A Web-based Database System for Providing Technical ...

Journal of Computing and Information Technology - CIT 11, 2003, 1, 1–13 1

A Web-based Database System forProviding Technical Information onATM Networking Platformsy

Kimon Kontovasilis�, George Kormentzas�, Anastasios Kourtis�,Nikolas Mitrou��, John Soldatos�� and Evangelos Vayias��National Center for Scientific Research “DEMOKRITOS”, Institute for Informatics & Telecommunications, Greece��National Technical University of Athens, Electrical & Computer Eng. Dept., Computer Science Division, Greece

This paper presents a Web-based database hosting tech-nical information about pioneering ATM networkingplatforms, associated research activities engaging theseplatforms, and related important trials conducted in theframework of these research activities. The paper out-lines the organisation and structure of the informationcontent in the database and discusses methods of accessthrough the WWW interface. Besides the “static” infor-mation offered by the database, other Java-based toolsprovide for the on-line monitoring of the status of theATM platforms and for manipulating data arising fromtechnological trials on these platforms. The integrationof these tools with the database, under a common WWWinterface is discussed.

Keywords: ATM networks, WWW, information systems,Java-based tools, remote monitoring, trials.

1. Introduction

The ACTS �Advanced Communication Tech-nologies and Services� research programme hasbeen the primary vehicle for research on ad-vanced telecommunication systems, conductedwithin the EU framework. During the lifetimeof ACTS, many relevant research projects main-tained means for electronic dissemination oftechnical information pertaining to these pro-jects. There were even projects, like InfoWin�The Multimedia Information Window forACTS — AC113� �see InfoWin Proj., 1996�that focused specifically on providingmeans forfacilitating information dissemination. In this

paper, we focus on the Web-based informationsystem developed by the WATT �WWW Win-dows for ACTS Trials and Testbeds — AC235�research project �see WATT Proj., 1996�, inwhich the authors have participated. The aimof the WATT system is rather different fromthat of other projects oriented towards infor-mation dissemination. Instead of dealing withthe technical results of specific projects, WATTtargets technical information relating to the Eu-ropean prototype ATM networking platforms.These network islands play a key role in thebroadband telecommunications research under-taken in Europe. They reflect the culminationof massive technical work undertaken over theyears, from the RACE �Research and develop-ment in Advanced Communication in Europe�to the ACTS framework. During the course ofthis work, the islands have been built, modifiedand supplemented, so as to be representative ofthe technological state of the art.

Relieved from the restrictions that necessarilyaccompany environments targeted to “produc-tion” work, these prototype networks are par-ticularly suitable as experimental testbeds �theterm of choice for referring to them in the voca-bulary of the described database� and, in reco-gnition of this fact, they have been directly en-gaged by many research projects in technolog-ical experiments �also called trials� demonstra-ting technical results. Thus, the said testbedshave become the focus of important technolo-

yWork partially funded by the European Union, through the research project AC-235 WATT �WWW Windows for ACTS Trialsand Testbeds�, in the ACTS �Advanced Communications Technologies and Services� research program.

2 A Web-based Database System for Providing Technical Information on ATM Networking Platforms

gical events that illustrate and advance the stateof the art of ATM and related technologies. Assuch, they are also ideal focal points for dissemi-nating this up-to-date technical information toa wider engineering and research community,both within and outside the European Union�Alles, 2000�.

The purpose of the system described in the pa-per, called the “WATT database” �and abbrevi-ated throughout as WDB� is twofold:

1. to provide information about importantATMtestbeds, thus demonstrating typical para-digms of early comprehensive ATM instal-lations; and

2. to become an information gateway for im-portant technological trials that employ theseATM testbeds.

The first objective has been met through the pro-vision of comprehensive information, mostly inHTML format, about the components and sub-systems comprising the testbeds, hierarchicallyorganised and appropriately cross-referencedfor effective perusal and retrieval. Note thatWDB is not a “classical” database in the sensethat no underlying DBMS engine is used. Itis the data organization that provides a disci-pline to the whole system �Ramakrishnan et al,2002�.

While the first objective addresses “static” in-formation �the configuration of the testbedsdoes not change very frequently�, the secondobjective is of a dynamic flavour, because tri-als are events, performed once, in a tight time-schedule. As such, trials have an important“live” component and it is desirable that thiscomponent be accessible to the largest audiencepossible. WDB is intended to enable remote au-diences to “participate” in important trial events.

Towards this end, trials planned for performanceon a testbed covered within WDB are “adver-tised” in the database, so that potential trial-watchers may be informed of the trial scenarioand of the way the testbed is involved. Further-more, during the actual performance of thesetrials, users of WDB may engage a Java-basedsoftware tool �seeWATTProj., 1997e, Mitrou etal., 1997b and Vayias et al., 1997b� that enablesremote monitoring of the testbed’s status in adynamic fashion, as the trial evolves. Finally,after the completion of the trial, the relevant

WWW page in WDB is updated to include asynopsis of the trial results.

