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Configuration Guide - QoS

CloudEngine 8800, 7800, 6800, and 5800 V200R002C50

This document describes the configurations of QoS functions, including MQC, priority mapping, traffic policing, traffic shaping, interface-based rate limiting, congestion avoidance, congestion management, packet filtering, redirection, traffic statistics, and ACL-based simplified traffic policy.
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Licensing Requirements and Limitations for Traffic Policing, Traffic Shaping, and Interface-based Rate Limiting (CE6870EI and CE6875EI)

Licensing Requirements and Limitations for Traffic Policing, Traffic Shaping, and Interface-based Rate Limiting (CE6870EI and CE6875EI)

Involved Network Elements

Other network elements are not required.

Licensing Requirements

Traffic policing, traffic shaping, and interface-based rate limiting are basic features of a switch and are not under license control.

Version Requirements

Table 5-7 Products and minimum version supporting traffic policing, traffic shaping, and interface-based rate limiting


Minimum Version Required

CE6870-24S6CQ-EI, CE6870-48S6CQ-EI






Feature Limitations

  • After traffic policing is configured, the device performs CAR for all packets, including both protocol packets and data packets.
  • The device applies CAR to interfaces of the same chip resource uniformly and applies CAR to interfaces on different chip resources separately. When the traffic policy containing traffic policing is applied to the Eth-Trunk, the system, or a VLAN, if interfaces of the object to which the traffic policy is applied belong to N chip resources, the actual rate limit is N times as large as the CAR value.

    Assume that 10GE1/0/1 and 10GE1/0/2 belong to chip resource 0 and 10GE1/0/25 and 10GE1/0/26 belong to chip resource 1. If 10GE1/0/1, 10GE1/0/2, 10GE1/0/25, and 10GE1/0/26 join VLAN 10 and the traffic policy containing the rate limit of 1 Mbit/s is applied to VLAN 10, the rate limit of 10GE1/0/1 and 10GE1/0/2 is 1 Mbit/s and the rate limit of 10GE1/0/25 and 10GE1/0/26 is 1 Mbit/s. That is, the rate limit is 2 Mbit/s after the traffic policy is applied to VLAN 10.

    Use the tool for querying relationships between ports and chip resources to query the relationship between ports and chip resources.

Limitations on MQC-based traffic policing

  • A traffic policy containing traffic policing can be applied only to a common physical interface in the outbound direction. A traffic policy containing traffic policing cannot be applied to the common physical interface that is added to an Eth-Trunk in the outbound direction.
  • When traffic policing is defined in a traffic behavior, ensure that the following conditions are met: PBS > CBS = CIR/8 x Coefficient x 1000, where the coefficient is in the range from 1 to 1.5.
  • Outbound MQC-based traffic policing cannot be used with outbound interface-based rate limiting, queue-based traffic shaping, PFC, and ETS.

  • When MQC-based traffic policing is configured in the outbound direction, if traffic exceeds the bandwidth of the outbound interface, the actual volume of forwarded traffic is lower than the interface bandwidth. In this case, ensure that the traffic volume is within the interface bandwidth.
  • When both QoS CAR and MQC are used on an interface for traffic statistics collection, statistics about packets to which a QoS CAR profile is applied contain only the packets that do not match the traffic policy.

Limitations on hierarchical traffic policing

  • A maximum of 512 QoS profiles can be created on the device.
  • Hierarchical traffic policing supports only the single-rate-single-bucket mechanism, and cannot be applied to the outbound direction.
  • Aggregated CAR in a traffic policy is performed only on an object to which the traffic policy is applied. For example, if the traffic policy p1 containing aggregated CAR is applied to interfaces 1 and 2, aggregated CAR is performed on interfaces 1 and 2 separately.
  • If a QoS CAR profile and a traffic policy containing the traffic policing action are applied to the same interface, QoS CAR parameters defined in the QoS CAR profile do not take effect. This is because the traffic policy takes precedence over the QoS CAR profile.
  • After a QoS CAR profile is applied to a tunnel interface:
    • you cannot use the display qos car statistics command to query packet statistics.
    • If ECMP load balancing is implemented for multiple tunnels, the QoS CAR profile does not take effect.

Limitations on traffic shaping

  • Traffic shaping can only be configured on an interface in the outbound direction.
  • If both queue-based traffic shaping and outbound rate limiting are configured on an interface, the CIR of outbound rate limiting cannot be smaller than the sum of CIR values of all the queues on the interface; otherwise, traffic shaping may be abnormal. For example, a low-priority queue preempts the bandwidth of a high-priority queue.
  • Traffic shaping increases the delay because it uses the buffer mechanism.

Limitations on interface-based rate limiting

The rate limit of traffic on the management interface cannot be smaller than 100 pps; otherwise, FTP, Telnet, SFTP, STelnet, and SSH functions may be affected.

Updated: 2019-03-21

Document ID: EDOC1000166640

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