ESB

 An enterprise service bus (ESB) is a bus-like architecture that helps integrate diverse applications and services in an enterprise. 

It incorporates a messaging engine, data integration and routing capabilities, web services, and analytics capabilities. 

You can use an ESB for the following:

• Decouple product components and allocate them to different compute resources
• Support migration between servers, private and public clouds, and hybrid cloud environments
• Support loose coupling - thereby enabling you to readily integrate existing systems and incorporate new technologies as they emerge
• Creation of new web services and functions seamlessly with in-built message brokering
• Build solutions with visual tooling, interactive debugging, and data mapping
• Analyze integration flows with advanced, customizable analytics capabilities

ESB’s guiding principles are:

• Orchestration - integrates two or more applications and services to synchronize data and process.
• Transformation - transforms data from canonical to application specific format.
• Transportation - protocol negotiation between multiple formats like HTTP, JDBC, JMS, and FTP etc.
• Mediation - multiple interfaces for supporting multiple versions of a service.
• Non-functional consistency - transaction management and security.

Below are some of the ESB products:

• Red Hat JBoss Fuse. 
• Mule ESB. 
• IBM Websphere ESB.
• Oracle ESB.
• Microsoft BizTalk.
• IBM DataPower Gateway