quity, and the advent of internet services have given service providers ... zing Ip networks in a hybrid IGP/MPLS environment", considers the routing design of ...
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Foreword Traffic engineering and routing
Advances in telecommunications networks have enabled the deployment of multimedia applications that are gradually being used in dayto-day life, integrating both data, voice and video. These applications are now entering new networked environments which encompass mobility and ubiquity. The development of new access and transport technologies which offer higher bandwidth, the deployment of mobile communications such as UMTSand WlANS which allow for universal ubiquity, and the advent of internet services have given service providers the opportunity to offer seamless services that require end-to-end performance and Quality of Service (QoS). In addition some services, such as peer-to-peer or grid applications which add dynamicity and complexity to networks, are greatly impacting network traffic. They therefore shed new light on issues related to the design, control and performance of networks and services. These new applications for networks which use the m protocols and paradigms now create a critical need to measure, characterize, and derive tractable models for m and mobile. Existing methods for traffic engineering and routing have once again to be revisited in this new context. The deployment of such networks has given rise to many issues that require further fundamental analysis in order to provide useful guidelines for engineering design. This is the subject area of this Special Issue of Annals o f T e l e c o m m u n i c a t i o n s which considers teletraffic in the context Of lP and advanced mobile networks. The impact of real applications on network traffic remains a very. challenging and important issue, since it should strongly influence the nature of the models to be used for network dimensioning and performance evaluation. The first paper in this Special Issue on "A f l o w - b a s e d a p p r o a c h to m o d e l i n g ADSL traffic on an IP b a c k b o n e link" by Nadia Ben Azzouna, Fabrice Clgrot, Christine Fricker and Fabrice Guillemin, deals with this issue and carries out a detailed flow analysis to derive a mathematical flow-level model from real data on an ADSL backbone link. Based on the well-known Mice/Elephants dichotom3; this paper provides useful insight and also considers peer-to-peer traffic which today represents a significant fraction of overall traffic. Further decomposition of traffic measurements helps to derive a simple flow model for each identified traffic catego~.
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The second paper by Sem Borst, Rudesindo Nunez-Queija and Bert Zwart, entitled "Bandwidth sharing with heterogeneous flow sizes", tackles another important issue in Traffic Engineering, i.e. resource allocation in It" networks. As in the previous paper, the authors consider that traffic can be represented according to the Mice/Elephants dichotomy exemplified by two heterogeneous traffic classes. They then derive a flow model that allows for optimal sharing of bandwidth in network elements that use a Processor-Sharing discipline. This model is used to analyze the mutual effect of both traffic types on each other, and to advocate for the implementation of a call admission policy so as to reduce the adverse impact on transfer delays. The next paper authored by Thomas Bonald, Philippe Olivier and James Roberts, "Dimensioning IP access links carrying data traffic'focuses on access link dimensioning in IP networks. Access indeed represents a critical aspect in network design since it concerns resources that are scarce (and likely to be congested); they are also more expensive to provision than in the backbone network. Therefore consistent models have to be derived in order to adequately determine the amount of resource that has to be provisioned in the access part, whilst offering a pre-defined grade-of-service. The authors establish a performance flow-level model that relates demand, capacity and QoS. As in the paper by Borst et al., they assume perfect bandwidth sharing modelled via the Processor-Sharing discipline. The paper focuses on data traffic only. The proposed flow-level model is easily tractable for design purposes and allows for the analysis of various traffic demand configurations. The paper by Peter Key, Laurent MassouliL Alan Bain and Frank Kelly, "Fair Internet integration: network flow models and analysis" considers a fluid model to analyze performance in Ie networks. The authors consider elastic traffic, which represents data transfer traffic (prominently TCe traffic), and streaming traffic which mahdy represents UDP traffic. Modelling two types of traffic having different QoS constrainst allows the authors to analyze the bandwidth