The HVNCP protocol provides the low-level communication means so that on top of the  Ethernet layer, the HM and VMM exchange messages for the following three main types of  communication flows: This section shows the communication flows between various components of a VM Recovery  Manager HA deployment. Example 2-65 on page 103 shows the complete list of possible KSYS to VIOS requests, as  documented in the  /usr/lib/vioHADR2.00.xsd  file at the VIOS level. Some of them are used  by KSYS to trigger communication flows by itself. Others are used in intermediate stages of  the flows that are initiated by other components. If the stages of different flows are similar, we  describe the first occurrence in detail and refer to it later. Section “CAA event monitoring” on  page 128 shows an example of a communication flow that is initiated outside of KSYS at the  VIOS CAA subsystem level underneath the host group SSP cluster. From the KSYS subsystem perspective, first we consider all the flows running periodically  during the normal steady state operation of the cluster. As described in “Quick Discovery and Deep  Discovery scheduling records” on page 72,  periodic discovery actions are scheduled to identify configuration changes that might have  occurred in the whole infrastructure. A Quick Discovery action is performed hourly and a  Deep Discovery action every 24 hours. Detailed flow examples for each of these actions are  shown in 2.3.1, “Discovery of a VM that is enabled for monitoring” on page 203. To shorten  the explanations, we use the simplest possible environment of a host group with two hosts  and two VMs, one on each host. VMs themselves are configured in the simplest possible way,  which still allows us to capture the aspects of interest for the scenario under study. Conversely, as described in “Failure Detection Engine” on page 94, two QuickQuery requests  and one NeedsAttention request are submitted at 20 seconds, one after the other, by the host  group FDE thread. The flows of these requests are described in 2.3.2, “Failure Detection  Engine: QuickQuery and NeedsAttention flows” on page 234. 202  Implementing IBM VM Recovery Manager for IBM Power Systems 2.3 Communication flows GLYPH<SM590000> Communication session establishment GLYPH<SM590000> Heartbeat messages from VMM toward KSYS GLYPH<SM590000> Application management messages between the VMM and KSYS sides HEL (1 bit) – Hello packet Checksum (8 bits) When  HEL  is set to 1, all other fields  except  Checksum  are ignored. This  special packet describes a  Hello message that is periodically broadcast  by HM to VMMs to signal that HM to  VMM communication can be  established. The checksum is obtained by  calculating the sum of all bytes of the  header and the frame except for the  checksum field itself. Any packet with  an invalid checksum is automatically  discarded.