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CX11x, CX31x, CX710 (Earlier Than V6.03), and CX91x Series Switch Modules V100R001C10 Configuration Guide 12

The documents describe the configuration of various services supported by the CX11x&CX31x&CX91x series switch modules The description covers configuration examples and function configurations.
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Configuring Congestion Avoidance

Configuring Congestion Avoidance

When packets are discarded due to congestion, configure congestion avoidance on the device. Then the device processes packets of different services (differentiated by CoS values or colors) in a different manner, and ensures bandwidth of important services so that less packets of important services are discarded.

Pre-configuration Tasks

Before configuring congestion avoidance, complete the following task:
  • Mapping the priority of packets to a per-hop behavior (PHB) and color

(Optional) Configuring CFI as the Internal Drop Priority

Context

The Canonical Format Indicator (CFI) in the VLAN tag, also called Drop Eligible Indicator (DEI), identifies the drop priority of packets in certain situations. When the rate of packets on certain devices exceeds the committed information rate (CIR) value, the value of the DEI field is set to 1. In this case, the drop priority of the packets is high. When congestion occurs, the devices first discard the packets whose DEI field is 1.

If packets whose rate exceeds the CIR need to be discarded, configure CFI as the internal drop priority.

Procedure

  1. Run:

    system-view

    Enter the system view.

  2. Run:

    interface interface-type interface-number

    The interface view is displayed.

  3. Run:

    dei enable

    CFI is configured as the internal drop priority.

    By default, CFI is not configured as the internal drop priority.

  4. Run:

    commit

    The configuration is committed.

Configuring a WRED Drop Profile

Context

WRED randomly discards packets based on drop parameters to prevent global TCP synchronization, and defines different drop policies based on packet colors. WRED discards packets based on packet priorities, so the drop probability of packets with higher priorities is low. A WRED drop profile defines upper and lower drop thresholds and maximum drop probability for packets of different colors. For more information about packet colors, see Configuring Priority Mapping.

Procedure

  1. Run:

    system-view

    The system view is displayed.

  2. Run:

    drop-profile drop-profile-name

    A WRED drop profile is created and the drop profile view is displayed.

    By default, the WRED drop profile default exists. The WRED drop profile default can be modified but cannot be deleted.

  3. Run:

    color { green | non-tcp | red | yellow } low-limit low-limit-percentage high-limit high-limit-percentage discard-percentage discard-percentage

    WRED parameters are set.

    By default, the upper threshold, lower threshold, and maximum drop probability of a WRED drop profile are 100.

  4. Run:

    commit

    The configuration is committed.

Applying the WRED Drop Profile

Context

On the device, you can apply a WRED drop profile to an interface or a queue on an interface.

Procedure

  • Apply a WRED drop profile to an interface.
    1. Run:

      system-view

      The system view is displayed.

    2. Run:

      interface interface-type interface-number

      The interface view is displayed.

    3. Run:

      qos wred drop-profile-name

      A WRED drop profile is applied to the interface.

      NOTE:

      The parameter drop-profile-name specifies the name of a WRED drop profile. The value must be the same as that configured in Configuring a WRED Drop Profile.

    4. Run:

      commit

      The configuration is committed.

  • Apply a WRED drop profile to a queue on an interface.
    1. Run:

      system-view

      The system view is displayed.

    2. Run:

      interface interface-type interface-number

      The interface view is displayed.

    3. Run:

      qos queue queue-index wred drop-profile-name

      A WRED drop profile is applied to a queue on the interface.

      NOTE:

      The parameter drop-profile-name specifies the name of a WRED drop profile. The value must be the same as that configured in Configuring a WRED Drop Profile.

    4. Run:

      commit

      The configuration is committed.

(Optional) Configuring ECN

Context

Combination of WRED and Explicit Congestion Notification (ECN) enables a terminal device to detect congestion and notify the source of congestion. After receiving the notification, the source reduces the rate of sending packets to prevent congestion from aggravating.

To limit the rate of packets sent by the upstream device to prevent congestion aggravation, configure ECN.

Procedure

  1. Run:

    system-view

    The system view is displayed.

  2. Run:

    interface interface-type interface-number

    The interface view is displayed.

  3. Run:

    qos queue queue-index ecn

    The ECN function is configured for a specified queue.

    NOTE:

    ECN can be enabled for a queue only after a WRED drop profile is applied to the queue.

  4. Run:

    commit

    The configuration is committed.

Checking the Configuration

Procedure

  • Run the display drop-profile [ brief | drop-profile-name ] command to check the WRED drop profile configuration.
  • Run the display qos configuration interface [ interface-type interface-number ] command to check all the QoS configurations on a specified interface.
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Updated: 2019-08-09

Document ID: EDOC1000041694

Views: 59095

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