The channel supports sequenced data delivery, heartbeat link liveness verification, and controlled reset on error.
Interfaces are entirely independent of each other.
Built on the channel layer, the link layer constructs a higher-level communications mechanism which binds together all available channels to any given host. No connection to remote host is held. We have had an error, and are temporarily resetting all of the channels in the link. When constructing a new cluster state, the upper layers will use a degraded link to perform a clean cluster transition evicting one of the nodes on that link from the cluster. We can use the degraded link to perform this eviction cleanly, adjusting quorum to take its departure into account.