  computing systems,
time-outs  in  real-time  systems, and  repair  times of components in
fault-tolerant systems.  Since qualitative properties of protocols can
also be  studied  by  means  of  Petri  Nets, DSPNs provide  a unified
modeling formalism for both  qualitative  and quantitative evaluation.
Due  to the  availability  of  a  graphical and  interactive  software
package,  named   DSPNexpress,  the   development,  modification,  and
quantitative  evaluation of  a  DSPN  is  typically  easier  and  less
error-prone than in the case of  a low-level  Markov model.   The same
holds  for stochastic simulation  based on  simulation languages (e.g.
CSIM  or  LANSF).  Furthermore,  a  DSPN  provides  a  more  intuitive
description  of  the  system  being  analyzed   than  a  corresponding
low-level  Markov  model  or  a  simulation  program.  These  features
constitute the main advantages of DSPNs over low-level  Markov  models
and simulation languages.  However, DSPNs incorporate several problems
as  well.  Since the numerical solution method of DSPNs does not allow
the  representation of  concurrent deterministic timing, the  modeling
power of numerically  solvable DSPNs is certainly smaller than the one
of simulation languages.

In  the first  part  of this talk a  comprehensive description  of the
required  steps  for calculating steady-state  solutions of  DSPNs  is
given  and  efficient  algorithms  are  discussed  which  have  become
available  recently. Furthermore, the main  features  of the  software
package  DSPNexpress  are introduced  which  have  been  designed  and
implemented by the  speaker  together with a  group of students at the
Technical  University  of  Berlin.   The  package  DSPNexpress  has  a
user-friendly graphical interface  running under  X11  and allows  the
solution  of DSPNs  with 100,000 states and several  millions of state
transition with  reasonable computation time on a modern  workstation.
The  second  part  of the  talk illustrates  applications of  DSPNs in
Performance  Modeling  of  Communication  Systems  and   Multicomputer
Systems.  In particular, DSPN models of single-server queueing systems
with  complex arrival  processes (e.g. MMPP) and deterministic service
times  and DSPNs of  Medium Access Control  Protocols  are  discussed.
Furthermore,  DSPNs  of   several  memory  consistency  protocols  for
multicomputers with  Virtually Shared  Memory are presented.  Finally,
open research problems are briefly mentioned.


       This talk will be held in the Main Lecture Hall at ICSI.
         1947 Center Street, Sixth Floor, Berkeley, CA 94704
      (On Center between Milvia and Martin Luther King Jr. Way)
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