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ABSTRACT
This article is devoted to the actual topic of our time.
The article describes the QoS classes of multimedia communication networks, the data transfer channel for QoS
classes through the UNI-UNI interface, and the network QoS channel. The article analyzes the methods of
decomposition of QoS indicators in an NGN class network, the principles of constructing an NGN network that are
essential for further research, a set of QoS indicators in an NGN class network, and research results regarding the
decomposition of QoS indicators.
KEYWORDS
Packet switching, multiservice networks, static distribution method, decomposition of quality indicators, QoS classes
INTRODUCTION
Analysis of the principles of decomposition of QoS
indicators in an NGN class network. Principles of
constructing an NGN class network. The evolution of
communication networks is accompanied by the
emergence and spread of new technologies. Their
most massive penetration is observed in networks with
the largest number of users, i.e. in the cellular mobile
network and in the public switched telephone network
(PSTN). The process of upgrading these networks is
aimed at creating the NGN network. This process
involves a complete transition to packet switching
technology and building a network that meets the
Research Article
ABOUT QOS CLASSES OF MULTIMEDIA COMMUNICATION NETWORKS
Submission Date:
December 17, 2022,
Accepted Date:
December 22, 2022,
Published Date:
December 27, 2022
Crossref doi:
https://doi.org/10.37547/ajast/Volume02Issue12-05
Bayjonova Lyudmila Egamberdievna
Senior Lecturer Of The Department Of Electronics And Radio Engineering, Tashkent University Of Information
Technologies Named After Muhammad Al-Kharezmi, Uzbekistan
Journal
Website:
https://theusajournals.
com/index.php/ajast
Copyright:
Original
content from this work
may be used under the
terms of the creative
commons
attributes
4.0 licence.
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VOLUME
02
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basic
principles
defined
in
international
recommendations. Since this process requires the
modernization of a significant amount of equipment of
existing communication networks, it cannot be carried
out in a short period of time. PSTN development
programs at different levels of the hierarchy must be
carefully coordinated so that the process of transition
to packet switching technology is carried out while
maintaining the functionality and quality of services in
communication networks.
The construction of the next generation network is
carried out on the basis of the so-called expanding core
principle. At the initial stage of NGN formation, packet
technologies are used only in the "core" of the
network. First, a long-distance IP network must be
created. Some countries have already implemented
such projects. The cost of such projects is determined
by the size of the country.
With the modernization of urban and rural telephone
networks, packet technologies are beginning to be
used outside the long distance network. This process
consistently involves networks of different levels, so it
can be considered as an expanding core.
Figure 1. shows a model illustrating the options for
establishing a connection between telephone sets of
two local networks. Switching technologies can
change at different points (they are indicated by letters
of the Latin alphabet). These points are located on the
borders with the NGN network. The classical approach
to building NGN is based on the fact that these points
are gradually shifting towards subscriber terminals.
Figure 1. - Interaction of circuit-switched and packet-switched networks
Volume 02 Issue 12-2022
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American Journal Of Applied Science And Technology
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The main criterion for evaluating the functioning of
communication networks is the quality of services,
since a communication service is the product for the
production of which any communication networks are
built. Therefore, one of the important criteria in
choosing solutions, upgrading existing networks,
building new communication networks and their
operation is to ensure the quality of services.
The quality of the provision of most modern
communication services is ensured by meeting the
standards for the physical parameters of the
functioning of communication networks, QoS (Quality
of Service) parameters. The set of these parameters is
defined in ITU-T recommendations and industry
documents. It should be noted that the development
of IT technologies and communication technologies
leads to the development of new services and a change
in perceptions of quality; therefore, it is possible that
the regulations will also evolve.
This article discusses approaches and methods for
decomposition of QoS indicators between UNIs
(between user-network interfaces) for packet
switching technology. Networks built on the basis of
"packet switching" technology are significantly
different from networks that have been implemented
on the "circuit switching" technology. These
differences can be viewed from several points of view.
