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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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Measurement Process

Measurement Process

IP FPM performance measurement includes the following actions:
  • TLPs color incoming service packets, count packets, and calculate the time packets enter the network. The DCP collects statistics from TLPs.
  • TLPs color outgoing service packets, count packets, and calculate the time packets leave the network. The DCP collects statistics from TLPs.
  • The DCP reports statistics to the MCP, and the MCP summarizes the statistics to obtain performance data.
NOTE:

For information about packet color, see Color Bit.

In Figure 16-3, the network contains target flow A and target flow B. The packet loss and delay statistics on flow A and flow B need to be collected.

Figure 16-3 Measurement process
Define measurement instance 1 and measurement instance 2:
  • Measurement 1 is used to collect the packet loss and delay statistics on flow A. Switch 1, switch 2, and switch 3 function as DCPs, and switch 1 functions as the MCP.
  • Measurement 2 is used to collect the packet loss and delay statistics on flow B. Switch 1 and switch 3 function as DCPs, and switch 1 functions as the MCP.

The measurement process is as follows:

  1. On the DCP, TLPA1, TLPA2, and TLPB1 color flow A and flow B entering the switch and generate statistics. DCP1 and DCP2 collect statistics.
  2. Target flow A and target flow B pass the network, and reach the egress node. TLPA3 and TLPB3 decolor target flow A and target flow B, and generate statistics. DCP3 collects statistics.
  3. DCPs report the collected statistics to their corresponding MCPs in IP FPM packets.
  4. After receiving statistics from DCPs, the MCPs calculate the packet loss rate and delay of target flow A and target flow B on the transit network.

Color Bit

The color bit is also called characteristics bit. In IP FPM, there are color bits for packet loss measurement and for delay measurement. The color bits indicate that a service packet is used for packet loss measurement or delay measurement. IP FPM recognizes only colored packets.

The ToS or Flags field in the IPv4 packet header can be used as the color bit. Figure 16-4 shows the position of the ToS or Flags field in the IPv4 packet header.

Figure 16-4 Color bit position
  • Type of Service (ToS) field

    The ToS field contains 8 bits. The leftmost 3 bits (bits 0-2) is the Precedence field that identifies the IP packet priority. Bits 3-7 are rarely used, and can be used as color bits.

    NOTE:

    RFC2474 defines the ToS field in the IPv4 packet header as the Differentiated Service (DS) field. In the DS field, the leftmost 6 bits (bits 0-5) are the DS Code Point (DSCP), and the rightmost 2 bits (bits 6 and 7) are reserved. When the DS field is used to provide differentiated service, it is not recommended that you configure bits 3-5 as color bits because the measurement result may be inaccurate.

  • Flags field

    The Flags field contains 3 bits. This field determines whether a packet can be fragmented. Bit 0 is reserved and can be used as the color bit.

NOTE:

When packet loss measurement and delay measurement are configured together, they cannot use the same color bit.

By default, the color bit for packet loss measurement is the 6th bit in the ToS field, and the color bit for delay measurement is the 7th bit in the ToS field. The default configuration is recommended.

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Updated: 2019-04-20

Document ID: EDOC1100075365

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