Technical University of Denmark,

Research Center COM – Communications, Optics and Materials

Technical University of Łód�

International Faculty of Engineering

Traffic engineering with MPLS

in core networks

Supervisors:

Lars Dittmann - Associate Professor

Henrik Christiansen - M.Sc.E.E., Ph.D. Student

Co-supervisor:

Sławomir Hausman - M.Sc., Ph.D.

August 2003 Master’s Thesis by

Emilia Dobranowska (Student number: s002758)

Emilia Dobranowska

Traffic engineering with MPLS in core networks

Emilia Dobranowska

Traffic engineering with MPLS in core networks

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Abstract

Farsighted anticipation and future network planning activities are issues concerning

both operators and users. The complexity of heterogeneous next generation solutions imposes

serious demands for technology interoperability and openness.

The status of current networks reveals problems associated with rapid traffic growth

rates, demands for qualitative traffic treatment and effective network resource utilization.

These challenges are addressed by Traffic Engineering (TE) practices. Analysis of TE

functions points out main objectives for controllable and accountable traffic organization

within the network. In this perspective there is Multi-Protocol Label Switching (MPLS)

technology emerging as a promising solution for the cores. The most encouraging benefits

come from separation of control and forwarding planes, which can result in enhanced

scalability and flexibility.

The main theme and objective of the thesis is investigation of TE potential of MPLS

technology. The study exposes MPLS means of implementing TE as well as methods for

providing resiliency. The subjects are presented in a broad context with research focused on

MPLS internal operation, its signalling protocols, and network resiliency concerns.

The MPLS TE features are verified by network model implementations and

simulations performed with OPNET Modeler tool.

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Acknowledgements

This Master’s Thesis is developed at Research Center COM at Denmark Technical

University (DTU) in collaboration with International Faculty of Engineering at Technical

University of Łód�.

I would like to thank my supervisors, Lars Dittmann, Henrik Christiansen from DTU

and Sławomir Hausman from Technical University of Łód�. The thesis would not have been

completed without their appreciation and trust in my capacities. I learnt a lot following an

independent study approach pointed out by Lars Dittmann. I appreciate help I received from

Henrik Christiansen who devoted his time to assist me in works on OPNET implementations. I

would like to thank Sławomir Hausman for his support and for giving me the chance to

develop the thesis abroad.

I am grateful for honest and invaluable help from Maciej Małycha who provided me

with good programming practices and code optimisation suggestions.

I would like to thank Stuart Glasson for his support and effort to correct my English.

An important acknowledgment is given to Rafał Wilkowski for his constant assistance

and understanding during my studies.

Finally, I sincerely thank my parents for their encouragement and support.

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INDEX

ABSTRACT ...................................................................................................................................1

ACKNOWLEDGEMENTS ...............................................................................................................2

OVERVIEW OF THE REPORT ........................................................................................................4

FOREWORD..................................................................................................................................7

PART I

"NETWORK IDEOLOGY, TRAFFIC ENGINEERING, MPLS, RESILIENCY"……..9

PART II

" IMPLEMENTATION, MODELLING, SIMULATION "………………………….…119

ABBREVIATIONS……………………………………………………………………………..234

REFERENCES…..……………………………………………………………………………..239

APPENDICES….………………………………………………………………………………246

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Overview of the report

The main report is divided into two parts and concludes with closing remarks.

Part I deals with theoretical concepts regarding networking issues.

Chapter 1 introduces fundamental networking models: B-ISDN, OSI, TCP/IP and

abstractions of communication systems. Basic access and core network structures are

presented with sample topologies and transmission means developed over time. It pictures

network foundations and evolution, together with arising problems including inefficient

network resource utilization, traffic congestion and insufficient non-qualitative treatment.

Chapter 2 presents traffic engineering as a solution for concerns indicated in chapter

1. It gives TE definitions specified by ITU-T and IETF and presents TE functions and

practical implementations by means of ATM and MPLS. In the view of present ATM

limitations MPLS approach of split data and control planes emerges as a flexible and

promising solution.

