Single-Ended Frame-Loss Measurements

Single-ended frame-loss measurement facilitates on-demand OAM. MEPs carry out frame-loss measurments by sending frames to peer MEPs with frame-loss measurement request information and receiving frames with frame-loss measurement reply information. This Y_1731 frame-loss measurement depends on VLAN statistics.

The PDU for single-ended frame-loss measurement requests is Loss Measurement Message (LMM). The PDU for single-ended frame-loss measurement reply is Loss Measurement Reply (LMR). Two-Way Frame-Loss Measurement shows the transmission of LMM and LMR for frame-loss measurement.

Two-Way Frame-Loss Measurement

A MEP maintains two local counters for each peer MEP it is monitoring for frame-loss:

TxFCl—in-profile data frames transmitted to the peer MEP.
RxFCl—in-profile data frames received from the peer MEP.

For an on-demand loss measurement, a MEP periodically transmits LMM frames with TxFCf (value of the local TxFCl counter at the time of LMM frame transmission). Upon receiving a valid LMM frame, a MEP sends an LMR frame to the requesting MEP. (Valid LMM frames have a valid MD level and a destination MAC address equal to the receiving MEP's MAC address.)

An LMR frame contains the following values:

TxFCf—TxFCf value copied from the LMM frame.
RxFCf—RxFCl value when the LMM frame was received.
TxFCb—TxFCl value when the LMR frame was transmitted.

Upon receiving an LMR frame, a MEP uses the following values to make near-end and far-end loss measurements:

Received LMR frame's TxFCf, RxFCf, and TxFCb values, and local counter RxFCl value at the time this LMR frame was received. These values are represented as TxFCf[tc], RxFCf[tc], TxFCb[tc], and RxFCl[tc]; where tc is the time the current reply frame was received.
Previous LMR frame's TxFCf, RxFCf, and TxFCb values, and local counter RxFCl value at the time the previous LMR frame was received. These values are represented as TxFCf[tp], RxFCf[tp], TxFCb[tp], and RxFCl[tp],where tp is the time the previous reply frame was received.

Far-End Frame Loss = (TxFCf[tc] – TxFCf[tp]) – (RxFCf[tc] – RxFCf[tp])

Near-End Frame Loss = (TxFCb[tc] – TxFCb[tp]) – (RxFCl[tc] – RxFCl[tp])

Published March 2020prev | next

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