Huawei NetEngine80E Configuration Manual - Reliability page 573

HUAWEI NetEngine80E/40E Router
Configuration Guide - Reliability
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Issue 02 (2011-09-10)
1. A MEP periodically sends DM frames carrying TxTimeStampf.
2. After receiving a DM frame, the remote MEP calculates the one-way frame delay
based on the following formula:
Frame delay = RxTimef - TxTimeStampf
The frame delay variation, namely, frame jitter, can be calculated based on the frame delay.
Jitter: is used as a measure of the variability over time of the frame delay across a network,
and is the absolute difference value between two delays.
Figure 9-3 Networking diagram of one-way frame delay measurement
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Two-way frame delay measurement
Two-way frame delay measurement is commonly performed on end-to-end MEPs. A MEP
receives a Delay Measurement Message (DMM) and returns a DMR to carry out two-way
frame delay measurement. As shown in
measurement is as follows:
1. A MEP periodically sends DMMs carrying TxTimeStampf.
2. After receiving a DMM, the remote MEP adds the RxTimeStampf value (the time of
receiving the DMM) to the DMM, generates a DMR with the TxTimeStampb value
(the time of sending the DMR), and sends the frame to the requesting MEP. Every
field in the DMM is copied to the DMR, except that the source and destination MAC
addresses are swapped and the message type is changed from DMM to DMR.
3. After receiving a DMR, the MEP that sends a DMM calculates the two-way frame
delay based on the following formula:
Frame delay = (RxTimeb - TxTimeStampf) - (TxTimeStampb - RxTimeStampf)
The frame delay variation, namely, frame jitter, can be calculated based on the frame delay.
Jitter: is used as a measure of the variability over time of the frame delay across a network,
and is the absolute difference value between two delays.
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1DM PDU
Y.1731
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Figure 9-4, the process of two-way frame delay
9 Y.1731 Configuration
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