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it 5/2006
Schwerpunktthema ���
ScaleNet – Converged Networksof the Future
ScaleNet – Konvergente Netze der Zukunft
M. Siebert, B. Xu, M. Grigat, E. Weis, N. Bayer, D. Sivchenko, Deutsche Telekom AG, Bonn,T. Banniza, K. Wünstel, S. Wahl, R. Sigle, Alcatel SEL AG, Stuttgart,R. Keller, Ericsson GmbH, Herzogenrath,A. Dekorsy, M. Bauer, M. Soellner, Lucent Technologies, Nürnberg,J. Eichinger, C. Fan, F. Pittmann, R. Kühne, M. Schläger, Siemens AG, München,I. Baumgart, R. Bless, S. Stefanov, Universität Karlsruhe (TH)
Summary This article provides an overview of ongoing re-search within the framework ScaleNet1. Considering IP as thebasis transport scheme, the wireless and the wireline worldhave just started to move towards each other. ScaleNet is push-ing this development by evolving a new system concept andby developing technologies2 for Fixed & Mobile Convergence.��� Zusammenfassung Der folgende Beitrag präsen-
tiert die aktuellen Arbeiten des Forschungsprojektes ScaleNet1.Der Einsatz von IP als gemeinsame Transportplattform sowohlfür schnurlose als auch für drahtgebundene Kommunikationführt zu einer immer stärkeren Annäherung beider Welten.ScaleNet treibt diese Entwicklung voran und liefert ein neuesSystemkonzept2 für die Konvergenz von Festnetz und Mobil-funk.
KEYWORDS C.2 [Computer-Communication Networks] Fixed & Mobile Convergence, System Architecture, Ubiquitous Mobility,Overarching Network Functions
1 IntroductionThe convergence of fixed and mo-bile networks is again a hot topic.The first discussion around Fixed& Mobile Convergence (FMC) inthe late 1990s encountered tech-
1 ScaleNet is partly sponsored by theGerman Ministry for Education and Re-search (Bundesministerium für Bildung undForschung, BMBF) within the framework‘Network of Tomorrow’.2 This paper summarizes research under-taken by the ScaleNet consortium with com-plementary contributions from the differentpartners: Alcatel SEL AG, Deutsche TelekomAG, Ericsson GmbH, Fraunhofer Institut fürNachrichtentechnik Heinrich-Hertz-Institut,Lucent Technologies, QUALCOMM CDMATechnologies GmbH, Siemens AG, and Uni-versität Karlsruhe, Institut für Telematik,together with a plurality of subscontractors.
nical, commercial and regulatoryproblems, which limited the avail-ability of products. Nevertheless,many trials and a lot of press hypetook place in the past. However,today’s playing field looks quite dif-ferent: We see massive use of IPfor all types of communication,wide deployment of both mobileand fixed broadband networks, flatrates for data and voice services,and advances in terminal technol-ogy. Therefore major players in themarket started to think about FMCsolutions. Mobile operators havelaunched home offerings, trying toreplace fixed phones and fixed In-ternet access. Wireline operators areoffering converged services based on
dual-mode terminals that can attachto both WLAN and cellular net-works.
All these efforts are just a firststep towards FMC for which theScaleNet framework has been ini-tiated in Germany [1]. WithinScaleNet, academia and industryjointly work from mid 2006 un-til autumn 2008 on the scaleableand converged multi-access opera-tor’s network from tomorrow, fo-cusing on 2010 onwards.
ScaleNet is addressing both ser-vice and network convergence. Themulti-play of services in ScaleNetembraces voice and video telephony,Mobile TV, massively multiplayeronline gaming and Internet access.
it – Information Technology 48 (2006) 5/ DOI 10.1524/itit.2006.48.5.253 Oldenbourg Wissenschaftsverlag 253
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Network convergence is seen as themigration of heterogeneous physi-cal and logical network elements offixed and mobile networks into onesingle (IP based) infrastructure.
Also other projects address net-work convergence, e. g., the ISTprojects Ambient Networks andDaidalos. The Ambient Networksproject addresses amongst othersthe dynamic composition of net-works owned by different operators,whereas the goal of the Daidalosproject is a seamless, pervasive ac-cess to content and services via het-erogeneous networks that supportuser preferences and context. Multi-access networks have also been ad-dressed within the BMBF frame-works IPonAir (focus on hierarch-ical multi-access management), andCOMCAR (focus on cooperation ofbroadcast and multicast network).In comparison with these projects,ScaleNet develops a Fixed & Mo-bile converged network architecture
Figure 1 High Level ScaleNet Architecture.
focusing on broadband access, ag-gregation and overarching networkfunctions, meeting the requirementsof both ETSI TISPAN NGN and3GPP LTE-SAE.
