
Chapter 4: Feature Description
Ethernet Features
Note
An additional state, Signal Degrade (SD), is planned for future release. The SD state is
similar to SF, but with lower priority.
Users can configure up to 16 ERPIs. Each ERPI is associated with an Ethernet service defined in the
system. This enables operators to define a specific set of G.8032 characteristics for individual
services or groups of services within the same physical ring. This includes a set of timers that
enables operators to optimize protection switching behavior per ERPI:
•
Wait to Restore (WTR) Timer – Defines a minimum time the system waits after signal failure is
recovered before reverting to idle state.
•
Guard Time – Prevents unnecessary state changes and loops.
•
Hold-off Time – Determines the time period from failure detection to response.
Each ERPI maintains a state machine that defines the node’s state for purposes of switching and
convergence. The state is determined according to events that occur in the ring, such as signal
failure and forced or manual switch requests, and their priority. Possible states are:
•
Idle
•
Protecting
•
Forced Switch (FS)
•
Manual Switch (MS)
•
Pending
As shown in the following figure, in idle (normal) state, R-APS messages pass through all links in
the ring, while the RPL is blocked for traffic. The RPL can be on either edge of the ring. R-APS
messages are sent every five seconds.
Figure 66 G.8032 Ring in Idle (Normal) State
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