=Paper= {{Paper |id=Vol-1837/paper16 |storemode=property |title=A Model for Transformation of Self-Similar Traffic into Poisson's Arrival Packets |pdfUrl=https://ceur-ws.org/Vol-1837/paper16.pdf |volume=Vol-1837 |authors=Gennadiy I. Linets,Svetlana V. Govorova,Sergey V. Melnikov,Viktor V. Medenec |dblpUrl=https://dblp.org/rec/conf/ysip/LinetsGMM17 }} ==A Model for Transformation of Self-Similar Traffic into Poisson's Arrival Packets== https://ceur-ws.org/Vol-1837/paper16.pdf
                      A Model for Transformation of Self-Similar
                        Traffic into Poisson’s Arrival Packets
         Gennadiy I. Linets,     Svetlana V. Govorova,        Sergey V. Melnikov,        Victor V. Medenec,
          kbytw@mail.ru           mitnik2@yandex.ru          territoreer@yandex.ru      Alximik2012@mail.ru


                            North-Caucasus Federal University, Stavropol, Russian Federation


                                                         Abstract
                         Using functional transformation, we propose an approach allowing to
                         convert a self-similar input packet stream of multiservice traffic and to
                         obtain a stream with the properties of the elementary stream and the
                         variation coefficient equal to one.



1 Introduction
    When used in transportation networks, various control mechanisms inevitably experience nonlinear dependence due
to the objective limitations of the available resources leading to various conflict situations and manifestation of the
fractal properties of the network load, which cannot be resolved by simple methods. If the flow control mechanisms are
not used in transportation networks, the network traffic demonstrates fractal properties to a lesser extent. The problem
arises with the use of flow control and congestion avoidance mechanisms, when additional non-linearity appears. In such
situations, the relation between traffic fluctuations and network control mechanisms may become complex. The problem
of the correct allocation of network resources becomes particularly acute in such situations. The arising non-linearity
with possible dynamic behavior of systems in packet based networks results in the manifestation of random properties,
which entails the following problems.
    Required:
1. To check the network traffic for self-similarity.
2. To measure the numerical values of the Hurst exponent.
3. To know the change rate of traffic characteristics when subjected to network management tools in the course of
transport networks operation.
4. To assess the impact of traffic on the productivity and efficiency of network management tools.
    In reality, the traffic verification for self-similarity is an extremely difficult task. The problem is that the real world
always operates finite datasets. Therefore, checking whether a route is self-similar is usually an impossible practical task.
It is important to explore various self-similarity properties in real traffic. The difficulty is that even if certain self-
similarity properties are confirmed, it does not conclude that the analyzed data are self-similar in structure, as other
impacts may cause the same traffic characteristics (for example, the arising transiency). Some transient processes (such
as processes with bias levels) may result in similar properties. This means that the pulsing network traffic can be caused
by both long-term dependence and transiency of the observed process. Studies have shown that the present transiency
may result in wrong conclusions when analyzing the results of self-similarity tests. It is also essential to apply
background information on the change rates within the critical values of self-similarity parameters. This would allow: to
simulate such processes in a real network environment, generating processes with given characteristics; to study the
transport network response when its inputs are exposed to self-similar traffic; to compile practical steps for self-similar
traffic management; to obtain analytical dependencies prior to optimization of the topological structure of transport
networks.

2 Current Problem Analysis
   The study of self-similar traffic management issues in the early stages of its development [She07]. The scale invariant
traffic structure brings new complexity to the overall picture of the transport network management, which complicates
the task of providing the required quality of service and efficient use of resources. The pulsating traffic structure with
self-similar properties implies the existence of congestion (high activity) periods in long time periods, which negatively
affects the overload management. However, the long-term dependence inherently implies the existence of an unusual

Copyright c 2017 by the paper’s authors. Copying permitted for private and academic purposes.
In: S. Hölldobler, A. Malikov, C. Wernhard (eds.): YSIP2 – Proceedings of the Second Young Scientist’s International Workshop
on Trends in Information Processing, Dombai, Russian Federation, May 16–20, 2017, published at http://ceur-ws.org.

