Hello everyone!
Today, let's continue to learn Type C protection in GPON networking protection.
Type C protection
The xPON type C protection switching is implemented through the redundancy configuration of the two PON ports on the ONU, backbone optical fiber, optical splitter, and tributary optical fiber on an xPON network. Each item is in a dual configuration. The protection improves the reliability of the optical distribution network (ODN) and prevents service interruption.
Single-Homing xPON Type C Protection
Networking: Single-Homing Type C Protection
Advantage: The networking mode is simple, and OLT and ONU can be managed easily.
Disadvantage: When the OLT becomes faulty, services are interrupted. Optical fibers are deployed on the same channel and therefore two optical fibers may be broken at the same time.
Scenario: This mode is used to protect important services, such as Enterprise private line services and base station services.
Scenario 1: Branch Fiber Connected to a Single ONU Becomes Faulty
1. Both the ONU and OLT check the link status and determine whether to trigger protection switching based on the link status.
If the OLT detects a fault on link A in the preceding figure, it automatically switches to the protection link and uses the protection link to send messages to ONU 1 to notify that protection switching has occurred. In addition, the OLT notifies ONU 1 of the switching cause.
If ONU 1 detects a fault on link A in the preceding figure, it automatically switches to the protection link and sends messages to the OLT to notify that protection switching has occurred. In addition, the ONU notifies the OLT of the switching cause.
2. After switching, services on ONU 1 are transmitted to the OLT through the protection port, all the feeder fibers connected to the OLT transmitted service packets, and ONU N is not affected. The changes on ONU 1 are as follows:
The state of the working port changes to standby.
The state of the protection port changes to active, and service packets are transmitted through link B in the preceding figure.
3. After protection switching, ONU 1 can automatically switch back to the working port. The OLT sends an automatic switchback message and the switchback time, called the wait to restore (WTR) time, to the ONU.
If the OLT learns that ONU 1's working port and the working line are functioning properly and the working line stays normal during the WTR time, the OLT automatically switches back to the working line when the WTR time expires. In addition, the OLT notifies the ONU of the switching and switching cause.
If ONU 1 learns that its working port and the working line are functioning properly and the working line stays normal during the WTR time, the ONU automatically switches back to the working line when the WTR time expires. In addition, the ONU notifies the OLT of the switching and switching cause.
Scenario 2: All Branch Fibers Connected to the ONU Are Faulty
1. Both the ONU and OLT check the link status and determine whether to trigger protection switching based on the link status.
If the OLT detects that all branch fibers connected to the working line become faulty, it automatically switches to the protection link and uses the protection link to send messages to all the ONUs to notify that protection switching has occurred. In addition, the OLT notifies all the ONUs of the switching cause.
If the ONU detects a fault on all the branch fibers connected to the working link, it automatically switches to the protection link and sends messages to the OLT to notify that protection switching has occurred. In addition, the ONU notifies the OLT of the switching cause.
2. After switching, services on the ONU are transmitted to the OLT through the protection port (that is, service packets are transmitted by the protection link). The changes on the ONU are as follows:
The state of the working port changes to standby.
The state of the protection port changes to active.
3. After protection switching, the ONU can automatically switch back to the working port. The OLT sends an automatic switchback message and the switchback time, called the WTR time, to the ONU.
If the OLT learns that the working port and working links are functioning properly and link A stays normal during the WTR time, the OLT automatically switches back to the working link when the WTR time expires. In addition, the OLT notifies the ONU of the switching and switching cause.
If the ONU learns that the working port and working link are functioning properly and link A stays normal during the WTR time, the ONU automatically switches back to the working link when the WTR time expires. In addition, the ONU notifies the OLT of the switching and switching cause.
Scenario 3: Backbone Fiber Becomes Faulty
1. Both the ONU and OLT check the link status and determine whether to trigger protection switching based on the link status.
If the OLT detects a fault on the working link, it automatically switches to the protection link and uses the protection link to send messages to all the ONUs to notify that protection switching has occurred. In addition, the OLT notifies all the ONUs of the switching cause.
If the ONU detects a fault on the working link, it automatically switches to the protection link and sends messages to the OLT to notify that protection switching has occurred. In addition, the ONU notifies the OLT of the switching cause.
2. After switching, services on the ONU are transmitted to the OLT through the protection port (that is, service packets are transmitted by the protection link). The changes on the ONU are as follows:
The state of the working port changes to standby.
The state of the protection port changes to active.
3. After protection switching, the ONU can automatically switch back to the working port. The OLT sends an automatic switchback message and the switchback time, called the WTR time, to the ONU.
If the OLT learns that the working port and working links are functioning properly and link A stays normal during the WTR time, the OLT automatically switches back to the working link when the WTR time expires. In addition, the OLT notifies the ONU of the switching and switching cause.
If the ONU learns that the working port and working link are functioning properly and link A stays normal during the WTR time, the ONU automatically switches back to the working link when the WTR time expires. In addition, the ONU notifies the OLT of the switching and switching cause.
Dual-Homing xPON Type C Protection
Networking: Dual-Homing Type C Protection
Advantage: When the active OLT or its uplink fails, services can be switched to the standby OLT.
Disadvantage: The networking mode is complicated and costly, and ONU management is difficult.
