Packet Bus Maintenance - Avaya MCC1 Maintenance Procedures

Packet and serial bus maintenance
Isolating and repairing packet-bus faults
TN771D Maintenance/Test — A Maintenance/Test board's fault may either:
— Falsely indicate a packet-bus fault
— Cause the inability to detect such a fault
If the test board's fault is on its packet-bus interface, the packet bus may also be alarmed.
Failure of any circuit pack's bus interface may alarm the packet bus due to shorting of packet-bus leads.
This typically disrupts all packet-bus traffic in the affected PN. Some packet-bus faults do not affect
every endpoint, so a packet-bus fault cannot be ruled out just because some packet service is still
available.
A circuit pack can fail in such a manner that it sends bad data over the packet bus. If this occurs on an:
• IPSI's Packet Interface circuit, all packet traffic either within the IPSI-connected PN or its scope
is disrupted.
• EI circuit pack may disrupt all packet traffic in its PN.
• ISDN-BRI circuit pack, every device connected to the circuit pack fails to function.
This failure may also disrupt the entire packet bus whenever the circuit pack tries to transmit data. Such a
disruption may be indicated by:
• Intermittent packet-bus alarms
• Intermittent failures of other packet circuit packs
• Interference with other connected endpoints
These failures are difficult to isolate because of their intermittent nature. In most cases, the failed circuit
pack is alarmed, and every connected endpoint on the circuit pack is out of service until the circuit pack is
replaced. These symptoms help in isolating the fault.

Packet bus maintenance

The following topics are covered in this section:
• Comparing the packet and TDM buses
• Packet Bus maintenance software
• General fault correction procedures
Comparing the packet and TDM buses
The packet and TDM buses have several similarities and differences. There are two physical TDM buses
in each PN. One of the buses can fail without affecting the other, but half of the call-carrying capacity is
lost. There is one packet bus in each PN. A failure of that bus can disrupt all packet traffic in that PN.
In critical-reliability systems, the Maintenance/Test circuit pack provides packet-bus reconfiguration
capabilities. This allows the packet bus to remain in service with up to three lead failures. There is no
corresponding facility on the TDM bus. Instead, the second physical TDM bus continues to carry traffic
until repairs are completed.
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Maintenance Procedures
December 2003