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Configuration Guide - Low Latency Network

CloudEngine 8800, 7800, 6800, and 5800 V200R005C00

This document describes the configurations of Buffer optimization of lossless queues, Fast ECN, Fast CNP, Dynamic ECN threshold of lossless queues, and Dynamic load balancing.
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Enabling the Fast CNP Function

Enabling the Fast CNP Function


Traditional Congestion Notification Packet (CNP) technology allows the forwarding device to send the packet tagged with the ECN field to the destination server after detecting queue congestion. After receiving the packet tagged with the ECN field, the destination server sends the CNP packet to the source server to notify the source server to reduce the packet sending rate. If the path where the CNP is transmitted is too long, the rate of traffic on the source server cannot be reduced immediately. As a result, the congestion of the forwarding device may further aggravate and even the entire network stops sending packets due to PFC.

After fast CNP is enabled on the forwarding device, the forwarding device records packet information in the flow table entry when forwarding the packet. It sends the CNP to the source server based on the learned flow entry information when receiving a packet tagged with the ECN field. The path where the CNP is transmitted is shortened. In this way, the traffic rate of the source server can be adjusted in a timely manner, which relieves the congestion of the buffer of the forwarding device.


  1. Run system-view

    The system view is displayed.

  2. Run low-latency fabric

    The low-latency network is enabled and the system view is displayed.

    By default, the low-latency network function is not enabled.


    The low-latency fabric command does not take effect immediately after configuration, but takes effect after you save the configuration and restart the device.

  3. Run qos fast-cnp enable

    The fast CNP function is enabled.

    By default, the fast CNP function is disabled.

  4. Run commit

    The configuration is committed.

Updated: 2019-04-20

Document ID: EDOC1100040243

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