3.1.5 Message Processing Events and Sequencing Rules
The following high-level sequence diagram illustrates the operation of the protocol.
Figure 3: Message processing sequence of the Windows Server Update Services: Client-Server Protocol
Self-update, authorization, and metadata sync MUST always be performed in the sequence illustrated in this diagram, although specific steps in the sequence MAY be omitted as an optimization. Many of the web method calls in the sequence produce an output that is needed as input to the next web method call, therefore the overall ordering of the web method calls need to be maintained. Content download and event reporting SHOULD be performed asynchronously from other operations. Each of these operations is specified in more detail in the following sections.