Packet-Bus Faults; Packet Bus Connectivity - Avaya MCC1 Maintenance Procedures

The packet bus carries various types of information:
• Signaling and data traffic destined for other port networks and/or Center Stage Switches (CSSs)
through the TN570 Expansion Interface circuit pack access.
• ISDN-BRI signaling information for ISDN-BRI stations, data modules and ASAI adjunct
connections. The TN556 ISDN-BRI circuit pack provides packet-bus access for these
connections.
• ISDN-PRI signaling information carried in the D channels of ISDN-PRI facilities connected to
the switch. The TN464F Universal DS1 circuit pack provides packet-bus access for these
connections.
A server's interface to a PN's packet bus is by way of an Ethernet link to the PN's TN2312AP IPSI circuit
pack, through the IPSI's Packet Interface circuit, and to the packet bus. When servers are duplicated,
there are two IPSIs in each PN. The TN771D Maintenance/Test circuit pack provides packet-bus
maintenance testing and reconfiguration capabilities. The circuit packs mentioned here are discussed in
more detail in Circuit packs that use the packet bus

Packet-Bus faults

Two types of packet-bus faults can occur:
Shorts
Opens
Shorts are far more common than opens since they can be caused by incorrect insertion of a circuit pack.
It is possible for a circuit pack to cause a packet-bus fault, but still operate trouble-free itself. For
example, the insertion of a TDM-only circuit pack such as a TN754 digital line could bend the packet-bus
pins on the backplane but remain unaffected, since it does not communicate over the packet bus.
Packet-bus faults do not necessarily cause service interruptions, but shorts on it usually do. Depending on
which leads are defective, the system may recover and continue to communicate. While this recovery can
provide uninterrupted service, it also makes isolating a fault more difficult. The Maintenance/Test circuit
pack enables the detection and, in some cases, correction of packet-bus faults.

Packet bus connectivity

Various maintenance objects communicate on the packet bus (see the next section). For more details, use
the following links for the following MOs:
• TN2312AP
• PKT-INT (Packet Interface)
• TN570
Maintenance Procedures
December 2003
A short occurs when different leads on the packet bus become electrically
connected to each other. This can occur due to failures of circuit packs, cables
between carriers, TDM/LAN terminators, or bent pins on the backplane. A
fault occurring during normal operation is usually caused by a circuit pack. A
fault that occurs while moving circuit packs or otherwise modifying the
switch is usually due to bent pins on the backplane.
An open occurs when there is a break on the packet bus such that the electrical
path to the termination resistors is interrupted. Usually, this break is caused
by a failed TDM/LAN cable or terminator. A less likely possibility is a failure
in the backplane of a carrier.
IP-SVR (IP Server Interface)
EXP-INTF (Expansion Interface Circuit Pack)
Packet and serial bus maintenance
Isolating and repairing packet-bus faults
on page 222.
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