For certain important trials, special data filesthat contain records of the testbed’s status dur-ing the course of the trial may become avail-able; in this case, they are reachable throughaccess to WDB, from within the WWW pagesdescribing the trials. The data files may bedownloaded by the user and subsequently pro-cessed, by means of a special software tool �seeWATT Proj., 1997c and Vaduva et al., 1997�,called the “demonstration authoring tool”, lo-cally, at the user’s computer, so as to generatea dynamic visualisation of the recorded statuschanges. Instances of this visualisation maybe saved in files and used as supporting ma-terial, towards the preparation of lecture notesor reports on the particular technological issueshighlighted by the trial.

Both the tools for monitoring trials on-line andthose for processing trial results off-line are ap-plications of a client�server software system,called the “WATT Monitoring System” �and ab-breviated throughout as WMS�, which enablesthe remote monitoring of the status of a tar-get testbed. The WMS client is Java software,typically invoked from within WDB through anappropriate link. Upon invocation, the WMSclient is loaded on top of the user’s WWWbrowser �which must be Java-capable�; sub-sequently the WMS client automatically es-tablishes a connection to the testbed that willbe monitored. Once this connection is estab-lished, the user may issue monitoring com-mands, choosing from a set of available opera-tions. A module of the WMS client software,called the “viewer”, acts as a graphical user in-terface that displays a graphical representationof the testbed’s topology and handles, throughmenu selections or mouse clicks, the monitor-ing requests. These requests are forwarded overthe Internet to the server part of WMS, whichresides at a computer by the testbed, for process-ing, then the replies are sent back to the user.Note that WMS requires appropriate supportfrom the testbed’s network management sys-tem, which must interface to the server part ofWMS. Because of this requirement, only someof the testbeds covered by WDB may be moni-tored remotely. For more details on the WMSarchitecture see �WATT Proj., 1997a�.

A Web-based Database System for Providing Technical Information on ATM Networking Platforms 3

The rest of the paper discusses the structureand features of the “static” component of WDBand the integration of this component with theother Java-tools. Section 2 presents generic fea-tures and capabilities that are important from theuser’s, implementor’s, or maintainer’s point ofview. These features have supplied the moti-vation for particular design decisions and haveserved as “checkers” of the appropriateness ofthe design afterwards. The abovementioned in-tegration issues are mainly discussed in this sec-tion. Subsequently, Section 3 outlines the infor-mation content and its structure, describing, inparticular, the various information categories in-cluded in WDB and specific information itemsfor these categories. Section 4 comments onimplementation issues and on the present ope-rational status ofWDB,while Section 5 presentsmajor trials that have been covered by WDB.Finally, Section 6 recapitulates the paper andprovides some concluding remarks.

2. Generic WDB Features and Capabilities

WDB was designed with the intention of pro-viding a versatile, convenient to use, and po-werful system. In the specific context of ATMnetworking platforms, these general attributestranslate into the following characteristics:

1. Modularity and extensibility;

2. Uniform structure and appearance, acrossdifferent testbed, project, or trial instances;

3. Comprehensiveness;

4. Easy navigation to the desired informationand balanced support for users aiming at dif-ferent information categories;

5. Provision for the potential of classified ac-cess to certain information items;

6. Integration with the WMS client and thedemonstration authoring tool.

The first feature is important from the imple-mentor’s and maintainer’s point of view, espe-cially when taking into account that, besides theATM testbeds initially covered by the database,additional testbeds, projects, or trials may be in-corporated in the future. Extensibility, in parti-cular, is primarily meant for incorporating addi-tional testbeds, not so much incorporating new

unanticipated information categories. In the lat-ter case, the design may have to be readjusted,although it is desirable that such adjustments bekept at a moderate level and remain localised.

In the context of the second characteristic, uni-formity is meant as similar structuring of the in-formation over different testbeds, despite the ex-pected �in some cases wide� variations in the ac-tual information content. Uniformity is a majorfactor towards ease of usage, seen both from apsychological and a procedural angle. Further-more, a homogeneous structure enables easycomparison between various testbeds over a cer-tain aspect, e.g., their switching technology, andthus increases the utility of WDB. A robust anduniform structure is also of paramount impor-tance in enforcing a discipline on the whole sys-tem since, as already remarked, no DBMS en-gine underlies WDB. Finally, note that, besidesstructure, the notion of uniformity is extendedto also imply a certain degree of similarity inthe visual appearance of information across dif-ferent testbeds; this promotes the sense of anintegrated environment. Similarity in appear-ance, however, is not overemphasised or exces-sively enforced, since it is indeed desirable thateach testbed participating in WDB maintains itsparticular character at this level as well.

The desire for comprehensiveness is self-expla-natory. Note that the objective ofWDB is to pro-vide information so as to cover not only ATMtestbeds, but also associated research projectsand important trial results. Thus, projects andtrials are important entities to be covered bythe database, although their association witha particular ATM testbed is an essential pre-requisite for their inclusion. Note that the re-quirement for comprehensiveness is partly an-tithetical to the desire for uniformity, due tothe fact that testbeds, especially those of an ex-perimental orientation, present wide variationsin their scope, configuration and functionality.The best compromise between the two objec-tives has been sought. Finally, it is to be re-marked that comprehensiveness does not nec-essarily imply that large amounts of informa-tion have to be stored in a single place. Undermany circumstances, links to information resid-ing elsewhere have been provided; this is fairlyeasy for a World Wide Web environment �seeChapin et al., 1997�.


User-friendly navigation �Feature 4� is a veryimportant contributor to the utility of WDB, es-pecially if one considers the large amounts andthe diversity of information held in the database.Uniformity in structure is very helpful in thisrespect. Note that user-friendliness should ap-ply equally to different categories of users. Forexample, there are users that may interrogatethe database for some particular project thatis active on a testbed, then follow down linksand reach trial results in the framework of thisproject. On the other hand, there may be usersdirectly interested in trial results on some par-ticular technological issue. Users of the sec-ond kind should have the possibility to followa path more natural for their needs, towards theinformation they are after; in this case, the alter-nate path may by-pass information on particularproject and immediately access a collective poolof trials on the relevant technological issue.

Given the security enforcement facilities presentat current WWW servers �Larson et al., 2000�,WDB employs some of these facilities for pro-viding the potential of classified access to partsof the database. This enables confidential orcopyrighted information items to be kept on thesame machine as the publicly available ones.Such an arrangement effectively permits the useof a single information source, namely WDB,by many classes of users with varying access-authorisation privileges.

The last feature in the list of items above re-lates to integration with WMS, namely the sys-tem that provides for the remote monitoring oftestbeds, including the monitoring of the evolu-tion of trials on these testbeds, and the demon-stration authoring tool that enables the retrievaland post-processing of files containing trial-data. �This issue is applicable only to testbedsthat support WMS through an appropriate inter-face to the Network Management System.� Theintegration is feasible because both the user in-terface to WMS and the demonstration author-ing tool are Java-based applications that run ontop of ordinary WWW browsers; thus their us-age meshes well with the WWW orientation ofWDB. Besides being feasible, the integration isalso desirable, because is increases the utility ofWDB. For example, a user that is about to login,through WMS, to a remote testbed to monitor aparticular activity, may before doing that, eas-ily consult the appropriate sections of WDB inorder to be briefed on the particular event tobe monitored, or to review the architecture andcapabilities of the ATM testbed.

3. Organisation of the Material in theDatabase

WDBcontains information aboutATMtestbeds,research projects associated with these testbeds

Fig. 1. Outline of the WDB structure.


and trials scheduled in the context of these re-search projects. All information relating toa particular testbed, is organised in a “tree-like” hierarchy, where there is one tree for eachtestbed included in the database. The hierarchyis depicted in Figure 1. The “root” of each treeis occupied by a WWW “home” page for therespective testbed that contains general infor-mation, including a brief profile of the testbed,and links to other pages, lower in the tree hierar-chy, that provide more specialised information.

The information below the “root” level is orga-nised into three major categories:

� Components and subsystems of the testbed:It contains information about the testbed perse, regarded as a network�system. This ca-tegory is further described in subsection 3.1.

� Research projects: This is a list of the re-search projects associated with the testbed.The list contains links that lead to individualpages �or sections in a page� describing eachproject. Details on the information contentrelating to projects is given in subsection 3.2.

� Trials run on this testbed: This is a listof important trials that have been performedon the testbed, or are scheduled for perfor-mance at a later time. Individual trials arefurther organised according to category andaccording to status, as it will be explained insubsection 3.3. The link at the “root” pageleading to trial-related information points tothe top level of this organisation. Note thatthe trials correspond to research projects thathave scheduled the trials as part of their ac-tivities. The link at the “root” page leads toa cumulative list of trials from all projects.Access to the subset of the trials that arerelevant to a particular project is possiblethrough another link from within the pagedescribing this project.

3.1. Information About the Componentsof a Testbed

This part of WDB includes detailed informa-tion about the devices and systems that combineto formulate the testbed. To manage the com-plexity of current ATM networking platforms,various components are organised into a num-ber of categories, according to function. Thesecategories are:

� Switching systems: It includes devices re-sponsible for switching and multiplexingwithin the ATM network.

� Terminal devices and servers: It includescomponents that may be viewed as “end-points” from the network’s point of view.Typical members of this category includecomputers with a network interface, mul-timedia terminals and video, multimedia, ordatabase servers.

� Interfaces to other transmission systems:Devices having an interconnection naturego in this category. Typical members in-clude mappers, interworking units, routersand bridges.

� Communication links: It provides a homefor the description of the actual media inter-connecting the components of the networkplatform �and connecting this platform tothe “outside world”�.

� Management system: It covers all systemsand functions relating to network manage-ment.

� Specialised devices: Devices of a somewhatspecialised or peripheral nature, with respectto the main networking or application envi-ronment. Typical members of this categoryare: measurement and testing devices, trafficgenerators and accounting and�or chargingunits.

