Resilient Packet Ring (RPR) switching
Introduction
Alcatel-Lucent 1665 DMX provides revertive RPR protection for Ethernet traffic on the LNW78 100/1G FSR Gigabit Ethernet circuit packs. The RPR protection switching takes place in response to automatically detected faults and external commands from the WaveStar® CIT or operations system (OS). Protection switching is provisioned using the WaveStar® CIT System View Configuration → Equipment menu and the supporting displays.
Protection switching priorities
The following table lists the RPR protection switch priorities (in descending order of priority).
Table 4-40: Protection switching priorities (RPR protection)
|
Switch Priorities (Descending Order) |
Source of Request |
|---|---|
|
Reset |
WaveStar® CIT or OS |
|
Signal Failure |
Automatic |
|
Signal Degrade |
Automatic |
|
Manual Switch |
WaveStar® CIT or OS |
|
Wait to Restore |
Automatic |
Operation
Alcatel-Lucent 1665 DMX supports the steering mechanism for RPR protection switching as defined in the IEEE 802.17 standard. When RPR topology discovery detects a fault in the ring, the topology change is communicated to each node in the ring.
Each node that originates traffic performs a head-end switch that steers traffic onto ringlet 0 or ringlet 1, on a destination node basis, to avoid the failed span. Each node uses its topology image to choose a ringlet. Traffic is reestablished in less than 50 milliseconds after the failure is detected.
The 50-millisecond protection time includes a ring with up to 255 nodes and up to 2000 kilometers in circumference. Protection switching is complete when all the nodes in the ring have been notified of changes in the protection state and start to re-steer traffic away from the fault. Refer to Figure 4-6, RPR protection switching example.
When RPR topology discovery detects the fault has cleared, the topology change is communicated to each node in the ring. When the fault and provisionable wait-to-restore interval clear, the traffic switches back (reverts) to the original ringlet. The RPR protection wait-to-restore timer is provisionable on an RPR span basis using Configuration → Equipment. For detailed information about provisioning RPR, refer to the Alcatel-Lucent 1665 Data Multiplexer (DMX) User Operations Guide, 365-372-301.
Figure 4-6: RPR protection switching example