This article focuses on the differences in traffic QoS
metrics. The main features of packet-switched
networks can be summarized as follows:
•
First, modern packet-switched networks are
multiservice, that is, they serve the traffic of various
services, such as voice, video, and data. Usually they
are built on the basis of the NGN concept.
•
Secondly, for packet-switched networks,
performance
indicators
are
introduced
that
characterize the process of servicing packet traffic.
First of all, these are probabilistic-temporal indicators
and reliability indicators, such as the mathematical
expectation of packet transfer time (IPTD), packet
transfer time variation (IPDV) and packet loss
probability (IPLR).
•
In the tasks of planning and operating
networks of the NGN class, determining the
requirements for their resources (the values of the
throughput of communication paths and the
performance of routers), it is required to evaluate the
numerical values of the parameters that must be
provided in the designed or operated network section.
In the general case, the considered network fragment
(the network of the telecom operator) participates in
the provision of communication services, i.e. only part
of the data transport route passes through it. The
quality standard must be ensured on the entire route,
i.e. between user interfaces UNI-UNI, which in general
can be in networks. To assess the target values of
quality indicators on the designed or operated section
of the network, it is necessary to decompose the main
IPTD, IPDV and IPLR, normalized on the UNI-UNI
section, for all the main network elements [26,1]. In
ITU-T Recommendation Y.1542, there are two
approaches for solving end-to-end IP packet delivery
between two IPSs, the distribution approach and the
impairment accumulation approach.
Based on these two approaches, several methods are
recommended
for
meeting
the
performance
standards, which are given in recommendation Y.1541.
Static methods are divided into the following types:
•
static divider method;
•
static allocation method based on the reference
path;
•
method of weighted elements.
•
pseudo-static method (left for further study);
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•
signaling methods;
•
interval distribution method;
•
method of accumulation of distortions.
In addition, Recommendation Y.1542 lists methods left
for further study.
It is contemplated that methods called "Costed Bids
Method" and "Bid Discovery Using a Global Registry"
may be proposed. These methods take into account
technical and economic factors. This approach seems
to be quite appropriate, taking into account the various
possibilities of the telecommunications market
participants in terms of ensuring the required level of
quality of traffic service. They ensure compliance with
quality of service requirements at a minimum cost for
telecom operators and info communication service
providers.
The div of Recommendation Y.1542 favors the static
allocation method based on the reference path.
Recommendation Y.1542 outlines the key proposals for
a method for decomposing all used traffic quality of
service metrics. In addition, new methods of
decomposition of IPTD, IPDV and IPLR indicators will
solve the problem of concluding service level
agreements - SLA, which are necessary for some part
of customers and telecom operators.
Next, we will consider the decomposition of the most
significant quality indicators IPTD, IPDV and IPLR on
the example of the NGN network model, which
provides for the participation of three telecom
operators in the provision of services. Detailing implies
consideration of one of the most important properties
of the network - its ability to minimize the duration of
IP packet delay by each telecom operator. It is
proposed to take this possibility into account when
distributing income from the type of service provided.
To ensure that the values of traffic quality of service
indicators comply with the standards when
exchanging IP packets between user-network
interfaces, it is necessary to develop new methods for
calculating
them
for
the
next
generation
communication network. Such a method is the
decomposition of traffic service quality indicators. It
should also be taken into account that the tendency for
operators to enter into SLA agreements may lead to
additional requirements for the decomposition
procedure.
There are two main approaches to solving this
problem. The first is to allocate quality metrics to a
finite number of networks that participate in the
organization of the IP packet exchange route between
two UNIs, based on well-known techniques that have
been developed and proposed by the International
Telecommunication Union. The second method is
based on the principles of concluding agreements
between telecom operators, the essence of which is
similar to concluding agreements on the level of SLA
service quality.
The disadvantage of the second technique is that it
does not take into account the state of the NGN
network of each operator involved in the provision of
the service. As a result, in some cases, the quality of
services will be below the required level. The
advantage of the methodology of the International
Telecommunication Union lies in the simplicity of the
calculations used.
