PDF of this tutorialAfter service is provisioned for a subscriber under a given QoS level, the service provider must ensure that the purchased level of service is delivered. In the EMS domain, this process involves the fault and performance management of the provisioned network resources.
The EMS plays a key role in maintaining the health of both NEs and transmission facilities. It does this in conjunction with other systems, typically at the NML and SML. The EMS can be the primary repository of detailed history of NE–specific faults, events, technicians' actions, and performance data. EMSs are key enablers of applications at the NML and SML to perform the TeleManagement Forum–defined high-level processes. The following links two of the five high-level processes to their support by EMS service-assurance functions.
- network maintenance and restoration
- network monitoring and control
The high-level processes are accomplished with these EMS–supported building blocks.
- fault management support—involves the monitoring of the network resources to detect malfunction, preempt failures, and detect faults. After faults are discovered, the operator must troubleshoot, repair, and restore the network as quickly as possible. Fault management ensures that service remains available.
- performance data collection support—involves the periodic collection of quality metrics that characterize the performance of the network resources over service intervals. It also facilitates the visualization of trends that can indicate periodic or gradual degradation of physical resources.
- resource utilization data collection support—involves the collection of data on the level of utilization of network resources assigned to subscribers. This data can be used to determine whether the service product is appropriately matched to the subscribers' usage characteristics. It can also be used to forecast demand and suggest service upgrades before QoS suffers.
- QoS assurance support—involves ensuring that the quality metrics characterizing network performance remain within the agreed limits. It requires proactive monitoring of the network fault, performance, and utilization parameters to preempt any degradation in service quality.
EMS Domain-Specific Tasks
Following are examples of the specific tasks that are in the domain of an EMS:
Fault Isolation
- Higher-level NML fault-management systems and SML trouble-ticketing systems provide a first alert and generally point to the source of a problem. Technicians can then use the EMS database and EMS tools to do a pinpoint diagnostic.
- Many EMSs provide an easy way to invoke and display the results of NE–diagnostic tools such as loopbacks to isolate faults.
EMSs provide one or more fault windows that contain detailed information on each alarm or event generated by the NEs in its domain. An alarm is a specific problem indicator with predefined actions that trigger the alarm. Events are typically service provider–set thresholds that, if crossed, send a message that appears in the alarm window along with faults. A common use of the event mechanism is to detect degrading transmission facilities in order to alert network operations personnel to a problem before it becomes customer affecting. Example thresholds are bit error rate (BER) and SLIPS. Figure 7 shows an advanced troubleshooting feature of clicking on an alarm and bringing up a drawing of the affected equipment. This enables a technician at the network operations center (NOC) to direct a generalist at a remote-equipment site to the proper bay, shelf, and slot to replace a failed port card.
Figure 7. A Comprehensive Alarm Window with Linkage to a Drawing of the Affected Equipment
Depending upon each unique service provider's methods, procedures, and organization, NOC technicians may be assigned different aspects of the service-assurance tasks. Figure 8 shows an alarm-filtering screen that allows each technician to view and manage alarms and events in a way that is optimized for their responsibilities.
Figure 8. Alarm Window Customization via an Alarm Filtering Mechanism
Quality of Service
- EMSs detect performance-threshold crossings such as SLIPS and BERs and forward those to the NML fault manager. This data can identify degrading facilities before they become apparent to the customer.
- EMSs can store the performance measurement (PM) data from NEs and make it available to either EMS report generators or to SML performance management and QoS systems.
- Depending on the capabilities of the NE and its EMS, EMSs sometimes provide the ability to perform diagnostics on NE equipment and even closely associated communication facilities on a scheduled or demand basis.
A key QoS component is the ability to pinpoint the cause of a problem quickly so that the proper repair resources can be applied quickly. The objective is to achieve the minimum mean time to repair (MTTR) possible. In some cases the repair can be done from the NOC or even by the customer under the direction of NOC technicians. Figure 9 shows the ability in the cable telephony application to remotely diagnose the RSU on the customer's house and to also perform tests that can determine if the problem is in the customer's telephone equipment or inside wiring.
Figure 9. An EMS Diagnostic Screen for Cable Telephony Testing
