M. Waldburger, Chr. Morariu, P. Racz, J. Jähnert, S ... · 34 PIK 30 (2007) 1 Waldburger, Morariu, Racz, Jähnert, Wesner, Stiller Grids in a Mobile World: Akogrimo’s Network and

32 PIK 30 (2007) 1

NETZWERKFORSCHUNG IN DER SCHWEIZ K.G. Saur Verlag, München, 2007

M. Waldburger, Chr. Morariu, P. Racz, J. Jähnert, S. Wesner, and B. Stiller

Grids in a Mobile World: Akogrimo’s Network and Business Views

Martin Waldburger holds a MSc degree in Computer Science,which he received in 2004 from the University of Zurich. In thesame year, he joined Prof. Dr. Burkhard Stiller’s Communica-tion Systems Group (CSG) at the University of Zurich in the po-sition of an assistant and doctoral student. His research work isconcerned with legal aspects of electronic service provisioningin multi-domain environments.

Cristian Morariu holds a MSc degree in Computer Engineeringfrom the Technical University of Cluj Napoca, Romania. Heworked as a network engineer for the Romanian EducationalNetwork (RoEduNet), where he was involved in developingtools to meter and monitor IP traffic. Since September 2004 heis pursuing the doctoral degree at the Department of Informat-ics, Communication Systems Group of the University of Zurich.His main research interests are in the area of IP flow account-ing, IP-based services accounting, and accounting in multi-do-main environments.

Peter Racz received his MSc degree in Computer Science fromthe Budapest University of Technology and Economics in 2000.He worked as a research engineer at the Department of MobileNetworks at Siemens AG, Germany, focusing on next genera-tion mobile networks and QoS provisioning in 3G networks.Currently, he is a research assistant and pursues his doctoraldegree at the Department of Informatics, Communication Sys-tems Group at the University of Zurich, Switzerland. His mainresearch area is accounting for IP-based services in mobile,multi-domain networks.

Jürgen Jähnert, holds a degree in electrical engineering fromthe University of Stuttgart, Germany and a degree in Marketingfrom the University of applied sciences in Berlin and is currentlyhead of the Networking and Communication Systems Depart-ment of the University of Stuttgart Computing Center. He hasworked in various research projects in the broadband accessand mobility area with a special focus on mobile network archi-tecture, network/service federation, service management, andAAA. He has published more than 40 publications in interna-tional journals and conferences.

Stefan Wesner is deputy director of the High PerformanceComputing Center Stuttgart and is leading the Applications andVisualization department. His research interests include distrib-uted systems, grids, and collaborative working environments.He is involved in leading positions in several ongoing large Eu-ropean research projects aiming at the definition of “Next Gen-eration Grids” and is the technical coordinator of the Akogrimoand BREIN projects.

Prof. Dr. Burkhard Stiller studierte Informatik bis 1990 an derUniversität Karlsruhe (T.H.) und promovierte 1994 zum Dr. rer.

nat. am Institut für Telematik. Anschließend war er von 1994 bis1995 als Post-Doc Compuer Lab der Univesity of Cambride,England tätig. Nach einem Wechsel an die ETH Zürich an dasComputer Engineering and Networks Lab TIK des Departe-ments für Informationstechnologie und Elektrotechnik, dem ernoch heute in assoziierter Stellung verbunden ist, wurde er dort1999 zum Assistenzprofessor gewählt. 2002 übernahm er dieC4-Stelle für Kommunikationssysteme am Institut für Informa-tionssysteme der Universität der Bundeswehr München. Nachder Berufung auf die Professur für Kommunikationssystemedes Instituts für Informatik an der Universität Zürich zum Sep-tember 2004 baute er dort die Communication Systems GroupCSG auf, die sich vor allen Dingen mit Kommunikationsar-chitekturen und Protokollen im Internet, der Abrechnung, Peer-to-Peer-Systemen und verteilten Verwaltungssystemen für bio-metrische Daten befasst.

ABSTRACT

The use of wireless networking technologies has emerged overrecent years in many application domains. The area of grids de-termines a potentially huge application domain, since the typi-cal centralized computing centers require access from any-where, e.g., from field engineers who are situated in a wirelessnetwork domain. Thus, the integration of suitable businessviews on mobile grids, of grid views on available technologies,and network views in a fully IP-based network domain deter-mines the key challenge. The Akogrimo project’s architecturedeveloped, is outlined and discussed in this paper and providesthe major details required to offer a fully integrated and interop-erable solution for those three views of concern.

Index TermsMobile Grid, Accounting, Charging, IP-based Grid Services,Multi-domain, Dynamic Virtual Organization

I. INTRODUCTION

Mobility has become a central aspect of life for people in busi-ness, education, and leisure. Related mobile 3G network infra-structures and user communities have surpassed correspond-ing Internet figures. Independent of this development, grid tech-nology is evolving from a niche market – solely addressing theHigh Performance Computing (HPC) domain – toward a frame-work useable within a broad business context. However, whileaffecting largely identical complex applications, determined asuser and provider domains, until now the grid community hasbeen basically mobility-unaware. Therefore, the Akogrimoproject (Access to Knowledge through the Grid in a Mobile

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Grids in a Mobile World: Akogrimo’s Network and Business Views Waldburger, Morariu, Racz, Jähnert, Wesner, Stiller

World) [2], [3] aims to radically advance the pervasiveness ofgrid computing across regions, basically by leveraging the largebase of mobile users. In order to achieve this goal and in addi-tion to embracing layers and technologies, which are supposedto make up the so-called Next Generation Grids (NGG) such asknowledge-related and semantics-driven web services, Akog-rimo architects and prototypes a blueprint of an NGG. Akogrimoexploits and closely co-operates with evolving mobile Internetinfrastructures based on IPv6 and integrates security as well asdynamicity aspects.

From a technical point of view, Akogrimo addresses in an inte-grated manner mobility, Quality-of-Service (QoS), Authentica-tion, Authorization, Accounting, Auditing, and Charging (A4C),and security functionalities, which are provided by correspond-ing network-related Akogrimo middleware systems. To pursuethis goal, Akogrimo addresses at the same time the Grid andthe Internet with an integrative architectural view. From a user’spoint of view, Akogrimo will provide the technologies and con-cepts to establish a ‘virtual home’, with nomadic and mobile en-vironments for solving complex problems across network tech-nology and provider domains.

In generalizing the core grid concept – namely the resource-sharing concept – Akogrimo patterns these environments asMobile Dynamic Virtual Organizations (MDVO) [36]. The MDVOconcept incorporates network-identity-based concepts of per-sonalization, profiling, privacy, security, and trust. Finally, fromthe provider’s and, thus, business point of view, an Akogrimoworld provides new business models and opportunities, makingNGGs a reality and preparing them commercially viable for fu-ture use.

