Message switching
In telecommunications, message switching was the precursor of packet switching
Packet switching
Packet switching is a digital networking communications method that groups all transmitted data – regardless of content, type, or structure – into suitably sized blocks, called packets. Packet switching features delivery of variable-bit-rate data streams over a shared network...

, where messages were routed in their entirety, one hop at a time. It was first introduced by Leonard Kleinrock
Leonard Kleinrock
Leonard Kleinrock is an American engineer and computer scientist. A computer science professor at UCLA's Henry Samueli School of Engineering and Applied Science, he made several important contributions to the field of computer networking, in particular to the theoretical side of computer networking...

 in 1961. Message switching systems are nowadays mostly implemented over packet-switched or circuit-switched data networks. Each message is treated as a separate entity. Each message contains addressing information, and at each switch this information is read and the transfer path to the next switch is decided. Depending on network conditions, a conversation of several messages may not be transferred over the same path. Each message is stored (usually on hard drive due to RAM limitations) before being transmitted to the next switch. Because of this it is also known as a 'store-and-forward' network. Email is a common application for Message Switching. A delay in delivering email is allowed unlike real time data transfer between two computers.


Hop-by-hop Telex
A teleprinter is a electromechanical typewriter that can be used to communicate typed messages from point to point and point to multipoint over a variety of communication channels that range from a simple electrical connection, such as a pair of wires, to the use of radio and microwave as the...

 forwarding and UUCP
UUCP is an abbreviation for Unix-to-Unix Copy. The term generally refers to a suite of computer programs and protocols allowing remote execution of commands and transfer of files, email and netnews between computers. Specifically, a command named uucp is one of the programs in the suite; it...

 are examples of message switching systems.

When this form of switching is used, no physical path is established in advance in between sender and receiver. Instead, when the sender has a block of data to be sent, it is stored in the first switching office (i.e. router) then forwarded later at one hop at a time. Each block is received in its entity form, inspected for errors and then forwarded or re-transmitted.
A form of store-and-forward network. Data is transmitted into the network and stored in a switch. The network transfers the data from switch to switch when it is convenient to do so, as such the data is not transferred in real-time. Blocking can not occur, however, long delays can happen. The source and destination terminal need not be compatible, since conversions are done by the message switching networks.

A message switch is “transactional”. It can store data or change its format and bit rate, then convert the data back to their original form or an entirely different form at the receive end. Message switching multiplexes data from different sources onto a common facility.
A message switch is a one of the switching technology.

In message switching, when a message consists of a block of data to be sent, it is stored in the first switching office (i.e. router) and then forwarded later, one hop at a time. Each block is received in its entirety, inspected and later retransmitted. A network using this technique is referred to as a store-and-forward network.

Store and forward delays

Since message switching stores each message at intermediate nodes in its entirety before forwarding, messages experience an end to end delay which is dependent on the message length, and the number of intermediate nodes. Each additional intermediate node introduces a delay which is at minimum the value of the minimum transmission delay into or out of the node. Note that nodes could have different transmission delays for incoming messages and outgoing messages due to different technology used on the links. The transmission delays are in addition to any propagation delays which will be experienced along the message path.

In a message-switching centre an incoming message is not lost when the required outgoing route is busy. It is stored in a queue with any other messages for the same route and retransmitted when the required circuit becomes free. Message switching is thus an example of a delay system or a queuing system. Message switching is still used for telegraph traffic and a modified form of it, known as packet switching, is used extensively for data communications.


The advantages to Message Switching are:
  • Data channels are shared among communication devices improving the use of bandwidth.
  • Messages can be stored temporarily at message switches, when network congestion becomes a problem.
  • Priorities may be used to manage network traffic.
  • Broadcast addressing uses bandwidth more efficiently because messages are delivered to multiple destinations.


See also

  • SMS
    Short message service
    Short Message Service is a text messaging service component of phone, web, or mobile communication systems, using standardized communications protocols that allow the exchange of short text messages between fixed line or mobile phone devices...

  • circuit switching
    Circuit switching
    Circuit switching is a methodology of implementing a telecommunications network in which two network nodes establish a dedicated communications channel through the network before the nodes may communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the...

  • message-oriented middleware
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