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Interconnected node failure

Multiple Links Failure Protection in Protected Inter-Ring Connection May 2007 Interim Meeting Geneva Switzerland zhaisuping@huawei.com yanw@huawei.com Huawei Technologies. Interconnected node failure.

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Interconnected node failure

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  1. Multiple Links Failure Protection in Protected Inter-Ring ConnectionMay 2007 Interim Meeting Geneva Switzerlandzhaisuping@huawei.comyanw@huawei.comHuawei Technologies IEEE 802.17 RPRWG

  2. Interconnected node failure • When one interconnected node fails, the other interconnected node shall take over all the inter-ring traffic forwarding. • The node failure may be of the following situations • The whole node failure • One ring component failure • The forwarding component failure IEEE 802.17 RPRWG

  3. Multiple links failure • From the node C2 viewpoint, scenario (a) can be equal to an interconnected node failure (one ring component failure). • In this case, the same protection action shall be taken just like the node C1 failure. • Scenario (b) can be protected by two interconnected nodes forwarding. • Scenario (a) can be regarded as a specific case of scenario (b). The mechanism for scenario (b) can also be used by scenario (a). IEEE 802.17 RPRWG

  4. Multiple links failure protection • C2 is selected to forward the inter-ring traffic. • Two links failure makes R1 can’t communicate with C2, inter-ring traffic from R1 fails. • Protection is achieved by both inter-ring nodes C1 and C2 forwarding all inter-ring traffic. IEEE 802.17 RPRWG

  5. The problem of transient loop • After link defect recovers, there are transient loop, because the two interconnected nodes C1 and C2 both are still in forwarding status. IEEE 802.17 RPRWG

  6. Transient loop prevention • When nodes R1 and R2 find the link recovers, they shouldn’t switch to normal status immediately. • Timer mechanism • They keep in protected status until their timers expire. • Before the timers expire, the correlative interconnected node C1 shall know the reversion and stop forwarding. • Notification mechanism • They keep in protected status until the correlative interconnected node C1 stops forwarding and notifies them. IEEE 802.17 RPRWG

  7. Performance consideration • In the dual-interconnected ringsthat there are 8-10 nodes on each ring • The two links failure protection time can be less than 50ms • During reversion, there is a transient interruption for some traffic because of the loop prevention mechanism. • The interruption time can be less than 50ms • The interruption time depends on • The interconnected nodes’ processing capability • The number of nodes on the ring IEEE 802.17 RPRWG

  8. Benefits vs. Shortages • Benefits • Enhanced inter-ring traffic protection ability. • Better utilization of the dual interconnected nodes. • Shortages • New mechanism to prevent transient loop during reversion. • Possibility of modifying the non-interconnected nodes. IEEE 802.17 RPRWG

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