The newly defined NIFO-discipline optimizes the performance of
large switching arrays by taking into account the spatial
distribution of incoming calls in these arrays [A7, A8].
The so called F/LIFO-discipline allows the combined operation
of a FIFO-shift memory and a LIFO-stack memory in queueing
systems [A34, A43].
The SRPT-discipline with preference of items with relatively
short service times offers the minimal mean delay time among
all conceivable disciplines, but has been neglected in the past
with respect to its potential applications in data networks. This
happened to be due to misinterpretations of several properties of
SRPT, which could be cleared by a series of investigations
[A36]:
-
In [A9, A10] it was shown for
queueing system M/G/1 that the overhead due to
service-interruptions caused by the SRPT-principle can be taken
into account by defining a modified SRPT-discipline, which keeps a
considerable mean value advantage compared to other disciplines.
-
In [A24, A25] it was proven that
the variance of delay time of system M/G/1 is for SRPT under typical
conditions not larger but even considerably smaller than for
FIFO. Another interesting performance advantage of SRPT was
discovered by simulation: SRPT yields a
decorrelated delay time, whereas FIFO and other disciplines are
affected by partially very strong correlation [A26].
-
In [A27, A28] it has been shown that the
mean delay performance of
priority queues can be essentially improved by applying SRPT.
-
According to a proposal in [A10] the preference
of relatively short messages (not short packages!) in accordance
with the SRPT-principle can be achieved in packet networks
by means of a reversed order numbering scheme for the packets
of each message. Therupon the results of an extensive simulation study
[A30, A31, A32] have shown that the mean value performance of
various LAN's including the Ethernet with CSMA/CD-protocol can be
essentially improved by a typical factor of 10 by introducing the reversed
packet numbering scheme and certain protocol modifications.
