You are designing a Windows Azure web application.  
The application must integrate with on-premise business services.  
The business services are running on an on-premise server and cannot be rewritten. The business services are not exposed externally.  
You need to recommend an approach for accessing the business services. 
What should you recommend？（）  

Your company hosts web services in the company intranet.  The intranet is secured by a firewall.  
Devices outside the firewall must be able to access the web services.  Company policies prohibit changes to firewall rules. 
You need to recommend an approach for enabling inbound communication. 
What should you recommend？（）