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Configuration Guide - Network Management and Monitoring

CloudEngine 8800, 7800, 6800, and 5800 V200R005C10

This document describes the configurations of Network Management and Monitoring, including SNMP, RMON, NETCONF, OpenFlow, LLDP, NQA, Mirroring, Packet Capture, Packet Trace, Path and Connectivity Detection Configuration, NetStream, sFlow, and iPCA.
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Calculation of the NetStream Sampling Rate

Calculation of the NetStream Sampling Rate

The NetStream sampling rate is configured by using the netstream sampler random-packets packet-interval { inbound | outbound } command. In the command, packet-interval specifies the NetStream sampling rate.

Switches except CE6880EI and CE5880EI

The NetStream sampling rate is related to the packet processing capability of a switch, number of interfaces with NetStream sampling configured, sampling direction, interface rate, and average packet length on the network.

The recommended minimum NetStream sampling rate is calculated as follows:

In this formula:
  • When NetStream sampling is configured only in the outbound or inbound direction, the forwarding bandwidth (in Gbit/s) is calculated as follows:

    Forwarding bandwidth = Number of interfaces x Interface rate

    When NetStream sampling is configured in both the outbound and inbound directions, the forwarding bandwidth is calculated as follows:

    Forwarding bandwidth = Number of interfaces x Interface rate x 2

    Here, the interfaces have sampling function configured.

    The interface rate is the rate of the interface.

    For example, when NetStream sampling is configured on four 10GE interfaces in the inbound direction and another six 10GE interfaces in the outbound and inbound directions, and the interface rate reaches the upper limit, the forwarding bandwidth is calculated as follows:

    Forwarding bandwidth = 4 x 10 + 6 x 10 x 2

  • The average packet length specifies the average length of packets on the network, in bytes.

  • 20 indicates the length of the interframe gap (IFG) and preamble, in bytes.

  • Packet processing capability of a switch is expressed in pps. A switch can use the CPU to perform NetStream sampling in non-enhanced mode or performs NetStream sampling in enhanced mode. Different sampling modes require different packet processing capabilities of a switch.

    • Non-enhanced mode: Packet processing capability of a switch is expressed in pps. The maximum packet processing capability of a switch (except the CE8860EI, CE8861EI, or CE8868EI) is 5000 pps. You are advised to use 3000 pps to reduce the impact on the CPU. For the CE8860EI, CE8861EI, or CE8868EI, the maximum packet processing capability of each subcard is 5000 pps. You are advised to use 3000 pps of each card to reduce the impact on the CPU.

    • Enhanced mode: The packet processing capability of a switch is about 1,500,000 pps. You are advised to use 1,500,000 pps. You can run the assign forward enp netstream enable command to enable NetStream sampling in enhanced mode. A switch does not use the CPU for NetStream sampling in this mode, which has no impact on the CPU.

NOTE:
  • The CE8868EI, CE8861EI, CE8850-64CQ-EI, CE6875EI, CE6857EI, and CE6865EI support NetStream sampling in enhanced mode.

  • In enhanced mode, when NetStream is configured in outbound and inbound directions on all the interfaces of a switch and the interface rate reaches the upper limit, if the calculated NetStream sampling rate is less than 2048, you are advised to set the NetStream sampling rate to at least 2048. In other cases, calculate the NetStream sampling rate according to the formula.

  • The recommended NetStream sampling rate is a power of 2. If the calculated value is not a power of 2, the NetStream sampling rate is suggested to be greater than the calculated value and a power of 2. For example, if the calculated value is 1020, the recommended NetStream sampling rate is 1024. If the configured NetStream sampling rate is lower than the calculated value, the CPU usage may be high, affecting the other services.

CE6880EI and CE5880EI Switches

The NetStream sampling rate is related to the packet processing capability of a switch, number of interfaces with NetStream sampling configured, sampling direction, interface bandwidth, and whether NetStream is used together with other services. When NetStream is used together with Layer 2 and Layer 3 forwarding services, the recommended NetStream sampling rate is 1024. When more services are used together with NetStream, configure a larger NetStream sampling rate.

It is recommended that the number of NetStream-enabled sub-interfaces be less than or equal to 16k. Otherwise, the forwarding capability of the switch will be affected.

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Updated: 2019-04-20

Document ID: EDOC1100075365

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