The paper is structured as fol-lows: Section 2 introduces the un-derlying ScaleNet architecture. Ourview on FMC together with an ar-chitecture discussion is presented inSection 3. Support of ubiquitousmobility is addressed in Section 4and Section 5 introduces overarch-ing network functions.
2 High-Level ScaleNetArchitecture
According to the goals of ScaleNet,a new integrated system architecturewill be specified bringing togetherthe wireless and the wireline world.Within this scope, two approachesfor multi-access integration are ofparticular interest: One being 3GPPSAE and one being ETSI NGN(the later is in the following re-
ferred to as ‘Unified Access NetworkArchitecture’). Both offer specificmulti-access integration solutions3
for which ScaleNet currently con-siders none of them superior to theother. In fact, convergence of bothapproaches, SAE and NGN, is en-visioned. Fig. 1 presents a high leveloverview picture of the ScaleNet ar-chitecture.
Enabled by ubiquitous mobil-ity, users may move arbitrarily whilebeing offered broadband networkaccess at guaranteed Quality of Ser-vice (QoS). Last mile access is notrestricted to any particular tech-nique, neither in the wireless norin the wireline domain. A particu-lar characteristic of the ScaleNetarchitecture is inclusion of con-verged access and metro networks(also called Aggregation Networks)
3 A detailed discussion and comparison ofthe two approaches is out of scope of thispaper.
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ScaleNet – Converged Networks of the Future ���
that serve as connector between sys-tem specific last mile technologiesand the IP Multimedia Subsystemcore and overlay networks. Particu-lar functions and entities herein(to be introduced in detail lateron) care for unified IP-based trans-port of traffic. Different services arehosted on top, offered via an NGNservice platform. For the delivery,the IP Multimedia Subsystem (IMS)will form the base in the ScaleNetcontext. It will be complementedby overlay networks that provideadditional enhanced services. Forthe control plane, centrally hostedScaleNet functions are foreseen toend up with an overarching systemconcept.
3 Fixed & MobileConvergence
The above-described system archi-tecture integrates a plurality of ac-cess networks. Some of today’s ac-cess networks (GSM, GPRS, UMTS,xDSL, HFC, ...) provide individ-ual end-user services like voiceand messaging, others provide onlyIP connectivity. These legacy net-works do not fulfil the requirementfor user-centric broadband requests,however their existences have tobe taken into account. In addition,service providers need to offer plat-form dedicated solutions, makingthe overall simultaneous introduc-tion of multiple services expensiveand risky. FMC as facilitated byScaleNet allows for homogeneousdelivery of service and network fea-tures via aggregation networks, in-dependently of the access network,the network technology or the end-user terminal.
The present section copes witharchitecture questions being im-portant for FMC within ScaleNet.The two considered standardizationapproaches (SAE, NGN) are shortlyintroduced. A complementing viewon Multi-Stage Access Networkscloses this architecture discussion.
3.1 IMS/TISPAN3GPP/IMS defines a standardizedmultimedia architecture which pro-
Figure 2 IP Multimedia Subsystem (3GPP/IMS).
vides the basic platform to intro-duce service and network conver-gence. Fig. 2 shows the overviewconcept of the FMC architec-ture distinguishing three planes: IPtransport, IMS platform and Appli-cation plane.
IP transport provides the pureIP based packet transfer for QoS-managed services as well as for best-effort services. The IMS platformprovides the control plane beingresponsible for, e. g., session estab-lishment, roaming, security, QoSand billing. Network convergenceon the control plane is given due tothe access network independent de-sign. The application plane allowsthe introduction of services com-monly accessible across all accessnetworks. Services only need to bedeveloped once and are introducedvia well defined reference points,e.g., within the home network of the
Figure 3 Reference Points in the TISPAN access network.
user. Different end user devices aresupported thanks to dedicated me-dia adaptation.
Within the TISPAN (Telecom-munication and Internet convergedServices and Protocols for Ad-vanced Networking) access networkas shown in Fig. 3, NASS (NetworkAttachment Subsystem) is responsi-ble for authentication, authorizationand access management and RACS(Resource and Admission ControlSubsystem) for QoS resource reser-vation, admission control and policyenforcement. The RACS assumesthat police enforcement RCEF (Re-source Control Enforcement Func-tion) shall assure that the associateduser traffic remains in accordancewith the policy decision. A-RACF(Access Resource and AdmissionControl Function) is always locatedin the access network and supportsthe resource reservation methods,
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admission control and final policydecisions employed by the operator.
Different independent applica-tion service providers can requestfor QoS and resources using the Rq′reference point, see Fig. 3.
