ELSM Timers

To determine whether there is a CPU or link failure, ELSM requires timer expiration between the ELSM peers. Depending on the health of the network, the port enters different states when the timers expire. For more information about the ELSM port states, see ELSM Port States.

The following table describes the ELSM timers. Only the hello timer is user-configurable; all other timers are derived from the hello timer. This means that when you modify the hello timer, you also modify the values for down, up, and HelloRx timers.

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ELSM Timers

Timer Description

Hello

The ELSM hello timer is the only user-configurable timer and specifies the time in seconds between consecutive hello messages. The default value is 1 second, and the range is 100 milliseconds to 255 seconds.

Down

The ELSM down timer specifies the time it takes the ELSM port to cycle through the following states:
  • Down—Indicates that the port is down, blocked, or has not received Hello+ messages from its peer.
  • Down-Wait—Indicates a transitional state.Up—Indicates a healthy remote system and this port is receiving Hello+ messages from its peer.

By default, the down timer is (2 + hold threshold) * hello timer, which is 4 seconds. If the hold threshold is set to 2 and the hello timer is set to 1 second, it takes 4 seconds for the ELSM port receiving messages to cycle through the states.

After the down timer expires, the port checks the number of Hello+ messages against the hold threshold. If the number of Hello+ messages received is greater than or equal to the configured hold threshold, the ELSM receive port moves from the Down-Wait state to the Up state.

If the number of Hello+ messages received is less than the configured hold threshold, the ELSM receive port moves from the Down-Wait state back to the Down state and begins the process again.

Up

The ELSM up timer begins when the ELSM-enabled port enters the UP state. Each time the port receives a Hello+ message, the timer restarts.

Up timer is the UpTimer threshold * hello timer. It is configurable and the range is 3 to 60 seconds.

By default, the UpTimer threshold is 6. Therefore, the default up timer is 6 seconds (6*1).

HelloRx

The ELSM HelloRx timer specifies the time in which a hello message is expected. If the port does not receive a hello message from its peer, there is the possibility of a CPU or link failure.

By default the HelloRx timer 6 * hello timer, which is 6 seconds.