Designing Advanced Services for Distributed ...

“Designing Advanced Services for Distributed Intelligent Broadband Networks” Odysseas I. Pyrovolakis, Fotis G. Chatzipapadopoulos, Menelaos K. Perdikeas, Iakovos S. Venieris

Dept. Electrical and Computer Engineering – National Technical University of Athens 9 Heroon Polytechniou Str, 157 73 Athens Greece e-mail: [ody|fhatz|perdikea]@telecom.ntua.gr, [email protected]

Abstract: The Intelligent Broadband Network (IBN) enables efficient provision of advanced multimedia services to users, exploiting the benefits of the ATM technology and hiding the limitations of current signalling systems to IBN service designers. The availability of technologies like DOT (Distributed Object Technology) and MAT (Mobile Agent Technology) opens new horizons towards the Distributed Intelligent Networks (DIN). Among the main issues that need to be addressed, in the area of the DIN, are the deployment, provision and control of advanced services. The potentials originating from the utilisation of DOT and MAT along with the employment of concepts and ideas coming from the object oriented design patterns community provide the basis for enhancements in the service design and creation process. This paper introduces a set of implementation principles for the service creation, deployment and management and shows their implications on the overall system architecture. We argue that with the proposed principles, reusability for easy and rapid deployment of services, extensibility towards new and updated services and flexibility on service design can be achieved.

1 Introduction Nowadays there is a growing demand for new and advanced services (i.e. services beyond plain old telephone services) from the telecom vendors. The customers now ask for Multimedia Services such as VideoConference and Digital Video on Demand. Fortunately the evolution of telecommunication networks towards current broadband networks made feasible the support of those services, at least in terms of offered bandwidth. What it remains as the main issue is to resolve the deployment, provision and control of Multimedia services [1]. Since 1992, ITU-T has proposed a reference architecture (called Intelligent Network-IN) for easy deployment of “additional telecommunications services” [2]. By the term additional services ITU-T considered the Freephone, the Virtual Private Networks etc. The proposed architecture consists of Service Control Points (SCPs), where the execution of the service logic is done and Service Switching Points (SSPs) which, in addition to providing users with access to the network and performing any necessary switching functionality, allow users to have access to the set of IN capabilities. Another important issue of IN was the adoption of Service Independent Building blocks (SIBs). A SIB is a standard, reusable, service independent component, which provides certain functionality. The SIBs can be chained together in various combinations to realize services [3]. In the last years the adoption of an extended Intelligent Network Architecture has been proposed as a rapid way to deploy of broadband Multimedia Services. In this paper, we are proposing a framework for designing Multimedia services for a novel IN architecture based on Distributed Objects (such as CORBA) and Mobile Agents Technologies. The main issue is to show how this architecture can enhance the deployment and provision of Multimedia Services on Broadband Networks. The Common Object Request Broker Architecture (CORBA) is an Object-Oriented middleware architecture that provides through the Object Request Brokers (ORBs) the mechanisms by which objects transparently make requests and receive responses. Hence, the ORB provides interoperability between ComCon 7 – Athens-Greece, June 1999, pp. 519 – 530

