General Troubleshooting Flowchart and Methods

This topic describes the general troubleshooting flowchart and the methods of preliminarily locating faults.

Context

Figure 1 shows the general troubleshooting flowchart.

Figure 1 General troubleshooting flowchart

Procedure

  1. Locate a fault preliminarily.
    Find the fault location and determine the cause of the fault. Table 1 lists the possible causes during preliminary fault locating.

    Table 1 Locate a fault preliminarily
    Fault Type Possible Cause
    ONT registration failure
    • The PON terminal goes online in an incorrect mode.
    • The optical fiber connected to the ONT is of poor quality or is loosely connected.
    • The optical power of the ONT is not within the normal range.
    • The optical module ages or is damaged under abnormal usage.
    • The minimum and maximum logical distances configured on the OLT port to which the ONT is connected are inconsistent with the actual distances.
    • The ONT auto-find function is disabled on the OLT.
    • When the ONT is added, the configured SN of the ONT is different from the actual ONT SN.
    • An ONT with the same SN is already connected to the OLT.
    • The ONT is a rogue ONT.
    Call failure or poor voice quality
    • The connection between the telephone set and the ONT is abnormal.
    • The ONT port to which the telephone set is connected is configured incorrectly.
    • The telephone set does not register with the voice server.
    • The voice service of the telephone set is not configured with a high priority.
    • The line connections are abnormal.
    • The telephone set is faulty.
    • The numbers configured on the ONT are incomplete.
    • The digitmap configuration is incorrect.
    • The codec and authentication configured on the ONT are incorrect.
    • A phone number conflict occurs during the registration.
    • The voice IP address fails to be obtained.
    Internet access failure
    • The user terminal or the loop line is faulty.
    • The PON port is faulty.
    • The data configuration of the upper-layer device is incorrect.
    • The PON board on the OLT is faulty.
    • The optical path is faulty.
    • The board or port on the ONT is faulty.
    • There are network attacks.
    • The WAN port fails to obtain the address.
    • The ping operation with the IP addresses of the ONT WAN port and the ONT fails.
    • The WAN MAC address of the ONT defaults to 000000000002.
    • The NAT function is disabled on the bound WAN port.
    • The LAN port on the ONT is a bridge Ethernet port, but the PC connected to the LAN port fails to obtain the IP address allocated by the upper-layer network.
  2. Check the status of the optical fiber.Check the following items:
    • Whether the optical fiber is properly connected.
    • Whether the optical fiber is bent excessively.
    • Whether the optical fiber connector is clean.
    • Whether the mean launched Tx optical power is normal.
    • Whether the Rx optical sensitivity is normal.
  3. Check the ONT status.Check the status of the LEDs on the ONT.

    You can also query the ONT status on the OLT.

    In the GPON mode, run the display ont info command to check the ONT information. Specifically, mainly check Control Flag, Run State, Config State, and Match State.

    • If Control Flag is active and Run State is up, it indicates that the ONT works in the normal state, that is, the user passes the authentication and goes online.
    • If Control Flag is active and Run State is down, it indicates that the user is offline.
    • If Control Flag is deactive, the ONT registration is disabled. In this case, run the ONT activate command in the GPON mode to activate the control flag.
    • If Config State is normal, it indicates that the ONT configuration recovery is successful.
    • If Config State is failed, it indicates that the ONT configuration recovery fails. A possible cause of this failure is that the ONT is bound to an incorrect ONT profile. To resolve this problem, run relevant commands to issue a correct ONT profile, or reset the ONT.
    • If Match State is match, it indicates that the configured capacity set of the ONT is the same as the actual ONT capabilities. If Match State is mismatch, it indicates that the configured capacity set of the ONT is different from the actual ONT capabilities, which will cause registration failure. In this case, add a new ONT service profile.
  4. Check the statistics of the ONT.
    • In the GIU mode, run the display port statistics command to query the traffic statistics of the upstream port of the ONT. Specifically, check whether receive and transmit traffic exists.
    • In the GPON mode, run the display statistics ont command to query the performance statistics of the ONT PON port.
    • In the GPON mode, run the display statistics ont-eth command to query the performance statistics of the ONT ETH ports.
  5. Check the data configuration of the ONT.
    • Run the display dba-profile command to check the DBA profile bound to the ONT.
    • Run the display service-port command to check whether the traffic stream configuration is correct.
    • Run the display vlan command to check whether the upstream port of the ONT is added to a VLAN.
  6. Check the status of the upper-layer device. Specifically, check whether the OLT is in the normal state.

FTTH Networking and Configuration Scenarios

Typical FTTH Networking

Figure 1 shows the typical FTTH networking.

