The MIB module to configure and perform Bit Error Rate Testing (BERT) on DS3, DS1/E1 and DS0/DS0Bundle interfaces. Bit error rate testing and loopbacks are used by carriers and ISPs to aid in problem resolution as well as for testing the quality of T1/E1 or T3/E3 links. Tests can be run on a full T1/E1 line or can be run on a fractional T1/E1 such as single DS0 or a group of DS0s. By using BERT, poor quality links could be detected early. BERT enables the user to test the quality of links by directly comparing a pseudo-random or repetitive test pattern with an identical locally generated test pattern. Terminology: BERT: Bit Error Rate Testing (BERT) involves generating a known data sequence into a transmission device and examining the received sequence at the same device or a remote device for errors. The use of BERT results in the computation of a bit error rate (BER), which is bits received in error BER = number of bits transmitted To perform a bit error rate test using one tester, communications equipment must be placed into a loop-back mode of operation and the BERT test can then be used to determine if equipment is operating correctly. When running a BERT, system expects to receive the same pattern that is transmitting. To help ensure this, two common options are available. - Use loopback somewhere in the link or network. This can be accomplished by putting the line in loop up mode; send the pattern; find the BER. - configure remote testing equipment to transmit the Same BERT pattern at the same time. Typical Sequence in Performing Bit Error Rate Test by the device is given below: - Loop Up: The tester issues special code to force the far end (CPE) into loopback. Upon recognition of the loop activation request code the CPE enters a loop mode in which it returns the port data back to the tester. - Send Pattern: After a loop has been established, the tester can generate test pattern toward the CPE and monitor the incoming data. - Loop Down: The tester issues a special code (loop down command) to release the far end from the loopback. Terminology Used: CPE - Customer's premise equipment. At CPE, following equipment is required: DSU CSU Usually DSU and CSU functions are incorporated by vendors into a single CSU/DSU unit. OCU - Office Channel Unit CSU - Channel Service Unit A CSU contains the last signal regenerator on the line before DTE and mechanism to put the line into loopback for testing from the central office. DSU - Data Service Unit.