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 220.127.116.11) 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 18.104.22.168) CS - A Controlled Slip is the replication or deletion of the payload bits of a DS1 frame. (See T1.231 Section 22.214.171.124.3) 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 126.96.36.199) 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 188.8.131.52) 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 184.108.40.206) 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 220.127.116.11) 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.