3.2 System ArchitectureEvolution
An architecture that is of par-ticular interest within ScaleNet isthe one of 3GPP LTE/SAE (LongTerm Evolution/System ArchitectureEvolution). Within this framework,the introduction of a new air in-terface and the evolution of thesystem architecture are discussed in-side 3GPP. The logical high-levelarchitecture is shown in Fig. 4. Itis envisaged to support seamlessterminal mobility between 3GPP ac-cess technologies (GSM, UTRA, EU-TRA) and towards non-3GPP accesssystems like WLAN (outside 3G op-erator control) via the 3GPP packetcore/evolved packet core network.Moreover, enhancements on the Rxinterface from the Policy and Charg-ing Rules Function (PCRF) towardsIMS are envisaged which is indi-cated by the ‘+’ in the figure. The
Figure 5 Unified Access Network Architecture.
Figure 4 Logical high level architecture for the evolved system.
Rx+ combines the former Rx andGq interfaces.
3.3 Unified Access NetworkArchitecture
The second architecture to be con-sidered by ScaleNet is inspired byETSI NGN and goes beyond the 3Gscenario. It integrates all availableaccess technologies within a sin-gle, fully converged access networkdomain, see Fig. 5. Wireline andwireless access nodes are connected
via a jointly managed, IP-basedtransport network with traffic-engi-neered routers or enhanced (Ether-net) switches. In a further stage, newelements like the ‘Unified Router’(UR), a specific realization of theGeneric Router in Fig. 1, will com-bine both technologies in just onesingle node with advanced packetrouting and forwarding functional-ity. With this approach, every link– either wireline or wireless – willbe equivalently treated as an IP hop
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associated with a generic link met-ric. This leads to a unified resourceand mobility management. The se-lection of the optimum connectionto be used is part of a routing al-gorithm that takes multiple pathswithin the converged access networkdomain into account. This can ofcourse include QoS policy require-ments set by the overall IMS servicecontrol function, but also micro-mobility (i. e., intra access networkmobility), when handled by ad-vanced routing protocols able tocope with the dynamic metrics ofwireless links.
Previous projects like ‘IPon-Air’ [2] already have indicated thatthe approach to integrate mostUMTS Radio Access Network func-tions on one single platform is tech-nically feasible. Nowadays, the BaseStation Router [3] is the pre-stagedevice of the proposed UR and it isstill able to support legacy handsets(UMTS Rel-99, UMTS Rel-5 etc.)with full QoS and mobility manage-ment.
Regarding terminals, it is ex-pected that a ScaleNet enabled ter-minal will have different networkinterfaces available. Such terminalsare studied in a complementing re-search project ‘MxMobile’ [4].
Figure 6 Multi-Stage Access Network within ScaleNet.
3.4 Multi-Stage Access NetworksWireless radio access systems be-come increasingly important for fastInternet access. Besides cellular net-works, more and more hot spotsare installed as public Local AreaNetwork (LAN) while mobile op-erators are addressing home exten-sions by wireless Digital SubscriberLine (DSL) solutions. This trendis accompanied by a continuouslyincreasing bandwidth demand. Al-ready in 2005, it was shown thatradio access systems are able to sup-port more than one Gigabit persecond over the air [20]. But withincreasing data rate, the suppliedarea of a radio cell decreases, whichin turn necessitates an increase inthe number of base stations. As eachbase station has to be connected tothe backbone network, a strong de-mand for efficient and high datarate backhaul means arises. Due tohigh bandwidth requirements of ac-cumulated transport traffic, fiber iscommonly regarded as the most fa-vourable medium. However, fiberdeployment is not expected toachieve exhaustive coverage even onthe long run.
On the other hand, demand forhigh bandwidth increases also inwired access systems. Here, the state-
of-the-art access technology is DSLthat suffers from similar coveragelimitations for increasing data rates.
It is obvious that there is a gapbetween user demands and theexisting technical and economic so-lutions. As fiber connections willnot be broadly available in short-and mid-terms, an intelligent com-bination and concatenation of thewireless and wireline access andbackhaul systems is required toovercome the individual reach lim-itations of these technologies inorder to• satisfy end users bandwidth de-
mands,• connect broadband RANs sys-
tems to the backbone,• achieve full coverage with mini-
mal transmit power,• achieve full indoor and outdoor
coverage, and• enable fast and easy deployment
based on the combination ofwired and wireless forwardingsystems.
The Multi-Stage Access Networkworking group within the ProjectScaleNet aims for an optimum net-work architecture using multi-hopand mesh connections as shownin Fig. 6. Multi-hop and mesh net-
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works have the potential to enhancethe range, availability and capacityof broadband access networks cost-effectively. Furthermore, the work-ing group will analyze which addi-tional MAC or IP based mechanismsare needed to combine the stages of,e. g., multi-hop applied above andbelow roof top or relaying over morewireless hops and in which way ra-dio systems equipped with multipleantennas can contribute to fill thisgap.
