5 Conclusion

14 On the receipt of the service request, the QoS manager translates this request on one or more logical configurations based on the profile concept, and produces the corresponding configurations by accessing the system information repository (4). To decide about the possibility of the establishment of a configuration which is the mapping result of a logical configuration, the QoS manager asks for information about the current states of the system components (4'), and runs the negotiation model (see Section 3) to select the optimal configuration (4 "). The QoS manager activity results on the establishment of a new configuration which supports the user request or simply the rejection of the request with preferably a proposal for an alternative configuration (5). During the active phase, the QoS monitor monitors the QoS of the established configurations. In other terms, for each operational configuration it compares the agreed QoS against the current QoS provided. When the agreed QoS is violated (6), the QoS manager tries, based on the information stored on system information repository and QoS oriented MIB, and the negotiation model to establish a new configuration for the affected configurations(s). This activity is called reconfigura-tion. If the QoS manager fails to establish a new configuration for the affected one(s), it simply applies the established policy: ignore the violation, initiate a renegotiation with the user, or clear the affected configurations. The paper presented a two-level negotiation model for distributed MM applications. Our model differs in may respects from the existing approaches. Unlike other models, it integrates the service negotiation and the QoS negotiation in an uniform way. Thus it takes benefit from the advantages of the distribution nature of the current systems. Indeed, our model supports the generation of all possible configurations that might support the requested service by mapping the service modules to the system components. The system equations that permit to select the optimal one are defined. A QoS management scenario using our negotiation model is proposed. Our negotiation model rises many issues that we are currently working on: (1) the QoS manager architecture [HAF94b], (2) The QoS monitoring mechanisms to use in order to collect dynamic information about the system components, (3) the heuristics required to solve the (complex) equations system that we have proposed, and (4) the system information repository and QoS-oriented MIB specification and distribution. 13 aged object, e.g. system component, is attached a set of attributes which …