Chapter 3 reveals MPLS technology with its potential towards TE. TE MPLS means

are seen in terms of FECs, traffic trunks, dynamic and static label switching paths mappings,

support for CBR and multiple recovery options.

Fundamental operational MPLS philosophy is augmented with detailed description of

signalling protocols (CR-LDP and RSVP-TE). The protocols are viewed in the perspective of

their capabilities and support for TE. At the end, their features are confronted and discussed

with regards to current and future concerns.

Chapter 4 deals with recovery mechanisms abilities and their employment in the

networks. It includes two main subchapters – one presenting network resiliency concepts and

another on recovery with MPLS.

There is background information introduced regarding failures, resilient network

objectives, availability and reliability. The main theme covers subjects of recovery

mechanisms considered in terms of protection and restoration activities, as well scope of the

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repair and the protection path requisites. To give broader context of the available approaches,

recovery schemes at physical and network layers are reviewed.

Finally, MPLS protection and restoration techniques are described. Example scenarios

are provided to demonstrate MPLS features and their operation. Moreover, prospect proposals

of MPLS innovative approaches are shortly considered.

Part II reports on simulations and discusses their results. It describes an

implementation performed to model and simulate relevant network scenarios. The simulated

situations relate directly to issues brought up in the theoretical part.

In this section one can find introduction of the simulation tool, an explanation of

specific configurations, as well as obtained and analysed results.

The remarks and conclusions are founded on theoretical assumptions aligned with

observed simulated effects. All comments, descriptions, settings as well as notes regarding

results are based on author’s individual view.

Chapter 5 presents general remarks regarding modelling and suggests simulation

practices.

Chapter 6 is dedicated to the implementation studies including network modelling and

simulations with OPNET. The scenarios can be categorized within four main subjects: TE,

topology generation, MPLS performance and recovery mechanisms.

TE simulations show means for improvement of standard Internet routing effects. The

results also reveal additional advantages brought with TE practices such as enhanced

performance of traffic treated according to its type. Global TE is presented in the scenarios to

demonstrate its capabilities in superior resource utilization efficiency. Resiliency engineering

is simulated to reveal its advantages.

Section on topology generation presents innovative mechanisms developed for

automatic topology generation in OPNET. It is considered fundamental framework for further

simulations regarding MPLS performance.

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Then, MPLS performance is evaluated by simulations relating topology factors and

signalling protocols operation.

Further, recovery mechanisms are modelled and simulated in terms of MPLS schemes

available for providing protections for the path. The solutions are compared with regards to

traffic reroute and path recovery times.

Eventually, chapter 7 provides final remarks and conclusions.

At the end, lists of abbreviations and references are presented.

Supplemented appendices contain additional information closing the content of the

report.

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Foreword

Language

The report is prepared to adhere to British English spelling.

Numbering and unit format

Comma notation within numbers (e.g. 1,000) points out an indication of a thousand.

Decimal fractions are indicated with a point (e.g. 0.5 ).

Formatting remarks

Formatting of the report is based on guidelines provided by dr. Sławomir Hausman.

Terminology

Terms used within the project are based on network standards and generally conform

to IETF and ITU-T definitions. However, as the context of the project is very broad

their meaning could be read in a more general context. Additional notes are provided

when terms need to be explicitly described. Some definitions, when not referenced to

the literature, are based on knowledge gathered from lectures and studies over last

years. Many basic definitions are assumed to be apparent, and thus are omitted in the

report.

Reading guidelines

Since the project entails large scope of topics and documentation of the work that has

been done, the report is organized in the way to help readers reach areas they are

interested in. The content of the report is introduces in section on Overview of the

report. The project consists of two main parts: Part I and Part II that start with indices

on their subjects. Chapters start with general objectives or introduction about their

content and end up with summary section. Final notes and conclusions are provided at

the final stage. At the end one may find list of references and abbreviations used within

the report. Additionally, appendices provide supplementary section.

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