Thus, this overview paper will address the essential businessmodel classifications for mobile grids as well as the key grid andnetworking technologies. Based on this description the devel-opment of the Akogrimo architecture handles the actor and roleinterrelations within mobile grids, addressing business, grid,and network views. This approach covers key characteristics aswell as major functional components required and integrates amiddleware design process with a business-driven view point.To enable a complete spectrum of grid services, the respectivenetwork support integrates mobility, QoS support, a SIP-basedsignaling infrastructure, authentication, authorization, account-ing, auditing, charging, context management, and service dis-covery. Thus, the key concern of a mobile grid, the offering ofintegrated services, has been mitigated.

The remainder of the paper is structured as follows. Section IIdiscusses the key backgrounds. While Section III outlines thebasic Akogrimo Architecture, sections IV, V, and VI determineits main business, grid, and network middleware-related as-pects. Section VII finally summarizes the work and draws pre-liminary conclusions.

II. BACKGROUND AND RELATED WORK

The areas of interest for an integrated view of grids in the wire-less domain require the careful study of next-generation gridsas such and their networking technology applied. This has to becompleted by a study of the usefulness of grids in the wirelessnetworking domain under business perspectives.

A. Next Generation Grids for Business

Grid principles are no longer only applied to the domain of HighPerformance Computing (HPC) but they are developed towardsa general purpose utility technology with the focus on servicevirtualization [16], [17]. Beside this technological developmentto change the underlying infrastructure from proprietary proto-cols towards standardized communication based on web serv-ices [1] technology there is a trend to virtualization, not only oflow level resources such as computing power and storage, butalso higher level resources such as knowledge [8].

Another important dimension is the development of businessmodels for grid-based infrastructures. The European researchproject Akogrimo is leveraging its attempts to implement a com-mercially sustainable grid solution for telecommunications op-erators and service providers supporting mobile users andworkers on these developments. Akogrimo, thus, envisagesmobile knowledge grids for business – subsequently refer-enced to as mobile grids for reasons of simplicity. Knowledge inthis context refers to pervasive access to knowledge, reflectedby adaptive workflows, rather than artificial intelligence, such asreasoning components.

Following the definition of the key properties for grids given byFoster in [15] Akogrimo defines a Mobile Grid as: “A MobileGrid consists out of resources that are not subject to centralizedcontrol, while it supports all kind of mobility (such as device,user, and session) and communicates using standard, open,general-purpose protocols and interfaces in order to delivernon-trivial and optimized Quality-of-Service (QoS) dependingon the current context of the resource or the user. Furthermore,a Mobile Grid is communicating with the underlying network inboth directions enabling cross-layer cooperation between gridmiddleware and the network.”

In other words, both mobile and fixed grid systems are reflectedfrom an economic viewpoint by a virtual organization (VO). Theterm virtual organization was originally defined as an organiza-tional model [33] in the domain of economics. Combining thiswith the idea of controlled resource sharing, as envisaged bythe grid community [14] and the requirements from Business-to-Business (B2B) interactions [33] a more generic view isneeded if mobility aspects should be considered. Mobile gridsare characterized by two key functional extensions of fixed gridsystems: First, the support of mobile grid nodes provides forpervasive, location-independent access to knowledge. Sec-ondly, mobile grid nodes may dynamically join and leave theVO. Both aspects, mobility and dynamicity, show impacts on theone hand on respective business opportunities, e.g., by imple-menting context-sensitive adaptive workflows, on the otherhand they demand for enhancements of the VO concept, whichdoes not reflect mobile and dynamic aspects as yet. This in-cludes for example session models allowing for temporary in-terruption of services, when a mobile node is uncovered by acommunications network. Accordingly, mobile grids are repre-sented from a business point of view by Mobile Dynamic VirtualOrganizations (MDVO), which are perceived as VOs that reflectmobile and dynamic aspects and that are defined in depend-ence on [24], [25], [35] as follows.

“An MDVO is a temporary or permanent coalition of geographi-cally dispersed potentially mobile individuals, groups, organiza-tional units, or entire organizations. They pool resources, capa-bilities, and information in order to contribute to the operationalgoals of the VO according to the dynamically established con-

34 PIK 30 (2007) 1

Waldburger, Morariu, Racz, Jähnert, Wesner, Stiller Grids in a Mobile World: Akogrimo’s Network and Business Views

tractual agreements that are accountable and chargeableacross administrative domains, incorporating mechanisms forparameterized and secure authentication as well as authoriza-tion.” However, note that the fully dynamic contractual negotia-tions required to operate an MDVO in an open environment maybe replaced by out-of-band, pre-negotiated contracts, whichare pre-established between major organizations. Concerningmobility support, the extension of mechanisms and algorithmsrequired to maintain a VO covers mobility management, identitymanagement, and mobility support protocols. Thus, a new in-stance of a VO, the MDVO forms the integrated concept forAkogrimo.

B. Networking Technology

The Akogrimo architecture sketched in Section III is based onstate of the art network technologies, covering (a) AAA (Au-thentication, Authorization, and Accounting) for access controland accounting, (b) Mobile Internet Protocol version 6(MIPv6) [21], (c) SIP (Session Initiation Protocol) [32] for ses-sion handover and signaling, and (d) Differentiated Services(DiffServ) [5] as well as IntServ for QoS reservations. Each ofthose is briefly addressed below on the context of mobilegrids.

(a) AAA systems provide standard means for user authentica-tion, authorization of service access and accounting of serviceusage. These tasks are essential in commercial networks andservice provisioning environments [29]. The generic AAA archi-tecture [10] defines network components and their interactionson an abstract level, together with a proposal of a layered struc-ture for AAA protocols. The RADIUS (Remote AuthenticationDial-In User Service) protocol [31] was designed initially to sup-port AAA functions in dial-up and terminal server access serv-ices, and it is the most widely deployed AAA protocol in currentnetwork infrastructures. Accounting support in RADIUS isspecified in [30], which is restricted to network access services.Diameter [6], which is considered as the next generation AAAprotocol, is based on RADIUS, however being more flexible andproviding reliable data transfer, failover mechanisms, better er-ror handling, and security mechanisms [6]. The Diameter proto-col consists of the generic base protocol and various Diameterapplications. The Diameter base protocol defines Diameter en-tities and specifies common functionalities, including Diametermessage delivery, capability negotiation between Diameternodes, and error handling. Diameter applications, such asNASREQ [7], enable the flexible extension of the protocol, de-fining service-specific commands and data units. Similar to RA-DIUS, Diameter message parameters and data units are codedin AVPs (Attribute-Value-Pair) allowing the protocol to be ex-tended in a flexible manner. Besides Diameter clients and serv-ers, the protocol defines agents, which provide more flexiblemeans in the message forwarding, supporting relay, proxy, redi-rect, or translation services. Additionally, Diameter enables, incontrast to RADIUS, server-initiated messages. Finally, Diame-ter supports secure communication based on IPSec (InternetProtocol Security) [22] and TLS (Transport Layer Security) [11]in intra- and inter-domain scenarios.

