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Simulation Method for Register Insertion Rings

IP.com Disclosure Number: IPCOM000109068D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 4 page(s) / 198K

Publishing Venue

IBM

Related People

Shedler, GS: AUTHOR

Abstract

This article describes a method for discrete-event stochastic simulation of bit-serial local area computer networks that use register (buffer) insertion. Bit-serial local area computer networks that use register (buffer) insertion dynamically switch longer delays (insertion buffers) into the ring when stations are transmitting a packet. (See, for example, (1,2,3,4).) The focus here is on static register insertion rings in the short-packet environment where the source station is responsible for packet removal. With this type of removal rule it is possible (2) for a station to execute its access control algorithms with only a short fixed in-line delay. The primary goal of a discrete-event simulation of a register insertion ring is the assessment of the delay/throughput characteristics of the network.

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This is the abbreviated version, containing approximately 32% of the total text.

Simulation Method for Register Insertion Rings

       This article describes a method for discrete-event
stochastic simulation of bit-serial local area computer networks that
use register (buffer) insertion.  Bit-serial local area computer
networks that use register (buffer) insertion dynamically switch
longer delays (insertion buffers) into the ring when stations are
transmitting a packet.  (See, for example, (1,2,3,4).)  The focus
here is on static register insertion rings in the short-packet
environment where the source station is responsible for packet
removal.  With this type of removal rule it is possible (2) for a
station to execute its access control algorithms with only a short
fixed in-line delay.  The primary goal of a discrete-event simulation
of a register insertion ring is the assessment of the
delay/throughput characteristics of the network.

      We use generalized semi-Markov processes (GSMPs) with
simultaneous trigger events to specify register insertion rings.
Heuristically, a GSMP is a stochastic process that makes a state
transition when one or more events associated with the occupied state
occur.  Events associated with a state compete to to trigger the next
state transition, and set of trigger events has its own distribution
for determining the next state. At each state transition of the GMP,
new events may be scheduled.  For each of these new events, a clock
indicating the time until the event is scheduled to occur is set
according to an independent (stochastic) mechanism.  If a scheduled
event is not in the set of events that triggers a state transition,
but is associated with the next state, its clock continues to run; if
such an event is not associated with the next state, it is cancelled,
and the corresponding clock reading is discarded.  The GSMP is a
continuous-time stochastic process with piecewise constant sample
paths that records the state as it evolves over time.  Formal
definition of a GSMP with simultaneous trigger events is in terms of
a general state space Markov chain (GSSMC) {(Sn,Cn): n/0} that
describes the process at successive state transition times.  (This
definition follows (5), except that events can occur simultaneously;
see (6,7,8).  The GSSMC takes values in the set S=  seS({s} x C(s)),
where S is a finite or countably infinite set of states and C(s) is
the set of possible clock-reading vectors when the state is s.

      Register insertion rings give rise to discrete-event
simulations in which events can occur simultaneously.  Events can
occur simultaneously if some of the clock-setting distributions have
discrete components.  Since stations are always monitoring the ring
and there is no confusion between idle bits and packet bits, a packet
can be inserted safely between two consecutive ring packets that have
no idle bits between them.  Consequently, the natural events
"observation by station of first bit of packet transmitted by station
J" and "observation by s...