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In the past several years there have been several technologies attempting to solve to these problems such as Enterprise Applicaton Integration (EAI) ¹, Business-to-Business (B2B) ², Service Oriented Architecture (SOA) ³, and Web Services ⁴. These solutions addressed some of the integration issues, but were proprietary, expensive, and time-consuming to implement. These solutions range from expensive solutions from vendors (cost, lock-in) to home-grown custom solutions (maintenance, cost). The overwhelming disadvantages of these solutions are cost and lack of flexibility due to being non-standard.

The ESB solves the integration problem without the flaws of the other solutions. The purpose of an ESB is to facilitate application and process integration by providing distributed processing ⁵, intelligent routing ⁶, security ⁷, and dynamic data transformation ⁸. In an ESB these services are provided so each application does not have to address these issues independently and in a proprietary manner; these are standard infrastructure services in an ESB.

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The enterprise service bus addresses the disadvantages of existing solutions by creating a standard infrastructure for integration. Point-to-point solutions, where each of n components requires n-1 interfaces for full communication, are replaced by a bus solution where each component requires a single interface to the bus for global communication. An ESB is an open standards based, distributed, and message-based. It provides routing, business process orchestration, reliability and security. The ESB provides pluggable services ⁹. Because of the standard nature of the bus these pluggable services can be provided by third parties and still interoperate reliably with the bus.

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An ESB also supports requirements such as security, orchestration ¹⁰, and transactionality ¹¹. These exist in "hard-wired" integration methods, but are not automatically available in a service-oriented architecture. One of the key requirements for the ESB is to give loosely coupled service-based integration methods a level of enterprise-class reliability and security.

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