RPR Interconnection Topologies IEEE WG Orlando, Florida USA March 11~16, 2007

Two Basic RPR Interconnection Topologies Topology A Topology B

Topology ATopology B Cost effective and maintenanceInterconnected stations are co-located, the cost is relatively economical. There are four box to be connected for the PIRC, more cost than topology A domain protection and load- balancing perspective Only the two interconnected stations are involved. All four interconnected stations are involved, and need more mechanisms such as synchronization message between the two directly interconnected stations, link failure detection/notification, link failure indication. Note: more discussion about this on the companion document ( rpr multi-links failover.ppt). Topology flexibilityThe interconnected stations are coupled, it is not flexible for the network deployment. The interconnected stations are decoupled, more flexibility Fast recoveryUse the domain recovery mechanism can reach 50ms failover time. Use the xSTP (or variation) may realize fast failover time. However it’s also feasible to use domain protection mechanism, however with more implementation complexity. The Comparison of Two Topologies

Tentative Conclusion (need further discussion): When the requirement of network deployment flexibility outweighs the cost, then the Topology B is used, or else the Topology A is recommended in the RPR interconnection rings network. The Comparison of Two Topologies – Cont.

The following slides will illustrate the different application scenarios for the interconnected RPR rings. The following figures take the Topology A as example, but the same topologies also apply to Topology B as well.

Application Scenario 1 There are several subtending rings across one ring. Each pair of interconnected stations ({A, B} and {C,D}) are independent and belong to different protection groups.

Application Scenario 2 There are several subtending rings across one ring, and these subtending rings share a common station. Each pair of interconnected stations ({A, B} and {B, C}) are independent and belong to different protection groups.

Application Scenario 3 There are several subtending rings across one ring, and these subtending rings share the same interconnection stations. For the usual deployment, subtending access rings are not communicated each other, they only need to communicate with the aggregation rings. But if the subtending access rings need to communicate each other, they still can at the cost of some implementation complexity.

Application Scenario 4 We don’t want support this disordered topologies. Do we want?

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