Implementing Service Quality in IP Networks / Edition 1

by Vilho R is nen

Overview

While more and more data is shifted from circuit-switched to packet-switched networks, the users of these networks expect a smooth, continuously unproblematic service (unrelated to the amount of data transported). Therefore, the reliability of a network as well as the satisfaction of its users relies largely on Quality of Service (QoS). Service quality through resource management in IP networks will ensure that sufficient resources are available to fulfil the delay of applications and packet loss requirements.

This year several books on QoS from the angle of operators/engineers have been published HOWEVER, none of these titles tackle the management side of the problem. This book shows how to determine quality requirements of services, it discusses and considers the various means of allocating network resources and of supervising the service quality. Furthermore, it explores strategies for allocating network resources and their relation to revenue or operator utility as well as service allocation optimization. The book concludes with a Nokia case study that illustrates the previously mentioned concepts.

Essential reading for networking professionals wishing to understand service quality management in IP networks, as well as students needing to understand principles and basic techniques of service quality management.

Product Details

ISBN-13:	9780470847930
Publisher:	Wiley
Publication date:	04/02/2003
Pages:	312
Product dimensions:	6.90(w) x 9.90(h) x 1.00(d)

About the Author

Vilho Räisänen is the author of Implementing Service Quality in IP Networks, published by Wiley.

Read an Excerpt

Implementing Service Quality in IP Networks

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By Vilho Raisanen

John Wiley & Sons

Copyright © 2003

Vilho Raisanen
All right reserved.


ISBN: 0-470-84793-X

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Chapter One

Drivers for the Adoption
of Multi-service Networks

Digitalization of entertainment and other consumer content makes
it possible to use available transmission media resources more efficiently,
to use universal storage solutions for the content while
providing end user quality experience equal to or better than analogue
media. This leads to the need for speech, music, pictures
and streamed content to be delivered to homes and mobile users
in digital form. Content delivery channels of this type exist or
are becoming available in the form of digital telephone networks,
digital mobile network systems and digital television. These technologies
are examples of mostly single-service networks at the
moment, although so-called "2.5 generation networks" (2.5G) can
already be used for transmitting pictorial and data content. The
challenge of the near future is to provide all kinds of services
over single delivery channels in a cost-efficient manner. Facing this
challenge in Internet Protocol (IP) based networks is the topic of
this book.

Conceptually, there are three parties involved in such a delivery
chain. The digital content is produced by aservice provider,
delivered to the end user by the network operator, and used
by a customer. Let us next study the implications of the situation
referred to above from the point of view of these three
parties.

In this section, only the access network operator viewpoint is
considered. We shall return to the interrelations of access and
backbone network operators later in this book.

1.1 CUSTOMER PERSPECTIVE

Currently, a home user is typically using multiple access technologies
for communication.Wireline telephony ("Plain Old Telephony
System, POTS") and cellular phones are used for two-way speech
delivery. Digital cellular phones also support text and picture
form messaging. Broadcast TV and radio are used for receiving
audio and video content such as news and entertainment. Usage
may be associated with a "flat-rate" subscription for the service or
be free of charge. Cable TV infrastructure may be used as a transmission
medium for paid audio and video content, in addition to
being used for the distribution of broadcast programs. Paid content
may be billed based on flat-rate subscription or usage-based.

Internet access can be handled via POTS local loop, Integrated
Subscriber Digital Network (ISDN) over POTS, some variant
of Digital Subscriber Line (xDSL), or a cable modem. Recent
additions to the repertoire include wireless broadband access
using meshed wireless routers or Wireless Local Area Networks
(WLAN). Each of these technologies is associated with a delivery
channel, as illustrated in Figure 1.1.

A noteworthy aspect of this situation is that the reception of
different service types is based on different kinds of technology:
POTS telephony and broadcast TV/radio are based on analogue
technology, whereas Internet access and cellular telephony (in
Europe and increasingly in other continents as well) is based on
digital technologies. Thus, the home user currently needs a POTS
telephone, radio receiver, TV receiver, radio receiver, cable TV set-top
box, personal computer (PC), and xDSL Customer Premise
Equipment (CPE). The mere existence of different kinds of equipment
is no bad thing as such; it is often good to use equipment
specifically designed for one service to have optimal usage experience.
What is not optimal is the inability to receive all types of
content in a single type of device, say, PC, if need be.

