Described are embodiments directed at providing a witness service that sends notifications with a resource state to clients. Embodiments provide a protocol that includes various messages for registering and receiving notifications regarding the state of a resource. The protocol may include a message for requesting node information from a first node in a cluster. The node information identifies nodes in the cluster that provide a witness service, which monitors a resource. The protocol includes a message that is used to register with the witness service for notifications regarding a state, or state change, of a network or cluster resource. The protocol also includes messages for sending notifications with state information of the resource.