� Applications: A repository for systems at anapplication level that rely on ATM network-ing facilities and operate on top of them,so as to provide a service, either general-purpose, or custom. A typical example isa hardware and�or software system inter-operating with the network to provide a dis-tributed multimedia service.

� Superstructures: It applies to cases wherethere is a tight interconnection between thedescribed testbed and other network islands,in such a way that a higher-level entity maybe identified. The notion of a superstructureapplies only if the individual islands may beregarded as independent interconnected enti-ties. Otherwise, the whole system logicallyis a single platform and the superstructurecategory is not relevant.


Fig. 2. Graphical representation of a tesbed’s topology.

These categories are “exhaustive”, in the sensethat they are intended to cover all possible casesthat may arise in an ATM platform. For an ac-tual testbed without any devices of a specificcategory, the respective description in WDBomits the irrelevant category altogether �ratherthan providing an “empty” header�. The infor-mation for each individual member in the ca-tegories above, has been further organized intofully specified information items, suitable forthe object under description. Description of aswitching device, for example, may include in-formation for:

1. the manufacturer, the relevant product line,the specific model, etc.; a link to a WWWpage maintained by the manufacturer anddescribing the particular piece of equipment�if such a page exists� may be included;

2. the basic architecture of the switching fabric�e.g., shared backplane, shared memory, orself-routing; input or output queueing, etc.�;

3. the number of I�O ports and the respec-tive physical layers involved �e.g., 155MbpsSDH, 34Mbps E-3�;

4. the buffering capabilities;

5. details about the network management capa-bilities;

Detailed lists of the basic information items ap-plying to other categories of components areomitted here, due to lack of space. For fulldetails on the WDB specification see �WATTProj., 1997b�.

WDB employs extensive cross-referencing, im-plemented as WWW links, between relateditems �e.g., devices neighbouring in the networktopology�. Besides the conventional method offollowing links from within WWW pages, thereis an alternative, topology-driven way to accessinformation about a specific device. The “root”page of each testbed provides a link that leads toa graphical representation of the testbed’s topo-logy. �For an example, see Figure 2.� Iconsare used to represent the various devices, ac-cording to their function. A legend providesidentification of the device-category associatedwith each icon. The graphical representation is“active”: clicking on the icon representing anitem leads to the appropriate location within theWWW page, that hosts the description for thisitem. Similarly, clicking to an icon in the legendleads to the “table of contents” for the particulardevice-category associated with this icon. Thetopology-driven method of access is a particu-larly suitable way of retrieving information fora set of interconnected devices. On the other


hand, the ordinary linkage �i.e., from within theflow of text� is more appropriate for an intro-ductory overview of the testbed’s capabilities.

3.2. Information About Research Projects

The main purpose of the page describing a re-search project associated with the testbed is toprovide a brief profile for the research activ-ity. Typical information items included in theproject’s description include:

� Identification of the partners involved in theactivity, and of any sponsoring parts; in casethe project belongs in a formal multi-projectresearch programme �e.g., ACTS�, this is soidentified.

� The time-frame over which the project is ac-tive.

� A statement of the major objectives of theproject.

� A statement of the main technical approach.

� A summary of the activity’s trial compo-nents, with particular emphasis on the usageof the testbed.

� A summary of the expected or realised achi-evements.

� Links to other information sources for thisactivity over the WWW, if applicable.

For research projects with a significant trialcomponent, the relevant WDB page also con-tains a link that points to information about im-portant individual trials. This link leads to theset of trials that belong to the context of thisproject only. A cumulative list of trials maybe accessed from within the testbed’s “root”WWW page.

3.3. Information About Trials

As already mentioned, the documentation ontrials may be accessed from either the “root”page of a testbed �for a cumulative list of alltrials relevant to the testbed�, or from within thepage documenting a particular project associ-ated with the testbed �for the partial list of thetrials that belong to the context of this project�.In either case, the Web pages documenting trials

are organised into the following thematic cate-gories, according to the particular technologicalissues highlighted by the trials:

� Performance: For trials whose focus is onthe quantitative assessment of some perfor-mance aspect of a component, subsystem, orthe testbed as a whole, under the presence ofspecified loading conditions.

� Network management: In this case the fo-cus is on all network management issues,including trials on algorithms or devicesthat perform functions supportive to ma-nagement. The category includes �but is notlimited to� trials on: connection acceptancecontrol; routing; accounting and charging.

� Application and service support: This cat-egory relates to the launching and testing ofapplications and services over the testbed.Trials on user-perceived QoS belong here.

� Interoperability: As the name indicates, thefocus here is on interoperability issues, ei-ther between the networking platform andan application system, or between distinctnetworking platforms.

Furthermore, and for all of the trial categoriesabove, individual trials are further classified asperformed or planned. As their names indicate,performed trials are accomplished events withfinalised results, while planned trials are futureevents designed and scheduled, but not yet per-formed. Entries on performed trials are storedin WDB for the record and for future usage ofthe results produced by the trials. Entries onplanned trials are, by their nature, temporaryand serve as “posters” announcing the trials-to-be.

