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. 

## 2.2.9 HVNCP protocol 

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: 

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. 