The advantage of the technique, which implies the
conclusion of agreements between all telecom
operators whose networks are involved in organizing
the connection, is that it allows you to guarantee the
quality of traffic service. On the other hand, the
method of decomposition of quality of service
indicators that are normalized between a pair of UNIs
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becomes noticeably more complicated. However, if
appropriate methods for calculating the NGN network
are developed, then the advantage of the second
option of decomposition of quality indicators will be
obvious.
General information about QoS classes.
This article discusses all the requirements of network
quality indicators that are used to transfer user
information when using packet technologies [5,67].
They are stated as IP layer specification parameters
and are defined in ITU-T Recs Y.1540 and Y.1543. It can
be noted here that from the user's point of view, these
network QoS requirements are not defined for all
characteristics, but only as part of the data
transmission characteristics.
To determine the QoS classes, the boundaries of the
values of network performance indicators between
UNI-UNIs are defined. [15,1]. In the event that users
(and individual network operators) do not reach the
negotiated capacity exceeded, or the traffic and bearer
contract is available (as defined in Recommendation
ITU-T Y.1540), network service providers are required
to enforce these UNI interface limits together. -UNI for
the duration of the session.
The practical network QoS that is assumed for a given
flow will depend on the distance and "complexity" that
the packet encounters along its path. In this case, the
word "complexity" denotes all potential problems that
are directly or indirectly related to the entire set of
normalized indicators of the quality of service of
multiservice traffic.
Often the quality will be higher than that defined by the
value limits described in the QoS classes (Table 1.). The
symbol "H" in Table 1 denotes an "undefined" or
"unlimited" value. In the case where performance is
related to a specific parameter whose value is defined
as "H", ITU-T does not specify specific requirements for
that parameter. In such a case, any requirements
defined in Recommendation Y.1541 may be
disregarded. Marking a parameter with the value "H"
also means that the performance in relation to this
parameter can be temporarily arbitrarily degraded
over a wide range.
Table 1
–
IP network QoS class definitions and network performance requirements
Network
performance
parameter
The essence
of the
network
performance
requirement
QoS
classes
0
1
2
3
4
5
IP
,
IPTD
packet
delivery delay
(Example 1)
100 ms
400 ms
100 ms
400 ms
1 s
Н
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IP
,
IPDV
Packet
Delay Variation
(Example 2)
50 ms
(Example
3)
50 ms
(Example
3)
Н
Н
Н
Н
IP
,
IPLR
Packet loss
ratio
(Example 4)
1x10-3
1x10
-3
1x10
-3
1x10
-3
1x10
-3
Н
IP
,
IPER
Packet
error rate
(Example 5)
1x10
-3
1x10
-3
1x10
-3
1x10
-3
1x10
-3
Н
Note:
1. Fairly long travel times eventually result in low end-
to-end latency requirements not being met. In some
cases, the IPTD requirements for classes 0 and 2 cannot
be met. All service providers face this circumstance, so
the range of IPTD requirements is divided into several
alternative QoS classes. Delay value requirements for
each of these classes are not prohibited by network
service providers, but are proposed in agreements
where they stipulate, for example, lower delay values.
In accordance with the definition of the IPTD delay
parameter in ITU-T Recommendation Y.1540, the
packet delivery time is included in the IPTD
requirement.
When evaluating these requirements, it was assumed
that the maximum size of the packet information field
is 1500 bytes.
2. The definition of the IPDV parameter requirement
(given in ITU-T Y.1540) is a point-to-point variation of IP
packet delay. See ITU-T Rec. Y.1540 and Appendix II for
more details on the nature of this requirement. For
scheduling purposes, the IPTD delay value constraint
can be derived from the upper limit of the IPTD
minimum delay value; therefore, the 0.999 quantile
limit can be obtained by adding the IPTD value and the
IPDV value (for example, 150 ms for class 0).
3. The value of the delay depends on the bandwidth of
the communication channels. A decrease in latency is
possible if the channel throughput values are higher
than the base rate (T1 or E1) or the packet size is less
than 1500 bytes.
4. The requirements for class 0 and 1 traffic in terms of
the IPLR parameter are based on studies showing that
a setting of 10-3 will not have a significant impact on
speech applications and speech codecs.
5. The value set assumes that the main cause of errors
is packet loss and that the specified value of the
indicator is valid when transmitting packets using IP
protocols over a network with asynchronous delivery
mode.
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The requirements in Table 1 apply to public IP networks
when analyzing network sections between two
measurement points (reference points) that define the
boundaries of an end-to-end IP network. In applying
these guidelines, it is assumed that the required values
can be provided in conventional implementations of IP
networks.
The first column of Table 1 lists the statistical network
performance requirements for which are listed in the
following columns of the table.
The performance requirement for IP packet delivery
delay is an upper acceptable bound for the IPTD value
in a multi-packet flow.
Individual packets of a flow may be delivered with a
delay greater than the limit given, but the average
value of the IPTD delay over the lifetime (observation)
of the flow (statistical estimate of the value) must be
no more than the value defined in Table 1.
The performance requirements for changing the delay
of an IP packet between two breakpoints are based on
an upper bound of 0.999 quantiles of the delay value
distribution (IPTD) for the packet stream. The use of
the 0.999 quantile allows relatively short estimation
intervals to be chosen (for example, the minimum
allowable interval for this estimation is a time interval
during which 1000 packets are transmitted). This
allows for the flexibility of the network model when
designing delay and queue length control buffers in
routers, for which the requirement for an IPLR value of
no more than 10
–
3 must be met. Using smaller quantile
values can lead to an underestimation of the size of the
dejitherization buffer. In this case, the actual packet
loss may exceed the requirement for IPLR (for
example, with a limit of 0.99 quantile, the packet loss
ratio can be 1.1% with the norm IPLR = 10
–
3).
•
The performance requirement for the IP packet
loss ratio is an upper bound on the IP packet loss
for a flow. Individual packets in a stream may be
lost in transit; in a short time interval, the loss may
exceed the limit, but the probability that any
individual packet will be lost during transmission in
the stream should be no more than the established
limit given in Table 1.
•
The assessment of the requirements given in table
1. is carried out as a result of measurements, i.e. not
instantly, but over time. During evaluation
intervals, subsets of the population of useful
packets (defined in ITU-T Rec. Y.1540) are formed.
It is desirable that the assessment (measurement)
intervals be:
•
sufficiently long and allowed to obtain the required
number of packets of the studied stream, taking
into account the actual data transfer rate;
•
long enough to reflect the typical usage period
(lifetime of the bit stream) for the given service.
•
short enough to provide a reasonable balance of
applied performance over each interval (poor
performance intervals should not be hidden in an
overly long evaluation interval, they should be
identified).
•
short enough to address the actual aspects of the
measurement.
To perform telephony-related assessments, the
minimum interval should be in the range of 10-20
seconds with a packet rate of 50 to 100 per second; the
upper limit of the interval should be within a few
minutes. The estimated (approximate) value is one
minute. In any case, the measurement interval value
used should be recorded along with the measured
value, with any expected and confidence intervals. Any
period of one minute must satisfy the requirements of
IPTD, IPDV and IPLR, which are described in Table 1.
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Static agreements for a QoS class can be developed by
attaching marking packets (eg, high-order bits of the
type of service or a differentiated services code
pointer) to a particular service class. The protocols that
are designated to support dynamic QoS requests
between users and network service providers, as well
as between network service providers themselves, are
still subject, according to the ITU, to study [8,5]. By
developing these protocols and support systems, users
and network operators will be able to request and
receive different QoS classes at the flow level. In this
regard, certain technical characteristics required for
different services and applications can be combined,
evaluated and adopted to solve operational problems.
Data link for QoS classes over UNI-UN interfaceI
The packet in each stream usually follows a specific
path. Any stream that satisfies the relevant
performance requirements can be considered fully
compliant with the guidelines set out in ITU-T
Recommendation Y.1541.