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traffic correlation structure, which can be used for handling the so-called overload control. Shelukhin et al.[She07]
demonstrate the possibility of forecasting random processes in terms of self-similar traffic transmission with high
reliability and at long time intervals. To achieve this, they propose a traffic regulation mechanism based on the multi-
scale structure of overload control, which may be used to enhance the efficiency of the network functioning [She11].
     The pulsating traffic structure invariant to the scale impacts the quality indicators and performance of a network and
is incompatible with the traditional models of network traffic. Therefore, it is an extremely important practical task to
determine the causes and reduce the consequences of self-similarity influence. When developing efficient integrated
network structures, within which the guarantee of the requested QoS (Quality of Service) is maintained using the
resources to the maximum effect, the issues of understanding and justification of self-similarity based on the physical
principles of the real network environment take the primary focus.
     Having analyzed 717 reference sources (mainly US), the authors present the main factors that may produce various
types of long-term dependence of network traffic [She07]: user behavior; data generation, structure and retrieval; traffic
packing; network control means; closed-loop control mechanisms; network development. It is noteworthy that the effect
of such mechanisms allows to impact the traffic structure by changing its nature, and if self-similarity is already inherent
in the traffic, in some cases it is reinforced [Lel94]. However, it is difficult to imagine that based on such factors, self-
similarity can occur independently. The emergence of fractal properties of traffic at the application level is possible only
where the source itself is a chaotic dynamic system generating traffic with self-similarity properties, which is unlikely.
[Yaz06]
     Numerous measurements have demonstrated that such traffic structure is not an irrelevant side effect but a unique
feature developed within the existing distributed network structures with intermediate accumulation, which include
modern transport and telecommunications networks. Therefore, it is natural to believe that self-similarity is based on just
one causative factor, which, despite the diversity of manifested forms, incorporates their entirety, by the same method of
information processing [Lel94]. Hence, self-similarity is an inherent property of packet networks.
     The statistical properties of flow packets are determined by the following factors [Lel94, Mil03]:
1. Randomly nature of traffic as a bit stream generated by the information source.
2. Specifics of the transformation of the bit stream into the packet stream subject to the technological mechanisms of
transformation.
3. Task-specific transformation of the flow in course of aggregation in order to improve quality indicators.
     Since in such three cases the packets arrive irregularly, the time interval between successive arrivals of packets is a
random value [Mil03]. The statistical characteristics and the structure of the received packet stream, in turn, are affected
by a range of factors [Lel94]:
a) Specifics of operating systems with time division. Each process in the system developing in the "virtual time",
primarily subject to the available resources. Within the process of transmitting information from the application to the
link level, the time intervals between the phases of the pack formation are uneven, even if the generated data flow is
uniform.
b) The dynamics of the information application work using the means of interworking is an important factor in
determining the nature of an aggregated data stream. An application may generate data at a rate determined by the
available resources (buffer memory and bandwidth of the communication channels).
c) Implementation of the transport layer protocol. It provides reliable packet delivery and regulation of their rates with
the use of a closed feedback loop between the receiver and the data source.
d) Features of link level protocols, such as collision, occurring at the division of the transmission medium increase the
time intervals between the packets with the growing link loads. This is particularly evident in networks using TCP/IP
protocols implementing "window management". According to [She11], the traffic not exhibiting any self-similar
properties previously, having gone through the network hubs is transformed into a network fractal.
e) Characteristics and administrative restrictions imposed on the intermediate network nodes in order to ensure the
specified service quality parameters.
     More complex relations in a data stream arise with the use of ATM and Frame Relay protocols which imply
integrated quality control functions for virtual connections using buffering, prioritization and protection strategies
[Lel94]. In this case, traffic shaping is focused on changing the flow packet characteristics compounding the virtual path
or channel so as to reduce the peak rate, limit the pack length or reduce the delay time by arranging the pack in time, as
well as to plan the traffic (Traffic Shaping). The right for traffic shaping is provided to both network operators and users
in order to agree on its parameters, passing through the "user network" interface, with an agreement on the traffic. For
network operators, traffic shaping becomes an effective method of the optimal use of network resources by the "delay-
performance" criterion [Lel94].
     One of the properties of multiservice traffic is its structural complexity, which is characterized by the variation
coefficient c(). The variation coefficient c() is the dispersion characteristic of the pack flow defined as the ratio of the
mean standard deviation () of the values of time intervals between the arrival of successive packets to their expected
value m(), i.e. с(  )   (  ) / m(  )
     Multi-service transport packet streams of modern telecommunication networks are characterized by transiency and
self-similarity, which, unlike the pack flows with Poisson distribution, have a variation coefficient greater than one, i.e.
 c(  )  1 . According to [Čuč09], the efficiency of using network resources for the traffic with the packet stream with




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Poisson distribution is much higher than the self-similar packet stream with the properties mainly described by Hurst
coefficient H.
   The work proposes a model, based on the functional conversion used to reduce the structural complexity of the self-
similar input stream pack and to obtain a stream with the elementary stream properties and the variation coefficient is
equal to one.

3 Problem Statement
    Based on the research target, we assume that the input packet stream G (τ 1) is subjected to the identification by the
known analytical techniques so as to determine its self-similar properties. We assume that the identification established
the time intervals distribution density between the packets G (τ1) as described by the Pareto Law. The function mapping
link of the switching node converts the distribution density of time intervals between flow packs G (τ 1), into the
exponential law G (τ2).
    As a result of the function mapping of the density distribution of time intervals between flow packs G (τ 1), its
structural complexity was reduced to one, creating stream G (τ 2) with the properties of the elementary stream.
    It is required to:
1. Develop a model converting the input packet stream G (τ1) with the distribution density of time intervals between
packs as per the Pareto Law and structural complexity c(  1 )  1 , into the flow G (τ2) with the density of time intervals
distribution between packs described the an exponential distribution law and with the structural complexity of c(  2 )  1 .
2. Find a functional link between the Hurst exponent and the variation coefficient determining the structural complexity
of the input packet stream with known self-similar properties.
    To ensure the solution accuracy we have introduced limitations:
1. Pack length L0 is a fixed value;
2. The length of the time interval τi is determined by the time of the pack forming in the buffer;
3. At relatively low values of the pack length L0 with a small error, the mean value of the process rate r ср may be
replaced by the instantaneous rate r(t) in the interval, i.e. rср = r(t);
4. The average value of the process rate in the interval τ generates a pack with the length L0, i.e. rср   = Lо;
5. The random variable Z has a distribution with a heavy tail, if the probability is PZ  x  cx  a , x   , where 0  a  2
is a tail index or a shape parameter, c is a positive constant [She11];
6. The correlation function R( t1 ,t2 )  M ( X ( t1 )  m )  ( X ( t2 )  m ) is invariant with respect to the burst shift, i.e. that is,
 R( t1 ,t2 )  R( t1  k ,t2  k ) for any t1 ,t2 , k  Z . It is expected that the first two points exist and are finite: m  M X ( t ) ,
 2  M X ( t )  m . Here, M (  ) is the averaging operation; m is the first central point;  is the dispersion of process X
                                                                                                         2



(t);
7. Random process X (t) is exactly self-similar to the second-order process with the Hurst exponent H (1/2