The abnormal and failure final states in the left side of the diagram must be resolved by  manual remediation of the root cause for the errors. To restart the application monitoring for  the affected application, the repair must be followed by an XML configuration reload. HM and VMM use the HVNCP proprietary protocol to communicate over the hypervisor  switch and the Ethernet layer in between. HVNCP implements a limited set of the capabilities  that are found in TCP/IP: 2.2.9 HVNCP protocol Chapter 2. IBM VM Recovery Manager High Availability components  199 Pairing A point-to-point communication is established between the HM  and each VMM.  Communication closure Communications remain active unless a new communication is  opened between the same HM and VMM or an error occurs. Flow control There is no flow control, so you avoid the processing impact of  communication for each message. We do not expect high packet  rates between the VMMs and the HM to justify the need for a flow  control that itself reduces the maximum packet rate that is  supported. Message fragmentation If a message is too long to be encapsulated in a single packet, it  can be divided into several ones.  Message building A message is composed of one or more packets. The first and  last packets are identified so that messages can be separated. Packet ordering Packets have a packet number, which is increased at each  packet sent, so that the receiver can restore the correct packet  order if needed. Acknowledgment A command or response packet can request an acknowledgment  so that you can detect lost packets if an acknowledgment was  required but not received.  Checksum If there is a checksum error when receiving a packet, the packet  is discarded. Error management If a packet that did not require an acknowledgment is lost, then it  is not retransmitted. If an acknowledgment was required and was  not received, then after reaching a timeout value the packet is  resent.