ODYSSEAS I. PYROVOLAKIS, FOTIS G. CHATZIPAPADOPOULOS, MENELAOS K. PERDIKEAS, IAKOVOS S. VENIERIS

applications on different machines in heterogeneous distributed environments and seamlessly interconnects multiple object systems [4]. There is an ongoing discussion about using CORBA in IN, which is reflected in the OMG request for proposals about interworking between CORBA and IN [5]. It is true that the introduction of a middleware layer in Application servers, and eventually also in switching systems, enables a component-based, distributed intelligence that replaces the “traditional” monolithic IN functional entities [6]. In a new revolutionary IN architecture the core of the signaling system would rather rely on a CORBA compliant system than on Common Channel Signaling System 7 (SS7) and classical IN protocols (e.g. INAP). The core of the system will be an enhanced ORB with features not available in current ORB implementations, such as high reliability, real time capabilities, time-out mechanisms etc. On top of ORB the Generic CORBA Services (such as Naming, Persistent Object, Event Channel Services) and CORBA Facilities (such as System, Information and Task Management Common Facilities) will reside. Telecom specific services could also be considered in a higher third layer that enables the adoption of CORBA as the communication environment for providing IN Services. This layer is the substrate for Mobile Agents based Service Logic. It can be also used as the core of a CORBA-to-legacy IN systems gateway. This last point (the CORBA to IN gateway) is a major issue for the viability of those systems since the existing investments on conventional IN must not demerit. Some recent responses to the request for proposal from OMG about the interworking between CORBA and IN are proposing an INAP/TCAP ASN.1 to CORBA Interface Definition Language (IDL) gateway [7], [8]. During the past few years there is a lot of discussion about Agent Technology and how this technology could be adopted in telecommunications [9]. Before looking at the various types of Agents and how they can be used in telecommunications environment, it is important to define what an agent is. In general, it is a software component (along with its state) that performs one or more common tasks by acting in a preset manner [10]. Two special groups of agents can be easily identified: Intelligent Agents and Mobile Agents. The term Intelligent Agents identifies those agents that have embedded Artificial Intelligent (AI) and in general, have the ability to learn and react. As Mobile Agents are considered those agents that can migrate between different hosts, execute certain tasks and collaborate with other agents. In this paper we are considering the use of Mobile Agents only, as a part of the proposed architecture. In the classical Client – Server model a “persistent” session needs to be active so that client and server can interchange messages which are parts of a predefined protocol. With remote programming, which is the basis of Mobile Agents, there is no need for communication among the client machine and the server. The client machine downloads from the server machine the Mobile Agent(s) which are then executed on the client. This is feasible since the agent includes not only the data to be processed, but also the procedures to be executed. In Figure 1 the conceptual model for mobile agent computing is given.

Server

Client

Mobile Agent Migration

AEE

Communication Infrastructure

Interacting Agents

AEE

Figure 1 Conceptual Model for Mobile Agent Computing Whenever a client asks the server for a certain task the server provides the specific mobile agent. In this way the MA is downloaded from server to client though the Agent Execution Environment (AEE) and the underlying communication infrastructure. The AEE is responsible for the management of the agents and for the migration of the agents through the underlying communication infrastructure. The way that mobile agents perform can lead to a reduction of the traffic on the network since there is no need for continuous connections between client and server. The paper is structured as follows: Section 2 gives a brief description of the proposed Distributed IN architecture. Section 3 presents a design methodology for providing advanced Multimedia Services for this

“Designing Advanced Services for Distributed Intelligent Broadband Networks”

distributed architecture. In Section 4 we examine how the proposed methodology can be applied on a specific Multimedia Service (the Interactive Multimedia Retrieval Service – IMR). Finally in Section 5 the advantages of the proposed architecture as well as some existing open issues are discussed.

2 Distributed IN Architecture 2.1

Proposed Reference Configuration

The Distributed Architecture proposed for IN services is based on both Mobile Agent Technology and CORBA. In Figure 2 the Basic Reference Model of the new distributed IN architecture is shown. SEN

SMCN AEE

AEE

ORB Terminal A

AEE SSN

Transport

AEE

Terminal B

SSN

Signaling

Figure 2 The Distributed IN Architecture CORBA is used as the communication mechanism among the different network elements. This is a completely different approach of this architecture compared to legacy Intelligent Broadband Networks. That is because in our approach there is no need for legacy IN protocols (such as INAP based on SS7), since CORBA is the communication mechanism among the Networks Elements. This makes the system more flexible and more open since other systems based on CORBA (e.g. novel network management systems) can interwork. Of course there is still the need for support of legacy systems, therefore a CORBA to INAP gateway is essential. Also for supporting the employment of MAT, Agent Execution Environments are part of the internal architecture of each network element.

