No relevant resource is found in the selected language.

This site uses cookies. By continuing to browse the site you are agreeing to our use of cookies. Read our privacy policy>Search

Reminder

To have a better experience, please upgrade your IE browser.

upgrade

CLI-based Configuration Guide - Reliability

AR100, AR120, AR160, AR1200, AR2200, AR3200, and AR3600 V300R003

This document provides guidance for configuring reliability services, including interface backup, BFD, VRRP, and EFM.
Rate and give feedback:
Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
Understanding Y.1731

Understanding Y.1731

Function Overview

Y.1731 can monitor performance, including two-way frame delay measurement and single-ended Synthetic Loss Measurement (SLM) on virtual local area networks (VLANs).

Table 10-1  Performance monitoring supported by Y.1731

Function

Purpose

Usage

Two-Way Frame Delay Measurement

Measures the network delay time on a bidirectional link between a MEP and its RMEP to determine the link quality.

Two-way frame delay measurement is used to measure the delay time on a bidirectional link between a MEP and its RMEP.

Single-ended SLM

Collects frame loss statistics on point-to-multipoint links to monitor the link quality.

Single-ended SLM is used to collect frame loss statistics on point-to-multipoint links to accurately monitor frame loss performance of the link.

Two-Way Frame Delay Measurement

Delay measurement (DM) measures the delay time and delay variation. A MEP periodically sends a message carrying Ethernet Delay Measurement (ETH-DM) information to its RMEP and then receives a response message carrying ETH-DM information from its RMEP at intervals.

A MEP sends a delay measurement message (DMM) carrying an ETH-DM request to its RMEP. After receiving the DMM, the RMEP sends a delay measurement reply (DMR) carrying an ETH-DM response to the MEP.

Two-way frame delay measurement can be implemented in either of the following modes:
  • On-demand measurement is initiated manually and calculates the two-way frame delay at a time or periodically during diagnosis.
  • Proactive measurement calculates the two-way frame delay continuously.

Figure 10-2 illustrates the procedure for two-way delay measurement.

Figure 10-2  Two-way frame delay measurement

Two-way frame delay measurement is performed by a local MEP to send a DMM to its RMEP and then receive a DMR from the RMEP.

The procedure is as follows:
  1. After the two-way frame delay measurement is configured, a MEP periodically sends DMMs carrying TxTimeStampf (the time when the DMM was sent) to its RMEP.
  2. After receiving the DMM, the RMEP replies with a DMR. The DMR carries RxTimeStampf (the time when the DMM was received) and TxTimeStampb (the time when the DMR was sent). The value in every field of the DMM is copied to the DMR except that the source and destination MAC addresses were interchanged.
  3. Upon receiving the DMR, the MEP records the RxTime and calculates the two-way frame delay by using the following formula:

    Frame delay = (RxTimeb - TxTimeStampf) - (TxTimeStampb - RxTimeStampf)

    The frame delay can be used to measure the delay variation.

    A delay variation is an absolute difference between two consecutive delays.

Service packets are prioritized based on 802.1p priorities and are transmitted using different policies. Traffic passing through a P on the network shown in Figure 10-3 carries 802.1p priority values of 1 and 2.

Two-way delay measurement is enabled on PE1 to send traffic with the priority value of 1 to measure the frame delay on a link between PE1 and PE2. Traffic with the priority value of 2 is also sent. After receiving traffic with the priority values of 1 and 2, the P forwards traffic with a higher priority, delaying the arrival of traffic with the priority value of 1 at PE2. As a result, the frame delay calculated on PE2 is inaccurate. 802.1p priority-based two-way frame delay measurement can be enabled to obtain accurate results.

Figure 10-3  802.1p priority-based two-way frame delay measurement

Single-ended SLM

In Figure 10-4, SLM frames are used to measure the frame loss. A MEP sends a frame carrying an ETH-SLM request to its RMEP and receives a frame carrying an ETH-SLM response from the RMEP to perform SLM. The frame carrying an ETH-SLM request is called SLM frame, and the frame carrying an ETH-SLM response is called SLR.

Figure 10-4  SLM networking
The procedure is as follows:
  1. When single-ended SLM is configured successfully, PE1 periodically sends an SLM frame carrying the ETH-SLM request to PE3. The SLM frame carries TxFCf, the value of TxFC1 (local transmit counter).
  2. After receiving the SLM frame from PE1, PE3 sends an SLR carrying the ETH-SLM response to PE1. The SLR carries TxFCb, the value of RxFCl (local transmit counter).
  3. When PE1 receives the SLR frame from PE3, the value of RxFCl is RxFCl. When PE1 receives the last SLR in each round, it uses the following values to measure the near-end and far-end frame loss:
    • TxFCf of the SLR received by PE1, TxFCb, and local transmit counter RxFCl value (the time when the SLR was received) are represented as TxFCf[tc], TxFCb[tc], and RxFCl[tc], respectively.

      tc is the time when the last SLR is received.

    • TxFCf of the last SLR received by PE1 in the previous round, TxFCb, and local transmit counter RxFCl value (the time when the SLR was received) are represented as TxFCf[tp], TxFCb[tp], and RxFCl[tp], respectively.

      tp indicates the time when the last SLR is received in the previous round.

    Far-end frame loss = |TxFCf[tc] – TxFCf[tp]| – |TxFCb[tc] – TxFCb[tp]|

    Near-end frame loss = |TxFCb[tc] – TxFCb[tp]| – |RxFCl[tc] – RxFCl[tp]|

Service packets are prioritized based on 802.1p priorities and are transmitted using different policies. Traffic from PE1 to PE3 shown in Figure 10-5 carries 802.1p priority values of 1 and 2.

When single-ended SLM is performed for the link between PE1 and PE3, SLM frames with different priorities can be sent to determine the impact of a physical link on loss of packets with different priority values. The network administrator then can adjust QoS policies on the path.

Figure 10-5  Networking of single-ended SLM
Translation
Download
Updated: 2019-03-06

Document ID: EDOC1100069338

Views: 15363

Downloads: 54

Average rating:
This Document Applies to these Products
Related Documents
Related Version
Share
Previous Next