The description for a trial, regardless of the trialcategory and classification, typically includesthe following common information:

� An indication of the time when the trial took�performed trials� or will take �planned tri-als� place.

� Objectives of the trial.

� An identification of key subsystems of thetestbed involved in this trial �and links toparts of WDB that include information forthese entities�.

� Particular actions that were, or will be, re-quired, including testbed setup details and


timing considerations �e.g., 10 minutes afterthe commencement of the trial, the load onlink X, leading to port Y of the switch Z,will be increased by 50 Mbps and for thesubsequent 30 minutes the losses occurringon switch Z will be monitored.�

� Expected results, as of the time the trial wasdesigned.

Additionally, the page may include a link to aJava-applet that provides a dynamic demonstra-tion of some aspects of the trial �this featurerequires usage of a Java-capable browser�; forexample, the applet may display an outline ofan important time-sequence of procedures orevents, or exhibit “typical” fluctuations of mea-surable quantities, in some appropriate graph-ical representation. The animation is intendedto recapitulate, in an intuitive manner, essentialinformation already supplied by other informa-tion items just mentioned.

For trials of “planned” status, typical users of theinformation described above are persons inter-ested to prepare before actually witnessing thetrial. The WDB information provides a suitablebriefing so as to enable these users to judiciouslyfocus on interesting elements during the evolu-tion of the trial. If the testbed that will host theplanned trial supports WMS, then it is possibleto actually “watch” the trial being performedremotely. For this purpose, the page describingthe planned trial will include �at some appro-priate time before the actual performance of thetrial� a link that may be used to invoke the ap-propriate WMS software and monitor the trialremotely.

In the end, a planned trial will be realised.Accordingly, the classification of the corre-sponding documentation in WDB will eventu-ally change into “performed” status. Along theprocess of doing this, the appropriate Web pagewill be modified, so as to include a descriptionof the trial results �together with a comparisonbetween expected and achieved results� and acomment summarising the conclusions drawnfrom the trial. Beyond these supplements, theupdated page may include links for download-ing data files containing material that resultedfrom the trial and that may be post-processed,or otherwise manipulated by the user, in an off-line fashion. For example, a trial that focuseson applications and user-perceived QoS may in-clude audio or moving video files, which, when

played back, exhibit deterioration of the QoSunder certain trial conditions.

An important special case of such data files ap-plies to testbeds that support WMS: on such atestbed, an operator may record fluctuations ofcertain aspects of the testbed’s status and savethis record in an electronic file. As alreadyremarked, in order to generate a dynamic visua-lisation of the recorded status changes, a usermay download and subsequently process thisspecially formated data file. He can do it locally,at his computer, by means of special software,namely the demonstration authoring tool. As ageneral rule, data files �of any format� accessi-ble from within the WDB page documenting aperformed trial are always accompanied with acommentary on their format, contents, and thepossible means for their processing.

4. Implementation Issues and OperationalStatus

A prototype of WDB has been implemented inthe framework of the WATT research project.The prototype is complete and operational; it isreachable over the World Wide Web, throughthe URL: http��www�telecom�ntua�gr�watt�wdb�� The system has been accessed usingmany different WWW browsers �including re-cent versions of Netscape Navigator TM andInternet Explorer TM� to ensure that it maybe effectively utilised through popular WWWbrowser software. In general, no special restric-tions on the usage of specific browser softwareexist. Certain features of the system �e.g., invo-cation of the WMS client� require that the Webbrowser be Java capable. Nowadays, this canhardly be considered a limitation.

Current initial deployment of WDB covers twomajor European experimental ATM testbeds;namely EXPERT �the largest broadband testplatform in Europe, located in Basel, Switzer-land� and AMUSE �a network of 7 broadbandcentres, located in Italy �Milan�, Germany �Mu-nich�, Belgium �Mons�, Switzerland �Basel�,England �Cambridge�, Portugal �Aveiro� andIceland �Reykjavik� and connected through theEuropeanATMnetwork�. TheEXPERT testbedsupports an interface to WMS and thus canbe monitored remotely. These two testbedsvary considerably in terms of orientation. The


EXPERT testbed focuses on Network Manage-ment andNetwork Interoperability issues, whileAMUSE aims at multimedia services over abroadband platform. Consequently, the twotestbeds are quite different in terms of con-figuration and setup. The fact that both plat-forms were able to fit in the WDB structureprovides an assurance that the design specifica-tion is grounded on a firm basis and that otherimportant ATM testbeds may be incorporated inWDB without a major effort. In fact, it is envis-aged that such extensions will indeed occur, asWDB matures. General guidelines for imple-menting extensions have already been issuedby the WATT project �see WATT Proj., 1997band WATT Proj., 1997f�. The initial prototypeitself may serve as a concrete implementationparadigm.