Security Assertion Markup Language (SAML) [27] is an XML-based framework for web services that enables the exchangeof authentication and authorization information. A method fortransporting SAML messages over Diameter protocol is pro-posed in [26].

(b) MIPv6 [21] defines a protocol that allows mobile nodes tobe reachable while moving around in the IPv6 Internet. Thenew protocol simplifies the Mobile IPv4 architecture by eliminat-ing the need of a foreign agent (FA) and enabling the binding ofa mobile’s node care-of address to its home address.

(c) SIP [32] defines an application layer control protocol for cre-ating, managing, terminating sessions between two or moreparticipants. The possible sessions include IP telephony, multi-media content distribution, multimedia conferences, and instantmessaging. SIP messages used to create sessions containsession descriptors that are used for negotiation of content me-dia types. The SIP architecture is based on SIP proxies, whichare elements concerned with routing messages to a user’s cur-rent location, authenticating and authorizing users for services,implementing session-routing policies and providing service-specific features to end-users. SIP implements a registrationfunction which allows users to upload their current location foruse by SIP proxies.

(d) Finally, DiffServ and IntServ define mechanisms for deliver-ing QoS in access networks (IntServ) as well as in core net-works (DiffServ). In [4], a framework is proposed for deliveringend-to-end IntServ services over heterogeneous DiffServ corenetworks.

C. Business Models for Current Grid Systems

Grid business models vary in their actual embodiment from in-stantiation to instantiation. However, grid business models con-sist – as business models do in general – of the following build-ing components [34]:

– A description of involved actors and assigned businessroles.

– An overview of various business flows, in particular product,information, and service flows.

– The value proposition, showing benefits for actors to be im-plemented.

– Sources of revenue, that indicate potentials for earnings,based on financial flows within a VO.

Besides these generic constituents of business models, spe-cific characteristics for grid business models have to be con-sidered. Due to the fact that grid systems offer non-tangibleproducts, based on electronic services, grid economics arehighly interrelated with electronic commerce business models.For e-business models, various taxonomies exist in parallelwhich is exemplarily documented by an embracing overview in[9]. These taxonomies are not directly comparable in the firstplace. However, the integrative approach followed in [12], iden-tifies 12 common criteria for classifying electronic businessmodels. This allows depicting typical characteristics of today’sgrid systems, in particular traditional high performance com-puting- and data-oriented grid computing as well as servicegrids that allow service virtualization in VOs. Accordingly, [Ta-ble 1 determines a grid business model classification for gridcomputing and service grids, as representatives of current gridsystems. As Table 1 outlines those mentioned classificationcriteria applied on the existing HPC-oriented grid computingand VO-driven service grid approaches, the respective busi-ness model classification for next-generation mobile grids,thus reflecting the MDVO case drawn in Section II. A., hasbeen determined as follows:

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Mobile grids will target B2C markets in a 1-to-Many way, in facta Many-to-Many way, which however is hidden from service us-ers, since virtualization is implemented by means of service ag-gregation. Services, thus, are composed over a distributedvalue chain, that is characterized by business process execu-tion and knowledge-integration in hierarchies. Targeting massmarkets requires a variety of charging models and tariffschemes to be supported, since various different market seg-ments with the need for customized pricing mechanisms areenvisaged. Customization is however not limited to pricing, butit includes user and device context information so that work-flows adapt to context changes, which in turn has conse-quences on the required security level of business flows: In anMDVO, where sensitive context information is exchangedacross administrative domains, where high-level resourcessuch as knowledge are integrated and made accessible to mo-bile users, security aspects in the single domains as well aswith respect to information flows between domains are of ut-most importance – in particular for trust-building, privacy issuesand commercial service provision supported by A4C mecha-nisms. Aiming at offering pervasive access to knowledge leadsto challenging issues to be addressed as knowledge by defini-tion is embedded in a certain field of application where it isneeded to solve a specific task. Whoever is able to provideknowledge according to context information, thus, qualifies for adifferentiation strategy. Providers however offering basic (grid)services with a low level of integration only, are assumed to fol-low a cost-leadership strategy by focusing on core competen-cies. High-level resource coordination in an MDVO will involvevarious content elements, so that high data volumes are ex-pected to be transmitted. If users then are able to solve com-plex problems right on scene, clearly determines a high level ofinnovation in the mobile grid, which puts successfully operatinggrid service aggregators and telecommunication providers intoa strong position.

Driven by those given indications on next-generation mobilegrid business models, an overview of the Akogrimo overall ar-chitecture is given in Section III, and detailed views subse-quently are drawn for business, grid, and network middlewareaspects in sections IV, V, and VI respectively.

Table 1 Grid Business Model Classification for Existing Grid Systems (Criteria Based on [12])

Crit

eria Criteria Description

Typical Values

Business Model Characteristics for Existing Grid Systems

Use

r R

ole

Determines whether the client is related to an end-user or a provider of a service which in turn is sold to other clients.

End-user-related or resel-ler. B2B or Business-to-Consumer (B2C)

Clients usually are related to end-users, however not individuals but rather organizations, i.e. B2B cus-tomer relations are maintained. A grid service provider for example might offer to solve data- or compu-tational-intensive simulation tasks in automotive.

Inte

ract

ion

Pat

tern

Denotes the number of involved service providers and service consumers

1-to-1, 1-to-Many (one service provider, many service consumers), Many-to-1 (many service provid-ers, one service consumer) or Many-to-Many [34].

1-to-1 or 1-to-Many in case of grid computing. By forming a virtual organization, as in service grids, Many-to-1 and Many-to-Many become possible, which however is not visible for service consumers. Due to today’s grids’ focus on niche solutions or non-commercial research projects, 1-to-1 and Many-to-1, respectively, are prevailing.

Nat

ure

of O

fferin

gs

Describes the basic offer-ing characteristics.

Content/information, serv-ice or complete product (including, e.g., after-sales services)

Offerings usually embrace electronic services, such as computational power in grid computing. In a VO, various service and content provid-ers are able to cooperate, whereas a service aggregator bundles basic services. Complete products typi-cally are out of scope, since the offered electronic services represent only one step in the user’s value chain.

Pric

ing

Sys

tem

Specifies the financial terms, under which a user can access the service.

