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Chapter 4
BNI (Trunk) Cards
In the BNI-3E3 the PLPP is replaced by a G.804 framer. The E3 framer obtains end-to-end
synchronization on the Frame Alignment bytes. And a E3 transmitter/receiver replaces the DS3
transmitter/receiver for the BNI-3E3.
Another major BNI function is queuing of the ATM cells waiting to be transmitted to the network trunk.
This is controlled by the Queue Service Engine. There are 32 queues for each of the three ports to support
32 classes of service, each with its programmable parameters such as minimum bandwidth, maximum
bandwidth, and priority. Queue depth is constantly monitored to provide congestion notification (EFCN)
status. The Queue Service Engine also implements a discard mechanism for the cells tagged with Cell
Loss Priority.
The destination of each cell is contained in the Virtual Path Identifier/Virtual Circuit Identifier VPI/VCI)
field of the cell header. This is translated to a Logical Connection Number via table lookup in the
Network Address Table. Both terminating and through connections can coexist on a port.
A Serial Interface Module (SIM) provides cell interface to the StrataBus backplane. This operates at 800
Mbps. It provides a serial-to-parallel conversion of the data and loopback and pseudo-random bit
generation for test purposes.
Both BNI-T3 and BNI-E3 cards support two clock modes that are selected by the system operator
through software control. Normal clocking uses receive clock from the network or user device for
incoming data and supplies transmit clock for outgoing data. The clock obtained can be used to
synchronize the node if desired. Loop timing uses receive clock from the network for the incoming data
and turns that same clock around for timing the transmit data to the network or connecting CSU.
Bandwidth Control
The transmit bandwidth can be throttled down for certain applications. For example, when interfacing
with an older IPX switch E3 ATM Trunk Card, the trunk transmit rate is limited to 40,000 cells/second.
If a T2 trunk adapter is used, the trunk transmit rate is limited to 14,000 cells/second.
Loopbacks and Diagnostics
There are two types of self-tests that can be performed:
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Loopback paths are provided:
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Release 9.3.30, Part Number 78-12907-01 Rev. E0, May 2005
A nondisruptive self test
This is automatically performed on a routine basis.
A more complete, disruptive test
This may be initiated manually when a card failure is suspected. If the card self-test detects a failure,
the card status LEDs displays an indication of the failure type.
A digital card loopback path
This is used by the node for self-test. It loops the data at the serial DS3 or E3 interface back toward
the node.
A digital line loopback
This loops the data at the electrical transmitter/receiver at the card output.
Broadband Network Interface Cards (BNI-T3 and BNI-E3)
Cisco BPX 8600 Series Installation and Configuration
4-5
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Table of Contents
Troubleshooting
