Telektronikk 2/3.2001

1 Introduction

Facing the steadily growing portfolio of services

that an IP-based network may support, it be-

comes essential for the operator to design the

network appropriately. Hence, tools for planning

and designing the network are needed. As for

“traditional” networks, a number of scopes and

settings may be given also for an IP-based net-

work. Some of these are described for the Traffic

Engineering taxonomy [Jens01].

A future IP-based network is expected to allow

for service differentiation to be efficiently man-

aged. Naturally, this depends on the cost of

introducing functionality allowing differentia-

tion compared with the gains that can be

achieved. Anyway, running design algorithms

would support an operator to fully exploit the

potential gains. Moreover, design algorithms are

needed even when a single class of service is

supported.

A further argument for executing design algo-

rithms is to find closer estimates for capacity

needed and tuning of traffic flow handling, and

thereby saving investments. Still the ensured ser-

vice levels stated in any Service Level Agree-

ments (SLAs) should be fulfilled. Even when no

strict guarantees are given, the users do have cer-

tain tolerance levels. A central part of carrying

out the design is to have estimates of the de-

mand. This implies that both the parameters and

their values have to be devised and assessed. As

ranges of users and applications appear, devising

adequate categories is not a trivial challenge.

Transporting IP packets has mostly been the

service delivered by the routers. Then more

“advanced” services are supported by a network

operator, like address translation and ensured

performance levels. For a number of cases sepa-

rate servers are introduced, sometimes referred

to as service handlers. An example is the call

handler for supporting telephony in IP-based

networks. Capabilities of such servers can also

be utilised when identifying the efficient net-

work design. That is, the servers may allow for

additional control abilities for handling the traf-

fic flows, like rejecting new flows and recom-

mending routing of flows. Besides support from

servers, other mechanisms also have to be

defined (e.g. ref. [Jens01a]), such as admission

control and policing.

An essential task when designing networks is to

introduce a number of logical networks in the

same physical network. An example is to have

a number of Label Switched Paths (LSPs) as

described in [Jens01a]. Each of these LSPs has

to be routed, its characteristics defined and the

relevant traffic flows mapped onto it. Therefore,

a design algorithm has to find which set of LSPs

to be set up and how the traffic flows relate to

these LSPs.

The main objectives of this paper are to describe

inputs and steps for planning and designing IP-

based networks, ways of characterising the traf-

fic demands, and an algorithm for designing

LSPs in a multi-service network. An overall

planning scope is described in Chapter 2. Chap-

ter 3 describes characterisation of applications

and their traffic flows. When designing net-

works, the network building blocks must also

be characterised. This is treated in Chapter 4.

As network planning and design have been con-

ducted for other networks, a few issues that can

be observed and fruitfully utilised for IP-based

networks, are described in Chapter 5. Then,

Chapter 6 outlines an algorithm for designing a

multi-service network. A few examples applying

this algorithm are given in Chapter 7. To man-

age a network, appropriate measurements have

to be conducted. Although this is treated in sev-

eral accompanying papers in this issue of Telek-

tronikk, a few complementary topics are also

mentioned in Chapter 8.

2 An Overall Picture

2.1 Inputs and Results

When investigating approaches for supporting

services there are several aspects that have to be

looked into. An overview of the main groups of

inputs for such deployment studies is sketched in

Figure 1. Here, a network is to be established or

changed to support the services. Hence, a set of

Planning and Designing IP-based Networks

TERJE JENSEN, METTE RØHNE, INGE SVINNSET,

RIMA VENTURIN AND IRENA GRGIC

Offering a range of services, it is essential for an operator to configure the network such that the perfor-

mance levels are achieved as expected. Hence, for a multi-service IP-based network the mechanisms

available have to be set up to support the service portfolio. Preparing for this, an operator has to have

an apparatus in place to estimate the demands and to design the network. These aspects are

addressed in this article.

Mette Røhne (35) is Research

Scientist at Telenor R&D, Kjeller.

Her main activities include

applied QoS, network design

and techno-economic studies,

performed both in international

and national projects. She re-

ceived her PhD degree in 1999

from the Norwegian University

of Science and Technology.

[email protected]

Terje Jensen (39) is Research

Manager at Telenor R&D,

Kjeller, responsible for co-ordi-

nating projects in the area of

QoS and network design. He

earned his PhD degree in 1995

from the Norwegian University of

Science and Technology. Other

activities include performance

modelling and analysis, dimen-

sioning and network evolution

studies. He was Task Leader in

EURESCOM P806-GI.

[email protected]

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