Dynamic or fixed pricing with sub-categories such as free access, usage rate, subscription fee or auc-tions.

The pricing scheme highly depends on the actual organiza-tional configuration of a grid-based solution as well on the type of offered services. Both, VO-exter-nally and VO-internally, fixed pric-ing schemes, based on service usage, are regarded as significant choices under the assumption that relevant usage parameters are available to be metered, accounted, and charged.

Leve

l of C

usto

miz

atio

n Determines how much a service is customized to a user’s individual require-ments.

Full range from mass con-tent to completely custom-ized content.

Since current grid systems are char-acterized by 1-to-1 or Many-to-1 business relations, whereas B2B relations prevail and users are end-users (cf. respective classification criteria), mass markets are not tar-geted. Consequently, offered serv-ices are customized to the user’s individual requirements.

Eco

nom

ic C

ontr

ol

Depicts the organizational alignment with respect to service provision

Full range from self-organi-zation to hierarchical design.

Independent from the existence of a VO, the organizational structure is assumed to be hierarchical within business grids. A central compo-nent manages the distribution of tasks to be completed. From a user’s viewpoint, in a commercial environment, only one organization is assumed to maintain direct cus-tomer relations, thus hiding organi-zational details of a potential VO from the user.

Leve

l of R

equi

red

Sec

urity Identifies the needed secu-

rity-level to monitor and verify purchases.

Low or high

With an orientation towards direct B2B customer relations in a 1-to-1 manner, the required level of secu-rity for monitoring and verifying pur-chases is assessed to be low. In the case of service grids (VO-enabled, Many-to-1) however, monitoring has to be increased VO-internally among the various VO members.

Leve

l of V

alue

Inte

grat

ion

Qualifies the degree of integrating and transform-ing components over differ-ent value chain steps.

Low or high

In a VO, several steps of the VO-internal value chain are integrated from the services provided by vari-ous VO members. The VO itself offers these electronic services in a bundled form to a user which in turn integrates them into its own value chain. Thus, assuming a service grid with service provision-ing in a VO, the level of value inte-gration is considered to be high. The opposite (i.e. a low level of value integration) however is the case in traditional, purely high per-formance computing-centric grid computing.

Crit


Typical Values


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III. AKOGRIMO ARCHITECTURE

Fig. 1 shows the Akogrimo Architecture [13] on a very high andconceptual level. Originally, a layered approach assuming isola-tion between them has been assumed. This strict viewpoint hasbeen given up during the evolution of the architecture as thecommon denominator for all these layers had been a virtualiza-tion of the different kind of resources as Web Services.

However, as indicated most intense interactions are between“areas” close to each other communication across areas is in-tentionally part of the architecture. As an example the collabo-

ration between the Network area and the network middlewarearea is more important than the interaction, e.g., with the GridApplication Support Services Layer.

The network area is providing the underlying IPv6 and MIPv6-based network infrastructure. For example, it provides neces-sary interfaces using Web Services-based virtualization tech-niques to allow the middleware or application providing net-work services, like Authentication, Authorization, Accounting,Auditing, and Charging (A4C), session control, and networkcontext in conjunction with the network. The Grid MiddlewareServices layer provides an infrastructure for a service provider(such as Service Level Agreement Management or ExecutionManagement) as well as the application support area providingVirtual Organization (VO) infrastructure services (such asBusiness Process Enactment or Support for the VO lifecycle)complete the overall conceptual architecture of the Akogrimoplatform.

A. Major Building Blocks

The 5 key building blocks shown in Fig. 2 are the network pro-vider, the service provider, the Operative VO (OpVO), the BaseVO (BVO), and the Customer domain.

The BaseVO (BVO) is providing the interface to the customerfor “buying a service”. This means that a customer can requesta certain offered complex service and is triggering with this thenecessary actions for the set-up of the Operative VO (OpVO)that is responsible for finding the appropriate service providers,setting up their relationships, e.g., fostering the negotiation ofService Level Agreements. The OpVO can be seen as the runt-ime environment for the orchestration, execution, and supervi-sion of the services.

The Service Provider publishes services it wants to offer withinthe BaseVO, e.g., in a service registry, together with some ad-ditional information which could be templates for Service LevelAgreements it is offering. Service providers are offering poten-tially a wide variety and large number of services and are au-tonomously managing them. This means that the resourcesneeded and the internal management are hidden from otherService Providers or the Customer and only the commitment isthe fulfilment of the agreed upon SLA, but not how this is inter-nally enacted.

A basic property of all building blocks is that they use function-ality across the areas shown in Fig. 1. For example the MobileTerminal from the customer domain uses functionality from the

Val

ue/C

ost O

fferin

gs

Reflects the envisaged competitive strategy.

Differentiation (adding value) or cost leadership (low-cost or low-price strat-egy)

Selling purely computational power implements a cost leadership strat-egy where services are imitable and offer only little value added, they however are offered to customers at comparably inexpensive conditions. In service grids, a higher level of added value is reached by offering aggregated, application domain-specific services, which allows the grid service provider to implement a differentiation strategy.

Sca

le o

f Tra

ffic Considers the expected

volume of data traffic that is generated.

Low or high

Grid systems are by design useful for solving computationally and data-intensive tasks. Accordingly, most grid services are expected to generate high data traffic rates.

Deg

ree

of In

nova

tion Assesses whether existing

business is directly trans-ferred to its electronic ver-sion or the electronic busi-ness offers new functional-ity [34].

Low or high

Both forms of current grid systems, grid computing and service grids, offer a high level of innovation, since new functionality is gained com-pared to non-electronic business. This includes high performance computing facilities and virtualiza-tion of electronic services in a VO.

Pow

er D

istr

ibut

ion Answers whether buyer or

seller is in a stronger posi-tion (e.g., with regard to negotiations).

Buyer or seller

At this early stage of commercializa-tion, distribution of power is difficult to be assessed. However, commer-cial grid service providers, repre-senting sellers, are not yet numer-ous which puts them into a better bargaining position, assuming a constant or growing demand.

Fig. 1 The Akogrimo Architecture

Crit


Typical Values


Network

AApppplliiccaattiioonn SSeerrvviicceess

Network Middleware

Grid Application Support

Services

Grid Middleware

Services

Fig. 2 Akogrimo Domains

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network area, such as QoS bundles of the MIPv6 infrastructure,the A4C client from the Network Middleware, and Grid Servicesfrom infrastructure, application support up to application serv-ices. All these components do interact and exchange informa-tion from the network to the application and vice versa.

