Edge-Core ECS4110-28T, Руководство по управлению, Страница: 504 / 1514

C
HAPTER
14
| Basic Administration Protocols
Ethernet Ring Protection Switching
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RPL Neighbor – Specifies a ring node to be the RPL neighbor.
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The RPL neighbor node, when configured, is a ring node
adjacent to the RPL that is responsible for blocking its end of the
RPL under normal conditions (i.e., the ring is established and no
requests are present in the ring) in addition to the block at the
other end by the RPL Owner Node. The RPL neighbor node may
participate in blocking or unblocking its end of the RPL, but is
not responsible for activating the reversion behavior.
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Only one RPL owner can be configured on a ring. If the switch is
set as the RPL owner for an ERPS domain, the west ring port is
set as one end of the RPL. If the switch is set as the RPL
neighbor for an ERPS domain, the east ring port is set as the
other end of the RPL.
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The east and west connections to the ring must be specified for
all ring nodes. When this switch is configured as the RPL
neighbor, the east ring port is set as being connected to the RPL.
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Note that is not mandatory to declare a RPL neighbor.
◆ Revertive – Sets the method of recovery to Idle State through
revertive or non-revertive mode. (Default: Enabled)
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Revertive behavior allows the switch to automatically return the RPL
from Protection state to Idle state through the exchange of protocol
messages.
Non-revertive behavior for Protection, Forced Switch (FS), and
Manual Switch (MS) states are basically the same. Non-revertive
behavior requires the RPL to be restored from Protection state to
Idle state using the Clear command (Configure Operation page).
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Recovery for Protection Switching – A ring node that has one or
more ring ports in an SF (Signal Fail) condition, upon detecting the
SF condition cleared, keeps at least one of its ring ports blocked for
the traffic channel and for the R-APS channel, until the RPL is
blocked as a result of ring protection reversion, or until there is
another higher priority request (e.g., an SF condition) in the ring.
A ring node that has one ring port in an SF condition and detects
the SF condition cleared, continuously transmits the R-APS (NR – no
request) message with its own Node ID as the priority information
over both ring ports, informing that no request is present at this
ring node and initiates a guard timer. When another recovered ring
node (or nodes) holding the link block receives this message, it
compares the Node ID information with its own Node ID. If the
received R-APS (NR) message has the higher priority, this ring node
unblocks its ring ports. Otherwise, the block remains unchanged. As
a result, there is only one link with one end blocked.
The ring nodes stop transmitting R-APS (NR) messages when they
accept an R-APS (NR, RB – RPL Blocked), or when another higher
priority request is received.