Black screen problem on some live IPTV channels under BRAS equipment

The telecom IPTV platform of a certain city found that the quality rate of a certain channel was poor and the number of users was small. Compared with other cities in the province, the number of users and the quality rate of this channel were much lower. After testing, it was found that the channel had a black screen or was stuck and could not be watched, which was a complete interruption of the flow, while other channels were normal. As shown in Figure 1, the multicast address of the channel is: 239.93.5.254.

Figure 1 IPTV channel statistics

According to the above fault phenomenon, analysis is carried out:

1. According to the statistics of users who reported the fault, it was found that similar problems occurred under different OLTs and different BRASs. After testing, it was found that the channel only had a few seconds of picture, which should be a unicast picture, and the multicast was completely interrupted.

2. Pull traffic on the OLT to collect traffic statistics.

3. Check the multicast table entries on the BRAS and perform traffic statistics.

1. Pull traffic on the OLT device to make traffic statistics.

By using the above method to perform traffic statistics on channel 239.93.5.254 on the OLT, it is found that the multicast group has no traffic and the traffic has not reached the OLT, so the problem should be checked from the upper-layer device.

2. Check the multicast table on the BRAS device.

The multicast address (S, G) and (*, G) entries can be found on the BRAS. It can be seen that the multicast entries are normal and the source port is the upstream port xgei-0/0/0/2.1. There are multicast entries, but the multicast flow is interrupted. You need to check where the multicast flow is interrupted section by section.

3. Since the OLT is directly connected to the BRAS device, it is necessary to capture packets or perform traffic statistics on the BRAS. Since the entire OLT does not have the multicast stream of this channel, traffic statistics are performed directly on the BRAS upstream port to check whether the multicast stream has not reached the BRAS. Because the BRAS upstream port has been bound to the anti-virus policy, you only need to add a rule for the address 239.93.5.254 in the anti-virus policy and turn on the traffic statistics function (add the log parameter after the rule) to test it. Add a rule 100 as follows:

Run the command again to view the statistics:

The number of matches did not increase. Possible reasons are:

1) The traffic does not reach the BRAS.

2) The traffic is matched and discarded in the previous deny rule, so it is necessary to do traffic statistics again. Change rule 100 to the front and count it again. During this period, the OLT keeps pulling traffic.

4. Modify the order of rules. After putting them at the front, the number of matches increases. This indicates that the traffic from this address has reached the BRAS upstream port and must have been filtered by other rules of the upstream port. Therefore, enable traffic statistics for all the previous rules and delete the rule permit ip 239.93.5.254 log. It is found that the number of matches for the following rule increases very quickly.

After deleting this rule and testing again, the traffic statistics of this multicast address on the OLT are normal.

IPTV live streaming is transmitted through the UDP protocol and uses UDP port numbers. If the port is blocked, the traffic will be interrupted. Through the above investigation process, it is found that the 239.93.5.254 channel uses UDP port 9996, which is consistent with the anti-virus port policy of the BRAS uplink port and is discarded by the BRAS uplink port, so the multicast stream is interrupted. When defining ports for opening new channels on the IPTV platform, it is necessary to avoid using commonly recognized virus ports.

The above troubleshooting process uses the traffic statistics function of the device, which is helpful for segmented troubleshooting of traffic packet loss. However, it is necessary to understand the traffic characteristics as accurately as possible to facilitate rapid location.

1. ZTE OLT multicast traffic statistics method:

2. Traffic statistics method for ZTE ZXR10 M6000-S as BRAS device: configure ACL access list, add log parameter, and enable the statistics function.

The specific configuration method of V3 version is as follows:

The specific configuration method of V5 version is as follows: