Message Service System

1. Message Service System

2. The Message System Paradigm • The Message System or Message-Oriented Middleware (MOM) paradigm is an elaboration ofthebasic message-passing paradigm. • A message systemserves as an intermediary among separate, independent processes. • A message system acts as a switchfor messages, through which processes exchange messages asynchronously, in a decoupled manner. • A sender deposits a message with the message system, which forwards it to a message queue associated with each receiver.

3. The Message System Paradigm

4. Message System Models Two subtypes of message system models: • Point-to-Point • Publish-Subscribe

5. The Point-To-Point Message Model • A message systemforwards a message from the sender to the receiver’smessage queue. Unlike the basic message passing model, the middleware provides a message depository, and allows the sending and the receiving to be decoupled. • Via the middleware, a senderdeposits a message in the message queueof the receiving process. • A receiving processextractsthe messagesfrom itsmessage queue, and handles each one accordingly. • Compared to the basic message-passing model, this paradigm provides the additional abstraction for asynchronous operations.

6. The Publish/Subscribe Message Model • Each message is associated with a specific topic or event. Applications interested in the occurrence of a specific event may subscribeto messages for that event. • When the awaited event occurs, the process publishes a message announcing the event or topic. The middleware message system distributes the message to all its subscribers. • The publish operation allows a process to multicast to a group of processes, and the subscribe operation allows a process to listen for such multicast. • This model offers a powerful abstraction for multicasting or group communication

7. Toolkits based on the Message-System Paradigm • The MOM paradigm has had a long history in distributed applications. • Message Queue Services (MQS) have been in use since the 1980’s. • The IBM MQ*Series6 is an example of such a facility. http://www-4.ibm.com/software/ts/mqseries/ • Other existing support for this paradigm are • Microsoft’s Message Queue (MSQ) • Java’s Message Service

8. Short Message Service (SMS) • The transmission of short text messagesto and from a mobile phone, fax machine and/or IP address. • Messages must be no longer than 160 alpha-numeric characters and contain no images or graphics. • Once a message is sent, it is received by a Short Message Service Center (SMSC),which must then get it to the appropriate mobile device. • The SMSC sends a SMS Request to the home location register (HLR) to find the roaming receiver. • Once the HLR receives the request, it will respond to the SMSC with the receiver’s status: 1) inactive or active 2) where receiver is roaming. • Ref: http://www.webopedia.com/TERM/S/short_message_service.html

9. Short Message Service (SMS) • If the response is "inactive", then the SMSC will hold onto the message for a period of time. • When the receiver accesses his/her device, the HLR sends a SMS Notification to the SMSC, and the SMSC will attempt delivery. • The SMSC transfers the message in a Short Message DeliveryPoint to Point format to the serving system. The systempages the device, and if it responds, the message gets delivered. • The SMSC receives verification that the message was received by the receiver, then categorizes the message as "sent" and will not attempt to send again. • Ref: http://www.webopedia.com/TERM/S/short_message_service.html

10. Sources of Information • Sun's JMS Tutorial http://java.sun.com/products/jms/tutorial/html/jmsTOC.fm.html • Microsoft's Message Queue(MSMQ) http://msdn.microsoft.com/library/psdk/msmq/msmq • IBM's MQ-Series http://www-4.ibm.com/software/ts/mqseries/