Why ONT reports LPAC and NFTF alarms at the MAC/IP layer:On ONT, the default MAC/IP flow payload type is set to Test Frame for both TX and RX. The proprietary test frame format is used by ONT to perform QoS analysis on received frames and also to measure flow service disruption.The NFTF alarm indicates that no flow test frames are being received on the RX flow(s). The LPAC alarm indicates a loss of performance assessment capability and is raised as a result of no test frames. Both alarms could be due to MAC frames not being received (i.e. traffic is not enabled), MAC frames not being filtered in on the RX flow, or the MAC frames received and filtered in are not the ONT proprietary test frame format. A count of the received frames being filtered in can be monitored on the MAC/IP, Statistics, RX MAC page while a measurement is running.Each MAC/IP RX flow configured on ONT acts as a frame filter by comparing its provisioned header fields (i.e. source and destination addresses, VLAN, EtherType, etc.) to those in the frames being received. If any header field values in the received frames do not match what is expected, the frames will not be filtered in for analysis. In that case the NFTF and LPAC alarms will be raised for the affected flow(s) and also be indicated in the consolidated alarm summary on the left side of the GUI window.If the RX Payload Type is set to "BERT Pattern" instead, then only the LPAC alarm is applicable and will be reported if, for a period longer than the LPAC timer (default 100x100ms = 10s), frames are not being filtered in on the RX flow(s), a loss of payload pattern is detected, or a loss of payload synchronization is detected.How to clear LPAC and NFTF alarms on ONT depending on test conditions (assumes starting from default settings):1) The ONT port receives the frames it transmits (looped directly to itself or through a DUT). Note performing the below steps should not be necessary for 40GigE, 100GigE and 400GigE as the "Rx coupled to Tx Settings" on the MAC/IP, MAC/IP Config., Mode page is enabled by default.
2) An ONT port receives frames from another ONT port (directly or through a DUT).
3) The ONT port receives frames from a non-ONT source and flow statistics monitoring is required.
4) The ONT port receives frames from any source and it is used to monitor total port frame statistics only (i.e. monitoring individual flow statistics, analyzing payload, and measuring flow disruption time are not required).
The above information is intended to help with the most common test configurations. If you are unable to clear the LPAC and/or NFTF alarms after following the instructions in this article, please contact the JDSU technical assistance center within your region. Be prepared to provide the type of ONT module/port you are using, signal structure, software version, and details of your test configuration.
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