hem, however, has to be filtered, since it is an indirect consequence of the other, SO that the agent produces only one alarm that is sent to the upper TMN layer. 3.2.8.2 Element Management Layer This layer is constituted by a software running on a workstation located in the central network management room. The role of the element management layer is essentially to monitor and configure the network elements of the network and to identify failures through alarms collection and filtering. The element manager can access all the network elements in the network and via this software, every card that is loaded in a network element can be configured. Moreover, the element manager has functions to load in a network element new cards (after the physical insertion at the network element location), to configure and test them and, finally, to free their resources to be assigned to live traffic paths. Thus, it is the element manager that physically implements the paths routed and reserved by the upper layer by suitably configuring the network hardware. The element manager has also the role of receiving alarms from the agents and of filter- ing them to avoid the alarms sequence that happen when a failure inhibits the working of all the network elements in a chain after the failed one. This operation is the fundamental instrument that the operators of network management use to locate failures after a protec- tion switches and to plan field interventions. Besides configuration and alarms management, the element management layer has a set of other functions. Among them, it is important to remember the following: Collection of statistical data on the utilization of network resources Measurement of data regarding the network element working like the consumed power Manage the software upgrade of the network elements both via firmware and software download and via the control of the local upgrade procedure 3.2.8.3 Network Management Layer This layer of the TMN is dedicated to manage the logical configuration of the network: that is n