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The PTN problem causes the service of the S9300 discarding packet

Publication Date:  2019-07-24 Views:  159 Downloads:  0

Issue Description

S9312A takes as the output switch and connects with the S9306B via PTN, and the S9306B interconnects with the AC and S9306C directly, the S9306B’s WLAN service discarding packet seriously.

Alarm Information


Handling Process

1. Confirm the location of discarding packet, S9312A ping S9306B doesn’t discard packet, S9312A ping S9306C doesn’t discard packet, and S9312A ping the management address of the AC doesn’t discard packet.
2. S9306B ping S9306C and the management address of the AC don’t discard packet. The interfaces the S9306B connecting with the S9312A, S9306C and AC are in the same board.
3. Through the ping test, locate the problem of the interconnection between the S9312A and S9306B, from the packet statistic, the S9306B has received and replied the ICMP packet sending from the S9312A.
4. Check the middle transmission PTN device, we find a low priority packet just has sent 13%, the detail content is as the attachment. Adjust the priority of receiving the S9306B’s packet to a higher level in the PTN side, the testing service doesn’t discard packet any longer.
5. Check the PTN device, and we find the traffic of multiple ports are large, and check the interface count, the private service has loop, which causes the low priority service of the congestion port has discarded packet. After have configured a level division group of the private network service, restore the priority of the S9306B’s service, it doesn’t discard any more.

Root Cause

1. The board of the S9312 or S9306 forwarding service discarding packet;
2. The interconnection between the S9312 and the S9306 discarding packet;
3. The transmission problem causes discarding packet.


The default priority of the 802.1P attached by the ICMP packet sending from the S9300 switch CPU is 6, and the PTN consider it as the trustable user’s 802.1P priority by default, so while connecting with the S9312A and S9306B, it can ping without discarding packet (the priority level is 6), however, the management packet and service packet of the AC don’t have the priority, which caused the low priority service may discard packet while the PTN is congested.