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The Ping Delay Is Long Because of the Incorrect QoS Parameter Configuration

Publication Date:  2013-01-07 Views:  65 Downloads:  0
Issue Description

Networking:

Non-Huawei router (11.74.31.201)—transmission---(S1/0/0/63:0 11.74.31.202) NE40E(GE)---PC

The NE40E functions as the gateway of the PC.

Symptom: Based on the feedback of the R&D engineers, the delay is extremely long when the PC pings 11.74.31.201 of the non-Huawei router by sending 3000-byte packets. The delay ranges from 330 ms to 400 ms. However, the delay is normal when the NE40E pings 11.74.31.201 of the non-Huawei router by sending 3000-byte packets. The delay ranges from 30 ms to 50 ms.

Handling Process

Use the PC to ping the NE40E. The delay is very short.

Change the interface and use the PC to ping the non-Huawei router. The delay ranges from 330 ms to 400 ms.

Change the slot and use the PC to ping the non-Huawei router. The delay ranges from 330 ms to 400 ms.

Check the interface configuration and the configuration is shown as follows.

interface Serial1/0/0/63:0                

 link-protocol hdlc

 ip address 11.74.31.202 255.255.255.252

 port-queue be wfq shaping cir percentage 2 pir percentage 3

 port-queue af1 wfq shaping cir percentage 5 pir percentage 6

 port-queue af2 wfq shaping cir percentage 5 pir percentage 6

 port-queue af3 wfq shaping cir percentage 15 pir percentage 16

 port-queue af4 wfq shaping cir percentage 10 pir percentage 11

 port-queue ef pq shaping pir 2048

The preceding configuration shows that the PIR of the traffic in the BE queue is 3%, that is, the peak information rate is 61.44 kbit/s (2.048 Mbit/s × 3%). When the PC pings the non-Huawei router by sending 3000-byte packets, the delay is about 3000 × 8/61440=390 ms.

Try to modify the PIR configuration and set the value to 100%. After the configuration, the delay of pinging is resumed. The configuration is as follows.

port-queue be wfq shaping cir percentage 2 pir percentage 100

Why is the delay normal when the NE40E pings 11.74.31.201 of the non-Huawei router?

The reason is that when the NE40E initiates the ping operation, the NE40E itself generates packets. These packets enter the CS7 queue for PQ scheduling. The bandwidth for traffic in the PQ queue is 2 Mbit/s. Therefore, the delay in this case is normal.

Root Cause

 The bandwidth for traffic in the PQ queue is 2 Mbit/s. Therefore, the delay in this case is normal.The problem is caused by the QoS configuration.

Solution

Try to modify the PIR configuration and set the value to 100%. After the configuration, the delay of pinging is resumed. The configuration is as follows.

port-queue be wfq shaping cir percentage 2 pir percentage 100

END