Second, with the exception of telephony and Internet use, the
services are typically one-way "broadcast" type of services with
an associated usage fee. This arrangement is rather inflexible; a
subscriber of such a service pays for all types of content and not
only the types the subscriber is interested in. Also, the selection of
the content "on-demand" basis is highly desirable. Digital TV is
now taking its first steps in Europe. Digital TV technologies allow
for interactivity to complement the distribution of the content over
the digital TV channel. This is a step in the right direction.

Third, the traditional arrangement ties the end user to a single
"access network" provider who is also the service provider.
Competition for the local loop access has not always succeeded
optimally. Thus, for each of the access technologies, the customer
has to pay a price that is not determined by competition in
a free market.

Fourth, messaging-type services have become popular recently,
allowing users to send notices to other users in near-instant fashion.
In addition to "traditional" e-mail, other examples of messaging
include the Short Message Service (SMS) and the Multimedia
Message Service (MMS) of GSM/GPRS (Groupe Special
Mobile/General Packet Radio Service) networks, and messaging
on the Internet. Such messaging requires that users are "on-line"
in order to receive messages addressed to them. In addition to
telephone networks, this is possible for Internet messaging using
xDSL and with the communication endpoint (PC) switched on.

Collecting some of the observations made so far, a wish
list of the customer for information access technology would
look as follows.

Communication endpoints (e.g. PC, mobile terminals) should
support accessing of different kinds of services. Dedicated terminals
such as TV sets can be used when optimal usage experience
or storing of received content is important.

Converged access network systems should support the delivery
of all kinds of services. The same network should support delivery
of messaging, data, and streamed content as well as being
suitable for supporting conferencing-type applications.

The end-to-end delivery chain should make it possible to
separate provision of services from provision of access to
services. This allows the choice of the most adequate access
technology according to the usage situation. Specific details of
the access medium should be as invisible to the user of the
service as possible.

Interactivity should be possible, in addition to receiving
broadcast or downloaded content. Specifically, support for near-instant
messaging is highly desirable.

1.2 NETWORK OPERATOR PERSPECTIVE

The business need fulfilled by the network operator is to provide
access to service types for the customer. Depending on access
technology, the competition is more or less fierce. In copper local
loops, for example, incumbent network providers are challenged
by new entrants, cable modems, and wireless access technologies.
In cellular networks, to take another example, most countries
have multiple operators. Due to competition, operators need to
consider both capital expenditure (CAPEX) and operating expenditures
(OPEX) of their network technology platform. In brief,
CAPEX considerations lead to the goal of utilizing built capacity
as efficiently as possible, whereas OPEX aspects boil down to
streamlining and automatization of technological solutions in use.
Both of these aspects will be discussed in this book.

The progress of content digitalization, the advent of new services,
and expectations of interactivity and converged technology
platforms pose further challenges to the access network operators.
It is in the interest of operators to develop technological platform
support for advanced service types.

The convergence of the multi-service network has been a
technological goal of the telecommunications industry for a long
time. One of the first attempts was narrowband ISDN (Integrated
Services Digital Network), supporting up to eight ISDN terminals
within the customer's premises and providing two simultaneous
circuit-switched connections from a single ISDN CPE using ISDN's
2D + B channel technology. Alas, business adoption of ISDN
occurred fairly late, in Europe during the latter half of the 1990s. In
ISDN, the bit rate of a single channel was limited to 64 or 56 kbit/s
because of the (Analogue/Digital) A/D conversion used in digital
POTS network.

The next attempt was broadband ISDN, also known as Asynchronous
Transfer Mode (ATM). ATM has advanced multi-service
capabilities and can support high bit rates. As a result of a long-drawn
standardization effort, the final ATM standard is fairly
complex, and failed to be implemented end-to-end. An issue that
became evident after taking ATM into production use, the management
of ATM networks is complicated. In addition to managing
the ATM network as such, the operator also needs to manage
the protocol layers below (for example, Synchronous Digital
Hierarchy, SDH) and above (for example, Internet Protocol, IP)
ATM. Subsequently, in the Internet domain ATM is mostly used
in backbone networks where the configuration is often static.

In the late 1990s, it turned out that the winning convergence
layer was IP. The main reasons for it being victorious stem from
existing wide-scale adoption of the technology in the Internet and
IP not being "owned" by a only a handful of vendors. In Internet
design philosophy, the state is maintained at the communication
endpoints and not in the network, allowing for cost-efficient
design of networking equipment. IP is a good convergence layer in
the sense that it can be run over multiple link layer technologies,
including ATM. On the applications side, the Internet Engineering
Task force has developed - and keeps on developing - a rich set
of protocols for interfacing different kinds of service applications
to IP using "Layer four" (L4) protocols such as Transfer Control
Protocol (TCP) and User Datagram Protocol (UDP). In particular,
the standard socket programming interface towards IP and
multiplexing protocols such as TCP and UDP is well known.