IV. BUSINESS VIEW

From a business viewpoint, Akogrimo’s interest is set on eco-nomic aspects of commercial mobile grids, which are charac-terized by two key functional extensions of fixed grid systems:First, the support of mobile grid nodes provides for pervasive,location-independent access to knowledge. Secondly, mobilegrid nodes may dynamically join and leave the VO. Both as-pects, mobility and dynamicity, show impacts on the respectivebusiness opportunities, e.g. by implementing context-sensitiveadaptive workflows, and they demand for enhancements of theVO concept, which does not reflect mobile and dynamic as-pects as yet, resulting in the respective definition of MDVOs (cf.Section II. A.).

Mobile grids are reflected by MDVOs from an organizationalviewpoint, but other perspectives also have to be considered inorder to gain an embracing view of relevant business aspects,particularly with regard to mobile grid business models. Follow-ing a top-down approach, starting at the organizational align-ment of mobile grids and going down to the underlying techni-cal infrastructure, two structural parts besides the MDVO areidentified, namely grid infrastructure and network infrastructure.These layers are drawn from an economic viewpoint and theyare not to be perceived as direct equivalents to the respectivearchitectural layers shown in Fig. 1.

With respect to the first element of business models (cf. SectionII. C.), i.e. involved actors and assigned roles, only MDVO andgrid infrastructure are regarded to cope purely with grid busi-ness models. However, since these depend on communica-tions infrastructure to be available, respective actors and roleson network infrastructure’s layer have to be included as well.Even though actors and role models show specific characteris-tics depending on the chosen scenario, generic constituents

relevant for any mobile grid’s role model are assumed to bepresent in all mobile grid scenarios. This assumption bases onmobile grids’ distinctive characteristics from Akogrimo’s com-mercial perspective. This means that Akogrimo scenariosadopt a mobile grid vision where, first, presumably only end-us-ers are mobile, which does not imply that user nodes are serv-ice consumers only, but computation- or data-intensive tasksare performed on fixed grid nodes. Second, in a commercial en-vironment, single grid services are bundled by a service aggre-gator that maintains end-user relations, thus taking exclusivelythe role of a grid solution provider towards end-users. Andthirdly, grid services are aggregated from a distributed supplychain that embraces n-tier grid service providers, whereas therole of a grid service provider can show more specific instantia-tions, such as the one of a content provider. Fig. 3 depicts theorganizational alignment being typical for Akogrimo mobile gridscenarios, incorporating actors and roles from an MDVO andgrid services perspective.

Actors and roles from the network infrastructure layer howeverare not explicitly shown in Fig. 3 for reasons of simplicity,though assumed to be present in every scenario, since networkservice providers, represented for example by mobile networkoperators, play the indispensable role of a communications en-abler. Accordingly, the following generic business roles areidentified as the basic set being relevant for mobile grids that in-clude Business-to-Consumer relations:

– End-user (potentially a separate organizational entity thanthe end-customer)

– Grid Service Aggregator– Grid Service Provider– Network Service Provider

Having denoted those four basic business roles, business mod-els for mobile grids are analyzed subsequently in further detailusing the three remaining business model building blocks,which embrace business flows, the respective value proposi-tions, as well as potential sources of revenue (as presented inSection II. C.). Regarding value proposition, Table 2 lists theidentified benefits for every basic business role, thus allowing todocument potential values to be envisaged and achieved.

Table 2 Value Proposition for the Basic Set of Mobile Grid Business Roles

Fig. 3 Generic Mobile Grid Actors and Roles in Akogrimo Scenarios

B2B B2C

Legend:

End-user

Grid Service Provider

Grid Services Aggregator

Mobile

Grid

Nodes

First

Tier

Supplier

Second

Tier

Supplier

N-Tier

Suppliers

Business Role Value Proposition

End-User End-users profit from being able to perform knowledge-intensive tasks while not being bound to a specific loca-tion anymore. Thus, services remain available even when changing locations and can be resumed after a tempo-rary loss of network coverage. Services are reflected by context-aware, adaptive workflows, implementing various types of mobility, such as user, terminal, and service mobility[24]. Furthermore, end-users are not only able to consume service, but also to provide them, e.g., by first retrieving content relevant to perform a current task, working on the content, and delivering respective results back.

Grid Service Aggregator

The grid service aggregator is the producer and the ven-dor of a mobile grid solution. This solution makes value-added services available for end-users in form of a prod-uct. As a producer, atomic services are aggregated to service bundles. This implies that the producer runs and maintains the Akogrimo service delivery platform. As a vendor contractual relationships towards end-users, here in terms of customers, are maintained. Thus, the vendor qualifies for billing. Furthermore, the vendor copes with marketing activities and customer service.

38 PIK 30 (2007) 1


Business flows and possible resources of revenue are on onehand highly interrelated, whereas on the other hand, specificindications highly depend on the chosen scenario. In general,business flows are based on technical requirements to bemet. This includes guarantees with respect to QoS or non-re-pudiation of messages exchanged among VO members. Sin-gle business processes, regardless whether executed withinan administrative domain of a grid service provider or seenfrom an aggregated VO perspective, all result in businessflows, which in turn cause financial claims that have to be set-tled.

Therefore, from a process angle, A4C (see Section VI. C. is re-garded as key element: Authentication, authorization, account-ing, charging, and billing document for every provider the com-plete process from service instantiation to finally billing a pro-vider’s customer. Hence, a grid accounting model, composed ofmeaningful accountable units that reflect process costs and re-source usage is needed. Accountable units are useful on theone hand with regard to service optimization and auditing, onthe other hand for price-building and billing purposes, influenc-ing finally direct sources of revenue. In a VO however, where or-ganization members remain legally independent, business-crit-ical accounting information is not assumed to leave administra-tive domains, so that only aggregated charging records are ex-changed.

Having presented various business-related aspects of commer-cial service provision in an MDVO leads to an in-depth investi-gation of the Akogrimo architecture, both from a grid and net-work middleware viewpoint as the two key elements by whichbusiness potentials are implemented. This includes for instanceSLA management and workflow enactment on grid level (cf.Section V.) and A4C as well as context management on net-work middleware layer (cf. Section VI.).

V. GRID VIEW

The deployment of grids has already achieved a significantnumber of deployments within organizations driven by the mo-tivation to move from large mainframes to clusters aiming at areduction of the Total Cost of Ownership (TCO). Also in purelyacademic environments, where the sharing of high perform-ance rare resources is the driver for the grid solution, cross-or-ganizational solutions are available. However, grid solutionsthat enable the sharing of resources across organizationalboundaries are not yet very common. The major obstacles pre-

venting the wide take up are related to the complexity of usermanagement, cross-organizational accounting, auditing andcharging of used resources and security considerations.

