Using MSMQ Subsystem A must send a message to Subsystem B without either knowing the address of the other subsystem.

• Subsystem A sends a request-reply message to Subsystem C asking for Subsystem B's address.
  • Subsystem A will provide a Return Address, so Subsystem C knows where to send the reply.
• Subsystem A will now send four messages to Subsystem B.
  • Message 1 and 2 will have the same correlation id.
  • Message 3 and 4 will have the same correlation id.
  • The messages will contain an object. The object contains an integer that Subsystem B can sum (aggregation). The object will also contain an id.
• Subsystem B will reply with two messages to Subsystem A.
  • Message 1 will contain the sum of message 1 and 2. The correlation id will be the id of the objects from message 1/2.
  • Message 2 will contain the sum of message 3 and 4. The correlation id will be the id of the objects from message 3/4.