The ETH-ED PDU is used to announce the expected defect window to peer MEPs. The peer MEPs uses the expected defect window value to prevent ETH-CC timeout (DefRemoteCCM) conditions for the announcing MEP. The MEP announcing ETH-ED does not time out any remote peers during the expected defect window. The expected defect window is not a configurable value.
At the start of the operation, a burst of three packets are sent over a 3-second window to reduce the chance that a remote peer may miss the expected defect window announcement.
It is possible to restrict the value that is installed for the expected defect timer by configuring the max-rx-defect-window command for the receiving MEP. A comparison is used to determine the expected defect timer to be installed during grace. Either the lower of the received expected defect timer values in the ETH-ED PDU or the configured maximum is installed if they are larger than the standard computation for ETH-CC timeout. The no max-rx-defect-window command is configured by default; therefore, the maximum received expected defect window is disabled, and it is not considered in determining the installed expected defect timer.
Subsequent ETH-ED packets are only transmitted at the completion of the Soft Rest function that triggered the grace function. The three-packet burst at the completion of the Soft Reset function contains an expected defect window size of 5 seconds. Receiving peers should use this new advertisement to reset the expected window to 5 seconds.
The termination of the grace window occurs when the expected defect window timer reaches zero, or when the receive function is manually disabled.