Inter-chassis link (ICL) is used to transfer synchronization information. Any logical connectivity serves this purpose, but it is crucial that this link is redundant. The loss of this link is a faulty scenario where the control channel for UM synchronization between the two chassis is broken. In this case, both nodes remain operational in a stand-alone mode and they continue to forward traffic. After the ICL is recovered, the UM counters are re-synchronized from the active to standby node automatically within the configured synchronization interval.