Scenario: This mode is used to protect a power system or Enterprise private line services and base station services.
Scenario 1: Branch Fiber Connected to a Single ONU Becomes Faulty
If ONU 1 detects a fault on link A in the preceding figure, it automatically switches to the protection link and sends messages to OLT 2 to notify that protection switching has occurred. In addition, the ONU notifies OLT 2 of the switching cause.
After switching, services on ONU 1 are transmitted to the OLT through the protection port, all the backbone fibers connected to the OLT transmit service packets, and ONU N is not affected. The changes on ONU 1 are as follows:
The state of the working port changes to standby.
The state of the protection port changes to active and service packets are transmitted through link B in the preceding figure.
After protection switching, ONU 1 can automatically switch back to the working port. The OLT sends an automatic switchback message and the switchback time, called the wait to restore (WTR) time, to the ONU. If ONU 1 learns that the working port, working link, and the uplink of OLT 1 are functioning properly and link A stays normal during the WTR time, ONU 1 automatically switches to the working link when the WTR time expires.
Scenario 2: All Branch Fibers Connected to the Active Link Become Faulty
If the ONU detects a fault on all the branch fibers connected to the working link, it automatically switches to the protection link and sends messages to OLT 2 to notify that protection switching has occurred. In addition, the ONU notifies OLT 2 of the switching cause.
After switching, services on the ONU are transmitted to OLT 2 through the protection port (that is, service packets are transmitted by the protection link). The changes on the ONU are as follows:
The state of the working port changes to standby.
The state of the protection port changes to active.
After protection switching, the ONU can automatically switch back to the working port. The OLT sends an automatic switchback message and the switchback time, called the WTR time, to the ONU. If the ONU learns that the working port, working links, and the uplink of OLT 1 are functioning properly and link A and link C stay normal during the WTR time, the ONU automatically switches to the working links when the WTR time expires.
Scenario 3: Backbone Fiber Becomes Faulty
If the ONU detects a fault on the backbone fiber, it automatically switches to the protection link and sends messages to OLT 2 to notify that protection switching has occurred. In addition, the ONU notifies OLT 2 of the switching cause.
After switching, services on the ONU are transmitted to OLT 2 through the protection port (that is, service packets are transmitted by the protection link). The changes on the ONU are as follows:
The state of the working port changes to standby.
The state of the protection port changes to active.
After protection switching, the ONU can automatically switch back to the working port. The OLT sends an automatic switchback message and the switchback time, called the WTR time, to the ONU. If the ONU learns that the working port, working links, and the uplink of OLT 1 are functioning properly and link A and link C stay normal during the WTR time, the ONU automatically switches to the working links when the WTR time expires.
Scenario 4: Associated Protection Switching Caused by a Fault on the OLT's Uplink
An OLT protection group is associated with the BFD or MEP session. Based on the association, when the upper-layer network connection (or IP layer link) of the OLT fails, the OLT instructs the ONU to trigger protection switching, which ensures service continuity.
On the OLT, the dual-homing protection group is associated with the BFD or MEP session. If the upstream route of the OLT fails, the BFD session status becomes Down or the MEP detection fails. In such a case, the OLT notifies the ONU of the uplink change.
After the ONU receives the switching instruction from the OLT, it determines to trigger the switching and switches to the protection link. After the switching, the ONU notifies OLT 1 of the switching using the working link and notifies OLT 2 of the switching using the protection link.
After switching, services on the ONU are transmitted to OLT 2 through the protection port (that is, service packets are transmitted by the protection link). The changes on the ONU are as follows:
The state of the working port changes to standby.
The state of the protection port changes to active.
After protection switching, the ONU can automatically switch back to the working port. The OLT sends an automatic switchback message and the switchback time, called the WTR time, to the ONU. If the ONU learns that the working port, working links, and the uplink of OLT 1 are functioning properly and link A and link C stay normal during the WTR time, the ONU automatically switches to the working links when the WTR time expires.
Scenario 5: Associated Protection Switching Caused by a Fault on the OLT's Layer 2 Physical Link
An OLT protection group is associated with the uplink Ethernet port status. Based on the association, when the Layer 2 physical link of the OLT fails, the OLT instructs the ONU to trigger protection switching, which ensures normal service transmission.
On the OLT, the protection group is associated with the uplink Ethernet port status. When the Ethernet port associated with the protection group becomes Down, the OLT notifies the ONU of the uplink change.
After the ONU receives the switching instruction from the OLT, it determines to trigger the switching and switches to the protection link. After the switching, the ONU notifies OLT 1 of the switching using the working link and notifies OLT 2 of the switching using the protection link.
After switching, services on the ONU are transmitted to OLT 2 through the protection port (that is, service packets are transmitted by the protection link). The changes on the ONU are as follows:
The state of the working port changes to standby.
The state of the protection port changes to active.
After protection switching, the ONU can automatically switch back to the working port. The OLT sends an automatic switchback message and the switchback time, called the WTR time, to the ONU. If the ONU learns that the working port, working links, and the uplink of OLT 1 are functioning properly and link A and link C stay normal during the WTR time, the ONU automatically switches to the working links when the WTR time expires.
Thanks for reading!