The adoption of IP in different Internet access networks together
with the rapid growth of Internet usage has brought with it very
rapid growth of traffic volumes in the network. At the time of
writing, this growth has slowed down due to economic factors,
but growth is expected to continue once a new wave of services
becomes available. This fast growth has led network operators
and other involved parties to pursue the goal of optimizing the
protocol stack. A protocol stack of IP over ATM over SDH over
Wavelength Division Multiplexing (WDM) is not optimal, neither
from CAPEX nor from an OPEX point of view - at worst, all the
protocol layers require software and hardware support as well as
trained maintenance personnel.

Light protocol stacks such as IP over 802.X in copper-based
networks or Internet Protocol/Multi-Protocol Label Switching
(IP/MPLS) over WDM have received lots of deserved attention
on the commercial side as well in research and standardization.

In brief, network operators are looking to light protocols stacks
with IP as the unifying end-to-end layer as a multi-service support
platform of the future. To accomplish this goal, management
of multi-service Internet needs to be made more streamlined
than that of ATM.

1.3 SERVICE PROVIDER PERSPECTIVE

Service providers compete in their ability to provide best service
selection to the customer at the best price. This goal can be pursued
by different strategies: providing a set of services and network
access in "bundled" packages, or by providing innovative services
with shortest time-to-market delay, for example.

It is in the interest of service providers to be able to provide
services to as wide an audience as possible with as small an overhead
as possible. The former goal leads to the ability of accessing
the services with multiple technologies being desirable, with market
mechanisms ensuring the interests of both the customer and
the service provider. The latter goal means in practice that the
service provider should be able to provide services for different
access methods with as little tailoring as possible. The tailoring
cannot always be fully avoided, as is the case with saving
streamed content in the server in multiple encoding formats, but
the per-access technology tailoring (conversion) can be made as
automated as possible.

The service provider wants to have a flexible mechanism
towards the network operator in providing services with
appropriate service-specific parameters specified as simply as
possible. The contractual interface between the service provider
and the network provider should be flexible to allow for the quick
implementation of novel service types.

Eventually, the time-to-market consideration ultimately comes
down to the abstract multi-service network interface being as
streamlined as possible. With such an interface, service creation
efforts can be concentrated on the construction of the new service,
instead of having to manage a multitude of access-technology
specific parameters.

1.4 SUMMARY

Having a single end-to-end convergence layer is in the interests
of all parties, namely customers, network operators and service
providers. The Internet Protocol (IP) emerged from the period of
rapid technological development during the late 1990s as the winning
candidate. Converged IP-based delivery of content service
allows IP to be used as the common denominator for services
above it, as well as different access technologies beneath it. Architecture
of this type is illustrated in Figure 1.2.

Different technologies can be used beneath the IP layer to support
delivery of services to the customers. The link layer access
network technology can be chosen according to the customer's
momentary needs. From the operator viewpoint, the transport network
connecting to the end user link should advantageously be
implemented with as few protocols as possible for flexibility, and
should make as good use of the installed capacity as possible. The
latter requirement, typically specific to access network operators,
leads to the need to implement service quality support mechanisms
in the network. Such mechanisms need to be implemented
either on the link layer, or in the IP layer. This is the main topic
of the present book.

Having a well-defined interface to specify the requirements of
services is important for service providers. A central theme in
service definition is service quality specification. In the following
chapters, we shall study the generic requirements of different service
types, network-sides service quality mechanisms in Internet
Protocol networks.

Another major area of interest in this book is the management
of services within a network domain, as well as between
different parties of the end-to-end delivery chain. Technologies
and the techniques for implementing this constitute a major
part of this book.

(Continues...)

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Excerpted from Implementing Service Quality in IP Networks
by Vilho Raisanen
Copyright © 2003 by Vilho Raisanen.
Excerpted by permission.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.

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Table of Contents

Preface.

Acknowledgements.

List of Figures.

List of Tables.

Abbreviations.

Drivers for the Adoption of Multi-service Networks.

Service Quality Requirements.

Network Mechanisms for Multi-service Quality Support.

Traffic Engineering for Multi-service IP Networks.

Mapping Service Requirements to Network Resources.

Service Level Management Techniques.

Measurements.

Mechanisms for Dynamic Service Quality Control.

Case Study: Service Quality Support in an IP-based Cellular RAN.

Conclusion.

References.

Index.