A. Web Services Base Technology

All major grid toolkits nowadays are based on web servicetechnology. Akogrimo is, despite its new challenges, comingfrom the business and network layer aiming to align with themajor trend in grids and Business-to-Business relations torely on cross organizational businesses based on web serv-ices. Besides those base technologies as defined in the WS-I Profile Akogrimo can rely on the wide range of composedspecifications including WS-Addressing [37], Web ServicesBase Notifications [28] and from the Web Service ResourceFramework [19]. Besides other specifications these are sup-ported by all WSRF-based grid toolkits such as the GlobusToolkit 4 [18] or WSRF.NET [38]. Those have been selectedas base technologies for the Akogrimo integration platform.One of the major design decisions that had to be taken withinAkogrimo was on which of the layers (cf. Fig. 1) the virtualiza-tion interface had to be designed. This interface provides theunderlying resources and services through web service inter-faces.

The originally anticipated, strictly layered approach to have thisboundary between the Network Middleware Layer and the GridInfrastructure Services Layer has been proofed to be not ben-eficial. Instead, and in line with the paradigm of Service Ori-ented Architectures (SOA) resources in the Network and Net-work Middleware Layer are exposed partially as Web Servicesand can be used by services from the Grid Infrastructure, theGrid Application Support “Layer”, and application-specificservices.

B. State and Asynchronous Communication

A major differentiator between stateless, distributed applica-tions and Grid Applications rely on the WS-RF specifications forexposing state information and WS Base Notification for a morepeer-to-peer like communication pattern between grid nodes.This approach is based on topic-based subscription and asyn-chronous message delivery.

For example, the context of a current user device might be ex-posed using WS-RF allowing to query and manipulate thestate and also to allow these states to be transferred in casethe user changes his device and wants to transfer its state tothe new device. Furthermore, if the context includes valuesuch as “Current Bandwidth” or “Screen Resolution” other gridNodes might want to subscribe to these state changes. Withinthe example of context change propagation the general con-cept of Akogrimo of cross-layer co-operation can be demon-strated. The collected state information from the network layer(see Section VI. D.) using a wide range of different mecha-nisms is virtualized by a web service interface and is providedto context consumers using a standardized web service inter-face, independent on how this information had been collected.As a result standard workflow engines or any application serv-ice can subscribe to these notifications and adapt their behav-ior accordingly.

Grid Service Provider

Grid service providers focus on their individual core com-petencies. Depending on the grid service characteristics, either both or only one, economies of scale and econo-mies of scope, allow a grid service provider to implement a differentiation or cost leadership strategy while keeping transaction costs as low as possible. By the use of open, standards-based interfaces, grid service providers are able to provide their grid services in many VOs.

Network Service Provider

Network service providers offer technology-transparent access to communications infrastructure, which forms the basis for grid services on top of communications services. Mobile network operators excel as both, net-work service providers and grid service aggregators, due to their experience in customer relations and marketing, allowing them to move from pure access providers to pro-viders of complex services.

Business Role Value Proposition

PIK 30 (2007) 1 39


C. Service Level Agreements (SLA) and Execution Management Systems (EMS)

Another basic building block for moving from e-science grids tobusiness grids is the support of service level guarantees to theconsumer of services. Akogrimo is relying in this case on the re-sults of the GRAAP working group of the Global Grid Forumnamely WS-Agreement and WS-Agreement Negotiation [20].As part of these specifications the possibility to negotiate thecontent of a Service Level Agreement (SLA) is described. In thevolatile context of Akogrimo, e.g., where service providersmight move from a high- to low bandwidth environment, the ac-ceptance of SLAs can only be done based under certain condi-tions (e.g., the minimum bandwidth) and through active man-agement of information technology and network resources.Within Akogrimo, besides the management of computationaland data resources the execution management system (EMS),which received the SLA to be enacted, is also able to benefitfrom virtualization interfaces provided by the network layer,since it is enabled to select from different sets of QoS bundles.Thus, if a consumer demands a certain SLA this might cause achange in its access network quality class or potentially even ina change of the access network provider.

Akogrimo is approaching SLA and QoS clearly with a conceptof bilateral agreements between consumers and providers.While these agreements might be brokered they determineclearly electronic contracts between consumers and providers.This point is emphasized, since many approaches within thegrid domain aim for a global or VO-wide resource optimizationstrategy, ignoring potentially customer-specific behavior of pro-vider.

D. Workflows, Operative VOs, and Application Services

A common workflow language for web service-based orches-tration is the Business Process Execution Language (BPEL).As described above all grid nodes within Akogrimo are poten-tially subject to context changes and may consequently requirea change in the execution of the workflow. For example, if theuser changes from a powerful workstation that is capable ofrendering complex medical data to a PDA the workflow needsto be adapted, e.g., by adding a rendering service that deliversa small picture of the rendered data together with a set of metadata optimized for the low resolution client. This might involvethe discovery, configuration, and integration of a new memberof the operational virtual organization (see [25] for details) anda switch of the current workflow. Furthermore, application serv-ices might be forced to change their behavior, e.g., through re-ducing the frequency of data updates or the provision of addi-tional textual metadata. In general, the dynamic and timely ad-aptation of services on the application layer is a key issue forthe success of a mobile grid, since they show a major impact onthe user’s experience.

VI. NETWORK MIDDLEWARE VIEW

In the Akogrimo network, mobile users will be roaming acrossdifferent access networks belonging to different administrativedomains. Further, there is no permanent network coverage ex-pected which leads to disconnected operations scenarios in or-der to maintain membership of an MDVO.

The underlying network and its components are required toprovide the necessary infrastructure to deliver services to usersas well as to provide supporting services for network and serv-ice providers. Fig. 4 gives an overview of the Akogrimo networkarchitecture. Users connect to the network via different end-de-vices, including portable devices and stationary terminals. Ac-cess networks provide wired or wireless connections via differ-ent physical access technologies. The core network connectsthe access networks, provides connectivity towards other net-works and comprises network components that provide net-work and grid services. The grid middleware and the grid appli-cation infrastructure provide grid services. Fig. 4 does not shownetwork domain boundaries but the depicted components sup-port inter-domain communication and can be deployed in sev-eral domains. If multiple network providers are present, hando-vers among the different networks are supported, assumingthat it is underlined by a commercial agreement.

Selected parts of the Akogrimo network architecture are de-scribed in the following sections in detail.

A. Mobility and QoS Support

One of the main challenges of Akogrimo is providing seamlessaccess to grid services and applications in a mobile environ-ment. The following three different types of mobility are identi-fied and supported [24]:

– Device mobility: In a mobile communication environment us-ers are allowed to move throughout different networks hav-ing access to the same set of services.

