rfc1406.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

   The terminology used in this document to describe error conditions on
   a DS1 interface as monitored by a DS1 device are based on the
   definitions from the ANSI T1M1.3/92-005R1 draft standard [13].  If
   the definition in this document does not match the definition in the
   ANSI T1M1.3/92-005R1 draft document, the implementer should follow
   the definition described in this document.

3.3.1.  Error Events

     Bipolar Violation (BPV) Error Event
          A BPV error event for an AMI-coded signal is the
          occurrence of a pulse of the same polarity as the
          previous pulse.  A BPV error event for a B8ZS- or HDB3-
          coded signal is the occurrence of a pulse of the same
          polarity as the previous pulse without being a part of
          the zero substitution code.

     Excessive Zeroes (EXZ) Error Event
          An Excessive Zeroes error event for an AMI-coded signal
          is the occurrence of more than fifteen contiguous zeroes.
          For a B8ZS coded signal, the defect occurs when more than
          seven contiguous zeroes are detected.

     Line Coding Violation (LCV) Error Event
          A Line Coding Violation (LCV) is the occurrence of either
          a Bipolar Violation (BPV) or Excessive Zeroes (EXZ) Error
          Event.



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     Path Coding Violation (PCV) Error Event
          A Path Coding Violation error event is a frame
          synchronization bit error in the D4 and E1-noCRC formats,
          or a CRC error in the ESF and E1-CRC formats.

     Controlled Slip (CS) Error Event
          A Controlled Slip is the replication or deletion of the
          payload bits of a DS1 frame.  A Controlled Slip  may be
          performed when there is a difference between the timing
          of a synchronous receiving terminal and the received
          signal.  A Controlled Slip does not cause an Out of Frame
          defect.

3.3.2.  Performance Defects

     Out Of Frame (OOF) Defect
          An OOF defect is the occurrence of a particular density
          of Framing Error events.

          For T1 links, an Out of Frame defect is declared when the
          receiver detects two or more framing errors within a 3
          msec period for ESF signals and 0.75 msec for D4 signals,
          or two or more errors out of five or fewer consecutive
          framing-bits.

          For E1 links, an Out Of Frame defect is declared when
          three consecutive frame alignment signals have been
          received with an error (see G.706 Section 4.1 [17]).

          Once an Out Of Frame Defect is declared, the framer
          starts searching for a correct framing pattern.  The Out
          of Frame defect ends when the signal is in frame.

          In-frame occurs when there are fewer than two frame bit
          errors within 3 msec period for ESF signals and 0.75 msec
          for D4 signals.

          For E1 links, in-frame occurs when a) in frame N the
          frame alignment signal is correct and b) in frame N+1 the
          frame alignment signal is absent (i.e., bit 2 in TS0 is a
          one) and c) in frame N+2 the frame alignment signal is
          present and correct.

     Alarm Indication Signal (AIS) Defect
          For D4 and ESF links, the 'all ones' condition is
          detected at a DS1 line interface upon observing an
          unframed signal with a one's density of at least 99.9%
          present for a time equal to or greater than T, where 3 ms



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          <= T <= 75 ms.  The AIS is terminated upon observing a
          signal not meeting the one's density or the unframed
          signal criteria for a period equal to or greater than
          than T.

          For E1 links, the 'all-ones' condition is detected at the
          line interface as a string of 512 bits containing fewer
          than three zero bits (see O.162 [14] Section 3.3.2).

3.3.3.  Performance Parameters

   All performance parameters are accumulated in fifteen minute
   intervals and up to 96 intervals (24 hours worth) are kept by an
   agent.  Fewer than 96 intervals of data will be available if the
   agent has been restarted within the last 24 hours.  In addition,
   there is a rolling 24-hour total of each performance parameter.

   There is no requirement for an agent to ensure fixed relationship
   between the start of a fifteen minute interval and any wall clock;
   however some agents may align the fifteen minute intervals with
   quarter hours.

     Line Errored Seconds (LES)
          A Line Errored Second, according to T1M1.3, is a second
          in which one or more Line Code Violation error events
          were detected.