The WDB design specification has intentionallyleft open the option of either using a single cen-tral WWW server for storing all the files con-stituting WDB, or, alternatively, distributing thefiles into more servers. From the security pointof view, the usage of many servers is preferableand the same turns out to be true in terms ofease of maintenance. In fact, the structuring ofinformation suggests that the “information tree”corresponding to a testbed is a “self-contained”unit of information. Using appropriate relativecross-referencing links, an entire tree may berelocated to a different WWW server in a waytransparent to the user. The relocation requiresonly the adjustment of one link pointing to the“root” of the tree-hierarchy.

The WDB prototype has used three WWWservers: one at National Technical University ofAthens �NTUA�, one by the EXPERT testbed,in Basel, and one by the AMUSE testbed, in Mi-lan. These servers include the following files:

In the NTUA server:

� Introductory pages describing the structureof WDB, various tools, etc.;

� the archives containing the demonstrationauthoring tool software, available for down-load; and

� other miscellaneous documents �e.g., WATTdeliverables in electronic form�.

In the EXPERT server:

� All WWW pages documenting the EXPERTtestbed and related projects and trials;

� the WMS client software �to be invoked ontop of the user’s browser for monitoring thetestbed�; and

� the WMS server software that must run onthat server for WMS to be operational.

In the AMUSE server:

� All WWW pages documenting the AMUSEtestbed and related projects and trials.

Most material in WDB is publicly accessible.Some pages, however, contain confidential ma-terial, inwhich case an authentication procedureis initiated when the page is entered. The or-ganisation of the material into multiple WWWservers facilitates the task of providing accessclassification, in that only servers containing“sensitive” material need to be secure servers,appropriately set-up to enforce restrictions ofaccess. For more details on the security featuresof WDB, see �WATT Proj., 1997d�. �WATTProj., 1997f� has additional details on imple-mentation issues encountered during the deve-lopment of the prototype.

5. Major Technological ExperimentsSupported by WDB

Two major experiments�trials supported byWDBand the associated Java-based tools �WMSand the demonstration authoring tool� took placein the scope of large distributed conferencesand were witnessed by wide audiences. Duringthese conferences, the Global-360 network �aninternational IP over ATM platform, configuredwith the support of National Hosts and Pub-lic Network Operators� was used to carry datato several remote sites monitoring the event.Global-360 supported high-bandwidth Internetapplications and, in particular, enabled video-conferencing among several sites around theworld.

The first trial involved distortion of the qualityof a video stream, due to multiplexing with ex-cessive background traffic �Mitrou et al., 1997a�.The video stream was transmitted from Basel�the EXPERT’s location� to Madeira �one of thelocations hosting a ’distributed’ conference onnetwork interoperability� over the Global-360platform. After being routed through a num-ber of ATM switches inside EXPERT, and just


before leaving the platform, the video streamwas multiplexed with background traffic origi-nating from traffic generators. The amount ofthe background traffic was fluctuating, so as toincur a visible distortion pattern on the videostream. WDB advertised the trial and WMSwas used to monitor the bandwidth consumedby the background traffic. In Madeira, the clientWMS software, running on top of a Java enabledWWW browser, was operated by a speaker pre-senting the trial to the conference audience in

Madeira. Additionally, people at other remotesites were given the ability to, either downloadthe client software on their browsers and moni-tor the trial, orwatch the presentation inMadeirathrough the video-conferencing application. Atthe same time, the video stream was reproducedon the video-conferencing terminal in Madeiraand other sites. The audience could examinedistortion of the video signal and associate itwith the bandwidth fluctuations that had causedit �see Figure 3�.

Fig. 3. Remote Monitoring of Background Traffic.

Fig. 4. Remote Monitoring of Bandwidth Consumed in Virtual Paths.


In the second trial �WATT Proj., 1998�, WMSwas used to measure the traffic flowing withinand outside the EXPERT platform. During thistrial, all the connections of Global-360 to theEXPERT platform in Basel passed through aFore ASX-200 ATM switch. WMS monitoredthe bandwidth consumed in the various portsof this switch, keeping track of the traffic flowpassing through the various connections. Theconnections used in this experiment are depictedin Figure 4.

6. Conclusions

WDB is a Web-based database system that pro-vides information windows �both static and dy-namic� for ATM networking platforms. Despiteits name, WDB is not a “classical” database,in the sense that it does not rely on specificDatabase Management Systems �DBMS� or onconventional data structures. Instead, it con-sists primarily of a set of appropriately orga-nized HTML pages �together with informationin other formats, e.g., digitised picture files�.Other Java-based tools, accessible through thesame WWW environment, provide for on-linemonitoring of the testbeds and for the post-processing of trial results in an off-line fashion.The whole system is readily accessible throughan ordinary WWW browser.

In the scope of the WATT project, WDB hasbeen deployed so as to cover two major Euro-pean experimental ATM platforms, EXPERTand AMUSE. However, WDB has been de-signed to support a framework much wider thanthat covering the two immediate target-testbeds,as it is envisaged that organisations, projects,consortia or other entities that possess and�ormanage ATM testbeds, not in the direct scopeof WATT, will be willing to join WDB anddisseminate thereby information about thosetestbeds and related activities. The design ofWDB includes a detailed list of required infor-mation items, for all potential information cate-gories, as well as a rigid hierarchical structurethat organises the information content. Boththe initial development and subsequent updatesof the WDB follow these design specifications.The implemented prototype provides a concreteparadigm that may serve as a guideline in futureextensions of the database.

