WebSphere WebSphere Application Server Network Deployment, Version 6.0.x Operating Systems: AIX, HP-UX, Linux, Solaris, Windows

Foreign buses

A foreign bus is a representation of another service integration bus, or a WebSphere MQ queue manager, with which an existing service integration bus, or a WebSphere MQ queue manger, can exchange messages. The purpose of a foreign bus is to extend the network of buses that can exchange messages.

A foreign bus is a property of a service integration bus or a WebSphere MQ queue manager. A foreign bus, and the service integration bus it represents, can exist in separate network cells or within the same cell. A foreign bus that represents a WebSphere MQ queue manger can exist in a separate WebSphere MQ network, or within the same WebSphere MQ network as the queue manager. The existing service integration bus or WebSphere MQ queue manager is referred to as the local bus.

Messages are routed to a foreign bus either directly through a link between the local bus and the foreign bus, or indirectly through one or more intermediate buses. Regardless of where the buses exist, if one is foreign to the other, it requires a foreign bus link. For example, if a cell contains more than one bus, each bus within it is regarded as foreign to each other bus. The link is defined in a routing definition, also known as a virtual link. The type of routing definition for a foreign bus indicates the type of physical link:

In the following figure, Figure 1, buses 1 and 2 are linked directly, and buses 1 and 3 are linked indirectly through bus 2.

Figure 1. Linking service integration buses. Three service integration buses connected through a service integration bus link on a messaging engine in each of the buses.
Before you create and configure a foreign bus link, you must create a foreign bus. The following restrictions apply to creating a foreign bus:

You can define an explicit destination on a foreign bus, to which an application can send messages. You can also configure default properties for use by messages sent to destinations on a foreign bus when there is no explicit foreign destination definition, and the application does not explicitly provide values for the properties. An application cannot receive messages from a foreign destination; it can only consume messages from a destination on the bus to which it is connected.

An application subscribing to a local topic space can receive messages published to a topic on a foreign bus. To allow publish/subscribe messaging between buses, topic space names on a local bus must be mapped to topic space names on a foreign bus.

A topic space mapping allows subscribers on the local topic space to receive messages published in the foreign topic space. For publications to flow from the local topic space into the foreign bus, an equivalent topic space mapping is required by the foreign bus.

Topic space mapping is administered through the routing properties for a foreign bus. Topic space names for the local bus are mapped to topic space names defined on the foreign bus. It is common for these two names to match. Note that mapping two topic spaces implies that the topics within them are "the same".

Related tasks
Connecting buses
Connecting buses directly
Extending the bus network
Configuring foreign buses
Adding a foreign bus
Configuring the properties of a foreign bus
Listing the foreign buses
Removing a foreign bus
Configuring destination defaults for a foreign bus
Creating a routing definition
Configuring a routing definition
Removing a routing definition
Configuring service integration bus links
Creating a foreign bus destination
Planning a bus topology
Planning a multiple-bus topology
Planning a topology that includes WebSphere MQ

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Last updated: 5 Oct 2005
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