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Applications
2-4 Issue 3 June 2001
A network which requires the bulk of its traffic to be dropped at a single node is an
ideal application for path switched rings. A typical loop feeder network, where
most traffic is between the subscriber loop to a central office, fits this mold. Such
an application calls for the delivery of protected DS1 and DS3 service to customer
locations. In many cases, where the network serves only voice traffic and DS1s, a
DDM-2000 OC-3/
SLC
-2000 path switched ring is a perfect fit. If DS3 service or a
mixture of DS1 and DS3 service is needed, multiple OC-3 rings or an OC-12 ring
may be necessary. Cost, fiber availability, and bandwidth flexibility all play a part in
determining whether a single OC-3 ring, multiple OC-3 rings, or an OC-12 ring will
be the best network solution.
The DDM-2000 OC-3 and OC-12 VT1.5 or STS-1 path switched rings operate as
shown in Figure 2-1(a.). Traffic entering a path switched ring node is sent onto
both rotations of the ring. At the receiving node, the signal having the highest
integrity (based on SONET path information) is selected and dropped as outgoing
traffic. At intermediate nodes, the traffic is "passed-through" without changing the
SONET path information. The DDM-2000 OC-3/OC-12's VT1.5/STS-1 Time Slot
Interchange (TSI) capabilities make the provisioning of add/drop and pass-
through traffic quick and easy.
The self-healing nature of the path switched ring is shown in Figure 2-1(b.). In this
case, the fiber failure between nodes C and D causes node C to switch from the
counterclockwise ring to the clockwise ring, thus maintaining service between
node A and C.
In addition, the backup and restoral capability of CPro-2000 can be used to
significantly reduce the effort and increase the accuracy of installing several
complex ring shelves having similar or identical configurations. After manually
provisioning the first node, CPro-2000 can be used to make a copy of the
configuration. This copy can then be used to quickly and easily configure all of the
remaining nodes using the restoral feature of CPro-2000. Using system backup
and restoral in this fashion provides a much quicker and less error-prone
installation than manual provisioning.
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