sharing mechanism and to consider the stability of te networks. Based on their analysis, the authors conclude on the positive effects of streaming and elastic traffic integration together with the implementation of call admission. The work by Onur Alparslan, Nail Akar and Ezhan Karasan, "AIMDBased online MPLS traffic engineering for TCP flOWS via distributed multipath routing" proposes a flow-based scheme for routing rcP flows in MeLS networks. The authors suggest the use of multi-paths for traffic which is routed between primary and secondary path at the MPLSnetwork edges to improve the performance Of TCP traffic. The following paper by Eueung Mulyana and Ulrich Killat, "Optimizing Ip networks in a hybrid IGP/MPLSenvironment", considers the routing design of Lses in an I6e/MeLS network. Combining the features of both 1GP routing and MPLS, they suggest the use of genetic algorithms for traffic engineering in order to guarantee performance while reducing the corn-
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plexity of constructing Lsps. The proposed approach is evaluated in the context of the German research network B-Win. Hieu T. Tran and Richard J. Harris address multicast applications in their paper entitled "QoS multicast routing with delay constraints". As in the previous paper, they propose a genetic algorithm heuristic to compute a source-based tree for multicast routing under delay constraints. The paper mainly focuses on the performance of the proposed algorithms and on their comparison with other schemes in order to recommend a combined approach that is feasible and efficient. The next two papers of this issue focus on the teletraffic challenges of cellular networks. The paper "Analysis of flow transfer times in IEEE 802.11 Wireless LANS" by Remco Litjens, Frank Roijers, Hans van den Berg, Richard J. Boucherie and Maria Fleuren presents an approach that encompasses both packet and flow level modeling in order to estimate throughput and transfer times in WLANs. The resulting analytical model appears to be tractable and allows the authors to evaluate the performance of w~Ns under various scenarios. Finally, Salah-Eddine Elayoubi, Tijani Chahed, Mazen Tlais and AbedEllatif Samhat present a call admission mechanism in UMTSnetworks in their paper on "'Measurement-based admission control in UMTS". The authors use the concept of effective bandwidth to develop a call admission control algorithm for both the uplink and downlink connections. They also introduce a prediction mechanism based on real-time measurements that allow the admission control to handle priorities between existing and future calls as well as to account for different traffic classes. In addition to these papers which focus on analytical and computational aspects of traffic engineering, the work by Philippe Cinquin, Yves Devillers, Annie Gravey and Elodie Larreur on "Network services and traffic engineering methods for supporting applications on the VTHD experimental gigabit network" describes how traffic engineering methods have
been implemented in an experimental network in order to support the needs of advanced network applications and services. The experimental network was developed in the framework of a national collaborative project and the traffic engineering issues considered range from metrology and QoS to routing and optimization. A variety of services such as multicast and active networks, as well as of end-user services such as telemedicine, videoconferencing or grid computing, are considered in this experimental network composed of heterogeneous equipment. As such, this paper provides a good example of how the fundamental aspects detailed in this Special Issue can be applied. As Guest Editors, we have been very pleased to organize this special issue and to introduce the various contributions which each deal with a typical issue regarding traffic engineering, including routing. In this way, we have attempted at providing a snapshot of the problems which are under study in the framework of lP and mobile networks: we hope to have provided the readers with a consistent flavour of these issues. We are grateful to the authors who have accepted to contribute this special ANN.TI~LI~COMMUN.,59, n° 11-12, 2004
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issue with highly relevant papers. We also sincerely thank the many experts who have thoroughly reviewed the papers and therefore contributed in the high quality of this Special issue dedicated to Traffic engineering and routing. Prosper C H E M O U I L France Telecom Research and Development 38-40, rue du Grnrral Leclerc 92794 Issy-les-Moulineaux Cedex 9 - France prosper.chemouil@ francetelecom.com Professor Erol GELENBE Dennis Gabor Chair Dept of Electrical and Electronic Engineeringg Imperial College London SW7 2BT - UK e.gelenbe @imperial.ac.uk
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