BizTalk Server 2006 R2 comes with WCF adapters and can work with WCF extensions (custom bindings and custom behaviors). It does require users to define these WCF extensions in machine.config.  However, machine.config is ideally used to store configuration information that is required across all applications that are running on a particular computer. On the other hand, WCF custom behavior extensions may be required only by BizTalk Server and not by all the applications running on the computer. So, although storing the custom behavior extensions in machine.config serves the purpose, it is not the optimal location.  

BizTalk Server 2006 R2 SP1 can fulfill this requirement by providing an alternative location for defining WCF extensions. WCF extensions can now be imported in the Handler properties for WCF-Custom and WCF-CustomIsolated adapters. In the new design, the code now looks in two places to form a cumulative list of binding extensions: machine.config and the Handler properties.  The list of bindings displayed in the Bindings tab in the WCF-Custom and WCF-CustomIsolated configuration user interface is a combination of bindings in machine.config and the imported configuration of the Handler; the user can then choose a binding from this combined list. Another benefit of using Handler properties is that once the WCF extensions are imported, they can be used by any computer in the BizTalk group.

For details, see New Features in BizTalk Server 2006 R2 Service Pack 1.

See Also

Another important place to find a huge amount of BizTalk related articles is the TechNet Wiki itself. The best entry point is BizTalk Server Resources on the TechNet Wiki.