A Service Composition Model for Automatically Switched Transport Networks Fabio Baroncelli 1 , Barbara Martini 1 , Luca Valcarenghi 2 , Piero Castoldi 2 1 National Laboratory of Photonic Networks - Consorzio Nazionale Interuniversitario per le Telecomunicazioni (CNIT) Email: fabio.baroncelli,barbara.martini@cnit.it - Via G.Moruzzi 1, 56124, Pisa (PI), Italy 2 Center of Excellence for Communication Networks Engineering - Scuola Superiore Sant’Anna Email: valcarenghi,castoldi@sssup.it - Via G.Moruzzi 1, 56124, Pisa (PI), Italy Abstract—Grid applications in Wide Area Networks (WANs) can benefit from the QoS-enabled dynamic connectivity offered by the Automatically Switched Transport Network (ASTN). To exploit this benefit, Grid middleware must be able to request ASTN network services with a level of abstraction that do not require the knowledge of the network implementation details. The Service Oriented Automatically Switched Transport Network (SO-ASTN) is an ASTN architectural enhancement able to export such network services by composing the ASTN connectivity services. This work presents a Service Composition Model (SCM) and a relevant Service Composition Language (SCL) suitable for SO- ASTN. The principal novelty of the proposed SCM consists in the reuse of the Intelligent Network Service Composition paradigm in conjunction with the XML technologies used in the Web Services. The SCL, based on the ontology theory, can describe not only the composition of the ASTN connectivity but also the modality of the service process execution. The proposed SCM and SCL are then experimentally validated on a testbed in which a Grid application requests the topology of a Virtual Private Network (VPN). Index Terms— ASTN, Services Composition Model, Ontology Language, Grid Services I. I NTRODUCTION Grid applications are currently moving from a dedicated Local Area Network (LAN) scenario, where all the network resources are under the customer control, to a Wide Area Network (WAN) scenario, where heterogeneous applications share the same network resources and the Quality of Service (QoS) connectivity is not guaranteed [1]. In such environment, the Grid middleware needs to be enhanced with network awareness capability to take under control the resources of network infrastructure, in particular QoS-enabled connectiv- ity [2]. Grid middleware currently implements network awareness capability using the informative services provided by IP- based applications probes (e.g., Ping, Traceroute or Pathchar) or using executive services that allocate network resources by increasing the active application sessions (e.g., GridFTP) [3]. Within the Grid High Performance Networking Research Group (GHPN-RG) the formalization of these operating ap- proaches is ongoing by introducing a specification of Grid Services, named Grid Network Services (GNSs), that com- bined with other GSs allow Grid Application to gain network awareness capability. Example of GNSs are the Network Information and Monitoring Service (NIMS) that provides up- to-date information on the Grid network status, and the Data Transport Service with Network Quality of Service (DTS- NQoS) that establishes QoS-enabled link connections among Grid Nodes [4]. The Service Oriented ASTN (SO-ASTN), presented in [5], was introduced in order to enhance the ASTN architecture with a middleware, named Service Plane (SP). By composing the connectivity services offered by the ASTN Control Plane (CP), that are named Basic Network Services (BNSs) in this work , the SP provides technology-independent network services with a level of abstraction suitable for being invoked by applications. Accordingly, applications can request network services without going through the details of the metro- core network infrastructure. In case of Grid applications, the GNSs can dynamically invoke network services to designated service nodes unburdening the Grid middleware about any technology details or actual topology of network infrastructure. The abstraction process performed by the SP must be based on a Service Composition Model (SCM) that specifies rules for the aggregation of network services in support of any application middleware. In particular, this SCM should be conceived taking into account SP architectural and perfor- mance constraints in order to be exploited by GNSs. Given the convergence of GS/GNS and Web Services (WSs) [6], the SP can adopt the WS SCM for the composition of the BNSs. Unfortunately, this solution is not feasible. In fact, WSs are discovered and invoked by applications without the need to know the entities that actually provide that WSs. On the contrary, the invocation of a connectivity service must be done directly on the specific network node that is able to satisfy that request. These arguments lead to the necessity to define a specific SCM for the network services provided by the SP. This work presents a SCM and the relevant Service Com- position Language (SCL) suitable for the SO-ASTN. The proposed SCL, based on the ontology theory, re-uses the Intelligent Network Conceptual Model (INCM) [7] defined by the International Telecommunication Union - Telecom- munication Standardization Sector (ITU-T), making extensive use of XML for information representation. The strength of the proposed SCL consists in the possibility to optimize the service composition implementation by describing not only how to interconnect the BNSs, but also the execution of each BNSs (serial/parallel) and the modality of the signaling ex- 0-7695-2622-5/06/$20.00 (c) 2006 IEEE