• Multiple MS commands cancel all MS commands
• Clear—Cancels an existing FS or MS command on the ring-port
• Used (at RPL Owner) to clear non-revertive mode
A G.8032 ring can support multiple instances. An instance is a logical ring running over a physical ring. Such
instances are used for various reasons, such as load balancing VLANs over a ring. For example, odd VLANs
may go in one direction of the ring, and even VLANs may go in the other direction. Specific VLANs can be
configured under only one instance. They cannot overlap multiple instances. Otherwise, data traffic or RAPS
packet can cross logical rings, and that is not desirable.
G.8032 ERP provides a new technology that relies on line status and Connectivity Fault Management (CFM)
to detect link failure. By running CFM Continuity Check Messages (CCM) messages at an interval of 100ms,
it is possible to achieve SONET-like switching time performance and loop free traffic.
For more information about Ethernet Connectivity Fault Management (CFM) and Ethernet Fault Detection
(EFD) configuration, refer to the Configuring Ethernet OAM on the Cisco ASR 9000 Series Router module
in the Cisco ASR 9000 Series Aggregation Services Router Interface and Hardware Component Configuration
Guide.
Timers
G.8032 ERP specifies the use of different timers to avoid race conditions and unnecessary switching operations:
• Delay Timers—used by the RPL Owner to verify that the network has stabilized before blocking the
RPL
• After SF condition, Wait-to-Restore (WTR) timer is used to verify that SF is not intermittent. The
WTR timer can be configured by the operator, and the default time interval is 5 minutes. The time
interval ranges from 1 to 12 minutes.
• After FS/MS command, Wait-to-Block timer is used to verify that no background condition exists.
Wait-to-Block timer may be shorter than the Wait-to-Restore timer
Note
• Guard Timer—used by all nodes when changing state; it blocks latent outdated messages from causing
unnecessary state changes. The Guard timer can be configured and the default time interval is 500 ms.
The time interval ranges from 10 to 2000 ms.
• Hold-off timers—used by underlying Ethernet layer to filter out intermittent link faults. The hold-off
timer can be configured and the default time interval is 0 seconds. The time interval ranges from 0 to 10
seconds.
• Faults are reported to the ring protection mechanism, only if this timer expires.
Single Link Failure
The following figure represents protection switching in case of a single link failure.
L2VPN and Ethernet Services Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x
219
Implementing Multipoint Layer 2 Services
Overview
To Next Page
Loading...
Need help?
General
