OTUk_LOM indicates an abnormal alarm of the frame alignment signal. If the frame alignment process is in the out-of-frame (OOF) state for 3ms continuously, this alarm is generated.

Question

Options

• ATrue
• BFalse

• A
  24% (9)
• B
  76% (28)

Explanation

B is correct because the question's definition describes OTUk_LOF (Loss of Frame), not OTUk_LOM. OTUk_LOF is the alarm triggered when the frame alignment process remains in the OOF (Out-of-Frame) state for 3ms continuously - that timing threshold is the LOF trigger, per ITU-T G.798.

OTUk_LOM (Loss of Multiframe) is a distinct alarm: it fires when the OTU multiframe alignment signal is lost, which involves a higher-level framing structure beyond the basic frame. The question incorrectly attributes the 3ms/OOF mechanism to LOM, which is the error.

Option A is wrong because accepting the statement as true would mean confusing two separate defect types - LOF and LOM - that monitor different layers of the OTN framing hierarchy.

Memory tip: The extra "M" in LOM stands for Multiframe - if a question mentions OOF and a millisecond timer, think LOF (frame-level). If it mentions multiframe structure loss, think LOM. Never swap the "F" and "M."

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