2.2

Network Physical Entities

In Figure 2 the physical entities of the proposed architecture, and their interconnections are shown. Even though there is a similarity between those Physical Entities and the physical entities of the conventional IN systems, the adoption of MAT along with the different communication mechanisms enforced by the deployment of CORBA, compels a radical change to almost all the entities. Service Switching Node (SSN): A SSN is the device responsible for providing users with access to the Network (if the SSN is a local exchange) and allows access to the IN services. To somebody familiar with IN terminology this would sound like the definition of the SSP. Actually the SSN can be considered as an enhanced SSP. The difference is that in conventional IN systems the entire Service Logic is executed in the SCP while the use of MA-based Service Logic Programs allows downloading and execution of a part of the logic to the SSN. This way a large number of signalling messages between SSN and Service Execution Node (SEN) are omitted. Service Execution Node (SEN). The SEN is the Physical Entity responsible for the proper operation of the Service Logic and Service Data as well as for providing Specialized Resources (e.g. Audio messages,

ODYSSEAS I. PYROVOLAKIS, FOTIS G. CHATZIPAPADOPOULOS, MENELAOS K. PERDIKEAS, IAKOVOS S. VENIERIS

Video Clips etc.). In terms of the classical IN Physical Plane, the SEN can be considered as a unified Service Control Point and Intelligent Peripheral. Another important issue is the capability of SEN to distribute the Service Logic along different Physical Network Entities (SENs and SSNs), depended on the requirement of the logic (e.g. mobility) and the traffic load. This can be accomplished with the use of Mobile Agent Technology. Service Management and Creation Node (SMCN): The Service Management Node is responsible for providing the management functions required for network as well as service operation. It also provides the environment for Service Creation and Testing. Apart from these straightforward tasks, the SMCN plays the role of a permanent repository of the Agents needed by all other physical element. So any time an element (e.g. SSN) needs an agent (or a group of agents) SMN will take care of tracking the distribution of agents throughout the network. SMCN is also responsible for updating the old versions of the agents that are already located in other Physical entities. This way the provision of new services or the updates of the old ones becomes an automated procedure (it is also much easier than any other existing method). Terminals: Since we aim at Broadband Multimedia Services, in both conventional and novel Architectures, the terminals need to have support for accessing Broadband networks (e.g. ATM). This means that they need to have special hardware (e.g. ATM cards) and firmware (e.g. UNI signaling stack). The idea of having Mobile Agent Technology and CORBA in the IN can be applied to all involved network physical entities with no exception for the terminals as well. Nevertheless, the commercial adoption of those the novel architectures can only be stepwise. Therefore a two step approach is considered for the deployment of Mobile Agent Technology and CORBA into the IN. In the first step only the physical entities of the core network deploy the new architecture while in the second step all the physical entities (terminals included) adopt the new technology.

3 Design Methodology One of the main goals of this new IN architecture is to provide an easy and efficient way of multimedia service deployment. It is true that in the existing IN systems the services are based on the creation of the Service Logic programs with the Service Independent Building Blocks.

3.1

SIBs Based Service Logic Design

The main issue on the design and provision of services in conventional IN is the use of the Service Independent Building blocks (SIBs). A SIB is a standard, reusable, service independent component, which provides certain functionality. The SIBs can be chained together in various combinations to realize services. Their main characteristics are that each SIB have a unified and stable interface and that individual SIBs must be defined using a standard methodology to allow service designers to have a common understanding of the SIB and the multi-vendor IN products to support them identically [3]. Each SIB has no knowledge about the previous or the subsequent SIBs. In order to describe service features in SIBs, data parameters are used. There exist two types of parameters: the Call Instance Data (CID) which are dynamic parameters and the Service Support Data, which are static parameters. In ITU-T standards has been defined a set of SIBs that can be used widely. For example the Authenticate SIB, this SIB provides functionality to establish an authorized relationship between the service logic and a database on behalf of a user [3]. In Figure 3, the graphical representation of a generic SIB and the Authenticate SIB are provided along with the modeling of a service’s functionality.

“Designing Advanced Services for Distributed Intelligent Broadband Networks”

Authenticate Name Authenticate Password Authentication Mechanism

SSD Parameters

Success Logic End

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Logic Start CID input Parameters

SIB1

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AUTHENTICATE Error Authenticate Name Authenticate Password

Error Cause

SIB4 POI : Point Of Initiation POR : Point Of Return CID: Call Instance Data

POI

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Basic Call Process

POR2

SSD: Service Support Data

Figure 3 Service Modeling based on SIBs The truth is that even though the SIB-based approach can be considered as an Object Oriented, service and platform independent design methodology, the practices followed for the provision of IN services is different. Current software platforms for the deployment of IN services does not support the well defined, standardised SIBs but they are supporting a set of proprietary SIB-like software components as a library for the development of IN services [1], [14].

