DEFINITY Enterprise Communications Server Release 7
Maintenance for R7r
555-230-126
Issue 4
June 1999
Alarms, Errors, and Troubleshooting
5-85Packet Bus Fault Isolation and Repair
5
Failure of any circuit pack’s bus interface may alarm the packet bus due to
shorting of the packet bus leads. This typically disrupts
all
packet bus traffic in
the affected PN. A failure of the packet bus in the PPN affects packet traffic in the
EPNs as well. Some packet bus failures do not affect all endpoints, so a packet
bus failure cannot be ruled out just because some packet service is still
available.
A circuit pack can fail in a manner such that it transmits bad data on the packet
bus. If the Packet Interface so fails, all Packet traffic is disrupted. Such a failure
on an Expansion Interface may disrupt all Packet traffic in that port network. If an
ISDN-BRI circuit pack fails such that it transmits bad data, all devices connected
to the circuit pack fail 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 packet bus alarms that occur and go away, intermittent failures of
other packet circuit packs, and/or 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 all connected endpoints on the
circuit pack are out of service until the circuit pack is replaced. These symptoms
help in isolating the fault.
Maintenance of the Packet Bus
The following topics are covered in this section:
■ ‘‘Packet Bus and TDM Bus: a Comparison’’
■ ‘‘Packet Bus Maintenance Software’’
■ ‘‘Fault Correction Procedures: Overview’’
Packet Bus and TDM Bus: a Comparison
The packet and TDM busses 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 3 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.
System response varies according by type of bus failure and whether or not the
failure occurs in the PPN or an EPN. In an EPN, a catastrophic TDM Bus failure
(one that affects both TDM Buses) disables
all
traffic in the PN. A catastrophic
packet bus failure affects only packet traffic, so that TDM traffic is unaffected,
while all ISDN-BRI, ASAI, X.25, and ISDN-PRI signaling traffic is disrupted. The
significance of this distinction depends on the customer’s applications. A
customer whose primary application requires ASAI would consider the switch to
be out of service, while a customer with a large number of Digital/Analog/Hybrid
sets and a small number of ISDN-BRI sets would probably not consider the
