Reception of SLRs
After an SLM frame (with a given TxFCf value) is transmitted, a MEP expects to receive
a corresponding SLR frame (carrying the same TxTCf value) within the timeout value
from its peer MEP. SLR frames that are received after the timeout value (5 seconds) are
discarded. With the information contained in SLR frames, a MEP determines the frame
loss for the specified measurement period. The measurement period is a time interval
during which the number of SLM frames transmitted is statistically adequate to make a
measurement at a given accuracy. A MEP uses the following values to determine near-end
and far-end frame loss during the measurement period:
•
Last received SLR frame's TxFCf and TxFCb values and the local counter RxFCl value
at the end of the measurement period. These values are represented as TxFCf[tc],
TxFCb[tc], and RxFCl[tc], where tc is the end time of the measurement period.
•
SLR frame's TxFCf and TxFCb values of the first received SLR frame after the test
starts and local counter RxFCl at the beginning of the measurement period. These
values are represented as TxFCf[tp], TxFCb[tp], and RxFCl[tp], where tp is the start
time of the measurement period.
For each SLR packet that is received, the local RxFCl counter is incremented at the sending
or source MEP.
Computation of Frame Loss
Synthetic frame loss is calculated at the end of the measurement period on the basis of
the value of the local counters and the information from the last frame received. The
last received frames contains the TxFCf and TxFCb values. The local counter contains
the RxFCl value. Using these values, frame loss is determined using the following formula:
Frame loss (far-end) = TxFCf – TxFCb
Frame loss (near-end) = TxFCb – RxFCl
Related
Documentation
Ethernet Synthetic Loss Measurement Overview on page 1140•
• Format of ETH-SLM Messages on page 1144
• Guidelines for Configuring ETH-SLM on page 1146
• Scenarios for Configuration of ETH-SLM on page 1147
• Managing ETH-SLM Statistics and ETH-SLM Frame Counts on page 1148
• Starting a Proactive ETH-SLM Session on page 1153
• Starting an On-Demand ETH-SLM Session on page 1156
• Troubleshooting Failures with ETH-SLM
• Ethernet Interfaces Feature Guide for Routing Devices
1143Copyright © 2017, Juniper Networks, Inc.
Chapter 34: Configuring Operations, Administration, and Management (OAM)
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