3.2

Software Modelling Techniques

With the endorsement of Distributed Object and Agents Technologies within IN, the need for adopting well-known software modelling and design techniques –instead of the SIBs based approach- is essential for designing advanced Broadband IN services in a rapid, flexible and reusable manner. The recent years the software engineering community has adopt the Unified Modelling Language (UML) as the key software design methodology. The Unified Modelling Language is a language for specifying, constructing, visualising and documenting the artifacts of a software-intensive system [11]. UML is the successor of past modelling languages as Booch, OOSE/Jacobson and OMT. As the primary goals in the design of the UML can be considered the following: • Provide users with a ready-to-use, expressive visual modelling language so they can develop and exchange meaningful models. • Provide extensibility and specialisation mechanisms to extend the core concepts. • Be independent of particular programming languages and development processes. • Provide a formal basis for understanding the modelling language. • Support higher-level development concepts such as collaborations, frameworks, patterns and components. The basic procedures during the design of software based on the UML model can be summarised into the following steps: User Requirements Analysis. The first thing is to analyse the needs of the end user, and provide a useful way to map those requirements into meaningful input for the design process. In UML the use case diagrams are used. A use case is a unit of functionality provided by a system or class as manifested by sequences of messages exchanged among the system and one or more outside interactors (called actors) together with actions performed by the system. Static Class Model Design. The second major step, and the first within the design process, is the identification of the concrete classes and their relationships, which constitute the static class model. For modelling the class identification, UML uses static class diagrams that are the graphic view of the static structural model.

ODYSSEAS I. PYROVOLAKIS, FOTIS G. CHATZIPAPADOPOULOS, MENELAOS K. PERDIKEAS, IAKOVOS S. VENIERIS

Dynamic Class Model Design. The follow up on the class identification, is the definition of the behaviour of the objects. The status, the behaviour of the objects and their data interchange can be represented by state, activity and collaboration diagrams respectively [11].

3.3

Proposed Service Logic Design

In the following paragraphs, we are proposing a design methodology for the deployment of Multimedia Services into the Distributed Broadband IN architecture. This methodology join the experience gained from the design of IN services in a SIB based environments with the UML technique and certain design needs coming from the adoption of CORBA and Mobile Agent Technology.

3.3.1

Design Roadmap

The need of a “roadmap” for the proposed design process is essential since the use of the rather new Mobile Agents Technology and/or the need for defining CORBA interfaces, introduces new parameters that must be considered during the design, deployment and enhancement of IN services. In Figure 4 this graphical representation of the introduced roadmap is shown. The whole process is decomposed into four phases [12].

Conceptual

Service Creation Roadmap Proze Description

Use Cases Analysis Multimedia Content Analysis

Decomposition into Components

Check Components’ Library

Yes

Reusable Components?

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Gateway Objects?

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IDL Interfaces Definition

No Agent?

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Backtrack Design Process System Performance Analysis

Figure 4 Design Roadmap of Multimedia Services for Novel IN Architectures Conceptual Phase. This is the first stage in the whole process. A Prose Description of the service is required to state the basic capabilities and requirements of the service. The second action is the transformation of the proze description into a set of use cases. The appliance of use cases analysis gives a more concrete image for the needs of the service. As a part of use cases analysis can be considered the Specialised Resources analysis. This subtask is essential for the successful deployment of multimedia services. In this task the type of the content (e.g. Video, Audio and their formats) must be decided as well as the requirements that may reveal from this content (video/audio servers, MPEG players etc.). The output coming from the use cases analysis is used as an input for the component decomposition, which is the next step, where the major units of functionality are identified. Specification Phase. In this second phase, the object decomposition is a further step from the identification of the components from the previous stage. In this task, the identification of the objects and its interrelationships are defined. After that, the decision of the CORBA enabled objects is following. Within this process the definition of the IDL interfaces takes place. The Mobile Agent Identification is the next

