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Reference Guide for the Centillion 50/100 and Model 5000BH Switches
4-8
893-01006-C
The dual ring and multicore designs are best suited for campus interconnects
where the primary data traffic is local to a building but there is some need to
connect across the campus. The two designs can be combined so that some
buildings have the meshed core of four switches and others have only two
switches.
The star design is the obvious preferred design for a single core data center and a
number of outlying buildings. This design is preferred when data flow is primarily
hierarchical, but physical constraints such as the distance between buildings and
the numbers of available fiber runs may not allow this design to work.
The semimesh design is the type of network design to use when there is
significant intracampus data flow among various buildings. As depicted, both this
design and the dual ring design allow the six buildings to connect and use the
same number of links and fiber runs out of each building. By redistributing the
cabling, the semimesh design provides better connectivity than the dual ring
design. However, physical constraints (for example, distance and numbers of fiber
runs) may not allow this design to work.
You can use these designs in three ways:
• Each building can be a PNNI peer group with IISP links between them. In a
pure Centillion 50/100 and Model 5000BH environment, this arrangement
will not provide the necessary fault tolerance for some of the designs.
• You can have a campus PNNI peer group with switches in each building as
shown in the diagrams. Building switches are connected to these via IISP.
• The switches can be Centillion 50/100 and Model 5000BH, and the buildings
can be set up as a hierarchy. You can attach additional ATM switches to the
Centillion 50/100 and Model 5000BH switches via PNNI or IISP. Note that
any Centillion 50/100 or Model 5000BH switches must use IISP to get to this
hierarchical core.
The dual ring is another version of an inefficient design. In a hierarchical PNNI
environment or in one where, as in the example, a network with 12 switches is a
single peer group, it works well. However, if the individual buildings are each peer
groups that are connected via IISP, then the network will not be fault tolerant if a
parallel pair of links fails.
The multicore design can be treated like the dual ring in many ways. However,
notice that the design drawn with only three cores does not have the recovery
problems of a ring with more than three cores.