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Cisco ONS 15600 SDH Reference Manual, Release 9.0
78-18400-01
Chapter 8 SDH Topologies and Upgrades
8.5.1 MS-SPRing DRI
•
An integrated DRI requires one pair of nodes to interconnect two networks. The two interconnected
nodes replace the interconnection ring.
For DRI topologies, a hold-off timer sets the amount of time before a selector switch occurs. It reduces
the likelihood of multiple switches, such as:
•
Both a service selector and a path selector
•
Both a line switch and a path switch of a service selector
For example, if an SNCP DRI service selector switch does not restore traffic, then the path selector
switches after the hold-off time. The SNCP DRI hold-off timer default is 100 ms. You can change this
setting in the SNCP Selectors tab of the Edit Circuits window. For an MS-SPRing DRI, if line switching
does not restore traffic, then the service selector switches. The hold-off time delays the recovery
provided by the service selector. The MS-SPRing DRI default hold-off time is 100 ms and cannot be
changed.
8.5.1 MS-SPRing DRI
Unlike MS-SPRing automatic protection switching (APS) protocol, MS-SPRing DRI is a path-level
protection protocol at the circuit level. Drop-and-continue MS-SPRing DRI requires a service selector
in the primary node for each circuit routing to the other ring. Service selectors monitor signal conditions
from dual feed sources and select the one that has the best signal quality. Same-side routing drops the
traffic at primary nodes set up on the same side of the connected rings, and opposite-side routing drops
the traffic at primary nodes set up on the opposite sides of the connected rings. For MS-SPRing DRI,
primary and secondary nodes cannot be the circuit source or destination.
Note
A DRI circuit cannot be created if an intermediate node exists on the interconnecting link. However, an
intermediate node can be added on the interconnecting link after the DRI circuit is created.
shows ONS 15600 SDHs in a traditional MS-SPRing DRI topology with same-side routing.
In Ring 1, Nodes 3 and 4 are the interconnect nodes, and in Ring 2, Nodes 8 and 9. Duplicate signals are
sent from Node 4 (Ring 1) to Node 9 (Ring 2), and from Node 3 (Ring 1) to Node 8 (Ring 2). The
primary nodes (Nodes 4 and 9) are on the same side, and the secondary nodes (Nodes 3 and 8) provide
an alternative route. In Ring 1, traffic at Node 4 is dropped (to Node 9) and continued (to Node 3).
Similarly, at Node 9, traffic is dropped (to Node 4) and continued (to Node 8).