4 Ubiquitous MobilitySupport of ubiquitous mobilityacross converged heterogeneous ac-cess systems is one of the mostimportant functions of a futureScaleNet. Wireless access networksplay the leading part for ubiquitousmobility because of their originalmobile nature. In addition, they areessential to provide network con-nectivity for mobile end users on themove. Within this scope, mobilitysupport is one of the most chal-lenging requirements as there is noabsolute guarantee for availabilityof wireless networks. Further, inter-operability between different accesssystems has to be ensured to grantcustomers smooth and seamless ser-vice continuity.
4.1 Terminal MobilityWhen talking about mobility, im-plicit considerations often relate toterminal mobility. Further types ofmobility will be addressed in thenext section, too.
Seamless IP Mobility Numerousreal-time services offered recentlyby network operators and serviceproviders like audio and video tele-phony, Mobile TV, etc. have com-pletely changed requirements onHandover (HO) performance aim-ing at provisioning of seamless ter-minal mobility. The real-time prop-erty of these services results inconsiderably high impact of avail-able network resources, packet lossand delay during HO on the serviceperformance. Hence, establishmentof seamless terminal mobility in
ScaleNet is not limited to reductionof typical HO delay caused by re-routing of incoming data packets tobe sent via the new network attach-ment point. Parameters of multime-dia sessions must be adapted to theachievable level of QoS in order toexploit available network resourceswith the best possible service qualityfor end users.
How to decide whether andwhen to conduct a HO and towhich network is an importantquestion for scenarios with overlap-ping heterogeneous access networks.For policy-based mobility manage-ment, the decision algorithm isspecified by policy rules consid-ering user preferences, applicationQoS requirements, mobile terminalcharacteristics and available accessnetworks. In ScaleNet, there areUE-centric decision features in theform of POLIMAND (Policy BasedMobile IP Handoff Decision) [5],and the network-centric decisionfeatures in the form of NAMM(Network Assisted Mobility Man-agement) [6]. One ongoing workin ScaleNet is to use a policy-based Meta Control (MC) functionto coordinate the decision mak-ing among several mobility decisionengines, be they on the user equip-ments, in the radio access networksor in the core networks, aiming toachieve a reasonable and dynamiccompromise between user auton-omy and network control.
Vertical Handover ScaleNet ismeant to support many differentlast mile technologies. This impliesthe disposition to switch the cur-rently used (air) interface in orderto maintain an active service. Verti-cal Handover (VHO) allows the enduser to move freely between hetero-geneous access networks wherebythe previously mentioned seamless-ness is a big challenge.
VHO becomes a special chal-lenge in ScaleNet while providingreal-time services for mobile cus-tomers. Data streams of real-timetraffic are not self-adaptive to vary-ing round trip packet delays and
available network resources sinceUDP/RTP protocols that are gener-ally used to transmit real-time datathrough the network, do not disposeof right mechanisms to accommo-date data streams to the varying linkconditions. Hence, VHO may endup in reduction of perceived QoS incase the new access network offerslower bandwidth or has larger trans-mission delays. It is hence to ensurethat the network dynamically adaptsto changes in order to prevent cus-tomer discontent caused by ‘freez-ing’ real-time streams. The followedapproach is adaptation of the ap-plication, or its components, or thenetworking environment, or a com-bination of these. ScaleNet addressesthis issue by means of the alreadydiscussed UE-centric POLIMANDand the network-centric NAMM.
In any case it is preferable toperform context-aware and proac-tive networking control. Such POLI-MAND and NAMM may anticipateupcoming VHO decisions based onrespective input information, alsoreferred to as trigger. The probablybest known trigger in today’s (wire-less) networks is indication of de-teriorating link quality where signalstrength is the base for (V)HO deci-sion. Signal strength is used as hand-over trigger in well-known MobileIP solutions, as well as in mostlink layer mobility approaches, e. g.,mobility support in IEEE 802.11.Hence, a wireline-wireless VHO be-comes a big challenge since the dis-connection from wireline networkis discrete and cannot be predictedthat way.
Location based Mobility Besidesphysical measurements, location in-formation is another valuable pieceof context information (trigger) thatis to be exploited to support sys-tem control in general, and terminalmobility in particular. Accordingly,ScaleNet applies location data fornetwork management and mobil-ity management in FMC networks.Knowing a terminal’s current posi-tion and being able to anticipateits future whereabouts allows for
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the required proactive management.Expected benefits are given in termsof, e. g., decreased handover latencyand increased Grade of Service.
