The Business layer (or middleware layer) incorporates the logic for encapsulating the business process. Within this layer it is the responsibility, from the Microsoft perspective, that COM and MTS (Microsoft Transaction Server) interact with other Distributed coordinated services to provide transactions for business "state" information. For example, while IIS and ASP deliver content COM objects either running with MTS or other middleware technologies, would provide the logic for managing the business process.
Microsoft Transaction Server provides support for distributed transactions and the co-ordination of those transactions. It also supports the notion of packaging components and web applications together within the same solution to provide faster access and Just In Time activation for their component parts.
MTS also provides a roles management system to enable a more "work flow" style approach to running the business components.
Microsoft also includes a Message Queue service. MSMQ aims to provide a queue and state management solution via a guaranteed delivery mechanism. The purpose of which is to enable designers to implement state machines and queues without repeat development. This frees developers from having to re-implement messaging technology for each solution.