References

�1� A. ALLES, “The Next Generation ATM Switch:From Testbeds to Production Networks”, White Pa-per, 2000, available at http��www�cisco�com�warp�public�c�c�so�neso�vvda��

�2� L. CHAPIN AND B. MEANDZIJA, “The Global Inter-net”, IEEE Transactions Magazine, Vol. 35, No. 5,pp. 50, May 1997.

�3� InfoWin AC113, Technical Annex, March1996. Information electronically available onthe WWW through the URL: http��www�infowin�org�ACTS�RUS�PROJECTS�INFOWIN�

�4� E. LARSON AND B. STEPHENS, Administrating WebServers, Security, & Maintenance, Prentice Hall,ISBN 0-13-022534-7, 2000.

�5� J. MAGID, R.D. MATTHEWS, AND P. JONES, The WebServer Book. Ventanna Press, 1998.

�6� N. MITROU, M. POTTS, AND K. KONTOVASILIS, “Re-mote Monitoring of an ATM platform throughthe WATT System”, In Proc. 2nd InternationalDistributed Conference on Network Interoperabil-ity, Madeira, Portugal, June 1997, available athttp��www�telecom�ntua�gr�watt�papers�htm

�7� N. MITROU, E. VAYIAS, J. SOLDATOS, K. KAVI-DOPOULOS, G. BRANIS, K. KONTOVASILIS, G. KOR-MENTZAS, AND C. VADUVA, “Remote Monito-ring of Networks through Gateway Programmingover the Internet”, In Proc. 13th UK Workshopon Performance Engineering of Computers &Telecom., Ilkley, UK, July 1997, available athttp��www�telecom�ntua�gr�watt�papers�htm

�8� R RAMAKRISHNAN AND J. GEHRKE, DatabaseManagement Systems, McGraw Hill, 3rd Edition,2002.

�9� E. VAYIAS, J. SOLDATOS, N. MITROU, K. KONTO-VASILIS, AND G. KORMENTZAS, “Managing Net-works over the Web: Classification of ap-proaches and an implementation”, In Proc. Int.Conference on Telecommunications, Chalkidiki,Greece, June 1998, available at http��www�telecom�ntua�gr�watt�papers�htm

�10� C. VADUVA, E. VAYIAS, J. SOLDATOS, N. MITROU,“Network Information Processing Systems”,In Proc. NIPS’97 Conference, Sofia, Bul-garia, October 1997, available at http��www�telecom�ntua�gr�watt�papers�htm

�11� WATT AC235, Technical Annex, March 1996.Information electronically available on theWWW through the URL: http�www�telecom�ntua�gr�watt

�12� WATT AC235, Project Deliverable D05 “Speci-fication of the interface between the databaseand N&SM”, May, 1997, available at http��www�telecom�ntua�gr�watt�deliverables�htm


�13� WATT AC235, Project Deliverable D02 “Reporton the database structure”, May 1997, available athttp��www�telecom�ntua�gr�watt�deliverables�htm

�14� WATT AC235, Project Deliverable D10 “Demon-stration authoring tool”, August 1997, available athttp��www�telecom�ntua�gr�watt�deliverables�htm

�15� WATT AC235, Project Deliverable D04 “Se-curity and confidentiality aspects”, August1997, available at http��www�telecom�ntua�gr�watt�deliverables�htm

�16� WATT AC235, Project Deliverable D06, “Inter-face between the database and N&SM”, Novem-ber 1997, available at http��www�telecom�ntua�gr�watt�deliverables�htm

�17� WATT AC235, Project Deliverable D03 “Informa-tion database structure”, November 1997, avail-able at http��www�telecom�ntua�gr�watt�deliverables�htm

�18� WATT AC235, Project Deliverable D011, “OnLine Demonstrations on Network Interoperabi-lity and Multimedia Service Integration”, Au-gust 1998, available at http��www�telecom�ntua�gr�watt�deliverables�htm

Received: June, 2000Revised: February, 2003

Accepted: February, 2003

Contact address:

Kimon KontovasilisGeorge KormentzasAnastasios Kourtis

National Center for Scientific Research “Demokritos”Institute for Informatics & Telecommunications

GR-15310 Ag. ParaskeviPOB 60228, Greece

Phone: �30 210 6503130Fax: �30 210 6532175

e-mail: fkkont�gkorm�kourtisg�iit�demokritos�gr

Nikolas MitrouJohn Soldatos

Evangelos VayiasNational Technical University of Athens

Electrical & Computer Eng. Dept.Computer Science Division9 Heroon Polytechneiou str.

