Chapter 13
| Basic Administration Protocols
Ethernet Ring Protection Switching
– 478 –
are terminated on the interconnection points. Since the sub-ring does not
provide an R-APS channel nor R-APS virtual channel beyond the
interconnection points, R-APS channel blocking is not employed on the
normal ring links to avoid channel segmentation. As a result, a failure at any
ring link in the sub-ring will cause the R-APS channel of the sub-ring to be
segmented, thus preventing R-APS message exchange between some of
the sub-ring’s ring nodes.
No R-APS messages are inserted or extracted by other rings or sub- rings at
the interconnection nodes where a sub-ring is attached. Hence there is no
need for either additional bandwidth or for different VIDs/Ring IDs for the
ring interconnection. Furthermore, protection switching time for a sub-ring
is independent from the configuration or topology of the interconnected
rings. In addition, this option always ensures that an interconnected
network forms a tree topology regardless of its interconnection
configuration. This means that it is not necessary to take precautions
against forming a loop which is potentially composed of a whole
interconnected network.
Figure 296: Sub-ring without Virtual Channel
◆ R-APS Def MAC – Sets the switch’s MAC address to be used as the node
identifier in R-APS messages. (Default: Enabled)
When ring nodes running ERPSv1 and ERPSv2 co-exist on the same ring, the
Ring ID of each ring node must be configured as “1”.
If this command is disabled, the following strings are used as the node
identifier:
■
ERPSv1: 01-19-A7-00-00-01
■
ERPSv2: 01-19-A7-00-00-[Ring ID]
◆ Propagate TC – Enables propagation of topology change messages from a
secondary ring to the primary ring. (Default: Disabled)
When a secondary ring detects a topology change, it can pass a message about
this event to the major ring. When the major ring receives this kind of message
from a secondary ring, it can clear the MAC addresses on its ring ports to help
the second ay ring restore its connections more quickly through protection
switching.
When the MAC addresses are cleared, data traffic may flood onto the major
ring. The data traffic will become stable after the MAC addresses are learned
Sub-ring
with Virtual
Channel
RPL Port
Interconnection Node
Ring Node
Major Ring
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