Northern Telecom DMS-100 Series Maintenance Manual page 179

About network bit error rate tests
The ENET BERT level of the MAP display allows operating company
personnel to perform network BERTs. The BERT tests only the ENET
performance. The system does all insertion and removal of data in the
ENET and does not include other components, for example, peripherals.
The DS30 Interface Paddle Board (NT9X41) and Quad DS512 Fiber
Interface Paddle Board (NT9X40) cards allow the system to generate and
compare test data on the respective receive and transmit ports. The test data
can be constant data or pseudo-random data. The system inserts
pseudo-random data at a from port and checks the data at a to port. Any
discrepancies between the inserted and extracted data cause a bit error
counter to increase. You can use a network BERT to measure the
performance of the hardware components which form the ENET switching
matrix.
A network BERT performs this function. To perform this function, the
network BERT establishes two-way block connections at the same time.
The network BERT establishes these connections over ENET speech paths.
The network BERT also measures the bit error rates over these connections.
A block connection consists of a block of 511 PCM channels. The channels
originate and terminate at the interface ports of an ENET link interface
paddle board. An example of a block connection is a speech path over all
the channels of a DS512 fiber. Another example is a speech path over one
DS30 cable. A DS30 cable consists of 16 DS30 links joined to a connector.
When the measured error rate of a test path exceeds the acceptable
threshold, the system records transmission errors, or hits. The test definition
specifies this threshold. One of eight BERT buffers can store these hits.
The buffers correspond to the available test records. The system uses hit
information to determine a performance rate for the ENET.
Note: The definition of a BERT on a single PCM channel is not a supported
test option. The amount of time required to run this test with an acceptable
target error rate is not acceptable.
The connections established during a BERT depends on the options you
chose when you implemented the test and the user definition of the test
record. The software supports BERTs. You rarely use BERTs on a single
entity smaller than a crosspoint card.
You can add one or more of the following entities to the user definition
section of a BERT record:
a network node (one plane of a shelf)
a single 16K X 16K channel crosspoint (NT9X35BA) card
Problem isolation and correction 8-43
DMS-100 Family Networks Maintenance Guide BASE10