          While many implementations are currently unable to detect
          the zero strings, it is expected that interface
          manufacturers will add this capability in deference to
          ANSI; therefore, it will become available in time.

          In the T1M1.3 specification, near end Line Code
          Violations and far end Line Errored Seconds are counted.
          For consistency, we count Line Errored Seconds at both
          ends.

     Controlled Slip Seconds (CSS)
          A Controlled Slip Second is a one-second interval
          containing one or more controlled slips.

     Errored Seconds (ES)
          For ESF and E1-CRC links an Errored Second is a second
          with one or more Path Code Violations OR one or more Out
          of Frame defects OR one or more Controlled Slip events OR
          a detected AIS defect.

          For D4 and E1-noCRC links, the presence of Bipolar



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          Violations also triggers an Errored Second.

          This is not incremented during an Unavailable Second.

     Bursty Errored Seconds (BES)
          A Bursty Errored Second (also known as Errored Second
          type B) is a second with fewer than 320 and more than 1
          Path Coding Violation error events, no Severely Errored
          Frame defects and no detected incoming AIS defects.
          Controlled slips are not included in this parameter.

          This is not incremented during an Unavailable Second.

     Severely Errored Seconds (SES)
          A Severely Errored Second for ESF signals is a second
          with 320 or more Path Code Violation Error Events OR one
          or more Out of Frame defects OR a detected AIS defect.

          For E1-CRC signals, a Severely Errored Second is a second
          with 832 or more Path Code Violation error events OR one
          or more Out of Frame defects.

          For E1-noCRC signals, a Severely Errored Second is a 2048
          LCVs or more.

          For D4 signals, a Severely Errored Second is a count of
          one-second intervals with Framing Error events, or an OOF
          defect, or 1544 LCVs or more.

          Controlled slips are not included in this parameter.

          This is not incremented during an Unavailable Second.

     Severely Errored Framing Second (SEFS)
          An Severely Errored Framing Second is a second with one
          or more Out of Frame defects OR a detected AIS defect.

     Degraded Minutes
          A Degraded Minute is one in which the estimated error
          rate exceeds 1E-6 but does not exceed 1E-3 (see G.821
          [15]).

          Degraded Minutes are determined by collecting all of the
          Available Seconds, removing any Severely Errored Seconds
          grouping the result in 60-second long groups and counting
          a 60-second long group (a.k.a., minute) as degraded if the
          cumulative errors during the seconds present in the group
          exceed 1E-6.  Available seconds are merely those seconds



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          which are not Unavailable as described below.

     Unavailable Seconds (UAS)
          Unavailable Seconds (UAS) are calculated by counting the
          number of seconds that the interface is unavailable.  The
          DS1 interface is said to be unavailable from the onset of
          10 contiguous SESs, or the onset of the condition leading
          to a failure (see Failure States).  If the condition
          leading to the failure was immediately preceded by one or
          more contiguous SESs, then the DS1 interface
          unavailability starts from the onset of these SESs.  Once
          unavailable, and if no failure is present, the DS1
          interface becomes available at the onset of 10 contiguous
          seconds with no SESs.  Once unavailable, and if a failure
          is present, the DS1 interface becomes available at the
          onset of 10 contiguous seconds with no SESs, if the
          failure clearing time is less than or equal to 10
          seconds.  If the failure clearing time is more than 10
          seconds, the DS1 interface becomes available at the onset
          of 10 contiguous seconds with no SESs, or the onset
          period leading to the successful clearing condition,
          whichever occurs later.  With respect to the DS1 error
          counts, all counters are incremented while the DS1
          interface is deemed available.  While the interface is
          deemed unavailable, the only count that is incremented is
          UASs.

          A special case exists when the 10 or more second period
          crosses the 900 second statistics window boundary, as the
          foregoing description implies that the Severely Errored
          Second and Unavailable Second counters must be adjusted
          when the Unavailable Signal State is entered.  Clearly,
          successive GETs of the affected dsx1IntervalSESs and
          dsx1IntervalUASs objects will return differing values if
          the first GET occurs during the first few seconds of the
          window.  This is viewed as an unavoidable side-effect of
          selecting the presently defined managed objects as a
          basis for this memo.

