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Configuration Guide - Network Management and Monitoring

CloudEngine 12800 and 12800E V200R005C10

This document describes the configurations of Network Management and Monitoring, including SNMP, RMON, LLDP, NQA, Service Diagnosis, Mirroring, Packet Capture, sFlow, and NETCONF.
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Performance Measurement Method

Performance Measurement Method

Overview

Performance statistics include packet loss rate and delay.

On a transit network with boundaries, flows enter and leave the network through some boundary devices. As shown in Figure 15-5, the number of packets entering the ingress interface on Switch(n) is PI(n) and the number of packets leaving the egress interface on Switch(n) is PE(n).

Figure 15-5 IP FPM measurement diagram

The following are the mechanisms of packet loss rate and delay measurement:

  • Packet loss rate measurement: Within a measurement interval, the number of lost packets is the difference between the number of packets entering a transit network and the number of packets leaving the transit network.
    • The total number of ingress packets is: PI = PI(1) + PI(2) + PI(3)
    • The total number of egress packets is: PE = PE(1) + PE(2) + PE(3)
    Therefore, the value (PI - PE) is the number of lost packets within a measurement interval.
  • Delay measurement: Within a measurement interval, the delay is the time difference between a flow enters and leaves a network.

To ensure statistics accuracy, the sender and receiver must follow the same standard to mark the measurement time so that they can obtain the data in the same period of time. Therefore, time synchronization between the two devices is the prerequisite of performance measurement. Before configuring IP FPM, you must configure NTP or 1588v2 to implement time synchronization on switches.

Packet Loss Measurement

Packet loss statistics include the number of lost packets and packet loss rate of the flows passing a network within a time range, which are calculated by comparing the number of packets entering a network with the number of packets leaving the network.

When using IP FPM to measure packet loss, you can specify the measurement time range. IP FPM then measures packet loss based on packet characteristics bits within the measurement time range. To be specific, IP FPM periodically sets and resets a certain color bit in service packet headers on the ingress interface to divide a measurement time range into measurement intervals, and measures packet loss within each measurement interval.

NOTE:

If the measurement time range is infinite, packet loss measurement is permanently performed until you disable it. The measurement time range can be set to 5, 10, 15, or 30 minutes. The default measurement time range is 10 minutes.

The measurement interval can be set to 10, 60, or 600 seconds. The default measurement interval is 10 seconds.

Figure 15-6 IP FPM measurement diagram

Figure 15-6 shows an example of packet loss measurement based on packet characteristics bits. On the network, the target flow enters through switch 1 and leaves through switch 2. Figure 15-7 illustrates how the packet loss measurement is implemented based on packet characteristics bits on each device. tn indicates an absolute time moment, and tn-tn+2 (n≤1) indicates a measurement interval.

Figure 15-7 Packet loss measurement based on packet characteristics bits
  • t0: Switch 1 sets the color bits in the service packets entering the network to 1, and starts the counter to count the service packets with color bit 1 sent within the first interval.
  • t1: The egress interface of switch 2 receives the first service packet with color bit 1 in the first interval, and starts the counter to count these packets.
  • t2: Switch 1 finishes counting the service packets with color bit 1 in the first interval, and obtains the number PI(1) of packets sent within the first interval.
  • t3: Switch 2 finishes counting the service packets with color bit 1 in the first interval, and obtains the number PE(2) of packets received within the first interval. The egress interface of switch 2 removes the color flags from service packets.
    NOTE:

    Switch 2 starts to receive the service packets with color bit 1 at t1. When the internal timer passes a measurement interval (at t3), switch 2 determines that receiving of the packets with color bit 1 in this interval is finished, but does not determine the finish of packet receiving when it receives a service packet with a non-1 color bit. This mechanism prevents the impact of packet unsequencing on service packet statistics, to ensure the accurate service packet counting within an interval.

The number of lost packets (LostPacket) within this measurement interval is PI(1) - PE(2), and the packet loss rate (LostPacketRate) is LostPacket/PI(1).

Delay Measurement

Delay is the time difference between a service flow enters and leaves a network.

In IP FPM, the device samples service packets, records the actual forwarding time of the service packets, and calculates the transmission delay of the service flow.

Figure 15-8 Delay measurement diagram

Figure 15-8 illustrates the delay measurement mechanism.

In the switch 1 -> switch 2 direction:
  • t1: Switch 1 sets the color bit in the service packet on an ingress interface to 1 and obtains time stamp t1.
  • t2: Switch 2 receives the service packet with the color bit of 1 at the egress and obtains the time stamp t2.
In the switch 2 -> switch 1 direction:
  • t3: Switch 2 sets the color bit in the service packet on an ingress interface to 1 and obtains time stamp t3.
  • t4: Switch 1 receives the service packet with the color bit of 1 at the egress and obtains the time stamp t4.

The delays in two directions are 1d (Switch1 -> Switch2) = t2 - t1 and 1d (Switch2 -> Switch1) = t4 - t3; the bidirectional delay is 2d = (t2 - t1) + (t4 - t3) = (t4 - t1) - (t3 - t2).

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Updated: 2019-04-20

Document ID: EDOC1100075344

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