Work conducted in ScaleNetcomprises a two-step procedure.First, according to the spirit ofconverged networks, hybrid posi-tioning techniques are evaluated toderive accurate location informa-tion. Then, dedicated means for fur-ther processing are derived includ-ing entities for (distributed) infor-mation storage or location proxiesfor fast and anonymous informa-tion requests. Location informationsubsequently needs to be exploredand evaluated to derive subscriber’swhereabouts in order to enablenew services. Valuable trigger inputcan then be generated to be con-sumed by POLIMAND and NAMM.Further input can be derived tosupport heterogeneous access man-
Figure 7 Personal Mobility.
Figure 8 Session Mobility.
agement (see Section 5.1 on Het-erogeneous Access Management) aswell as overarching mobility man-agement.
4.2 Personal andSession Mobility
While Terminal Mobility as ad-dressed in the previous section isrelated to physical movement ofa mobile terminal, Personal Mobil-ity [7; 8] focuses on the handoverof a session across different userdevices and different platforms. Ses-sion Mobility [8] comprises bothmobility features.
One main focus of Personal Mo-bility is the usage of several end-user terminals either one after theother (serial) or in a parallel way.Transferring a session between theseterminals that may be located in dif-ferent networks is supported, butPersonal Mobility does not cover
terminals that are moving acrossnetwork borders (Terminal Mobil-ity). Accessing subscribed services atdifferent terminals is possible due topersonal identifiers.
Fig. 7 presents an exemplaryPersonal Mobility scenario, wherea user who holds a session withUAS (User Agent Server) changesfrom a mobile terminal (UAC-A) toa fixed terminal (UAC-B). Anothermore complex scenario is to splitup the session and to see the videostream on a high resolution screendevice (laptop) and to hear the au-dio stream on a mobile phone. Thelatter scenario describes the paralleluse of several terminals.
Session Mobility, see Fig. 8, isan umbrella term which includesTerminal and Personal Mobility. Itis the ability of the mobile userto maintain active sessions whilechanging between terminal devices
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and moving across various accessand core networks.
Within ScaleNet, dedicatedmeans to support both, Personaland Session Mobility will be ex-plored. One candidate approachto enable mobility across networkboundaries is SIP (Session Ini-tiation Protocol) based mobilitywhich is characterized as applicationlayer mobility. SIP based mobilityhence shows the most attractive ad-vantage due to mobility supportindependent of the underlying ac-cess network technology. This isfully in line with the requirementsfrom the FMC perspective.
5 Overarching NetworkFunctions
An integrated FMC approach ac-cording to ScaleNet needs to providean overarching view. Real integra-tion entails more potentials thanjust the accumulation of featuresfrom each single system. The follow-ing section picks out some of theoverarching topics being served inthe wide scope of ScaleNet.
5.1 Heterogeneous AccessManagement
The Heterogeneous Access Manage-ment (HAM) is one of the mainScaleNet control functions, whichis needed for the IP optimised in-tegration of heterogeneous accesssystems. The HAM hides the het-erogeneity of the different accesssystems towards the mobile termi-nals as well as towards the net-work elements of the metro andcore network domain. The Hetero-geneous Access Management intro-duces Multi-Radio Resource Man-agement (MRRM) in the termi-nal and access network controllers,which adapts to the underlyinglegacy radio access network func-tions. Moreover, the MRRM ina HAM server, interfacing with theabove-mentioned MRRM compo-nents, provides two main services:• Neighbour-Cell Information
Provisioning: This service givesindividual information abouta terminal’s possible neighbour
cells to optimise the terminal’sscanning for promising cells.For this, the HAM server main-tains a neighbour data base,which contains static informa-tion like cell coordinates butalso dynamic information likethe current load situation fora service-aware optimisation ofthe neighbour cell list.
• Access Selection: The HAMserver carries out an access se-lection to materialise the ‘alwaysbest connection’ vision. The ac-cess selection can be based onthe QoS requirements of theservice, user profile, terminal ca-pabilities and status, policies,and resource availability in thedifferent access systems.
In order to provide these twoservices, some auxiliary functionsare needed• Capabilities Exchange: The
HAM server informs the net-work elements about its pres-ence and its capabilities.
• Cell/Access Registration: Cellsmust register themselves withthe HAM server to keep theneighbour data base up to date.
• Update Cell Information: Cellsmust report the current cellstatus to HAM server, e. g., up-date the cell load values, sothat HAM server’s access deci-sions and neighbour cell lists arebased on the actual situation ofthe system.
The HAM functionality isclosely related to the mobility man-agement as it provides access selec-tion decisions which trigger inter-access system handovers. It must bedesigned to interwork with existingand future mobility managementmechanisms. Moreover, through aninterface towards the session con-trol, optimised service adaptationis supported. Heterogeneous AccessManagement can be implementedin a variety of architectures in-cluding centralised and distributed3GPP based solutions as well as uni-fied router approaches.
