With the advent of the cloud and enterprises building cloud-based apps, enterprises will still want to use their existing on-premise apps. Thus, one of the key requirements in building hybrid cloud-based apps across on-premise and on-cloud environments is the ability to use pre-existing on-premise apps.
BizTalk Server 2010 AppFabric Connect for Services feature now allows BizTalk users to expose their on-premise BizTalk Applications as WCF Services on the cloud, by adding Windows Azure AppFabric Service Bus endpoints. These Service Bus endpoints can subsequently be consumed by clients residing outside the enterprise's organizational firewall.
Read the full Wiki below: