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S12700 V200R011C10 Configuration Guide - Network Management and Monitoring

This document provides the configurations of network management and monitoring features supported by the product, including SNMP, RMON and RMON2, LLDP, Performance Management, iPCA, NQA, Service Diagnosis, Mirroring, Packet Capture, Traffic Distribution, NetStream, sFlow, and TWAMP Light.
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Device-Level Packet Loss Measurement

Device-Level Packet Loss Measurement

Device-level packet loss measurement is based on IP Local Performance Measurement (IP LPM). IP LPM can measure network performance indicators, such as packet loss ratio and number of lost packets, on direct links or on devices. Different from IP FPM, IP LPM does not allow target flow definition, and only collects statistics on IP unicast traffic entering/leaving a device or on a direct link. Similar to network-level packet loss measurement, device-level packet loss measurement is also implemented based on packet characteristics bits.

Packet Loss Measurement on a Direct Link

In Figure 5-13, the link between directly connected devices is considered an independent system. After packet loss measurement is enabled for a direct link, the devices measure packet loss on the link based on packet characteristics bits at measurement intervals.

Figure 5-13  Packet loss measurement on a direct link

Within a measurement interval, the number of packets received by an independent system is the sum of the following values:

  • PI(1) packets received from Switch_1 interface
  • PI(2) packets received from Switch_2 interface

The number of packets sent by the system is the sum of the following values:

  • PE(1) packets sent through Switch_1 interface
  • PE(2) packets sent through Switch_2 interface

Switch_1 is used as an example here. Within a measurement interval, the number of lost packets from the local device to remote device (LostPacket) is PE(1) - PI(2), and the packet loss ratio (LostPacketRate) is LostPacket/PE(1). The number of lost packets from the remote device to the local device (LostPacket') is PE(2) - PI(1), and the packet loss ratio (LostPacketRate') is LostPacket'/PE(2).

Similar to network-level packet loss measurement, the devices on two ends of a link must follow the same standard to mark the measurement time so that they can obtain their data within the same period of time. Therefore, time synchronization between the two devices is the prerequisite of packet loss measurement on direct links. Before configuring iPCA, configure NTP to allow the two switches to synchronize time with each other.

Packet Loss Measurement on a Device

In Figure 5-14, the X series cards on the network device within the dashed box form an independent system. After packet loss measurement is enabled for a device, the device measures packet loss on the link based on packet characteristics bits at measurement intervals.

NOTE:

This function only applies to devices with X series cards installed, and the packet loss statistics can be collected only on X series cards.

Figure 5-14  Packet loss measurement on a device
NOTE:
  • Type 1 card: X series cards
  • Type 2 card: all the other cards

Within a measurement interval, the number of packets received by an independent system is the sum of the following values:

  • PI(1) packets received by ports on the front panel of Type 1 cards
  • PI(2) packets received by CPUs on the device and sent to all Type 1 cards
  • PI(3) packets received by all Type 2 cards on the device and sent to Type 1 cards

The number of packets sent by the system is the sum of the following values:

  • PE(1) packets sent out by ports on the front panel of Type 1 cards
  • PE(2) packets sent from all Type 1 cards to the CPUs
  • PE(3) packets sent from all Type 1 cards to Type 2 cards.

Within the measurement interval, the number (LostPacket) of packets lost on the device is PI(1) + PI(2) + PI(3) - PE(1) - PE(2) - PE(3), and the packet loss ratio (LostPacketRate) is LostPacket/PI(1) + PI(2) + PI(3).

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Updated: 2019-10-21

Document ID: EDOC1000178113

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