Mechanism to maintain the current state of network elements

Overview

The NFM-P uses several mechanisms to maintain and display the current state of the network elements it manages. These mechanisms can include:

These mechanisms are built into the Nokia 7950 XRS, 7750 SR, 7450 ESS, 7450 SR, 7210 SAS, and 7705 SAR network elements and the NFM-P network element interaction layers.

IP connectivity (ping) verification

The NFM-P can be configured to ping all network elements at a configurable interval to monitor IP connectivity. If the network element is unreachable, an alarm will be raised against the network element. Details of the alarm are the following:

Ping verification is disabled by default. IP connectivity checks using ping must be scheduled through the default policy.

SNMP connectivity verification

The NFM-P performs an SNMP communication check every 4 minutes. If the NFM-P cannot communicate via the SNMP with a network element, it will raise a communications alarm against that network element. The NFM-P will also color the network element as red on the map to indicate the communication problem. Then, the NFM-P will clear the alarm and color the network element as green once the NFM-P detects that SNMP connectivity to the network is re-established. Details of the alarm are the following:

This behavior occurs by default and is not configurable.

SNMP traps

The NFM-P listens to SNMP traps to receive changes from the network elements. The NFM-P configures the trap log ID on each network element when it is first discovered. The network element then uses that trap log ID to send all configuration changes and updates to the NFM-P. The NFM-P will react to the traps it receives and make appropriate changes to the database, alarms, and related object as required.

SNMP trap sequence verification

The NFM-P retrieves the last trap sequence number sent from all network elements at a configurable interval. This interval is configurable on a per resource group basis. Resource groups allow the user to configure the communications behavior of a group of network elements. By default, the core resource group includes all network elements, and verifies the trap sequence number every 4 minutes. The NFM-P compares that sequence number with the sequence number of the last trap it received from that network element. If they do not match, the NFM-P will request only the missing traps from the network element. If at any point the NFM-P realizes that it is missing more than 200 traps from a network element, or if the network element no longer has the missed trap, the NFM-P will request a full resynchronization on that network element rather than just request the missing traps.

This behavior occurs by default and is not configurable.

Scheduled SNMP MIB polling

The NFM-P can poll all data SNMP MIBs from the network elements at a configurable interval. The Polling policy is disabled by default. This behavior is configurable via the Polling tab of the network elements properties form.

Network outages and recovery

When a Nokia 7x50 based network element loses visibility of the NFM-P, it is unable to send traps to the network manager, and the traps are queued on the network element. See SNMP trap sequence verification for a description of the NFM-P behavior with regards to trap handling. When a network outage occurs, the network element configuration in the NFM-P will be made consistent with the network element, but any event notifications, such as SNMP traps, that have occurred during the network outage will not be processed. This will cause intermediate state change alarms to not be reflected in the NFM-P during the network outage.