Carrier Access SNMP manual Glossary

GLOSSARY

10Base-T:10Base-T is an IEEE standard for operating Ethernet local area networks (LANs) on twisted- pair cabling using the home run method of wiring (the same as the phone company uses) and a wiring hub that contains electronics performing similar functions to a central telephone switch. The full name for the standard is IEEE 802.3 10Base-T.

AIS (Alarm Indication Signal): Also known as a “Blue Alarm Signal” or “All Ones Keep Alive,” an AIS is an unframed all ones bit pattern sent by equipment at the far end to indicate that an alarm condition exists upstream in a circuit leading to the downstream equipment. Keep-alive signals are required by the network facilities to prevent oscillation of the line repeaters which causes interference (i.e. cross-talk and bleeding) within adjacent channels.

AMI (Alternate Mark Inversion): An AMI encoded signal is a bipolar pseudo-ternary signal conveying binary digits (bits) in which successive “marks” are normally of alternating, positive and negative, polarity. This is the traditional method of line encoding used with bipolar DS1 (T1) signals. However, use of AMI does not preclude long strings of zeros being sent in the signal entering the public network from the DTE in violation of the pulse density requirements mandated in Part 68 of the FCC Rules and/or AT&T Publication 62411.

ANI (Automatic Number Identification): ANI is a service available from the telephone company on certain links that identifies the phone number of the caller to an attached computer telephony system.

B8ZS(BINARY 8-ZERO SUBSTITUTION): This line coding scheme is one of the methods used to avoid long strings of zeros in a bipolar DS1 signal entering the network from the DTE. Every string of eight zeros is replaced by a special code (token) for transmission over networks that are sensitive to long strings of ze- ros. The code contains a pattern of bipolar violations that is identified by the recipient and then removed in the decoding process to recreate the original string of zeros. This particular method of line coding is the evolving standard, but one that is not yet fully supported by all carriers.

BIT ERROR RATE (BER): The ratio of bits received in error to total bits transmitted. The time over which this rate is calculated is not inherent to the definition of BER and, therefore, can be separately specified.

BERT (BIT ERROR RATE TESTER): A test instrument for performing Bit Error Rate testing on a T1 line. See BER.

BLUE ALARM SIGNAL: See AIS.

BPV (BIPOLAR VIOLATION): A violation of the T1 bipolar AMI transmission pattern in which succeed- ing “ones” (pluses) are sent at opposite polarities. A BPV normally indicates a transmission error. However, B8ZS patterns contain bipolar violations, which are not counted as errors.

CENTRAL OFFICE (CO): Telephone company facility where subscribers’ lines are joined to switching equipment for connecting other subscribers to each other, locally and long distance.