Is Biztalk a ESB?
First let us explain what an ESB is. An Enterprise Service Bus (ESB) is an enterprise architectural pattern and a key enabler to implement the infrastructure for a service-oriented architecture (SOA).
The increasing adoption of SOA and the proliferation of Web services have revealed an ever growing need to provide a managed layer between services and their consumers. There must be support for interaction between heterogeneous services and interfaces that might be mismatched, or that might change over time.
An ESB addresses such integration problems in a way that maximizes the re-use of services and that maintains the flexibility to easily change the solution.
Biztalk can be used as a foundation for implementing an Enterprise Service Bus. So Yes Biztalk is a ESB enabler.
Microsoft has the Biztalk ESB ToolKit which is a collection of built tools and libraries that extend the capabilities of Biztalk Server to support loosely coupled messaging architecture. It can be used as a middle ware ESB to connect enterprise applications. Read more on Biztalk ESB Tool Kit 2.1
The Biztalk ESB Toolkit provides the following feature to enable a Service Oriented Infrastructure (SOI) implementation.
1. Endpoint run-time discovery and virtualization
2. Dynamic message transformation and translation
3. Loosely coupled service composition
4. Dynamic routing
5. Quality of service
6. Centralized exception management
7. Protocol transformation
Video Using Microsoft BizTalk ESB Toolkit and Integration Patterns to Improve Business Agility