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Chapter 13
| Basic Administration Protocols
Ethernet Ring Protection Switching
Recovery with non-revertive mode is handled as follows:
■
a.
The RPL Owner Node, upon reception of an R-APS (NR)
message and in the absence of any other higher priority
request does not perform any action.
b.
Then, after the operator issues the Clear command (Configure
Operation page) at the RPL Owner Node, this ring node blocks
the ring port attached to the RPL, transmits an R-APS (NR, RB)
message over both ring ports, informing the ring that the RPL is
blocked, and flushes its FDB.
c.
The acceptance of the R-APS (NR, RB) message triggers all ring
nodes to unblock any blocked non-RPL which does not have an
SF condition. If it is an R-APS (NR, RB) message without a DNF
indication, all ring nodes flush their FDB. This action unblocks
the ring port which was blocked as result of an operator
command.
◆
Major Domain – The ERPS ring used for sending control packets.
This switch can support up to two rings. However, ERPS control packets can
only be sent on one ring. This parameter is used to indicate that the current ring
is a secondary ring, and to specify the major ring which will be used to send
ERPS control packets.
The Ring Protection Link (RPL) is the west port and can not be configured. So
the physical port on a secondary ring must be the west port. In other words, if a
domain has two physical ring ports, this ring can only be a major ring, not a
secondary ring (or sub-domain) which can have only one physical ring port.
The major domain therefore cannot be set if the east port is already configured.
◆
Node ID – A MAC address unique to the ring node. The MAC address must be
specified in the format xx-xx-xx-xx-xx-xx or xxxxxxxxxxxx. (Default: CPU MAC
address)
The ring node identifier is used to identify a node in R-APS messages for both
automatic and manual switching recovery operations.
For example, a node that has one ring port in SF condition and detects that the
condition has been cleared, will continuously transmit R-APS (NR) messages
with its own Node ID as priority information over both ring ports, informing its
neighbors that no request is present at this node. When another recovered
node holding the link blocked receives this message, it compares the Node ID
information with its own. If the received R-APS (NR) message has a higher
priority, this unblocks its ring ports. Otherwise, the block remains unchanged.
The node identifier may also be used for debugging, such as to distinguish
messages when a node is connected to more than one ring.
◆
R-APS with VC – Configures an R-APS virtual channel to connect two
interconnection points on a sub-ring, allowing ERPS protocol traffic to be
tunneled across an arbitrary Ethernet network. (Default: Enabled)
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