Figure 1 Typical FTTH networking diagram
Networking Scenario Description
Bridging ONT + HGW Network Scenario The HGW integrating an IAD provides Internet, voice over Internet Protocol (VoIP), and Internet Protocol television (IPTV) services to users.

Services are implemented on the HGW, and the bridging ONT works with the OLT to provide Layer 2 channels.

Bridging+Voice ONT Network Scenario The ONT integrating an integrated access device (IAD) provides Internet, VoIP, and IPTV services to users.

The bridging+voice ONT provides Layer 2 data and voice services. This scenario provides transparent transmission channels and requires simple service configuration, so this scenario applies to Layer 2 networking.

  • For data services, a PC directly performs dial-up. Then, the upper-layer broadband remote access server (BRAS) device authenticates and accesses the PC. The PC can also access the Internet using the Dynamic Host Configuration Protocol (DHCP) or static IP address.
  • The ONT with a built-in voice module encapsulates voice service packets, and the OLT transmits them to the upstream next generation network (NGN) or IP multimedia subsystem (IMS).
Gateway ONT Network Scenario The ONT integrating an IAD provides Internet, VoIP, and IPTV services to users.

The HGW ONT facilitates interconnection of home devices by providing Layer 3 services, such as Point-to-Point Protocol over Ethernet (PPPoE)/DHCP dial-up, network address translation (NAT), and Internet Group Management Protocol (IGMP) snooping. This scenario provides fine-grained management channels and service control, and applies to Layer 3 networking.

FTTH Deployment Schemes

FTTH service application includes the deployment process and service provisioning process. The FTTH deployment process includes OLT deployment (configuration) and configuration of basic data. No deployment, however, is required on the ONT and the ONT is plug and play once services are provisioned.

Table 1 lists the FTTH deployment schemes and service provisioning methods.

Table 1 FTTH deployment schemes
Pre-configuration Service Provisioning
Scheme
  • On the NMS: Profiles can be issued in batches.
  • Using commands on the OLT: Configuration scripts containing commands can be imported to the OLT.
  • Using the OSS: This method is recommended and it can implement automatic service provisioning, and eliminate problems caused by manual service provisioning, such as large workload, low efficiency, and difficult management.
  • Using OSS+ITMS: This method is recommended if the multiple private nodes are customized for carriers. Using a TR069 server, new gateways and value-added voice services can be simply added.
    • Layer 2 configuration data is issued on the NMS or OLT.
    • Other configuration data such as voice, Layer 3, and Wi-Fi data is issued using the ITMS.
  • On the NMS: It applies to the scenario when no OSS is available and services need to be provisioned manually on the NMS.
  • On the ONT web page: When it is not feasible to provision services on the OSS or NMS, you can log in to the ONT web page and configure or modify parameters to provision services.
Parameter
  • DBA profile
  • Line profile
  • Service profile
  • IP traffic profile
  • Service level profile
  • Global OLT configurations (rather than FTTH user configurations) such as multicast VLAN, multicast mode, and policy of forwarding unknown packets
  • FTTH user service VLAN configurations including adding VLANs, setting the attributes of VLANs, and adding upstream ports for VLANs
See Table 2.

ONT service provisioning parameters are classified into common parameters and customized parameters:

  • Customized parameters are usually issued by the upper-layer system during service provisioning.
  • Common parameters are usually configured at delivery or during data pre-configuration.

Table 2 Parameters required for ONT service provisioning
Parameter Type Layer 2 Voice Above Layer 2 (Layer 3, Wi-Fi, and User Security)
Customized parameters Parameters for adding ONTs, adding service flows, activating ports, configuring port rate limitation, and adding multicast users
  • Registration information: IP address and port number of the local end and the proxy
  • User data: SIP user name and H.248 TID
Login user name and password
Common parameters Various pre-configured profile data
  • Digitmap: includes the digitmap timer and digitmap character strings.
  • Time configuration: includes registration heartbeat and protocol timers.
  • Encoding and decoding: includes voice encoding and decoding priorities and packetization period, G.711/G.729/G.722.
  • Fax/Modem
  • Service permission and service data
  • VAG: implements multiple virtual AG devices on one physical device.
  • Configurations for the interconnection between IMSs of softswitches of different specifications
  • WAN port configurations (routes, bridge WANs, and VLANs)
  • LAN/WAN binding
  • IGMP mode
  • URL for the ITMS
  • NTP server
  • Default Wi-Fi configurations
  • Local login IP address
ONT type
  • Bridging ONTs (SFUs)
  • Bridging+voice ONTs
  • Gateway-type ONTs (HGUs)
  • Bridging+voice ONTs
  • Gateway-type ONTs
Gateway-type ONTs
The following describes the involved configuration scenarios:

  • Service configuration on the NMS: Pre-configurations and service provisioning are implemented on the NMS.
  • Service configuration using commands: Pre-configurations are implemented using commands, and service provisioning is implemented on the ONT web pages.
  • Service provisioning on the ITMS: Pre-configurations are implemented on the NMS or using commands, and Layer 3 and voice services are provisioned on the ITMS. Huawei U2560 is used as an example to describe how to provision the services on the ITMS.