5.2 Overlay NetworksOne of the goals of ScaleNet isto allow the rapid introduction ofnew services in a flexible and cost-saving way. Besides IMS based solu-tions, another promising approachto address these issues in ScaleNetis to use overlay networks. Theseare logical networks above the net-work layer that utilize their ownrouting mechanisms and addressingschemes independently of the net-work layer.
In ScaleNet, the typical appli-cations for overlay networks willinclude: terminal mobility sup-port [9], distributed storage ser-vices [10; 11], or the provisioning ofgroup communication services [12;13] that are not present on the net-work layer. Network applicationslike Massively Multiplayer OnlineGaming (MMOG) traditionally usea client/server architecture. Onemajor disadvantage of such anapproach is the fact that all com-munication between two playersis forwarded through the centralserver, thus making it a poten-tial bottleneck. By using applicationlayer multicast services, such anarchitecture can be replaced by a de-centralized peer-to-peer approach,which will significantly reduce theoperating costs and makes the sys-tem more scalable.
Although the use of overlay net-works in the Internet has beenwidely studied in the last coupleof years, the heterogeneous accessnetworks and a high degree of ter-minal mobility, which are typical forScaleNet, require further studies onhow the existing overlay protocolswill behave in a ScaleNet scenario.Most of the modern overlay net-works used today (e. g., for file-sharing) are peer-to-peer systems,where only end-systems are part ofthe overlay. In ScaleNet however,there are additional dedicated over-lay devices in the access and corenetworks. In our work, we ana-lyze in which ways these devicescan be used to optimize the overlaynetwork. In order to make effi-cient use of these devices, we also
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have to adapt the overlay topologyto the topology of the underlyingnetwork layer [14]. As the end-sys-tems move between different accessnetworks and thus change the top-ology of the underlay network, thisadaptation process has to be trig-gered using cross-layer informationfrom the HAM. In addition to thereduction of network traffic sucha topology adaptation also leads tolower latencies between two arbi-trary end-systems when communi-cating through the overlay network.This is especially important for real-time applications like video con-ferencing or the already mentionedMMOG.
Today, most applications thatuse overlay networks implementtheir own overlay network protocol.To minimize the costs of develop-ing new applications in ScaleNet,the implementation of the overlaynetwork has to be strictly separatedfrom the applications. For this rea-son, in ScaleNet there is a genericinterface between the applicationsand the overlay network, which en-ables us to reuse the same overlaynetwork by different applications.
5.3 Quality-of-ServiceIn order to support use cases like‘Triple Play’ (the possibility to shareand play guaranteed quality voiceand video with data) and ‘Broad-band everywhere’ (provisioning ofbroadband services right to the bor-der of the access networks) QoSsupport by the network is essential.For instance high volume down-loads should not adversely affecthigh quality broadband voice/videoconnections. Authentication, Au-thorization, and Accounting (AAA)functions must be considered in thecontext of QoS provisioning, too,because otherwise every user maysimply request services with highestQoS leading to no effective servicequality distinction.
Providing an overarching QoSand AAA functionality for sucha network is a challenging task, be-cause we need to develop new mech-anisms for handling the different
technologies in terms of admissioncontrol, resource reservation andmobility. The IP-based abstractionhelps hiding the underlying tech-nology diversity. Moreover, there areobviously interactions between IP-layer QoS, QoS provided by theHeterogeneous Access Managementat link layer level, and QoS re-quirements at the application level.Main functions of an overarchingQoS control are admission controland management of resources. Inorder to provide QoS on demand,an appropriate signalling is requiredto request resources for QoS-basedcommunication services.
One objective is to achievea high state of integration of QoSand AAA in order to provide se-cure and seamless QoS-based com-munication even for mobile users.We also aim towards achieving ro-bustness of the control mechanismsagainst failures and Denial-of-Ser-vice (DoS) attacks towards the con-trol plane. Further goals are toprovide a suitable functionality fordifferent types of networks in orderto support QoS guarantees end-to-end as well as charging in a secureand reliable manner, which justifiesa tight coupling between QoS andAAA.
For QoS signalling and admis-sion control, we currently concen-trate mainly on two approaches,namely an IMS-based and an NSIS4-based solution for AAA and QoScontrol. For achieving FMC we con-sider anticipated handovers and au-thentication tokens for enabling theopportunity to keep the QoS, AAAcredentials and respectively the ses-sion of a user unchanged duringhandovers. We investigate differentpossibilities for a tight couplingbetween the Diameter QoS [15]and QoS NSLP [16] applications toachieve a flexible, reliable and secureScaleNet.
5.4 Charging and AccountingServices
The economic success of a net-work operator in the future does4 NSIS = Next Steps In Signalling.
not only depend on his ability toprovide attractive services to hiscustomers in a heterogeneous envi-ronment but also on the capabilityto efficiently and correctly chargethese customers.
