teraction management. The internal struc- ture of the SCIM is not standardized. For the IN service brokering as well as the IMS-based SCIM, the main characteristic is that they trigger the service invocation from each other's independent services according to an interaction script/order/ rule. As the messaging protocol is standardized in either case, no changes to the service internal logic are needed in order to interact with the service broker. The service itself only interacts with the service broker instead with many different ser- vices. So far it appears simple, but for the separation of the network for the service layer, the understanding of the service invocation of the SCIM for IMS networks are not as straightforward as in the IN service brokering understanding. As for now, the details of the SCIM have therefore, not been defined and agreed upon, and left for each vendor's understanding. 4.2.3.2 Service Orchestration From the functional perspective, there is no much difference between service brokering and service orchestration, except for the applicability of the domain. The term Service Orchestration describes the IT-level service brokering and is closely linked to the services and concepts of the service-oriented architecture (SOA). It is directly associated with service composition and service component reuse. Service orchestration is a way to describe how loosely coupled are service fragments-the so-called SOA services-offered by open, standard interfaces cooperate within a new single large composite service. SOA services are invoked remotely through standard protocols, have well-defined interfaces, and are self-contained. SOA service orchestration uses standard Web service protocols like Simple Object Access Protocol (SOAP) for invoking services, Web Service Description Language (WSDL) for service definitions, and the Universal Definition, Discovery and Integration (UDDI) for service discovery. In the IT domain, the service broker is called the Enterprise Service Bus (ESB), which refers to a softwa