3.3.4.  Failure States

   The following failure states are received, or detected failures, that
   are reported in the dsx1LineStatus object.  When a DS1 interface
   would, if ever, produce the conditions leading to the failure state
   is described in the appropriate specification.






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     Far End Alarm Failure
          The Far End Alarm failure is also known as "Yellow Alarm"
          in the T1 case and "Distant Alarm" in the E1 case.

          For D4 links, the Far End Alarm failure is declared when
          bit 6 of all channels has been zero for at least 335 ms
          and is cleared when bit 6 of at least one channel is
          non-zero for a period T, where T is usually less than one
          second and always less than 5 seconds.  The Far End Alarm
          failure is not declared for D4 links when a Loss of
          Signal is detected.

          For ESF links, the Far End Alarm failure is declared if
          the Yellow Alarm signal pattern occurs in at least seven
          out of ten contiguous 16-bit pattern intervals and is
          cleared if the Yellow Alarm signal pattern does not occur
          in ten contiguous 16-bit signal pattern intervals.

          For E1 links, the Far End Alarm failure is declared when
          bit 3 of time-slot zero is received set to one on two
          consecutive occasions.  The Far End Alarm failure is
          cleared when bit 3 of time-slot zero is received set to
          zero.

     Alarm Indication Signal (AIS) Failure
          The Alarm Indication Signal failure is declared when an
          AIS defect is detected at the input and the  AIS defect
          still exists after the Loss Of Frame failure (which is
          caused by the unframed nature of the 'all-ones' signal)
          is declared. The AIS failure is cleared when the Loss Of
          Frame failure is cleared.

     Loss Of Frame Failure
          For T1 links, the Loss Of Frame failure is declared when
          an OOF or LOS  defect has persisted for T seconds, where
          2 <= T <= 10.  The Loss Of Frame failure is cleared when
          there have been no OOF or LOS defects during a period T
          where 0 <= T <= 20.  Many systems will perform "hit
          integration" within the period T before declaring or
          clearing the failure e.g., see TR 62411 [16].

          For E1 links, the Loss Of Frame Failure is declared when
          an OOF defect is detected.

     Loss Of Signal Failure
          For T1, the Loss Of Signal failure is declared upon
          observing 175 +/- 75 contiguous pulse positions with no
          pulses of either positive or negative polarity.  The LOS



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          failure is cleared upon observing an average pulse
          density of at least 12.5% over a period of 175 +/- 75
          contiguous pulse positions starting with the receipt of a
          pulse.

          For E1 links, the Loss Of Signal failure is declared when
          greater than 10 consecutive zeroes are detected (see
          O.162 Section 3.4.4).

     Loopback Pseudo-Failure
          The Loopback Pseudo-Failure is declared when the near end
          equipment has placed a loopback (of any kind) on the DS1.
          This allows a management entity to determine from one
          object whether the DS1 can be considered to be in service
          or not (from the point of view of the near end
          equipment).

     TS16 Alarm Indication Signal Failure
          For E1 links, the TS16 Alarm Indication Signal failure is
          declared when time-slot 16 is received as all ones for
          all frames of two consecutive multiframes (see G.732
          Section 4.2.6).  This condition is never declared for T1.

     Loss Of MultiFrame Failure
          The Loss Of MultiFrame failure is declared when two
          consecutive multiframe alignment signals (bits 4 through
          7 of TS16 of frame 0) have been received with an error.
          The Loss Of Multiframe failure is cleared when the first
          correct multiframe alignment signal is received.  The
          Loss Of Multiframe failure can only be declared for E1
          links operating with G.732 [18] framing (sometimes called
          "Channel Associated Signalling" mode).

     Far End Loss Of Multiframe Failure
          The Far End Loss Of Multiframe failure is declared when
          bit 2 of TS16 of frame 0 is received set to one on two
          consecutive occasions.  The Far End Loss Of Multiframe
          failure is cleared when bit 2 of TS16 of frame 0 is
          received set to zero.  The Far End Loss Of Multiframe
          failure can only be declared for E1 links operating in
          "Channel Associated Signalling" mode.

3.3.5.  Other Terms

     Circuit Identifier
          This is a character string specified by the circuit