GR-15773 Zografou, GreecePhone: �30 210 7721639

Fax: �30 210 7722534e-mail: mitrou�cs�ntua�gr,

fjsoldat�evayiasg�telecom�ntua�gr

KIMON KONTOVASILIS was born inAthens, Greece on 1964. He receivedthe Diploma in Electrical Engineering from the National Technical Uni-versity of Athens �NTUA� in 1987, the M.Sc. in Computer Science fromthe North Carolina State University �NCSU� in 1990 and the Ph.D. inElectrical Engineering from NTUA in 1993. Since 1996 he is with theInstitute of Informatics and Telecommunications of the National Cen-tre for Scientific Research “Demokritos” as a member of the researchstaff, currently ranking as Senior Researcher. His research interestsinclude modelling, performance evaluation, dimensioning and trafficcontrol of broadband wired and wireless telecommunication networks,distributed architectures for network management systems, queueingtheory, as well as numerical methods for the solution of Markov Chainmodels and numerical linear algebra. He has published extensively inthe fields above, in international scientific journals, edited books andconference proceedings. Dr. Kontovasilis is a member of IFIP, WG6.3and the Technical Chamber of Greece.

GEORGE T. KORMENTZAS was born in Athens, Greece on 1973. Hereceived the Diploma and the Ph.D. in Electrical and Computer En-gineering from the National Technical University of Athens �NTUA�in 1995 and 2000 respectively. Since 1996, he is a research associatewith the Institute of Informatics & Telecommunications of the GreekNational Center for Scientific Research “Demokritos” working on re-search projects in the areas of traffic analysis, network control, resourcemanagement and quality of service in high-speed wired and wirelessnetworks. He has over fifteen publications in the above fields, in inter-national scientific journals, edited books and conference proceedings.Dr. Kormentzas is a member of WSEAS and the Technical Chamber ofGreece.

ANASTASIOS KOURTIS was born in Athens, Greece in 1956. He receivedhis BS degree in Physics in 1978 and his PhD degree in Telecommu-nications in 1984, both from the University of Athens. From 1986 hehas been a member of the research stuff in the Institute of Informaticsand Telecommunications of the Greek National Centre for ScientificResearch “Demokritos”. Currently he is a Senior Researcher. He hasworked on encryption systems, digital modulation techniques, spreadspectrum systems and multimedia applications. His current researchinterests are in the areas of broadband wireless networks, Local Mi-crowave Distribution Systems �LMDS� and digital interactive TV.

NIKOLAS M. MITROU was born in Greece on October 5, 1957. Hereceived the undergraduate Diploma degree in Electrical Engineeringfrom the National Technical University of Athens �NTUA� in 1980, theMSc degree in Systems and Control from the UMIST, Manchester, in1982 and the PhD degree in Electrical Engineering from NTUA in 1986.In 1988, he joined the NTUA as a Senior Researcher and he is currentlya Professor in the Department of Electrical and Computer Engineering.His research interests are in the areas of digital communication systemsand signal processing, with emphasis on the architecture, modelling,performance evaluation and optimisation of integrated networks, localarea networks and mobile communication systems, digital video andmultimedia, having published extensively in these fields. Dr. Mitrouhas a leading participation in many research projects �RACE, ESPRIT,STRIDE, ACTS� and he was also the Project Manager of the ACTSWATT project. Prof. Mitrou is a member of the IEEE and the TechnicalChamber of Greece and member of IFIP WG 6.3.


JOHN K. SOLDATOS was born in Athens, Greece in 1973. He receivedthe Dipl.Eng. degree from the Department of Electrical and ComputerEngineering, National Technical University of Athens, Greece, in 1996.Since 1996, he is a Research Associate with the TelecommunicationsLaboratory of the Department of Electrical and Computer Engineer-ing of the National Technical University of Athens working on re-search projects in the areas of Integrated Communication Networkscontrol, management, performance evaluation and WWW based mul-timedia�hypermedia systems. Mr. Soldatos has had a very active rolein a number of European research activities within the ACTS frame-work �EXPERT AC-094, WATT AC-235�, as well as in the ESPRIT’Chameleon’ project. He has also been actively involved in the ACTSIMPACT AC-324 project implementing an ATM resource control andmanagement system using intelligent agents. He is also finishing hisPh.D. thesis dealing with Traffic Control and Resource Management inIntegrated Services Networks. Mr. Soldatos is a student member of theIEEE and a member of the Technical Chamber of Greece.

EVANGELOS K.VAYIAS was born inAthens, Greece in 1973. He receivedthe Dipl. Eng. degree from the Department of Electrical and ComputerEngineering, National Technical University of Athens, Greece, in 1996.Since 1996, he is a Research Associate with the TelecommunicationsLaboratory of the Department of Electrical and Computer Engineeringof the National Technical University of Athens, working on researchprojects in the areas of Integrated Communication Networks control,management and performance evaluation. He has participated in theACTS EXPERT, NICE and WATT projects and in the ACTS IMPACTproject �the latter dealing with the implementation of an ATM resourcecontrol and management system using intelligent agents�. He is alsoin the final stage of his Ph.D. thesis dealing with Traffic Control andResource Management in Computer Networks for end-to-end quantita-tive QoS. Evangelos Vayias is a member of the Technical Chamber ofGreece and student member of the IEEE.

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