– User mobility: Users of a mobile grid should have access totheir services regardless of the device they use or the placeand technology they use to access these services.

– Session mobility: Session mobility refers to seamless trans-fer of an ongoing service session from a device to another.

Device mobility is provided by mobile IPv6 extended with fasthandover support [23]. The home agent (HA) in the core net-work serves as a location register for mobile terminals. Userand session mobility are supported by the overall authentica-tion process integrated in the network and the SIP infrastruc-ture. Besides mobility the Akogrimo network infrastructure pro-vides also QoS support. According to Fig. 4 access routers

Fig. 4 Akogrimo Network Architecture

Core Network

Access Network

AR

SIPProxy

QoSBroker

Access Network

AR

SIPProxy

QoSBroker A4C

ServiceDiscovery

PBNMS

HomeAgent

ContextManager

SIPServer

MT

MT

Grid ApplicationsInfrastructure

Grid Middleware

40 PIK 30 (2007) 1


(AR) in the access network provide the interface for end-termi-nals to connect to the network. The AR performs access controlto network resources based on user authentication and metersnetwork service usage. It receives QoS requests from the mo-bile terminal, controls QoS signaling and communicates withthe QoS Broker. The QoS Broker is the central entity to manageQoS within the network. It decides on QoS requests, managesavailable network resources and exchanges these informationwith other QoS Brokers. Mobility and resource managementare integrated in order to support QoS management duringhandovers and to ensure that handovers between different ac-cess networks are possible.

B. SIP Infrastructure

The integrated SIP-based communication is provided by theSIP infrastructure, supporting a common session managementand session mobility. The central part of the infrastructure is theSIP server in the core network, which contains the SIP proxyand the SIP registrar for user registration (cf. Fig. 4). SeparateSIP proxies can be deployed in several access networks to dis-tribute the load of the SIP server. The SIP server also providespresence information of the user to the context manager whichcollects and distributes these information to other network com-ponents.

C. A4C

In Akogrimo, the A4C system provides the necessary function-ality for authenticating users, authorizing access to services,accounting and charging for service usage, based on agreedSLAs, as well as auditing. By its heterogeneous nature, interms of services and service providers (SP) involved, a VOneeds strong support from the A4C infrastructure for managinginter-domain security and inter-domain accounting and charg-ing. Emerging from a network technology, the A4C will deliverAAA services not only to network services, but also to grid-based services.

A mobile grid infrastructure aggregates services from multipleSPs in order to build new applications to be delivered to end-users. The new applications will require QoS support acrossthe different domains and will need to be charged according tothe quality experienced by the service customers. Such ag-gregations require trust agreements between SPs (for simplic-ity network providers are also seen as SPs) at the A4C infra-structure level. Trust agreements are similar to the roamingagreements between mobile operators and allow a user toconsume services from multiple SPs while keeping a businessrelationship with a single SP – his home domain. A user usu-ally has an initial contact with his home domain representedby signing a contract between the two parties, and then a per-manent security relationship between them. The trust relation-ship between the user and his home domain and the trust re-lationships of that domain and other SPs enable the user toestablish temporary, transitive trust relationships with newSPs thus allowing the user to access services provided byother SPs. The newly created trust relationship however doesnot imply any business relationship between the user and thenew SP.

Challenges in designing and implementing the A4C systemarise from the need to extend mechanisms developed initiallyfor network services in order to deliver their functionalities to

mobile grid services. Akogrimo’s A4C infrastructure is based onthe Diameter protocol and it follows the IETF AAA generic ar-chitecture. The main components of A4C are the A4C server,the A4C client and the SAML authority. Their physical deploy-ment in an existing network and grid infrastructure is depictedin Fig. 5.

The A4C server performs authentication of users, authorizationof network services, accounting of service usage and chargingof service consumption. Besides these tasks, it also handlesthe inter-domain communication with A4C servers of other SPsbased on existing cross-domain trust agreements.

The SAML authority is a component built based on [27] and isused by the A4C server for providing single-sign-on supportacross multiple domains. Its task is to generate and checkSAML assertions during user authentication sessions.

The A4C client is a module used by any network or grid compo-nent that requires A4C functionalities. Its main task is to estab-lish and manage communication with the A4C server in order toprovide access to the A4C infrastructure to any component thatneeds it.

The following paragraphs shortly describe the tasks performedby the A4C system.

1) Authentication

Two different authentication mechanisms are used in Akog-rimo. Network authentication is the first one that is used whena user attaches to an access network (AN). During the net-work authentication a user is identified based on a usernameand a password. If the AN belongs to the home domain theauthentication is processed by the local A4C server, other-wise the local A4C server will redirect the request to thehome domain of the user for further processing. As result ofa successful authentication the user receives a SAML artifact(IDToken) which will be used for further service request as aproof of being an authenticated user. An IDToken is gener-ated by the SAML authority from the user’s home domain dur-ing the authentication process, and it can only be validated bythe SAML authority that generated it. The validation of IDTo-kens is the second authentication mechanism used in Akog-rimo.

2) Authorization

In Akogrimo, service authorization has two distinct aspects: onthe one hand there is network services authorization which al-lows the user to have network connectivity and on the other

Fig. 5 A4C View of the Network Architecture

A4CServer

A4C Client

Network layercomponents

A4CServer

SAMLAuthority

Domain A Domain B

A4C Client

Gridcomponents

SOAP

Diamet

erDiameter

Diameter

PIK 30 (2007) 1 41


hand there is a more complex authorization mechanism that isused inside a VO for enabling the interoperation of differentservices belonging to different SPs. The A4C server will onlyperform network services authorization while the authoriza-tions needed for the VO internal operations will be performedby VO management components. The Akogrimo componentsthat will make use of the authorization mechanisms of the A4Cserver are the QoS broker, the VO manager and the ContextManager. Whenever a user attaches to an access network, theQoS broker responsible for that access network will requestfrom the A4C details on the QoS that needs to be de1livered tothe user. The VO manager will contact the A4C server when-ever a user will request to join a VO. The VO manager requeststhe generic user profile (GUP) of a user. Based on a user pro-file, further authorization decisions will be made at the VOlevel. The Context Manager will use the authorization mecha-nism of the A4C infrastructure to perform access control tocontext of users.

3) Accounting

The A4C server controls and manages the accounting process.It collects and stores accounting records, which describe theusage data for a certain service session. An accounting ses-sion is related to the service usage of a user. Service usagedata is gathered on different components by metering networktraffic, grid resources utilization or other user activities. Thecomponents which perform metering and generate accountingdata are access router (AR) and the EMS. A commercial mobilegrid platform for being successful is required to offer differentlevels of QoS and charge its users based on the QoS they re-ceive during service provisioning. The A4C system performsthis task by specifying for every service metrics that define thequality of that service as well as the degree of the service us-age. The acceptable values for these metrics are part of an SLAagreement and are continuously monitored and accounted forduring the service session.