For future scenarios it is im-portant that mobile operators areable to swiftly and efficiently deploynew services, bundle existing ser-vices to new product offers that ad-dress their customers’ needs, allowfor an extended cost transparencyfor instance by means of a service-dependent advice of charge as wellas change the employed chargingand tariff models to gain a compet-itive advantage over their competi-tors.
All these aspects have to be sup-ported by the charging system. To beboth, scalable and efficient as it isaspired by the ScaleNet project, thecharging system should be service-oriented, highly configurable basedon policies, allow for an easy andsecure interaction between differ-ent operators and providers as wellas be convergent regarding onlineand offline charging functionality.The convergence feature must beintroduced in a way that the addi-tional requirements regarding real-timeliness that come along with on-line charging do not outweigh thegains by combining the two charg-ing mechanisms.
Since certain aspects of the clas-sical charging process are in naturenot specific to the charging task,the charging approach that is fur-ther developed and refined in theScaleNet project [17; 18] splits theclassical charging architecture intotwo parts, one that takes care ofthe charging-specific areas, like rat-ing and credit control and onethat serves as a generic accountinginfrastructure which is highly con-figurable and therefore can be usedfor different tasks beside chargingsuch as intrusion detection. This ac-counting infrastructure comprisingall network elements with account-ing capabilities provides its account-ing service via well-defined inter-faces and employs protocols like
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Schwerpunktthema
NSIS (Next Steps In Signalling) [19]for carrying the configuration infor-mation to the measurement pointson the network elements therebyattaining a synchronisation of theaccounting processes in the net-work.
6 Summary and OutlookFuture fixed and mobile networksthat are being standardized in ETSITISPAN and 3GPP LTE will havemany common features. Both willbe all-IP based and support broad-band multimedia services. Bothneed new network functions to sup-port mobility, QoS, security, AAACand others. But fixed and mobilenetworks are also inherently differ-ent. The ScaleNet project has takenup the challenge to converge thefuture fixed and mobile networksto exploit the advantages of both,which nowadays is known as Fixed& Mobile Convergence.
The present paper providesa high-level view on ongoing re-search activities within ScaleNet,focussing on the scaleable and con-verged network of the multi-accessoperator of tomorrow.
Starting from a high-level ar-chitecture, related work with re-spect to FMC has been discussed.In this scope, particular interest isput on existing specifications from3GPP SAE and ETSI NGN. How-ever, instead of adopting one ofthese approaches, ScaleNet aims topropose its own concepts, includ-ing the vision of a converged ar-chitecture with Multi-Stage AccessNetworks. Besides architecture is-sues, ubiquitous mobility is a keyfeature of the future converged net-works. Seamless vertical handoveris one means to be applied, loca-tion based context information an-other to support Terminal Mobility.Moreover, Personal and Session Mo-bility based on SIP are consideredas well. Since real integration entailsmore potentials than just the ac-cumulation of features from singlesystems, overarching network func-tions have also been investigated inScaleNet. Exemplary presentations
on Heterogeneous Access Manage-ment, Overlay Networks, Quality ofService as well as Charging andAccounting Services are major over-arching topics that are addressedwithin ScaleNet.
There are still a couple of otherinteresting fields to be explored in-cluding NGN services and broad-band everywhere in ScaleNet. Atthe end of the project in 2008,development of a new system con-cept will be completed together witha prototypical implementation of anintegrated demonstrator.
References[1] ScaleNet, project overview,
http://scalenet.mwrl.net/, and
http://www.dlr.de/pt_it/kt/foerderbe-
reiche/mobile_breitband_kommunika-
tionssysteme/scalenet/
[2] IPonAir, Project funded by BMBF,
http://www.iponair.de
[3] Lucent press announcement at
3GSM world congress Barcelona:
http://www.lucent.com/press/0206/
060214.coa.html
[4] DLR, Projektträger-Informations-
technik, “Netz der Zukunft”,
http://www.dlr.de/pt_it/kt/netz_der_
zukunft
[5] S. Aust, D. Proetel, N.A. Fikouras,
C. Pampu, and C. Görg: Policy
based Mobile IP handoff decision
(POLIMAND) using-generic link layer
information. In: Proc. of the 5th IEEE
Int’l Conf. on Mobile and Wireless
Communication Networks (MWCN
2003), Oct. 2003.
[6] Berlin’s Beyond-3G Testbed and
Service aware Framework for
Advanced Mobile Solutions
http://www.bib3r.de/Mobile_
Networking_Support.19.0.html
[7] ETSI: TISPAN_NGN; Release 1: Release
Definition. Version 0.3.1, ETSI Draft,
05TD138, January 2005.
[8] ITU-T Recommendation Q.1703:
Service and network capabilities
framework of network aspects for
systems beyond IMT-2000. Geneva,
2004.