We will call the traffic served by the communication
network between user interfaces with the network
(user-network)
"end-to-end"
traffic[44,3].
The
performance requirements between user-network
interfaces are defined for IP protocol metrics
according to IP packet transmission reference events.
These IP requirements for UNI-UNI interfaces apply
from the end user-network interface to the user-
network interface at the other end of the span (Figure
2). Let the route between these two user-network
interfaces pass through several network segments (NS
- Network Segment) and inter-network links that
provide the transfer of IP packets from the UNI
interface at the sender side (SRC) to the UNI interface
at the other end of the destination (DST). The lower
layer protocols, covering the IP layers from layer 1 to
layer
3,
according
to
the
Open
Systems
Interconnection (OSI) model [45], are also considered
part of the IP network. NS network segments (defined
in ITU-T Rec. Y.1540) are equivalent to carrier domains
and may include IP network architectures as described
in ITU-T Rec. E.651 [94] and Y.1231. The data link shown
in Figure 2 is an adaptive performance model from ITU-
T Recommendation Y.1540.
The consumer equipment includes terminal equipment
(TE), such as a host and a router or, if available, a local
area network (LAN). It is assumed that there is only one
user in several applications.
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Figure 2 - UNI-UNI data link for network QoS requirements
The edge routers connected to the terminal equipment
must also act as access gateways. Reference channels
have the following characteristics (attributes):
1)
An IP network can provide user-to-user, user-to-
host, and other connection endpoint options.
2)
Network segments can be represented as areas of
the network between border routers and an
indefinite number of internal routers that perform
various functions.
3)
The number of network segments in a given path
may depend on the offered class of service along
with the topology and geographic extent of each
network segment.
4)
The scope of Recommendation Y.1541 allows one
or more network segments to be used on a route.
5)
Network segments supporting the transmission of
packets in a bitstream may change during its
lifetime.
6)
IP connectivity extends beyond international
network boundaries, but does not follow identical
circuit switching conventions (eg, there may be no
identifiable gateways at the international
boundary).
Network QoS classes. The article deals with the
(currently defined) traffic QoS classes. Each such class
has a certain combination of restrictions on
performance values. 1. The table contains rules that
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indicate the possibility of using each of the traffic
service classes. These rules do not impose restrictions
on the choice of any particular class of service in a
predetermined environment[8,3].
Quality of Service requirements apply to public IP
networks. It is assumed that the QoS requirements can
be
achievable
on
conventional
IP
network
implementations. The network service provider's
obligation to the user is to deliver packets in a manner
that ensures that all applicable requirements are met.
The vast majority of IP circuits claimed to comply with
ITU-T Y.1541 should satisfy these requirements. For
some parameters, performance on short and/or easy
routes can be significantly better than the specified
values.
The evaluation of parameters in the communication
network is carried out according to the data obtained
as a result of measurements (observations). In this
case, the accuracy of the estimates obtained depends
on the number of observations and on the duration of
the observation interval. For the parameters IPTD,
IPDV and IPLR, the estimated time interval is assumed
to be one minute. In any case, both the measured value
and the duration of the observation interval must be
recorded. Any period of time in one minute must
satisfy the specified requirements. Individual Service
Providers may offer agreements with better network
performance values than those provided by the
general requirements.
In the general case, a communication session can be
represented as consisting of three phases -
establishing a connection, transmitting information,
and terminating the connection. ITU-T Y.1540 considers
only the session phase, the IP packet delivery phase.
Recommendation ITU-T Y.1540 defines the following
parameters that characterize the delivery of IP
packets:
IP packet transfer delay (IPTD). The IPTD parameter is
defined as the amount of time required to deliver a
packet between source and destination for all packets,
both successfully transmitted and packets delivered
with errors.
IP packet delay variation (IPDV). IP packet delivery
delay variation, or jitter, is manifested in the fact that
successive packets arrive at the recipient at random
times.
