1. Customer set QOS level as below.
traffic AF2-2E1-Backbone cdr 205 cbs 12288
traffic AF3-2E1-Backbone cdr 820 cbs 12288
traffic AF1-2E1-Backbone cdr 410 cbs 12288
traffic AF4-2E1-Backbone cdr 205 cbs 12288
traffic EF-2E1-Backbone cdr 600 cbs 12288
2. Customer set diffserv rules on MP interface as below.
diffserv output-queue af1 AF1-2E1-Backbone
diffserv output-queue af2 AF2-2E1-Backbone
diffserv output-queue af3 AF3-2E1-Backbone
diffserv output-queue af4 AF4-2E1-Backbone
diffserv output-queue ef EF-2E1-Backbone
3. Try PING test, the time delay was over 500ms.
PING 10.169.113.2: 56 data bytes, press CTRL_C to break
Reply from 10.169.113.2: bytes=56 Sequence=1 ttl=255 time = 555 ms
Reply from 10.169.113.2: bytes=56 Sequence=2 ttl=255 time = 639 ms
Reply from 10.169.113.2: bytes=56 Sequence=3 ttl=255 time = 562 ms
Reply from 10.169.113.2: bytes=56 Sequence=4 ttl=255 time = 518 ms
Reply from 10.169.113.2: bytes=56 Sequence=5 ttl=255 time = 569 ms
--- 10.169.113.2 ping statistics ---
5 packet(s) transmitted
5 packet(s) received
0.00% packet loss
round-trip min/avg/max = 518/568/639 ms
4. If undo QOS on MP interface, PING test is quite smooth with low time delay.
Time delay of PING was over 500ms even upon PING opposite direct connection interface.
1. Checked the quality of transmission, it's quite normal. And the test without QOS also proved that transmission was OK.
2. Checking the traffic rate on this MP interface, totally only 1.8Mbps on this MP interface. There should be no congestion on MP link.
3. We made the statistics about the traffic rate of each queue. About EF stream, the traffic rate was 450Mbps. It was close to cdr value.
4. We tried to modify the cdr value of EF from 600 to 1000, the time delay was improved much to tens of seconds.
5. We believe this problem related to QOS policy. If there was no QOS policy, or traffic rate was low, the PING test would be OK.
1. Transmission quality was not great.
2. Congestion maybe happened on this link, it affected the performance.
3. PING delongs to EF stream. In theory, it should be strictly guaranteed. Why great time delay still took palce? Maybe there's congestion in EF stream.
PING time delay problem always is hard to be handled. Even though we set EF QOS for this stream, at same time it's also the limit to EF level. The cdr value can guarantee the EF stream, as well as restrict it. When similiar problem happens, we need pay attention to the traffic rate of EF stream.