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Ethernet Frame Delay Measurement
Two key objectives of OAM functionality are to measure quality-of-service attributes
such as frame delay and frame delay variation (also known as "frame jitter"). Such
measurements can enable you to identify network problems before customers are
impacted by network defects.
JUNOS Software supports Ethernet frame delay measurement between MEPs
configured on Ethernet physical or logical interfaces on Dense Port Concentrators
(DPCs) in MX Series routers. Ethernet frame delay measurement provides fine control
to operators for triggering delay measurement on a given service and can be used
to monitor SLAs. Ethernet frame delay measurement also collects other useful
information, such as worst and best case delays, average delay, and average delay
variation. The JUNOS Software implementation of Ethernet frame delay measurement
(ETH-DM) is fully compliant with the ITU-T Recommendation Y.1731, OAM Functions
and Mechanisms for Ethernet-based Networks. The recommendation defines OAM
mechanisms for operating and maintaining the network at the Ethernet service layer,
which is called the "ETH layer" in ITU-T terminology.
One-Way Ethernet Frame Delay Measurement
In one-way ETH-DM mode, a series of frame delay and frame delay variation values
are calculated based on the time elapsed between the time a measurement frame
is sent from the initiator MEP at one router and the time when the frame is received
at the receiver MEP at the other router.
1DM Transmission
When you start a one-way frame delay measurement, the router sends 1DM
frames—frames that carry the protocol data unit (PDU) for a one-way delay
measurement—from the initiator MEP to the receiver MEP at the rate and for the
number of frames you specify. The router marks each 1DM frame as drop-ineligible
and inserts a timestamp of the transmission time into the frame.
1DM Reception
When an MEP receives a 1DM frame, the router that contains the receiver MEP
measures the one-way delay for that frame (the difference between the time the
frame was received and the timestamp contained in the frame itself) and the delay
variation (the difference between the current and previous delay values).
One-Way ETH-DM Statistics
The router that contains the receiver MEP stores each set of one-way delay statistics
in the ETH-DM database. The ETH-DM database collects up to 100 sets of statistics
for any given CFM session (pair of peer MEPs). You can access these statistics at any
time by displaying the ETH-DM database contents.
Chapter 44: Configuring ITU-T Y.1731 Ethernet Service OAM
Ethernet Frame Delay Measurements Overview
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