Chapter 13
| Basic Administration Protocols
Ethernet Ring Protection Switching
– 465 –
■
The RPL owner node detects a failed link when it receives R-APS (SF - signal
fault) messages from nodes adjacent to the failed link. The owner then
enters protection state by unblocking the RPL. However, using this
standard recovery procedure may cause a non-EPRS device to become
isolated when the ERPS device adjacent to it detects a continuity check
message (CCM) loss event and blocks the link between the non-ERPS
device and ERPS device.
CCMs are propagated by the Connectivity Fault Management (CFM)
protocol as described under
“Connectivity Fault Management” on
. If the standard recovery procedure were used as shown in the
following figure, and node E detected CCM loss, it would send an R-APS (SF)
message to the RPL owner and block the link to node D, isolating that non-
ERPS device.
Figure 299: Non-ERPS Device Protection
When non-ERPS device protection is enabled on the ring, the ring ports on
the RPL owner node and non-owner nodes will not be blocked when signal
loss is detected by CCM loss events.
■
When non-ERPS device protection is enabled on an RPL owner node, it will
send non-standard health-check packets to poll the ring health when it
enters the protection state. It does not use the normal procedure of waiting
to receive an R-APS (NR - no request) message from nodes adjacent to the
recovered link. Instead, it waits to see if the non-standard health-check
packets loop back. If they do, indicating that the fault has been resolved,
the RPL will be blocked.
After blocking the RPL, the owner node will still transmit an R-APS (NR, RB -
ring blocked) message. ERPS-compliant nodes receiving this message flush
their forwarding database and unblock previously blocked ports. The ring
is now returned to Idle state.
◆
Holdoff Timer
– The hold-off timer is used to filter out intermittent link faults.
Faults will only be reported to the ring protection mechanism if this timer
expires. (Range: 0-10000 milliseconds, in steps of 100 milliseconds)
In order to coordinate timing of protection switches at multiple layers, a hold-
off timer may be required. Its purpose is to allow, for example, a server layer
protection switch to have a chance to fix the problem before switching at a
client layer.
When a new defect or more severe defect occurs (new Signal Failure), this event
will not be reported immediately to the protection switching mechanism if the
provisioned hold-off timer value is non-zero. Instead, the hold-off timer will be
started. When the timer expires, whether a defect still exists or not, the timer
non
-E
RPS
A
non
-E
RPS
RPL
Owner
RPL
X
X
b
l
ocked
b
l
ocked
fau
l
t
B
C
D
E
F
Содержание GTL-2881
Страница 30: ...Figures 30 Figure 450 Showing RIP Peer Information 669 Figure 451 Resetting RIP Statistics 670 ...
Страница 34: ...Section I Getting Started 34 ...
Страница 48: ...Section II Web Configuration 48 Unicast Routing on page 651 ...
Страница 151: ...Chapter 4 Interface Configuration VLAN Trunking 151 Figure 69 Configuring VLAN Trunking ...
Страница 152: ...Chapter 4 Interface Configuration VLAN Trunking 152 ...
Страница 229: ...Chapter 8 Congestion Control Automatic Traffic Control 229 Figure 135 Configuring ATC Interface Attributes ...
Страница 230: ...Chapter 8 Congestion Control Automatic Traffic Control 230 ...
Страница 596: ...Chapter 14 Multicast Filtering Multicast VLAN Registration for IPv6 596 ...
Страница 620: ...Chapter 15 IP Configuration Setting the Switch s IP Address IP Version 6 620 ...
Страница 670: ...Chapter 18 Unicast Routing Configuring the Routing Information Protocol 670 Figure 451 Resetting RIP Statistics ...
Страница 672: ...Section III Appendices 672 ...
Страница 678: ...Appendix A Software Specifications Management Information Bases 678 ...
Страница 688: ...Appendix C License Statement GPL Code Statement Notification of Compliance 688 ...
Страница 696: ...Glossary 696 ...
Страница 706: ...GTL 2881 GTL 2882 E112016 ST R01 ...