Benefits of Using Multicasting Limitations of Using Multicasting Using WebLogic Server Unicast

8 Using Multicasting with WebLogic JMS 8-1 8 Using Multicasting with WebLogic JMS Multicasting enables the delivery of messages to a select group of hosts that subsequently forward the messages to subscribers in a cluster. The following sections provide information on the benefits, limitations, and configuration of using multicasting with WebLogic JMS: ■ Section 8.1, Benefits of Using Multicasting ■ Section 8.2, Limitations of Using Multicasting ■ Section 8.4, Configuring Multicasting for WebLogic Server

8.1 Benefits of Using Multicasting

The benefits of multicasting include: ■ Near real-time delivery of messages to host group. ■ High scalability due to the reduction in the amount of resources required by the JMS server to deliver messages to topic subscribers in a cluster.

8.2 Limitations of Using Multicasting

The limitations of multicasting include: ■ Multicast messages are not guaranteed to be delivered to all members of the host group. For messages requiring reliable delivery and recovery, you should not use multicasting. ■ For interoperability with different versions of WebLogic Server, clients cannot have an earlier release of WebLogic Server installed than the host. They must all have at least the same version or higher. For an example of when multicasting might be useful, consider a stock ticker. When accessing stock quotes, timely delivery is more important than reliability. When accessing the stock information in real-time, if all or a portion of the contents is not delivered, the client can simply request the information to be resent. Clients would not want to have the information recovered, in this case, as by the time it is redelivered, it would be out-of-date.

8.3 Using WebLogic Server Unicast

WebLogic Server provides an alternative to using multicast to handle cluster messaging and communications. Unicast configuration is much easier because it does not require cross network configuration that multicast requires. Additionally, it reduces potential network errors that can occur from multicast address conflicts. 8-2 Programming JMS for Oracle WebLogic Server JMS topics configured for multicasting can access WebLogic clusters configured for unicast because a JMS topic publishes messages on its own multicast address that is independent of the cluster address. However, the following considerations apply: ■ The router hardware configurations that allow unicast clusters may not allow JMS multicast subscribers to work. ■ JMS multicast subscribers need to be in a network hardware configuration that allows multicast accessibility. For more details, see Communications In a Cluster in Using Clusters for Oracle WebLogic Server.

8.4 Configuring Multicasting for WebLogic Server