2014年8月6日星期三

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.
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