Figure 18: Ethernet Oam Overview - Juniper JUNOS OS 10.4 Manual

Junos OS 12.1 MX Series 3D Universal Edge Routers Solutions Guide
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delay measurement provides fine control to operators for triggering delay measurement
on a given service and can be used to monitor Service Level Agreements (SLAs).
Ethernet frame delay measurement also collects other useful information, such as worst
and best case delays, average delay, and average delay variation. Ethernet frame delay
measurement supports hardware-based timestamping in the receive direction for delay
measurements. It also provides runtime display of delay statistics when two-way delay
measurement is triggered. Ethernet frame delay measurement records the last 100
samples collected per remote maintenance end point (MEP) or per connectivity fault
management (CFM) session. You can retrieve the history at any time using simple
commands. You can clear all Ethernet frame delay measurement statistics and PDU
counters. Ethernet frame delay measurement is fully compliant with the ITU-T Y.1731
(OAM Functions and Mechanisms for Ethernet-based Networks) specification.
Ethernet frame delay measurement uses the IEEE 802.1ag CFM infrastructure.
An overview of the architecture established for Ethernet OAM is shown in
page 120. Generally, Ethernet frame delay measurements are made in a peer fashion from
one MEP or CFM session to another. However, these measurements are not made to
Maintenance Intermediate Points (MIPs).

Figure 18: Ethernet OAM Overview

There are two types of Ethernet frame delay measurements:
One-way
Two-way (round-trip)
For one-way Ethernet frame delay measurement, either MEP can send a request to begin
a one-way delay measurement to its peer MEP. However, the statistics are collected only
at the receiver MEP. This feature requires the clocks at the transmitting and receiving
MEPs to be synchronized. If these clocks fall out of synchronization, only one-way delay
variation and average delay variation values are computed correctly (and therefore valid).
Use the show commands at the receiver MEP to display one-way delay statistics.
For two-way (round-trip) Ethernet frame delay measurement, either MEP can send a
request to begin a two-way delay measurement to its peer MEP, which responds with
timestamp information. Run-time statistics are collected and displayed at the initiator
Figure 18 on
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