Cisco ASR 920 series Configuration Guide Ethernet Router

A MEP transmits frames with ETH-DM information using the TxTimeStampf information element.
TxTimeStampf is the time stamp for when the ETH-DM frame was sent. A receiving MEP can compare the
TxTimeStampf value with the RxTimef value, which is the time the ETH-DM frame was received, and
calculate one-way delay using the formula frame delay = RxTimef – TxTimeStampf.
One-way frame-delay measurement (1DM) requires that clocks at both the transmitting MEP and the receiving
MEPs are synchronized. Measuring frame-delay variation does not require clock synchronization and the
variation can be measured using 1DM or a frame-delay measurement message (DMM) and a frame-delay
measurement reply (DMR) frame combination.
If it is not practical to have clocks synchronized, only two-way frame-delay measurements can be made. In
this case, the MEP transmits a frame containing ETH-DM request information and the TxTimeStampf element,
and the receiving MEP responds with a frame containing ETH-DM reply information and the TxTimeStampf
value copied from the ETH-DM request information.
Two-way frame delay is calculated as frame delay = RxTimeb – TxTimeStampf, where RxTimeb is the time
that the frame with ETH-DM reply information was received. Two-way frame delay and variation can be
measured using only DMM and DMR frames.
To allow more precise two-way frame-delay measurement, the MEP replying to a frame with ETH-DM request
information can also include two additional time stamps in the ETH-DM reply information:
• RxTimeStampf—Time stamp of the time at which the frame with ETH-DM request information was
received.
• TxTimeStampb—Time stamp of the time at which the transmitting frame with ETH-DM reply information
was sent.
The frame-delay and frame-delay variation measurement processes are aborted when faults related to
continuity and availability occur or when known network topology changes occur.
Note
An MIP is transparent to the frames with ETH-DM information; therefore, an MIP does not require information
to support the ETH-DM function.
Carrier Ethernet Configuration Guide (Cisco ASR 920 Series)
323
ITU-T Y.1731 Performance Monitoring in a Service Provider Network
Frame Delay and Frame-Delay Variation

Cisco ASR 920 series Specifications

General

Brand	Cisco
Model	ASR 920 series
Category	Network Router
Language	English