Contents Telektronikk - Telenor

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costs will be such that decisions should be taken on a basis of
guesswork, or even experience of poor functioning. A solid
theoretical basis of analysis and dimensioning, updated to cover
the system state of the art, will always be necessary.
It is not the ambition to cover every aspect of teletraffic in the
present issue of “Telektronikk”. The Norwegian base is deliberately
emphasised by inviting mainly national authors. Thus, the
colouring of the present issue is very much given by the present
traffic oriented activities in Norway. The limitations of this are
very clear, since there has to be a rather modest number of traffic
specialists in a small country with no dominant telecom industry.
Still, there are very capable people who did not have the opportunity
to participate on this occasion. In view of the good Scandinavian
co-operation, primarily through the regular Nordic
Teletraffic Seminars, the scope is extended to a very limited
number of contributions from our neighbours. Many more would
be desirable. As is well known, the Scandinavian contributions
to teletraffic theory and applications have been very substantial.
As the guest editor of the present journal issue I was asked by the
chief editor to produce an extensive introduction to the main subject.
The introduction ought to be readable by non-experts in teletraffic
matters and in the more demanding mathematics. The result
appears on the following pages. In view of the fundamental importance
of A.K. Erlang’s works, a reprint of his historic paper from
1917 in English translation, along with a brief introduction, is
included. Another paper, by R.B. Haugen, is dedicated to the Scandinavian
pioneer Conny Palm.
The more general concept of quality of service is approached by
F.A. Aagesen. He points out that the quality of service often has
got less attention than the functional properties, and more so in
connection with data packet networks than in traditional telephone
networks. A general QoS approach related to the OSI
model is discussed. The results of very extensive traffic measurements
in Finland are presented by A. Parviala, showing
among other that traffic tends to vary more over time than what
is often assumed in dimensioning practice. B. Wallstrøm has
submitted a new extension to the equivalent random theory
(ERT) for point to point blocking calculations in a hierarchical
network. U. Kørner discusses overload conditions in common
control equipment, and G. Nossum & al present structure and
dimensioning principles for the S12 system with emphasis on
remote ISDN units. Structure, routing and dimensioning principles
in a new target network based on SDH with mesh and ring
topologies are presented by A. Østlie. T. Jensen is responsible
for the only contribution on performance analysis and simulation
of mobile systems.
A traditional set of observations on a large digital PBX, where
data collected by charging equipment is the main source of traffic
observations, is presented by B. Feng & al, and an example
of traffic measurements in 14 different local area networks
(LANs) is reported by S. Gaaren.
It must be expected that a high proportion of the contributions
would centre around the hot area of high speed (broadband)
communication. Already the mentioned measurements of LANs
point in that direction. No less than 7 of the papers are directly
related to the asynchronous transfer mode (ATM). A survey of
analytical methods in the study of ATM is offered by I.
Svinnset, and S.O. Groven discusses objectives and methods
regarding measurements on ATM switches. Even some initial
measurement results are reported, focused on cell loss, errors,
delay and delay variation. K. Moldeklev & al present throughput
observations with TCP/IP transmissions over ATM. The requirements
regarding access control, largely determined by the
diversity of capacity needs of multiservice networks, is dealt
with in the paper by H. Pettersen & al. Experimental results are
included. A comprehensive study of the traffic generation process
is reported by B. Helvik, along with a description of a synthesised
traffic generator for ATM traffic. The appearance of
very infrequent significant events in ATM transmission and
switching is the background for a study on speed-up techniques
in simulation, reported by P. Heegaard.
With the stated intention of keeping mathematics at a reasonable
level in spite of its importance in traffic analysis, I am
pleased to note that we have succeeded to a reasonable extent.
We must, however, recognise the need for more sophisticated
methods. It is only fair to include some illustration of the high
complexity inherent in many traffic problems. An example of
complex mathematical modelling is offered by O. Østerbø in a
study of queuing models for ATM. Also the paper by E. Jensen
on processor performance in call processing within contemporary
switching systems is demanding in its mathematical formulation.
Before closing the edition of this special issue, as a guest editor
I want to express my appreciation to all those involved. First of
all this goes to the authors, who so enthusiastically participated
in the efforts. The very competent editorial staff at TF (Telenor
Research) has carried out the chore of details, and even added
the more artistic traits. I thank chief editor Ola Espvik, who
incited me to accept the task, and who has given me a free hand,
still giving all the support asked for.