Exchange architectural overview of a RoundTrip server session

The major components of the RoundTrip server session monitor are

• Session, Send and Timer component (SST): This component contains session information for all the RoundTrip server sessions that are currently active; three sets of timers for the send interval, alarm interval, and warn interval; and a module to send email messages to the target server.
• Event Sink component (ES): This component registers with the Microsoft Message Notification system and is notified whenever a mail message has arrived at a particular mailbox on the server.
• PATROL Agent Communication/Data Multiplexer-Demultiplexer component (PAC): This component handles communication between the SST and ES components and the PATROL Agent and also multiplexing and demultiplexing of various data streams.

The interaction between the various components is shown in the following figure for an active RoundTrip server session: 

 Roundtrip server session architecture 

1. The Send Interval timer for the active session expires and a component (1) on the source Exchange server sends an email message to the target Exchange server.
2. A component (5) on the target Exchange server is notified of the arrival of the email message from the source Exchange server.
3. The component (5) on the target Exchange server responds to the message from the source Exchange server by sending a reply.
4. The component (2) on the source Exchange server is notified of the arrival of the reply email message from the source Exchange server. After it parses the reply message, it calculates the RoundTrip response time. If a reply message does not arrive at the source Exchange server within the Alarm or Warn interval, the corresponding Alarm or Warn timers in component (1) time out.

5. The component (3) on the source Exchange server notifies the PATROL Agent with the calculated RoundTrip times if they were obtained or sends an Alarm or Warn notification if a response from the target server was not obtained within the Alarm or Warn intervals.

   Note

   All the components listed are contained in the processes MSEXCHE2E.exe and MSEXCHRoundtrip.exe on the source and target server machines.