Recently I was involved in troubleshooting a client discovery issue, sometimes becomes a nightmare troubleshoot the SMS logs if you don't have a clear understanding of the components and SMS flow. To help us with that, MS has released the troubleshooting flowcharts package which includes the complete flow of the most common scenarios based on the following categories:
I found this information very useful to understand how SMS works and reduce the time invested in researching the Components involved in a particular situation. You can download this material from the following location: