The MIB module to describe DS1/E1 interface objects. This is
an extension to the standard DS1/E1 MIB (RFC 2495).

Unless mentioned, the DS1 interface refers to both 
T1/E1 interfaces.

Terminology ( Taken From RFC2495)

AIS - Alarm Indication Signal

LOS - Loss Of Signal

LOF - Loss Of Frame

Yellow Alarm - Far End LOF.
  
Red Alarm    - Near End LOF.

BPV - Bipolar Violation 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 part of the zero
      substitution code. (See TR-TSV-000773 Section 3.5.1.1)

EXZ - 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.

LCV - Line Coding Violation is the occurrence of either
      Bipolar Violation (BPV) or Excessive Zeroes (EXZ)
      error event.

PCV - A Path Coding Violation error event is a frame
      synchronization bit error in the D4 and E1-noCRC formats,
      or a CRC or frame synch. bit error in the ESF and E1-CRC 
      formats. (Also known as CV-P; See T1.231 Section 6.5.2.1)

CS - A Controlled Slip is the replication or deletion of the 
     payload bits of a DS1 frame. (See T1.231 Section 6.1.1.2.3)
     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.

LES  - Line Errored Seconds. A LES is a second in which one or
       more LCV error events are detected. (See TR-TSV-000773 
       Section 3.5.1.1)

ES   - Errored Seconds (ES). For ESF and E1-CRC links an ES
       is a second with one or more PCV or one or more OOF 
       defects OR one or more CS events OR a detected AIS
       defect. (See TR-TSV-000773 Section 3.5.1.1)

       For D4 and EN-noCRC links, the presence of BPVs also 
       triggers an ES.

       This is not incremented during an UAS.

BES  - Bursty Errored Seconds. A BES is a second with fewer
       than 1 PCV error events, no Severely Errored Frame 
       defects and no detected incoming AIS defects. The
       CS are not included in this parameter.

       This is not incremented during an UAS. It applies to 
       ESF signals only.

SES  - Severely Errored Seconds. A SES for ESF signals is a 
       second with 320 or more PCV error events OR one or 
       more OOF defects OR a detected AIS defect.
       (See TR-TSV-000773 Section 3.5.1.1)

       For E1-CRC signals, a SES is a second with 832 or
       PCV error events OR one or more OOF defects.

       For E1-noCRC signals, a SES is a 2048 LCVs or more.

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

SEFS - Severely Errored Framing Second. An SESF is a second
       with one or more OOF defects OR a detected AIS defect.
       (Also known as SAS-P (SEF/AIS second).
       (See TR-TSV-000773 Section 3.5.1.1)

DM   - Degraded Minutes. A DM is one in which the estimated
       error rate exceeds 1E-6 but does not exceed 1E-3.

UAS  - Unavailable Seconds. The UAS are calculated by counting
       the number of seconds that the interface is unavailable.

CSS  - Controlled Slip Seconds. A CSS is a one-second interval 
       containing one or more controlled slips. This is not
       incremented during an Unavailable Second.

LSES - Line Severely Errored Seconds is defined as a count of
       1-second intervals with 1544 Bipolar Violations plus
       Excessive Zeros event or one or more LOS defects.

PSAS - Path SEF/AIS (PSAS) encountered.