How to Troubleshoot the One-Way Audio Encountered by ONU (A) Voice Users

How to troubleshoot the one-way audio encountered by ONU (A) voice users because the broadband remote access server (BRAS) incorrectly sets the canonical format indicator (CFI). Here you can

Fault Description

Network topology: ONU(A) -> optical line terminal (OLT) -> SE800-> Huawei NE5000E -> session border controller (SBC)

After dual-homing migration is performed on an Huawei OLT on a site, ONU(A) voice users encounter one-way audio. Specifically, the ONU(A) voice users cannot hear the voice of the peer end. The ONU(B) connected to the same OLT is functional.

The version of the ONU(A) is V800R305C01B123.

The version of the ONU(B) is V800R308C01SPC503.

Possible Causes

• The SBC is faulty.
• Packet loss occurs on the network.
• The OLT is faulty.
• The ONU(A) is faulty.

Procedure

1.        Replace the ONU(A) with a functional ONU(B) and perform the test again. One-way audio does not occur. Therefore, the fault is not caused by an SBC fault, packet loss on the network, or an OLT fault.

2.        Capture packets on the uplink port of the ONU(A). The packets sent from the peer end are detected, which indicates that the uplink port of the ONU(A) has received the packets sent from the peer end. It is suspected that packets are lost on the digital signal processing (DSP) drive side.

3.        Compare the media packets sent from and received by the uplink port. It is found that the CFI is 1 in the VLAN tag of the received packets, while the CFI is 0 in the VLAN tag of the sent packets. It is confirmed that the ONU(A) sends the packets from the peer end to the DSP chip for processing. The DSP chip determines that the CFI with the value 1 is invalid and discards the packets. As a result, the fault occurs on the ONU(A). The packet processing flow on the ONU(B) is different from that on the ONU(A). Specifically, the ONU(B) processes the packets in Real-Time Transport Protocol (RTP) mode and sends the packets to the DSP chip for processing. Therefore, the voice service of the ONU(B) is functional.

4.        Use access control list (ACL) rules to determine the location where the CFI is set to 1 segment by segment. Collect downstream packets from the voice gateway on the OLT to check whether the packets received by the OLT are correct.

    huawei(config)#acl 5002

huawei(config-acl-user-5002)#rule  permit 02003b04 ffffffff 6 07c8  ffff 10 81001fa1 ffff1fff 12 ipoe 

//Map the packets with the following configurations: Source MAC address is the MAC address of the voice gateway,

VLAN ID is 4001, and CFI is 1.

huawei(config-acl-user-5002)#rule  permit 02003b04 ffffffff 6 07c8  ffff 10 81001fa1 ffff1fff 12 ipoe 

//Map the packets with the following configurations: Source MAC address is the MAC address of the voice gateway,

VLAN ID is 4001, and CFI is 0.

huawei(config-acl-user-5002)#quit

huawei(config)#traffic-statistic inbound user-group 5002 port 0/19/1

//Configure the ACL on the uplink port of the OLT to collect statistics for downstream packets on the network side.

huawei(config)#display qos-info traffic-statistic port 0/19/1

 Inbound:                                                                       

  Matches: Acl 5002 rule 5     running                                        

  27983 packets             //The CFI of the packets received on the OLT is 1.

  Matches: Acl 5002 rule 10    running                                         

  0 packet

Based on the terminal display, the CFI in the VLAN tag of the voice gateway packets received on the uplink port of the OLT is set to 1. Therefore, the CFI with value 1 is not set on the OLT.

5.        The BRAS connects to the Layer 3 network, where packets do not have a VLAN tag. It is confirmed that the BRAS (SE800) sets the CFI in the VLAN tag to 1, which causes the one-way audio. Change the CFI to 0. The fault is rectified.

Suggestions and Summary

The CFI in a VLAN tag must be set to 0. Otherwise, exceptions will occur.

The more information about technical support you can consult with our technician - Bill, and his e-mail address is as below:  

bill@huanetwork.com

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ONU Frequently Goes Online and Offline(2) - Unmatched Optical Fiber Connectors

SmartAX MA5600T/MA5603T Multi-service Access Module Troubleshooting: ONU Frequently Goes Online and Offline: TC-C6311 An ONT Frequently Goes Online and Offline Because of Unmatched Optical Fiber Connectors

This topic describes how to troubleshoot the fault when the deployed ONT frequently goes online and offline because the optical fiber connectors do not match.

Fault Description

When an ONT is installed in the deployment, the optical path attenuation is -23 dBm, which is within the normal attenuation range. After the optical fibers are connected, the LED of the PON port blinks. In addition, the ONT fails to register with the OLT normally, and the ONT goes online and offline frequently.

Alarm Information

The up and down alarms about the ONT (OT928) are generated on the OLT.

Cause Analysis

l The optical path attenuation is very large.

l The optical fiber connectors are not clean or not connected properly.

Procedure

Step 1 Use an optical power meter to measure the optical path attenuation. It is found that the optical path attenuation is -23 dBm, which is within the normal range of the optical path attenuation.

Step 2 It is suspected that the poor quality of optical signals is caused by the dirty optical fiber connectors of the ONT (OT928). Clean the optical fiber connectors, and remove and then insert the optical fiber connectors again. The fault, however, persists.

Step 3 Replace the ONT with another ONT (OT928) to conduct a test. The fault, however, persists, which indicates that the hardware of the ONT (OT928) is normal.

Step 4 Check the fiber patch cord of the ONT (OT928). It is found that the connector of the fiber patch cord does not match the optical fiber connector of the ONT. Though the connector of the fiber patch cord is square, the color is different. After verification, the optical fiber connectors used in the ONT (OT928) are green, square, and SC/APC.

NOTE

The BOM is 14130252, and the name is Patch Cord, SC/APC-FC/PC, Singlemode-G.652, 3mm, 3m.

Step 5 Replace the fiber patch cord with a correct fiber patch cord (SC/APC-FC/PC). As a result, the LED of the PON port is stable, and the ONT can register with the OLT normally.

----End

Suggestion and Conclusion

Currently, the type of the fiber patch cord used in the ONT (OT928) is seldom used in China, but is mostly used abroad. Therefore, note that you should use the correct fiber patch cord.

The greatest difference between green and blue fiber patch cords is as follows: The

interconnection section between the fiber patch cord with green connectors and the OT928 is oblique. The interconnection section between the fiber patch cord with blue connectors and the ONT is plane, which can result in 3-6 dBm optical attenuation.