WebSphere Message Brokers
File: ac00470_
Writer: Kate Hostler

Concept topic

This build: July 31, 2007 21:16:44

WebSphere MQ Telemetry Transport

WebSphere MQ Telemetry Transport is a lightweight publish/subscribe protocol flowing over TCP/IP for remote sensors and control devices through low bandwidth communications.

This protocol is used by specialized applications on small footprint devices that require a low bandwidth communication, typically for remote data acquisition and process control.

A typical system might comprise several hundred client devices communicating with a single WebSphere Message Broker, where each client is identified by a unique ID. A single broker can manage a maximum of approximately 2000 clients.

WebSphere Message Broker uses the SCADAInput node to receive messages from WebSphere MQ Telemetry Transport client applications. The node interacts with a TCP/IP port to receive the messages.

Output is typically returned to the client application using a Publication node which embeds a SCADAOutput node. The Publication node filters and sends output from a message flow to subscribers who have registered an interest in a particular set of topics. If an application is using WebSphere MQ, the Publication node puts the message to the WebSphere MQ queue on the queue manager. For WebSphere MQ Telemetry Transport applications, the embedded SCADAOutput node routes the message to a subscribing WebSphere MQ Telemetry Transport client using a TCP/IP port.

z/OS platform SCADAInput nodes are available on all platforms except z/OS.

It is unlikely that you will use the SCADAOutput node directly, unless you write your own publication node for advanced applications.

Unlike WebSphere MQ and WebSphere MQ Everyplace, WebSphere MQ Telemetry Transport does not provide any security, although you can encrypt data, if required.

Quality of Service

You can specify a maximum Quality of Service (QoS) in a WebSphere MQ Telemetry Transport subscription message. QoS is similar to persistence in WebSphere MQ. There are three levels of QoS:

QoS0
"At most once" delivery. Delivery is not assured; acknowledgment is not expected.
QoS1
"At least once" delivery. Successful delivery is assured and an acknowledgment sent.
QoS2
"Exactly once" delivery. Similar to QoS1, but the message is assured not to be duplicated.

For further information about QoS see Quality of Service levels and flows

Related concepts
Publish/Subscribe
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This build: July 31, 2007 21:16:44

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