[9] S. Zhuang, K. Lai, I. Stoica, R. Katz,
and S. Shenker: Host Mobility Using an
Internet Indirection Infrastructure. In:
MobiSys 2003.
[10] I. Stoica, R. Morris, D. Liben-Nowell,
D. Karger, M. Kaashoek, F. Dabek, and
H. Balakrishnan: Chord: a scalable
peer-to-peer lookup protocol for
Internet applications. In: IEEE/ACM
Trans. Netw. 11(1), 2003.
[11] S. Rhea, B. Godfrey, B. Karp,
J. Kubiatowicz, S. Ratnasamy,
S. Shenker, I. Stoica, and H. Yu:
OpenDHT: A Public DHT Service and
Its Uses. In: Proc. of ACM SIGCOMM
2005.
[12] I. Stoica, D. Adkins, S. Zhuang,
S. Shenker, and S. Surana: Internet
indirection infrastructure. In: Proc. of
the ACM SIGCOMM Conf. 2002.
[13] J. Vogel, J. Widmer, D. Farin, M. Mauve,
and W. Effelsberg: Priority-Based
Distribution Trees for Application-
Level Multicast. In: Proc. of NetGames
2003.
[14] M. Castro, P. Druschel, Y. Hu, and
A. Rowstron: Exploiting network
proximity in distributed hash tables. In:
Proc. of the Int’l Workshop on Future
Directions in Distributed Computing
2002.
[15] F. Alfano, P. McCann, H. Tschofenig,
and T. Tsenov: Diameter Quality
of Service Application. IETF,
Work in progress, Feb. 2006,
http://www.ietf.org/internet-
drafts/draft-tschofenig-dime-diameter-
qos-00.txt
[16] J. Manner, G. Karagiannis, and
A. McDonald: NSLP for Quality-of-
Service Signaling. IETF NSIS Working
Group, Work in progress, June 2006,
http://tools.ietf.org/wg/nsis/draft-ietf-
nsis-qos-nslp/
[17] R. Kühne, M. Schläger, and G. Carle:
Dienstorientiertes und konvergentes
Charging für Mobilfunknetze der
nächsten Generation. In: VDE/ITG
Mobilfunktagung, Osnabrück, May
2006.
[18] R. Kühne, U. Reimer, M. Schläger,
F. Dressler, C. Fan, A. Fessi, A. Klenk,
and G. Carle: Architecture for
a Service-oriented and Convergent
Charging in 3G Mobile Networks and
Beyond. In: Proc. of the 6th IEE Int’l
Conf. on 3G & Beyond (3G 2005),
London, UK, Nov. 2005.
[19] Next Steps in Signaling (NSIS) Charter,
http://www.ietf.org/html.charters/nsis-
charter.html
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on
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ed
with
writte
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old
er.
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[20] Technology Review Archiv, “Auf dem
Weg zum Super-UMTS”, 2/2006, p. 100,
http://www.heise.de/mobil/artikel/68984
Matthias Siebert studied Electrical Engin-
eering at RWTH Aachen University of
Technology where he subsequently served
as research engineer at the Chair of Com-
munication Networks. Since 2005, he is
with T-Systems Enterprise Services GmbH.
His research interests cover system inte-
gration from service and network point
of view, fixed- and mobile convergence
as well as location based networking. He
has more than 40 publications in confer-
ences, journals and book chapters and holds
several patents in the mobile and wireless
domain.
1 M. Siebert, B. Xu, M. Grigat, E. Weis,
N. Bayer, D. Sivchenko
Address: Deutsche Telekom AG, Friedrich-
Ebert-Allee 140, 53113 Bonn,
E-Mail: [email protected],
2 T. Banniza, K. Wünstel, S. Wahl,
R. Sigle
Address: Alcatel SEL AG, Lorenzstr. 10,
70435 Stuttgart,
E-Mail: {stefan.wahl|rolf.sigle}@alcatel.de
3 Ralf Keller
Address: Ericsson Eurolab Deutschland
GmbH, Ericsson Allee 1,
52134 Herzogenrath,
E-Mail: [email protected]
4 A. Dekorsy, M. Bauer, M. Soellner
Address: Lucent Technologies GmbH, Bell
Labs Europe, Thurn- u. Taxisstr. 10,
90411 Nürnberg,
E-Mail: [email protected]
5 J. Eichinger, C. Fan, F. Pittmann,
R. Kühne, M. Schläger
Address: Siemens AG, St.-Martin-Str. 76,
81541 München,
E-Mail: [email protected]
6 I. Baumgart, R. Bless, S. Stefanov
Address: Universität Karlsruhe (TH), Institut
für Telematik, Lehrstuhl Prof. Dr.
M. Zitterbart, Zirkel 2, Geb. 20.20,
Postfach 6980, 76128 Karlsruhe,
E-Mail: [email protected]
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