Hello everyone!
Today, let's learn about GPON networking protection.
GPON Network Protection
GPON networking protection is classified into the following types:
Single-homing Type B protection and Dual-homing Type B protection
Single-homing Type C protection and Dual-homing Type C protection
Type B protection
xPON type B protection allows dual-channel redundancy protection for OLT PON ports and backbone fibers on an xPON network. This feature improves ODN network reliability and ensures service continuity.
Single-Homing xPON type B Protection
Type B single-homing protection mainly protects the OLT PON port and backbone fibers. When the OLT PON port or the backbone fiber is faulty, services can be automatically switched to another OLT PON port or the backbone fiber.
Networking Scenario: Single homing type B protection
Advantage: Networking, OLT/ONU management, and service provisioning are simple.
Disadvantage: An OLT fault will interrupt services. In addition, two optical fibers routed in one pipe may both be broken.
Usage Scenario: Protects important services, such as the enterprise private line service and the base station private line service.
Scenario 1: Active Optical Fiber Is Cut
When detecting a loss of signal (LOS) alarm (generated due to the active optical fiber cut), the working port disables the transmission of the optical module.
The protection port detects a LOS alarm (generated due to the failure of the ONT to transmit optical signals), enables the transmission function of the optical module, and performs ONU ranging.
If the optical fiber connected to the protection port is functional, and ONU ranging is successful, the protection port reports an LOS clear alarm.
The working port switches to the standby state. The protection port switches to the active state. Then, the protection switching ends.
Scenario 2: All ONUs Go Offline
When detecting an LOS alarm (generated because all ONUs go offline), the working port disables the transmission of the optical module.
The protection port detects a LOS alarm (generated due to the failure of the ONT to transmit optical signals), enables the transmission function of the optical module, and performs ONU ranging.
No ONU connected to a PON port goes online due to a ranging failure. Therefore, the OLT cyclically detects the working and protection ports until an ONU goes online.
After the ONU goes online, switching is performed between the PON ports if the protection port is detected. If the protection port is not detected, the working port continues working.
Dual-Homing xPON type B Protection
Type B dual-homing protection mainly protects the OLT, OLT PON port, and backbone fibers. When the OLT, OLT PON port, or backbone fiber is faulty, services can be automatically switched to another OLT, OLT PON port, or backbone fiber.
Networking Scenario: Dual-Homing type B Protection
Advantage: Each of the two OLTs connects to a backbone fiber for remote disaster recovery.
Disadvantage: The networking is complex, and networking costs are high. In addition, the OLT configuration is complex.
Usage Scenario: Protects important services, such as the enterprise private line service and the base station private line service. This type of networking is especially used for remote disaster recovery.
Scenario 1: Active Optical Fiber Is Cut
When detecting a loss of signal (LOS) alarm (generated due to the active optical fiber cut), the working port disables the transmission of the optical module.
The protection port detects a LOS alarm (generated due to the failure of the ONT to transmit optical signals), enables the transmission function of the optical module, and performs ONU ranging.
If the optical fiber connected to the protection port is functional, and ONU ranging is successful, the protection port reports an LOS clear alarm.
If the optical fiber connected to the protection port is functional, and ONU ranging is successful, the protection port reports an LOS clear alarm.
Scenario 2: All ONUs Go Offline
When detecting an LOS alarm (generated because all ONUs go offline), the working port disables the transmission of the optical module.
The protection port detects a LOS alarm (generated due to the failure of the ONT to transmit optical signals), enables the transmission function of the optical module, and performs ONU ranging.
No ONU connected to a PON port goes online due to a ranging failure. Therefore, the OLT cyclically detects the working and protection ports until an ONU goes online.
No ONU connected to a PON port goes online due to a ranging failure. Therefore, the OLT cyclically detects the working and protection ports until an ONU goes online.
Scenario 3: Associated Protection Switching Is Caused by a Connection Failure in the OLT's Upstream Transmission Network
If a BFD session has been configured on the OLT, the BFD session can be bound to a protection group for creating an association between them. If CFM has been enabled on an OLT, an MEP session can be bound to a protection group for creating an association between them. Based on the associations, when the upper-layer network connection of the active OLT fails, the active and standby OLTs perform a switchover and notifies the ONU of the switchover. In this way, services are restored.
On the OLT, the dual-homing protection group is associated with the BFD or MEP session. When the upstream route of the working OLT (OLT 1) fails, OLT 1 checks whether the protection OLT (OLT 2) and the upstream route of OLT 2 are functional. If they are functional, and both OLTs do not carry out a forcible switchover or locking operation, OLT 1 data has been synchronized to OLT 2. Then, the two OLTs perform a switchover.
OLT 2 starts to work. It enables the transmission of the optical module and performs ONU ranging.
After the switchover, the ONU service data is sent to OLT 2 through the protection port, and service data is transmitted over the protection link. The OLT status changes as follows:
OLT 1 becomes standby.
OLT 2 becomes active.
Scenario 4: Associated Protection Switching Is Caused by an OLT's Layer 2 Physical Link Fault
An OLT protection group is associated with the uplink Ethernet port status. Based on the association, when the Layer 2 physical link of the active OLT fails, the two OLTs perform a switchover and notify the ONU of the switchover. In this way, services are restored.
On the OLT, the dual-homing protection group is associated with the uplink Ethernet port status. When the Ethernet port associated with the protection group on the working OLT (OLT 1) becomes Down, OLT 1 checks whether the protection OLT (OLT 2) and the physical link of the protection OLT are functional. If they are functional, and both OLTs do not carry out a forcible switchover or locking operation, OLT 1 data has been synchronized to OLT 2. Then, the two OLTs perform a switchover.
OLT 2 starts to work. It enables the transmission of the optical module and performs ONU ranging.
After the switchover, the ONU service data is sent to OLT 2 through the protection port, and 7service data is transmitted over the protection link. The OLT status changes as follows:
OLT 1 becomes standby.
OLT 2 becomes active.
Thanks for reading!
