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9-9
Cisco ONS 15310-MA SDH Reference Manual, Release 9.1 and Release 9.2
78-19417-01
Chapter 9 SDH Topologies and Upgrades
Overlay Ring Circuits
mainly provided as error recovery for the wizard. The Span Upgrade Wizard and the manual span
upgrade procedures require at least two technicians (one at each end of the span) who can communicate
with each other during the upgrade. Upgrading a span is non-service affecting and will cause no more
than three switches, each of which is less than 50 ms in duration. To initiate the span upgrade, right-click
the span and choose Span Upgrade.
Note Span upgrades do not upgrade SDH topologies (for example, a 1+1 group to a Linear Multiplex Section
Protection configuration). Refer to the “Convert Network Configurations” chapter of the
Cisco ONS 15310-MA SDH Procedure Guide for topology upgrade procedures.
9.6.1 Span Upgrade Wizard
The Span Upgrade Wizard automates all steps in the manual 1+1 span upgrade procedure, if you are
upgrading two ONS 15310-MA SDH nodes. The wizard can upgrade both lines of a 1+1 group. The Span
Upgrade Wizard requires that spans have DCCs enabled.
The Span Upgrade Wizard provides no way to back out of an upgrade. In the case of an error, you must
exit the wizard and initiate the manual procedure to either continue with the upgrade or back out of it.
To continue with the manual procedure, examine the standing conditions and alarms to identify the stage
in which the wizard failure occurred.
9.6.2 Manual Span Upgrades
Manual span upgrades are mainly provided as error recovery for the Span Upgrade Wizard, but they can
be used to perform span upgrades. You can perform a manual span upgrade on a 1+1 protection group,
if you are upgrading two ONS 15310-MA SDH nodes.
Downgrading can be performed to back out of a span upgrade. The procedure for downgrading is the
same as upgrading except that you provision a lower-rate PPM (STM1 or STM4 for the 15310-MA SDH)
and install a lower-rate PPM (if you are not using a multi-rate PPM). You cannot downgrade if circuits
exist on the VCs that will be removed (the higher VCs).
9.7 Overlay Ring Circuits
An overlay ring configuration consists of a core ring and subtended rings (Figure 9-11). An Overlay
Ring Circuit routes traffic around multiple rings in an overlay ring configuration, passing through one
or more nodes more than once. This results in multiple cross-connections on the nodes connecting the
core ring to the subtended rings. For example, a customer having a core ring with cross-connects
provisioned using TL1 can create cross-connects on subtended rings, due to a business need, without
having to hamper the existing cross-connects on the core ring. This circuit can be either protected or
unprotected.
A typical path protected overlay ring configuration is shown in Figure 9-11, where the circuit traverses
the nodes B, D, and F twice resulting in two cross-connections on these nodes for the same circuit. In
Figure 9-11, the circuits on the STM4 path are unprotected. The DS3/E3 drop traffic is protected on the
drop nodes by provisioning a primary and secondary destination, making it a path protected circuit.