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FAQ - How to Configure Rate Limitation for Subinterfaces on NE40E/NE80E

Publication Date:  2013-09-22 Views:  111 Downloads:  0
Issue Description
How to configure rate limitation for subinterfaces on NE40E/NE80E?
Handling Process
Root Cause

The following methods are available for configuring rate limitation for subinterfaces on NE40E/NE80E:

Method 1: configuring a traffic policy

1. Configure an ACL.
acl number 3000
rule 5 permit ip 

2. Configure traffic classification matching the ACL.

traffic classifier 20M operator or if-match acl 3000

3. Configure the traffic limitation behavior.

traffic behavior 20M
car cir 20480 pir 20480 cbs 2048000 pbs 2048000 green pass yellow pass red discard

4. Associate the traffic classification with the traffic limitation behavior.

traffic policy test
classifier 20M behavior 20M

5. Apply the traffic policy under the subinterface view (in the inbound and outbound directions within a period).

interface GigabitEthernet1/0/1.XXXX
description test
vlan-type dot1q XXXX

ip address 
traffic-policy test inbound
traffic-policy test outbound

Method 2: configuring the QoS CAR.

interface GigabitEthernet1/0/1.XXXX
description test
vlan-type dot1q XXXX

ip address 
qos car cir 20480 pir 20480 cbs 2048000 pbs 2048000 green pass yellow pass red discard

Method 3: configuring a user queue.

interface GigabitEthernet1/0/1.XXXX
description test
vlan-type dot1q XXXX
ip address 
user-queue cir 20480 pir 20480 outbound

On the live network, the traffic policy and QoS CAR often fail to accurately limit traffic rates. The FTP download rate is far less than the actual CAR. The CAR uses a token-mechanism to implement traffic limitation. If the tokens are not enough for traffic, excessive traffic is discarded. FTP, as a TCP protocol, features retransmission and sliding windows. For example, if traffic is greater than the CAR, some packets are lost. Upon detecting packet loss, an FTP client requests retransmission and the sliding window automatically decreases, which greatly reduces the downloading rate. Therefore, the user queue scheme must be used to adjust queue scheduling, implementing accurate traffic limitation.