IP packet loss ratio (IPLR). The IPLR loss ratio is defined
as the ratio of the number of packets lost to the total
number of packets in a selected set of transmitted and
received packets.
IP packet error ratio (IPER). The IPER ratio is defined as
the number of packets received with errors divided by
the sum of successfully received packets and packets
received with errors. The IPER value determines the
portion of the IPLR that is due to packet loss due to
corruption. For this reason, there is no point in studying
the value of IPER from the point of view of its
subsequent decomposition.
Also, the ITU-T Y.1541 recommendation defines the
numerical values of the parameters that must be
performed in IP networks on international routes
connecting user terminals [24,2]. Quality objectives are
divided into different QoS classes, which are defined
depending on the applications and network
mechanisms used to provide them.
One of the basic services of communication networks
is a telephone service, so let's consider the basic
principles of its implementation. Among the basic
principles for the construction and development of
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705
)
OCLC
–
1121105677
METADATA
IF
–
5.582
Publisher:
Oscar Publishing Services
Servi
telephone networks, it is advisable to single out three
aspects that are directly or indirectly related to the
issues discussed in the article:
-
network structure at all levels of the hierarchy;
-
indicators of the quality of service for voice traffic;
- - services provided to subscribers.
The telephone network model proposed by the ITU in
the Y series of recommendations is shown in Figure 3.
This model is universal for communication networks of
any kind, including NGN networks.
Figure 3 - Telephone network model proposed by ITU
In the basic network model (core network), it is
customary to conditionally allocate four fragments -
Figure 3. These fragments form the upper levels of the
PSTN hierarchy. The bottom layer is the access
network. Strictly speaking, the access network is an
integral part of any local telephone network. Its
allocation as a separate "cloud" is explained by a
number of important properties of the access network.
CONCLUSION
1. One of the tasks of building communication
networks of the NGN class is to support normalized
quality indicators for the provision of communication
services. It can be provided by monitoring the quality
of service parameters of QoS traffic in a packet-
switched network.
2. The indicators of the quality of service for traffic in
the NGN network are the parameters that have the
greatest impact on the quality of service provision.
These include parameters characterizing the speed and
reliability of data (packet) delivery, defined by ITU-T
recommendations as IPTD, IPDV and IPLR.
3. Ensuring the quality of service provision in the NGN
network is achieved by normalizing these parameters
on the data delivery route, which is defined as the
User premises
equipment
Access network
Core network
Service Support
Tool
PSTN Operator Responsibilities
Volume 02 Issue 12-2022
43
American Journal Of Applied Science And Technology
(ISSN
–
2771-2745)
VOLUME
02
I
SSUE
12
Pages:
32-43
SJIF
I
MPACT
FACTOR
(2021:
5.
705
)
(2022:
5.
705
)
OCLC
–
1121105677
METADATA
IF
–
5.582
Publisher:
Oscar Publishing Services
Servi
route between user interfaces (UNI-UNI). Normative
values of QoS parameters are defined in ITU-T
recommendations for various traffic service classes.
4. In general, the UNI-UNI traffic route passes through
the networks of several telecom operators. Therefore,
the task of ensuring the quality of the service is solved
by the interaction of the networks of all operators
involved in servicing traffic. To solve this problem, the
decomposition of quality indicators (standard values)
into sections of the UNI-UNI route in the areas of
responsibility of each of the telecom operators is
required.
5. Currently, only one of the options for solving the
problem of decomposition of the IPTD indicator is
described in the ITU-T materials. The task of
decomposition of IPLR and IPDV indicators currently
does not have a definite solution. It should also be
noted that the described IPTD decomposition method
does not take into account the peculiarities and
interests of telecom operators.
6. Thus, the development of a method for the
decomposition of quality indicators is relevant. Its
solution, taking into account the interests of telecom
operators, will optimize the relationship between
telecom operators and avoid unnecessary costs for re-
equipment of networks, while ensuring normalized
requirements for the quality of service for multiservice
traffic.
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