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C
HAPTER
15
| Basic Administration Protocols
Ethernet Ring Protection Switching
– 429 –
Operational Concept
Loop avoidance in the ring is achieved by guaranteeing that, at any time,
traffic may flow on all but one of the ring links. This particular link is called
the ring protection link (RPL), and under normal conditions this link is
blocked to traffic. One designated node, the RPL owner, is responsible for
blocking traffic over the RPL. When a ring failure occurs, the RPL owner is
responsible for unblocking the RPL, allowing this link to be used for traffic.
Ring nodes may be in one of two states:
Idle – normal operation, no link/node faults detected in ring
Protection – Protection switching in effect after identifying a signal fault
In Idle state, the physical topology has all nodes connected in a ring. The
logical topology guarantees that all nodes are connected without a loop by
blocking the RPL. Each link is monitored by its two adjacent nodes using
Connectivity Fault Management (CFM) protocol messages.
Protection switching (opening the RPL to traffic) occurs when a signal
failure message generated by the Connectivity Fault Management (CFM)
protocol is declared on one of the ring links, and the detected failure has a
higher priority than any other request; or a Ring – Automatic Protection
Switching protocol request (R-APS, as defined in Y.1731) is received which
has a higher priority than any other local request.
A link/node failure is detected by the nodes adjacent to the failure. These
nodes block the failed link and report the failure to the ring using R-APS
(SF) messages. This message triggers the RPL owner to unblock the RPL,
and all nodes to flush their forwarding database. The ring is now in
protection state, but it remains connected in a logical topology.
When the failed link recovers, the traffic is kept blocked on the nodes
adjacent to the recovered link. The nodes adjacent to the recovered link
transmit R-APS (NR - no request) message indicating they have no local
request. When the RPL owner receives an R-APS (NR) message it starts the
Wait-To-Recover (WTR) timer. Once WTR timer expires, the RPL owner
blocks the RPL and transmits an R-APS (NR, RB - ring blocked) message.
Nodes receiving this message flush the forwarding database and unblock
their previously blocked ports. The ring is now returned to Idle state.
Содержание DG-FS4526E
Страница 4: ...ABOUT THIS GUIDE 4...
Страница 34: ...CONTENTS 34...
Страница 50: ...TABLES 50...
Страница 52: ...SECTION I Getting Started 52...
Страница 62: ...CHAPTER 1 Introduction System Defaults 62...
Страница 80: ...CHAPTER 2 Initial Switch Configuration Managing System Files 80...
Страница 82: ...SECTION II Web Configuration 82...
Страница 100: ...CHAPTER 3 Using the Web Interface Navigating the Web Browser Interface 100...
Страница 128: ...CHAPTER 4 Basic Management Tasks Resetting the System 128...
Страница 166: ...CHAPTER 5 Interface Configuration VLAN Trunking 166...
Страница 198: ...CHAPTER 6 VLAN Configuration Configuring VLAN Mirroring 198...
Страница 516: ...CHAPTER 17 IP Services Displaying the DNS Cache 516...
Страница 562: ...CHAPTER 19 Using the Command Line Interface CLI Command Groups 562...
Страница 652: ...CHAPTER 22 SNMP Commands 652...
Страница 660: ...CHAPTER 23 Remote Monitoring Commands 660...
Страница 714: ...CHAPTER 24 Authentication Commands Management IP Filter 714...
Страница 802: ...CHAPTER 27 Interface Commands 802...
Страница 824: ...CHAPTER 29 Port Mirroring Commands RSPAN Mirroring Commands 824...
Страница 846: ...CHAPTER 32 Address Table Commands 846...
Страница 874: ...CHAPTER 33 Spanning Tree Commands 874...
Страница 886: ...CHAPTER 34 ERPS Commands 886...
Страница 928: ...CHAPTER 35 VLAN Commands Configuring Voice VLANs 928...
Страница 942: ...CHAPTER 36 Class of Service Commands Priority Commands Layer 3 and 4 942...
Страница 998: ...CHAPTER 38 Multicast Filtering Commands Multicast VLAN Registration 998...
Страница 1022: ...CHAPTER 39 LLDP Commands 1022...
Страница 1064: ...CHAPTER 40 CFM Commands 1064...
Страница 1084: ...CHAPTER 42 Domain Name Service Commands 1084...
Страница 1090: ...CHAPTER 43 DHCP Commands DHCP Client 1090...
Страница 1122: ...CHAPTER 44 IP Interface Commands IPv6 Interface 1122...
Страница 1124: ...SECTION IV Appendices 1124...
Страница 1129: ...APPENDIX A Software Specifications Management Information Bases 1129 Trap RFC 1215 UDP MIB RFC 2013...
Страница 1130: ...APPENDIX A Software Specifications Management Information Bases 1130...
Страница 1152: ...COMMAND LIST 1152...
Страница 1161: ......
Страница 1162: ...DG FS4526E 042012 HW R01...