11/07/2007 IEEE 802.17 RPRWG Yan Wang

Some aspects to be determined in PIRC

July 2007 802.17 Plenary Meeting San Francisco, U.S.

yanw@huawei.comHuawei Technologies

11/07/2007 IEEE 802.17 RPRWG Yan Wang

Status message

• Status message is respectively transmitted periodically by two inter-ring nodes of a protection group to notify the status the to opposite inter-ring node.– Only inter-ring nodes process the status message– New controlType– Broadcast address or new multicast address– Appropriate transmission interval

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Status message function• Status message notifies the local inter-ring node’s status

to the opposite inter-ring node.– Active: Notify status change of the local inter-ring node to the

opposite inter-ring node• When the inter-ring node can’t forward traffic because forwarding

function failed or one ring function failed.• When the failed inter-ring node recovers.

– Passive: When no status messages from opposite inter-ring node are received

• Through two rings: the opposite node is down.• Through one ring: one ring function of the opposite node is down.

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11/07/2007 IEEE 802.17 RPRWG Yan Wang

controlDataUnit of the status message

• Status message could include the following information,– Protection group ID

– Forwarding status (None, Traffic set 1, Traffic set 2, Both)• Traffic can be classified by VLAN ID, MAC address and/or other

information.

• The inter-ring node may forward none, one, or both parts of the traffic.

• Under normal status, the forwarding status is decided by configuration or negotiation.

• Under protection status, the forwarding status is decided by the protection mechanism.

• To TTL balancing method, this field may be not needed.

11/07/2007 IEEE 802.17 RPRWG Yan Wang

controlDataUnit of the status message (cont’)

– Failure indication (No Failure, Partial failure, inter-ring forwarding failure) : Indicate the inter-ring node’s forwarding function failure, one ring function failure and the failure’s recovery.

– Configuration information (Priority, DevID etc.): May be used to negotiate the forwarding status during initialization or during the running time dynamically.

– Any others?

11/07/2007 IEEE 802.17 RPRWG Yan Wang

Back-to-back interconnected PIRC rings

• The status of the two back-to-back nodes should be synchronized.

• The message is needed to notify the status between two back-to-back nodes. This message is not a RPR message.

• Should new message and new mechanism be defined for this scenario?

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11/07/2007 IEEE 802.17 RPRWG Yan Wang

Multiple links failure protection

• Multiple links failure can be detected by– Status message

• One inter-ring node can’t receive the status message from the opposite node through one ring.

• But no inter-ring node failure notification is received through the other ring. This can be used to differentiate with one ring RPR function failure.

– TP message

• In order to protect the inter-ring traffic, both inter-ring nodes should be in forwarding status.

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11/07/2007 IEEE 802.17 RPRWG Yan Wang

Transient Loop in PIRC

• The possibility of two inter-ring node forwarding when one inter-ring node recovers from failure.

• For multiple links failure protection, both inter-ring nodes are in forwarding status. After link defect disappears, there will be transient loop.

• In relax mode, transient loop could be tolerated. • In strict mode, transient loop should be avoided.

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11/07/2007 IEEE 802.17 RPRWG Yan Wang

Strict mode for loop prevention

• In a protection group, anytime only one inter-ring node forwards traffic between the rings.– Don’t support multiple links failure protection.

– Guarantee two inter-ring nodes not in forwarding status at the same time.

• When one inter-ring node switch into forwarding status, it should make sure that the other one is not in the forwarding status.

• Sometime failed inter-ring node should take action and/or notify the other inter-ring node

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11/07/2007 IEEE 802.17 RPRWG Yan Wang

Strict mode for loop prevention (cont’)

• Modify the node’s recovery mechanism– When inter-ring node recovers, it shouldn’t switch into

forwarding status immediately.– When nodes adjacent to the failed link 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 shall know

the reversion and stop forwarding.• Notification mechanism

– They keep in protected status until the correlative interconnected node stops forwarding and notifies them.

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