24 Migrating from WebSphere Application Server Community Edition to WebSphere Application Server
difficult to make generic, one-size-fits-all recommendation as to the
interoperability option to be used.
In some cases, a complete migration can take several months; in other cases,
parts of applications will never be migrated. There are also clients who decide to
perform all new development and deployment with IBM software, but keep their
existing applications intact. It is likely that these existing applications need to
communicate with the new ones, as in the case of a phased migration. This leads
us into the interoperability discussion.
3.2 Application servers interoperability
In recent years, the concept of universal interoperability became widely
accepted. It is called Enterprise Service Bus (ESB). IBM and many other vendors
see ESB as an architectural pattern that can be implemented in different ways
using different protocols and products.
In Table 3-1 on page 26, we have tried to summarize some of these
considerations as they apply to J2EE application servers. The following list
provides a description of each protocol that you can use to interoperate between
different application server instances as well as between different vendor
products:
JMS over WebSphere MQ
WebSphere MQ provides JMS as one of its programming APIs. You can use
WebSphere MQ as a JMS provider from within any J2EE application server,
C, or COBOL, and it supports over 40 platforms. WebSphere MQ provides
great quality of service for its messages and is one of the fastest messaging
engines with 80% market share in the message-oriented middleware market.
Note that the performance of this protocol is heavily dependent on the quality
of services configured in the messaging engine. Because of the persistence
and assured delivery options, we did not give it the highest mark for
performance, because we compared it to low latency synchronous protocols
that do not have high quality of service. If you need very high performance
and do not require full crash recovery, you can configure non-durable
in-memory messaging and achieve very high performance levels comparable
to those of synchronous protocols. JMS over WebSphere MQ is a very
popular choice for interoperability between WebSphere and other application
servers.
Simple Object Access Protocol
Simple Object Access Protocol is a popular Web services communication
protocol. most often used over HTTP, although it can also use JMS, SMTP or
other lower level protocols. Recent developments in Web services have

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