Fault in Standby XCE Board Results in Abnormal Communication of AUX board in Extended Subrack

The XCE board in the extended subrack is faulty. As a result, the communication between the extended subrack and the main subrack becomes abnormal. To solve this problem, replace the XCE board.

Product

OptiX OSN 3500

Fault Type

  • DCN fault
  • BD_STATUS

Symptom

The OptiX OSN 3500 is configured with an extended subrack. The AUX board on the extended subrack is abnormal. The communication over the EXT port fails. As a result, the main subrack fails to communicate with the extended subrack through the Ethernet path. The services, however, are normal. Connect the ETH, COM, and EXT ports on the AUX board. It is found that the STAT indicator is on and green, and that the other indicators are grey. The PQ1 boards in the extended subrack report the BD_STASTUS alarm.

Cause Analysis

The possible causes are as follows:

  • The pins in the slots for the SCC (that is, slots 17 and 18) on the backplane in the extended subrack are bent.
  • The pins in the slot for the AUX (that is, slot 37) on the backplane in the extended subrack are bent.
  • The pins in the slots for the XCE (that is, slots 59 and 60) on the backplane in the extended subrack are bent.
  • The XCE board in the extended subrack is faulty.

Procedure

  1. Check the pins in slots 17 and 18 on the backplane in the extended subrack. It is found that the pins are normal but the fault persists.
  2. Remove the AUX board from the extended subrack. Check the pins in slot 37 on the backplane in the extended subrack. It is found that the pins are normal but the fault persists.
  3. Remove the XCE board from slot 59 in the extended subrack. It is found that the fault is rectified. Check the pins in slot 59 on the backplane in the extended subrack. It is found that the pins are normal. Then, it is determined that the standby XCE board is damaged in the extended subrack. In this case, replace the XCE board. It is found that the fault is rectified.

fter Main XCS Board Is Switched to Standby Mode, Resetting of Main XCS Board Results in Resetting of All Boards

If the main and standby XCS boards are inserted and removed repeatedly, all the boards will be reset in the case of switching when the standby XCS board is not activated. Hence, do not insert and remove the main and standby XCS board repeatedly and check whether the services may be affected before you perform switching for the main and standby XCS boards if the HSC_UNAVAIL is reported on the standby XCS board.

Product

OptiX OSN 3500

Fault Type

Fault in the XCS board

Symptom

In the active/standby XCS switching test, the XCS board is switched from slot 9 to slot 10. Then, the XCS board in slot 10 is removed and then inserted back. As a result, all the boards are reset and cannot be restored to the original state.

Cause Analysis

When the standby XCS board starts to work, it needs to synchronize certain data with the main XCS board. In the switching test, the main XCS board is reset before the standby XCS board in slot 9 starts to work. As a result, all the boards start to synchronize and the other boards on the same subrack are reset.

Procedure

  1. Wait until the resetting of the boards is complete.

Reference Information

If the main XCS board is reset, or removed and then inserted back before the standby XCS board starts to work, all the boards are reset. Hence, do not switch the XCS boards frequently.

To preventing all the boards from being reset, the standby XCS board reports the HSC_UNAVAIL alarm. When the HSC_UNAVAIL alarm is reported, it does not necessarily indicate that the switching of the active and standby XCS boards is affected. The HSC_UNAVAIL alarm is used to inform the user of not performing cold reset on the main XCS board or not removing and then inserting the main XCS board back, thus preventing the services from being affected.

LWM Output Optical Power Is Unstable upon Forced Light Generation

LWM output optical power is unstable upon forced light generation.

Product

OptiX BWS 1600G

Fault Type

Optical Power Abnormity

Optical Transponder Unit

Symptom

When there is no input light to the LWM board, the board is forced to emit light for system commissioning. Then, it is found that the output power of the light fluctuates at about 1 dB. There is no such problem in the OTUs in other type such as the LWF.

Cause Analysis

The LWM processes signals in a way that is different from other OTUs. The LWM does not process the signals. When the engineer forces the LWM to emit light, optical signals are random. There may be multiple continuous “0”s or “1”s in an optical signal. In this case, the optical power fluctuates significantly at 10 dB.

