Message Service System

1
Message Service System
2
The Message System Paradigm

• The Message System or Message-Oriented Middleware
  (MOM) paradigm is an elaboration of the basic
  message-passing paradigm.
• A message system serves as an intermediary among
  separate, independent processes.
• A message system acts as a switch for 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 system forwards a message from the
  sender to the receivers message 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 sender deposits a message
  in the message queue of the receiving process.
• A receiving process extracts the messages from
  its message 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 subscribe to
  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 1980s.
• The IBM MQSeries6 is an example of such a
  facility.
• http//www-4.ibm.com/software/ts/mqseries/
• Other existing support for this paradigm are
• Microsofts Message Queue (MSQ)
• Javas Message Service

8
Short Message Service (SMS)

• The transmission of short text messages to 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 receivers 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
  Delivery Point to Point format to the serving
  system. The system pages 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/jm
  sTOC.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/