“Designing Advanced Services for Distributed Intelligent Broadband Networks”

action, which is a very important task for the entire design process. Since the part of the Service Logic that would be implemented as Mobile Agents is also the part that can migrate along the different Physical Entities, the selection and design of those Mobile Agents is a crucial point. After the identification of the mobile agents, there is a need for deciding their mobility characteristics (such as type of migration and object persistency). Implementation Phase. This phase concerns all the work that has to be done for the implementation of the designed services. So the first task is the objects’ internal analysis (methods, variable, types etc.). The language specific implementation is following. It must be stressed that one great advantage of the proposed architecture is the machine independence design of the services and the migration of the code. For achieving those targets is the use of machine independent programming language (such as Java) is essential. Integration and System Testing Phase. This is the last phase of all the process, beginning with the integration procedures within its physical element and proceeding with the system integration. A prime task in this phase is also the performance modelling and performance measuring of the system. Since we are considering for Multimedia Services in advanced telecommunication environments, one of the main goals is the proper behaviour of the system in all circumstances and its scalability. So the various network elements must be modelled and the performance of the new technologies (CORBA and MAT) must be measured. The results coming from this phase provide input to the Backtrack Design Process. By this term, we mean the re-evaluation and the improvement of all steps of the design process if and where this is applicable (see Figure 4).

3.3.2

Class Identification

In the previous section the design roadmap has been described. One of the most important tasks in this design methodology of Multimedia Services is the class identification. The appliance of well-known Object-Oriented Techniques (such as UML) can serve the need for service independent components. In this way three major goals can be achieved: reusability for easy and rapid deployment of services, extensibility towards new and updated services and flexibility on service design. The better way to identify the individual objects that are used in the service logic is to make a fine classification based on their type of functionality. An additional reason for the necessity of this classification is the extra requirements coming from the fact that we are considering Multimedia IN services instead of simple narrowband IN services. The main object categories that can be identified are: System Objects. In this category we consider the objects that support the correct and efficient operation of the overall system. Typical examples of objects of this category are the load monitor, event loggers and objects for providing secure communication and various error handlers. Service Objects. This category includes all objects that have a central role in the proper performance of the service. Examples of this kind of objects are the service logic manager, user and terminal profiles and the service info. Specialized Resources Objects. This category is crucial for multimedia services. This is because the objects of this category are strongly related to the handling of multimedia contents, so examples of objects within this category can be Video stream handlers, content previewers and browsers. Auxiliary Capabilities Objects. This last category is referred to the objects, which are related to auxiliary – supporting services. The most common example of supporting service is the mobility management service. The adoption of CORBA and Mobile Agents enforces the clear definition of the interfaces among the objects. We can determine two different types of interfaces internal and external. With the clause external interface we are referring to the CORBA interfaces. Those interfaces are described with the use of Interface Definition Language – IDL. With the clause internal interfaces we are referring to all the other interfaces of the objects. The specification of both internal and external interfaces is crucial since this is the criterion concerning which of the objects will be CORBA compliant.

3.3.3

Mobile Agents Adoption

As it has been mentioned before, one of the advantages of this architecture is the use of mobile agent as the medium towards a more distributed and flexible configuration. Mobile Agents can be classified depending on the “way they move” during their life cycle. It must be stressed that there are two different types of agent move. The first type of move is off-line (or in a zero state). This move is from an agent repository to the point of execution. In the classification below the

ODYSSEAS I. PYROVOLAKIS, FOTIS G. CHATZIPAPADOPOULOS, MENELAOS K. PERDIKEAS, IAKOVOS S. VENIERIS

SMCN (see Figure 1) is considered as an agent repository. The second type of move is on-line (or in a non zero state). In this case we have real migration (or cloning) of the agent from one execution point to another. This is the basic criterion for this classification. • Move-once MAs: in this category are all those agents that are usually downloaded only once from the SMCN. These agents can be considered stationary since once they are downloaded on a predefined physical entity they remain there. Also these agents usually have the longest life cycle. • Dynamic Move-once MAs: in this category are the agents that also downloaded only once from the SMCN but in a rather “dynamic” way. Dynamic means that it is a run-time decision where the agent will be executed. • Dynamic Multiple Moves MAs: this category is similar to the former one. The difference is that in this category the agent can migrate from the one physical entity to another (apart from the first migration from the repository) to complete its task. • Travelling MAs: this is the last category of Mobile Agents. They are moving along different physical entities, collecting data and/or executing specific tasks. Apart from the agent classification there is several other decisions that must be taken about agents’ characteristics. One of the main objectives in today’s networks is security. Since mobile agent is movable parts of code, great deal in providing security mechanisms for preventing the whole system from malicious use. Another issue is the persistency of the agents. In telecommunications environments the prime concern is the reliability of the services. By providing persistency of the agents’ data we can avoid problems from a possible malfunction of the agent during migration or execution.