The LWF, however, processes the input signals. Even when there is no input signal, the light that is emitted by the LWF is scrambled. Therefore the output power is stable.

Procedure

  1. It is normal.

Reference Information

  • When a board is forced to emit light, the fluctuation in the output optical power varies with the board type because different types of boards have different mechanisms to process signals.
  • At the commissioning stage, use instruments and meters.
  • This problem does not mean the equipment is not stable.

GPON Networking Applications

GPON Networking Applications

GPON is a passive optical transmission technology that applies in FTTx solutions, including fiber to the building (FTTB), fiber to the curb (FTTC), fiber to the door (FTTD), fiber to the home (FTTH), fiber to the mobile base station (FTTM), fiber to the office (FTTO), and fiber to the WLAN (FTTW), for voice, data, video, private line access, and base station access services. Figure 1 shows FTTx networking applications.

Figure 1 FTTx networking applications
图片1

The FTTx network applications in GPON access have the following in common: The data, voice, and video signals of terminal users are sent to ONUs, where the signals are converted into Ethernet packets and then transmitted over optical fibers to the OLT using the GPON uplink ports on the ONUs. Then, the Ethernet packets are forwarded to the upper-layer IP network using the uplink port on the OLT.

  • FTTB/FTTC: The OLT is connected to ONUs in corridors (FTTB) or by the curb (FTTC) using an optical distribution network (ODN). The ONUs are then connected to user terminals using xDSL. FTTB/FTTC is applicable to densely-populated residential communities or office buildings. In this scenario, FTTB/FTTC provides services of certain bandwidth for common users.
  • FTTD: uses existing access media at user homes to resolve drop fiber issues in FTTH scenarios.
  • FTTH: The OLT connects to ONTs at user homes using an ODN network. FTTH is applicable to new apartments or villas in loose distribution. In this scenario, FTTH provides services of higher bandwidth for high-end users.
  • FTTM: The OLT is connected to ONUs using an ODN network. The ONUs are then connected to wireless base stations using E1. The OLT connects wireless base stations to the core IP bearer network using optical access technologies. This implementation mode is not only simpler than traditional SDH/ATM private line technologies, but also drives down the costs of base station backhaul. FTTM is applicable to reconstruction and capacity expansion of mobile bearer networks. In this scenario, FTTM converges the fixed network and the mobile network on the bearer plane.
  • FTTO: The OLT is connected to enterprise ONUs using an ODN network. The ONUs are connected to user terminals using FE, POTS, or Wi-Fi. QinQ VLAN encapsulation is implemented on the ONUs and the OLT. In this way, transparent and secure data channels can be set up between the enterprise private networks located at different places, and therefore the service data and BPDUs between the enterprise private networks can be transparently transmitted over the public network. FTTO is applicable to enterprise networks. In this scenario, FTTO implements TDM PBX, IP PBX, and private line service in the enterprise intranets.
  • FTTW: The OLT connects to ONUs using an ODN network, the ONUs connect to access points (APs) using GE for WLAN traffic backhaul. FTTW is the trend in Wi-Fi construction.

Unsuccessful 1: N Protection Subnet Search

Unsuccessful 1: N protection subnet search.

Product

OptiX BWS 1600G

Fault Type

Protection

Symptom

Use one OCP and two LWF boards to form the OTU 1:N protection. After the physical fiber is connected, the protection group is configured on the two stations, respectively. But search of the WDM protection subnet on the T2000 always fails.

Cause Analysis

On the T2000, the search of WDM protection subnetwork is based on the WDM path, and the WDM path on the T2000 is based on the fiber connection on the T2000. Therefore, after the physical fiber connection is completed, the fiber connection between the OCP and OTU should be created on the T2000. After that, search the WDM path. Then, search of WDM SNCP according to the WDM path will be successful.

Procedure

  1. First create the fiber connection between the OCP and LWF on the T2000, and then search the WDM path. It is found that search of the WDM path fails.
  2. After an inspection, it is found that the transmit frequency and the receive frequency of the protection LWF board are different. Under this situation, though the service can be available, path search on the WDM side will fail.
  3. Replace the LWF board at the opposite end to ensure the transmit frequency and the receive frequency is consistent. Search the WDM path again. At this stage, the search of the WDM path and SNCP is successful.

Reference Information

  • The transmit frequency and receive frequency of the OTU board that used for OCP protection must be consistent.
  • Fiber connection between the OCP and OTU should be created on the T2000.
  • Search the WDM path before searching the SNCP.