
Plexus 9000 Planning and Engineering Guide
System Overview
Section 130-110-000
Issue 6, May 14, 2004
Telica, Inc.
3-23
The system allows any slot to accept any IOM termination. The same
IOM can be used for active and protection functions and for both trunk-
and line-side terminations. IOMs feature extremely high densities of 28
DS1, and three or eight DS3/STS-1 interfaces per module.
3.4.3 System
Redundancy
The Plexus 9000 is fully redundant. Without redundancy as part of the
foundation, it would not be possible to achieve the fault tolerance levels
required for today's network requirements. In the case of other
architectures using separate building blocks for signaling and switching
functions stitched together by non-redundant LANs, overall reliability
quickly degrades and problem isolation becomes problematic.
Redundancy encompasses every part of the Plexus 9000 system including
IOMs, SF and SP modules, and integrated SS7 terminations. This high
degree of attention to redundancy has virtually eliminated any opportunity
for service failure. To more easily explain system redundancy the
following architecture discussion is divided into two parts: hardware and
software.
3.4.3.1 Hardware
Architecture
Each IOM is connected to both switch fabric modules and delivers traffic
to both. The switches in turn deliver traffic to the destination IOM. The
destination modules are configured by the protection subsystem to accept
traffic from either the A or B fabric. If the working fabric fails, the
destination modules can instantly switch to the identical streams being
delivered from the other fabric.
In the case of an IOM failure, traffic is switched from the working to the
protection module at the electrical interface. The standby module is
already connected to the switch fabric. New routing tables are delivered
throughout the switch so that other modules with traffic destined for this
particular interface can route their cells to the switch port connected to the
standby IOM rather than to the port connected to the failed module. The
standby module is provisioned with all appropriate line interface
parameters to match the module it is to replace. This fault-tolerant
architecture protects against the loss of active calls in case an IOM fails.