What is the pF_EBC (Far-End Errored Block Count) Performance Monitoring Parameter for the OTUk Layer?
The purpose of this blog post is to briefly define and describe the pF_EBC (Far-End Errored Block Count) Performance Monitoring parameter that the OTN (Sink) STE (or OTUk_TT_Sk Atomic Function) will compute and tally.
The Sink STE (or OTUk_TT_Sk function) will include information on the pF_EBC parameter within each Performance Monitoring report it sends to System Management.
NOTES:
- The OTN PTE (ODUP_TT_Sk Atomic Function) also monitors and generates information on the pF_EBC (Far-End Errored Block Count) parameter at the ODUk Layer. Please see the pF_EBC at ODUk Layer Post for more details on this parameter.
- Throughout this post, I will use the terms: OTN STE and OTUk_TT_Sk Function interchangeably. In the context of this blog post, these two terms mean the same thing.
Introduction
At the OTUk Layer, the OTN (Sink) STE is the entity that is responsible for detecting and reporting Far-End Errored Block Counts (or SM-BEI errors).
As the Sink STE receives and monitors its incoming OTUk signal, it will check for many things. It will continuously scan the incoming OTUk signal for bit (or symbol) errors (e.g., SM-BIP-8, FEC, etc.). It will also check for Service-Affecting defects (e.g., dTIM, dLOM, dLOF, dAIS, dLOS-P, etc.).
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Definition of Terms:
Before we proceed, we need to define the following terms for this blog post:
- Block: In this case, we define a block as an OTUk frame.
- Far-End Errored Block: In this blog post, we define a far-end errored block as any OTUk frame that contains a value for the SM-BEI count that ranges anywhere between 1 and 8. Anytime the OTN STE receives a block with an SM-BEI count value of 0x0, we consider that block to be un-erred.
As the Sink STE checks the incoming OTUk signal for errors and defects, it will also record the total number of far-end errored blocks it detects for each one-second period.
At the end of a given one-second period, the Sink STE will load the total number of far-end errored block counts (detected in the most recent one-second period) into the variable pF_EBC.
The Sink STE will then report this value for pF_EBC to System Management as a part of its Performance Monitoring report.
Table 1 presents the number of blocks/second that each type of OTUk signal will transport for each value of k.
Table 1, Number of Blocks/Second for each OTUk Rate.
| OTUk Type | Number of Blocks/Second |
|---|---|
| OTU1 | 20,421 |
| OTU2 | 82,026 |
| OTU3 | 329,492 |
| OTU4 | 856,388 |
| OTUCn | n x 860,177 |
So How does the OTN STE tally Errored Blocks for the pF_EBC parameter?
As the Sink STE receives and monitors its OTUk signal, it will continually check the SM-BEI counts within each incoming OTUk frame (or block).
Anytime the Sink STE receives an OTUk frame in which the SM-BEI value is anywhere from 1 to 8, it will increment its internal (pF_EBC Counter) by 1.
NOTE: This means that even if the Sink STE receives an SM-BEI value of “8”, it will still just increment its pF_EBC Counter by 1 (not 8).
Conversely, the Sink STE will not increment its internal pF_EBC Counter whenever it receives an OTUk frame (or block) that contains an SM-BEI value of 0, or 9 through 15. The Sink STE consider these type of OTUk frames to be un-erred.
At the end of each one-second period, the Sink STE will load the contents of this internal counter into the pF_EBC parameter. The Sink STE will then include that information within its Performance Monitor report that it sends to System Management.
Are there any Times or Conditions during which the Sink STE will NOT tally Errored Block Counts for the pF_EBC parameter?
ITU-T G.798 states that the OTUk_TT_Sk function will stop tallying Errored Blocks for the pF_EBC parameter whenever the upstream circuitry (e.g., the OTSi/OTUk_A_Sk or OTSiG/OTUk_A_Sk Atomic Function) asserts the CI_SSF input of the OTUk_TT_Sk function.
In other words, the Sink STE will not tally any Errored Block Counts (for the pF_EBC parameter) whenever it (e.g., the OTSi/OTUk_A_Sk or OTSiG/OTUk_A_Sk functions) declare any of the following service-affecting defect conditions.
- dLOS-P – Loss of Signal – Path
- dAIS (e.g., OTUk-AIS)
- dLOF – Loss of Frame
- dLOM – Loss of Multi-Frame
- dLOFLANE – Loss of Frame – Logical Lane Signal (for OTL3.4, OTL4.4, or OTL4.10 applications ONLY)(*)
- dLOL – Loss of Lane Alignment (for OTL3.4, OTL4.4, or OTL4.10 applications ONLY)(*)
- Or if the upstream Optical circuitry is asserting the AI_TSF-P input pin to the OTSi/OTUk_A_Sk or OTSiG/OTUk_A_Sk function.
NOTE: (*) – Indicates that one must have a membership to THE BEST DARN OTN TRAINING PRESENTATION…PERIOD!!!, to access this information.
Additionally, the OTUk_TT_Sk function is not supposed to increment any pF_EBC counts whenever it declares the dBIAE (Backward Input Alignment Error) defect condition.
Is there such a thing as Near-End Errored Block Counts?
Throughout this post, we have used the term Far-End Errored Block Count. Does this mean that there is another parameter called Near-End Errored Block Count?
Answer: Yes, there is such a parameter. See the Near-End Errored Block Count post at the OTUk Layer for more details.
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