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 b us interface may alarm the p acket bus due to
shorting of the pack et bus leads. This typically d isrupts
all
packet bus traffic i n
the affected PN. A failure of the packet b us in the PPN affects packet traffic in the
EPNs as well. Some packet bus failures do not affect all endpoints, so a packe t
bus failure cannot be ruled out just because some p acket service is still
available.
A circuit pack c an fail in a manner such that it transmits b ad data on the packet
bus. If the Packet Interface so fails, all Pac ket traffic is disrupted. Suc h a failure
on an Expansion Interface may disrup t all Packet traffic in that port network. If an
ISDN-BRI circuit pack fails suc h that it transmits bad data, all d evices connected
to the circuit pac k fail to function. This failure may also disrupt the entire p acket
bus whenever the circuit p ack tries to transmit data. Such a disrup tion may be
indicated b y packet bus alarms that oc cur and go away, intermittent failures of
other packet circ uit packs, and/or interferenc e with other connected end points.
These failures are difficult to isolate becau se of their intermittent nature. In most
cases, the failed circ uit pack is alarmed, and all connected end points on the
circuit pack are out of servic e until the circuit pack is rep laced. These symptoms
help in isolating the fault.
Maintenance of the Packet Bus
The following topics are cov ered 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 sev eral similarities and differences. There are
two physical TDM buses in eac h PN. One of the buses can fail without affecting
the other, but half of the call-carryi ng capacity is lost. There is

one

packet bus in
each PN. A failure of that bus can d isrupt all packet traffic in that PN.
In critical reliability systems, the Maintenance/Test circuit pack provid es packet
bus reconfiguration c apabilities. This allows the packet bus to remain in service
with up to 3 lead failures. There is no corresp onding facility on the TDM Bus.
Instead, the second p hysical 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) disab les
all
traffic in the PN. A catastrophic
packet bus failure affec ts only packet traffic, so that TDM traffic is unaffec ted,
while all ISDN-BRI, ASAI, X.25, and ISDN-PRI signaling traffic is disrupted. The
significance of this d istinction depend s on the customer’s app lications. A
customer whose primary ap plication requires ASAI would co nsider the switch to
be out of service, while a c ustomer with a large number of Dig ital/Analog/Hybrid
sets and a small number of ISDN-BRI sets would p robably not consider the