4) Auditing

Services in Akogrimo are monitored for the parameters negoti-ated in the SLA. The auditing component gathers informationon the SLA violations occurring during service consumption.The data recorded during auditing processes will be used lateron during the charging process.

5) Charging

Based on the accounting records collected during accountingprocess and the charging specification stored in the A4Cserver, the charging subsystem calculates the charge for eachservice session and creates associated charging records. Acharging record contains the result of the charge calculationand it includes attributes like the username, accessed service,domain where the service was provided, currency used, andthe charge for the service. To support service provisioning in amulti-domain environment where users receive a single billfrom their home provider, the exchange of charging records be-tween providers is required. Charging records are used both forthe transfer of end-user charges and for the exchange of settle-ment data between providers.

D. Context Management

The Akogrimo context manager gathers basic context data,processes and refines it according to common Akogrimo con-text requirements and allows context consumer to add exten-sion modules to handle domain-specific context inference. Theoverall Akogrimo context management approach is shown inFig. 6.

The context manager gathers raw context data from differentcontext data sources across well-defined interfaces. Given thevariety of possible context data sources, the context managerneeds to handle multiple protocols for collecting data from dif-ferent sources. The context manager has a set of rules (poli-cies) describing the logic for context gathering (e.g., whichsources provide context, at what schedule, action to take whensomething fails). These rules are configured through an admin-istrative interface. The context manager refines raw contextdata to provide standard formats (e.g., geographical coordi-nates, temperatures), performs processing according to com-mon Akogrimo requirements and stores the context data in acontext database.

Context consumers can either execute queries towards thecontext manager to get specific context information or sub-scribe for notifications about changes in certain context data.The context manager is responsible for distributing context datato context consumers accordingly. To handle domain-specificcontext inference, the context manager offers interested partiesinterfacing with extension modules. One example is the transla-tion of location coordinates to a map of a building, such that thecontext will also specify which room a person is in and whatphysical facilities he is able to use. Context extension modulesalso allow context consumers to combine basic context infor-mation with additional domain-specific context sources, e.g.,data from specific medical sensors.

E. Service Discovery

The functional role of the service discovery service (SDS) is toallow a service requestor to find an appropriate service pro-vided by a service provider. A service provider must describethe service capabilities (service description, SD) and publishthe service through the service discovery service. The SDSmaintains a list of available services and their capabilities.

Fig. 6 Context Management Functional Layers

Extension modules

Context gathering

Queries Subscribe/notify

Basic context data sources

Processing and storage

Context gathering

Queries Subscribe/notify

Basic context data sources

Processing and storage Domain specific context sources

Context consumers

42 PIK 30 (2007) 1


Since within the Akogrimo architecture very diverse servicesmust be handled, a unified service description is a key issue.The different types of service discovery protocols target differ-ent types of services, such as people, places, or web services.In order to embrace the greatest number of SD types severalprotocols will be used, which may encounter service directoryprotocols and their access protocols.

Within the Akogrimo environment, the general service discov-ery system (GSDS) is in charge of supplying a particular serv-ice from a particular client request. GSDSes have to deal withservices of very different nature. On the one hand, with the so-called local services/resources such as printers, beamers, vir-tual hard disks, and on the other hand with the grid servicesthat can be defined as stateful web services, which are suitedfor the semantic grid.

The system in charge of discovering local resources (services)is called local service discovery system (LSDS), whereas gridservice discovery system (GrSDS) is the name for the moduledealing with proper Grid Services as presented in Fig. 7.

VII. SUMMARY AND CONCLUSION

In this overview paper, a new approach on grid business mod-els – mainly driven by the Akogrimo context, however, takinggeneral requirements into account – has been developed inwhich the detailed list of classification criteria as well as keycharacteristics have been exploited. Based on an extensiverelated work discussion, the Akogrimo Architecture has beenoutlined by addressing business, grid, and network middle-ware views. Driven by a three layer model, the network serv-ices layer, the network middleware services layer, and the gridinfrastructure services layer, the grid application support interms of virtual organization (VO) memberships, workflow en-hancements, and Service Level Agreements (SLA) can begranted. This approach results in a highly flexible system,which addresses modern mobility requirements at the sametime.

To show the integrated understanding of networking and gridaspects, three different views have been introduced. While thebusiness view of Akogrimo focuses on economic aspects of

commercial mobile grids as such, the grid view determines theservices, infrastructure, and technology available for now. Fi-nally, the network view provides insights into the supportive dis-tributed systems, which provide mobility and Quality-of-Service(QoS) support, signaling support, and authentication, authori-zation, accounting, auditing, and charging (A4C) support, con-text management support, and service discovery support.Thus, these elements form the base for a single technology so-lution, in which networking and grid approaches are harmo-nized in the sense of a common A4C system and joint signalingsystem.

As the project Akogrimo is being implemented in its currentstate, the architectural design steps undertaken have resultedin an integrated view of grids and networks. This integration isbelieved to leverage off the effort seen so far in pure grid ap-proaches, which do not address explicitly the potential knowl-edge of underlying networking technologies. Neither the sup-port of roaming users nor the integrated provisioning of full-fledged and automated accounting schemes have been visi-ble so far in existing systems. Thus, Akogrimo provides aunique solution for accessing knowledge through the mobilelink.

The feasibility of this concept has been successfully demon-strated already several times including large demonstrationssuch as during the IST2006 event. The final phase of theproject will now focus on the validation in larger scale of theplatform according to the viewpoints used here in this paper,but additionally also from an implementation viewpoint.

ACKNOWLEDGEMENTS

This work has been performed in the framework of the EU ISTproject Akogrimo “Access to Knowledge through the Grid in aMobile World” (FP6-2004-IST-2-004293). The Akogrimo part-ners are acknowledged highly for their collaboration.

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Fig. 7 Service Discovery

Service Providers ( Proximity services )

Service Requestor

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SLP UPnP Tag Badge

Services Device People Places , Things ...

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[37] World Wide Web Consortium (W3C): Web Services Addressing(WS-Addressing). http://www.w3.org/Submission/ws-addressing/,August 2004.

[38] WSRF.NET Forum: WSRF.NET. http://www.cs.virginia.edu/~gsw2c/wsrf.net.html, March 2006.

Documents

M. Waldburger, Chr. Morariu, P. Racz, J. Jähnert, S ... · 34 PIK 30 (2007) 1 Waldburger, Morariu, Racz, Jähnert, Wesner, Stiller Grids in a Mobile World: Akogrimo’s Network and