4 A case study For better understanding the design methodology described in the previous paragraphs, we are giving in this section a case study of a Broadband Multimedia service. The first paragraph provides a prose description of the Interactive Multimedia Service (IMR) along with its requirements. In the follow up, the Service Logic Design based on the model given in Section 3 is described.

4.1

Interactive Multimedia Retrieval (IMR) Service

IMR was, originally, developed in the framework of the ACTS project INSIGNIA [13] (which focuses on Broadband IN). IMR is a service that provides transfer of digitally compressed and encoded video and audio data across a telecommunication network. The information is retrieved on the user’s demand and on an individual basis. The user not only defines the exact time at which the information stream is to be transmitted but has also an overall control during the transmission. [14] The IMR service consists of three different Sub-services: Video On Demand (VoD), News On Video (NoV) and Karaoke / Music On Demand (KoD/MoD). The KoD sub-service can be regarded as identical to the MoD as far as our further description is concerned. The general service scenario is as follows: The user is selecting one of the different Sub-Services mentioned above. After an authorisation procedure, the user profile is processed and depending on the preferences of the user, a list of content is available. After some (optional) previewing the user may select the desired content and a connection with the Server (e.g. Video Server) is established. When the transmission of the content has finished the connection between the user’s terminal and the server closes after the execution of certain procedures concerning the deallocation of network resources and billing. The structure of a service logic program for IMR is presented in Figure 5 by means of a simplified flowchart. The Network receives the user’s request for an IMR service session and consequently interacts with the user and collects user preferences during the “navigation” phase of the service, consisting of three stages. At this point, in case of a network failure or a time-out the service session is closing. When navigation is completed then the evaluation of the user’s selections is done and if the service session is to be continued it resolves the Video Server address and connects the video server with the user. When the viewing process is completed, the control is returned to the IMR’s Service Logic Program.

“Designing Advanced Services for Distributed Intelligent Broadband Networks”

Service request Service Provider Selection

Request User to Service Interaction

Success Net. Failure / Time-out

Exit

Authentication Authorisation Exit

Check Selection Success

Viewing

Failure / Time-out

Exit

Success

Type of Content Selection

Failure Time-out

Route call & Connect to VS

End

Figure 5 Service Logic Program for IMR Service The process of transforming the specifications for an IN multimedia service into an operational product passes through two strategic decisions: • The definition of the service functionality parts that are supported by each network node and • The selection of appropriate tools for service logic development. In conventional Broadband IN, the latter is achieved by graphical environments [15] that provide libraries of building blocks for IN services, analogous to the SIBs specified by ITU-T [3]. On the other hand service functionality distribution may be rather limited (obeying to the traditional roles of IN network elements). In any case the description of the service logic given above, is independent from the physical architecture of the Broadband Intelligent Network. For example in legacy Broadband IN, service logic can be divided between the B-SCP and the B-IP. The B-SCP executes a core service logic program, which is responsible for all routing, monitoring, and management functions, while the B-IP is responsible for querying the user and gathering user responses. In the distributed architecture there is no restriction what would be executed on the SSN and what in the SEN since both can execute parts, or even all, SLP. As a matter of fact the decision, sometimes, can be taken runtime depending on various aspects (network traffic, processing load, availability etc.)

4.2

IMR Service Logic Design for Agent-Based IN

In contrast to the classical service provisioning in IN with SIB-based Service Logic Programs, in an agent-based architecture the Service Logic is based on agents’ execution and interaction. In the following paragraphs we are identifying the agents (or group of agents) used for implementing the IMR Service. User Interaction. Those agents are responsible for making possible the User to Network interaction. • User Profile. This mobile agent is “injected” from the terminal (e.g. from a smart card) to the network and contains all the necessary data, about the user, for Identification and about his/her preferences. • Terminal Equipment Profile Manager. This mobile agent carries out every action needed for identifying the capabilities and requirements of the terminals. • Authoriser. This mobile agent is responsible for authorisation processes (such as login validation, encryption mechanisms etc.) • Service Provider Selection. This mobile agent provides the functionality needed for selecting a service provider for IMR Service • Application Selection/Preview. This mobile agent provides the logic and the data for selecting a movie and proceeds with a preview of a short promo.

