A service integration bus messaging topology can contain multiple interconnected service integration buses. For each bus in the topology, the other buses that are connected to it via a link are its foreign buses. It is also possible to connect service integration buses with a collection of WebSphere MQ resources such as WebSphere MQ queue managers. The WebSphere MQ resources are regarded as foreign buses.
A bus must be contained within a single cell; that is, a bus cannot span multiple cells. However, a cell may contain more than one bus. In this case, each bus in the cell is foreign to each other bus in the cell. You can connect buses together within a cell, or between different cells. Regardless of where a bus exists, if one bus is foreign to the other, a foreign bus link must be created in both directions.
When buses are connected using a foreign bus link, applications can send messages to applications on other buses, and use resources provided on other buses. Published messages can span multiple buses where the links between the buses are configured to allow it.
To create a link between two buses, the administrator of the local bus creates a foreign bus that represents the second bus, as a property of the local bus. The administrator of the second bus also creates a foreign bus to represent the first bus, as a property of the second bus. Each administrator then creates a virtual link and a physical link (called a service integration bus link) from the local bus to the foreign bus.
The route between two buses can be made indirectly, through one or more intermediate foreign buses. In Figure 1 Bus 1 can be connected to Bus 5 indirectly. For a conceptual overview of the two methods, refer to Direct and indirect routing between service integration buses.
For more information about foreign buses see Foreign buses. Conceptual overviews of achieving point to point and publish subscribe messaging can be found in Point-to-point messaging across multiple buses and Publish/subscribe messaging across multiple buses.
If you want to connect your local bus to a foreign bus, and the remote messaging engine is in a cluster, you must change the bootstrap endpoint value. It should list all bootstrap endpoints used by the cluster to allow access to the messaging engine.
For more information, see steps 1 and 2 of Configuring a connection to a non-default bootstrap server. Although this task primarily describes how to configure a JMS connection factory, it is also applicable to setting several bootstrap endpoint values if the remote messaging engine is in a cluster.There is no difference in how you set up the link for buses within the same cell or in different cells. In both cases, you provide values for the bootstrap endpoints. In the first case, you provide the host name of a node with a server in the same cell, and in the other case the host name of a node with a server in a different cell.