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PNC-DUP (PNC Duplication)
Issue 1 June 2005 1851
PNC-DUP (PNC Duplication)
S8700 MC only
In systems with the Critical Reliability option, the following components, which together
comprise the Port Network Connectivity (PNC), are duplicated:
● Expansion Interface (EI) TN570 circuit packs in the port networks (PNs)
● Switch Node Interface (SNI) TN573 circuit packs in switch nodes
● DS1 Converter (DS1C) TN574 circuit packs for remote PN connections
● Fiber-optic cables (metallic in certain cases) connecting the above circuit packs
● DS1 facilities between the DS1Cs
● Switch Node Clock (SNC) TN572 circuit packs
● IP Server Interface (IPSI) TN2312AP circuit packs
Although not part of the PNC, Tone-Clock circuit packs are also duplicated in each PN. The
PNC is available in two different configurations: direct connect, in which each port network is
connected directly by fiber optic links to each other PN; and Center Stage Switch (CSS) which
utilizes one or two switch nodes to interconnect the PNs. Direct connect systems can have up to
two PNs. CSS systems with one switch node can have up to 15 PNs. CSS systems with three
switch node can have up to 44 PNs. See the following figures.
PNC duplication architecture utilizes an active/standby duplication scheme, in which one
complete set of PNC components supports call processing, while the duplicate PNC is held in
reserve. All calls on the active PNC are simultaneously set up, or shadowed, on the standby
PNC in order for it to be capable of instantly assuming active status when necessary, allowing
for interchanges without service disruption (in the case of single faults).
The PNC-DUP MO tracks the health of the active and standby PNCs, controls planned and
spontaneous interchanges, and manages related functions such as double call refresh and
unrefresh, anti-thrashing, and so on. The main responsibility of PNC-DUP is to recover the
system to full service in the event of a fault. In the event of multiple faults PNC-DUP will do its
best to maximize service continuity.
PNC duplication does not introduce any additional types of hardware or hardware faults, and
there are no tests associated with the PNC-DUP MO. Instead, error log entries are used to log
useful information about the occurrence and causes of interchanges. This is done in order to
facilitate diagnosis of problems, which can then be addressed by using the documentation for
the individual MO involved.
MO Name in
Alarm Log
Alarm
Level
Initial Command to Run Full Name of MO
PNC-DUP NA status pnc PNC duplication