ODYSSEAS I. PYROVOLAKIS, FOTIS G. CHATZIPAPADOPOULOS, MENELAOS K. PERDIKEAS, IAKOVOS S. VENIERIS

Service Management. This group of agents is responsible for the correct execution of the Service. • Service Dispatcher. It activates procedures needed for Identification of the service selected, from the SSN and SEN • Service Execution Handler. Every service specific action can be considered as a component of a service execution handler. • Charger: This agent provides the functionality needed for the charging of the service Mobility Management. In this category are included all the agents that are responsible for providing the mobility management capabilities to the services. It must be noted that although only agents for supporting user mobility are described the design can be extended to support mobile terminals as well. • Registrar. This is the agent responsible for the registration procedures of a user to the specific terminal. It also interacts with user profile agent to update the terminal information. • De-registrar. This agent is spawned from a registrar agent when a user registers. Its purpose is to update the previous terminal, where the user was registered, about the move of the user. • Roamer. Its responsibility is to locate the location of the called user. This agent has a limited use for the IMR (since most of the time the Video server, who is the called user, is not a mobile user) but it is very useful in case of a videoconference service. Network Management. This group of agents is responsible for the correct operation of the whole network and can also be used for either proactive and reactive network management operations. Since network management is out of scope of this paper we will not proceed in a further description of the agents of this category.

4.2.1

Scenario Description

In order to provide a better understanding of the way that the agents mentioned above collaborate in IMR, we proceed with a typical scenario description. The User connects to the network through the terminal. The User profile agent is “injected” to network. On the SEN, the user preferences are checked from the authorizer and a customized menu of services is appeared on the terminal’s screen. The user selects IMR service and with the help of the service dispatcher agent the service is identified on the SEN. After the identification of the service, the Service Execution Handler triggers the group agents, which are providing the service functionality. When the user selects some content e.g. a movie the session manager is responsible for the certain actions needed for the establishment, reservation and release of a transport link between the user terminal and the Video Server. When the user exits the application the session manager releases the reserved network resources and the charger proceeds with the charging of the user. In addition to the trivial scenario description, we will proceed to a brief mobility management description. In this scenario we are considering only user mobility and not terminal mobility (e.g. GSM or UMTS networks). The starting point is the user registration. So when the user connects to the network the registration procedure starts. The registrar agent (who is located on the SEN) updates the information on the user profile agent about the terminal. In parallel checks if the user was connected in another terminal before, if that is so, a de-registrar agent is spawn and update the data in the registrar agent (possibly in another SEN) who was responsible for the previous terminal. Those very simple scenarios show only part of the functionality provided by the agent technology. For example during the service execution a number of monitor agents would retrieve information about the resources and the status of every physical entity participating in the execution of the service and will proceed on management procedures when needed. Also we have not mentioned any problematic situations.

5 Conclusions In this paper we described a design methodology for the provision of multimedia services in a new architecture for Intelligent Broadband Networks based on CORBA and mobile agents technology instead of the conventional IN architecture. This solution provides an Open Object Oriented Design approach instead of proprietary SIBs based approach. In this way three major goals can be achieved: reusability for easy and rapid deployment of services, extensibility towards new and updated services and flexibility on service design. Even though the proposed architecture and the service design methodology offers great advantages towards the provision of multimedia services on modern telecommunications environments there are

“Designing Advanced Services for Distributed Intelligent Broadband Networks”

certain issues that need further elaboration. The most important is the immaturity of the involved technologies (e.g. CORBA and MAT). This is because the standardization effort is still in its early steps and a great deal of interoperability problems still exists, especially in a multivendor environment of future networks. Another important issue is the performance of the proposed architecture, since the research is in an early stage, no detailed performance modeling and measurement have been made. It is expected that in the near future, much more effort will be allocated on the resolution of these issues.

Acknowledgments This work has been partially funded by the ACTS project MARINE (Mobile Agent enviRonments in Intelligent NEtworks - AC340) [16]. The opinions appearing are those of the authors and not necessarily of the other members of the consortium.

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